Data Fields - SMAP L1B Radiometer Half-Orbit Time-Ordered Brightness Temperatures

This page provides a description of all data fields within the SMAP L1B Radiometer Half-Orbit Time-Ordered Brightness Temperatures (SPL1BTB) product.

For a description of metadata fields for this product, refer to the Metadata Fields document.

Brightness_Temperature

Table 1 lists the elements in the Brightness_Temperature group. This group provides the time-ordered footprint averaged brightness temperatures (TBs) referenced to the Earth's surface with error sources removed. The group also includes geolocation information, antenna temperatures referenced to the feedhorn, before and after Radio Frequency Interference (RFI) mitigation, error sources, quality flags, brightness temperature error, and Noise Equivalent Delta Temperature (NEDT).

Within the Brightness_Temperature group, a distinct HDF5 data set stores each data element. The name of each data set object matches the data element that it stores. Table 1 lists the elements in the Brightness Temperature group. All the data elements in the Brightness Temperature group have the AntennaScan_Tb_Array shape. TheAntennaScan_Tb_Array shape describes a two-dimensional array. The slowest moving dimension represents a particular antenna scan and the second dimension represents the footprint.

Table 1. Brightness Temperature Data Fields
Data Field Name Type Shape Valid_Min Valid_Max Units Fill/Gap Value
antenna_earth_azimuth Float32 AntennaScan_Tb_Array 0 359.999 Degrees -9999.0
antenna_look_angle Float32 AntennaScan_Tb_Array 0 180 Degrees -9999.0
antenna_scan_angle Float32 AntennaScan_Tb_Array 0 359.999 Degrees -9999.0
antenna_sideloble_correction_3 Float32 AntennaScan_Tb_Array -0.5 6 Kelvin -9999.0
antenna_sideloble_correction_4 Float32 AntennaScan_Tb_Array -0.5 6 Kelvin -9999.0
antenna_sideloble_correction_h Float32 AntennaScan_Tb_Array -0.5 6 Kelvin -9999.0
antenna_sideloble_correction_v Float32 AntennaScan_Tb_Array -0.5 6 Kelvin -9999.0
atm_correction_h Float32 AntennaScan_Tb_Array 1 4 Kelvin -9999.0
atm_correction_v Float32 AntennaScan_Tb_Array 1 4 Kelvin -9999.0
atm_loss Float32 AntennaScan_Tb_Array 1 1.02 Kelvin -9999.0
earth_boresight_azimuth Float32 AntennaScan_Tb_Array 0 359.999 Degrees -9999.0
earth_boresight_incidence Float32 AntennaScan_Tb_Array 0 90 Degrees -9999.0
faraday_rotation_angle Float32 AntennaScan_Tb_Array -90.0 90.0 Degrees -9999.0
faraday_rotation_correction_h Float32 AnntenaScan_Tb_Array -3.9 5.6 Kelvin -9999.0
faraday_rotation_correction_v Float32 AntennaScan_Tb_Array -3.9 5.6 Kelvin -9999.0
galactic_direct_correction_h Float32 AntennaScan_Tb_Array 0.3 0.6 Kelvin -9999.0
galactic_direct_correction_v Float32 AntennaScan_Tb_Array 0.3 0.6 Kelvin -9999.0
galactic_reflected_correction_3 Float32 AntennaScan_Tb_Array -0.4 4 Kelvin -9999.0
galactic_reflected_correction_4 Float32 AntennaScan_Tb_Array -0.4 4 Kelvin -9999.0
galactic_reflected_correction_h Float32 AntennaScan_Tb_Array -0.4 4 Kelvin -9999.0
galactic_reflected_correction_v Float32 AntennaScan_Tb_Array -0.4 4 Kelvin -9999.0
lunar_direct_phi Float32 AntennaScan_Tb_Array 0 360 Degrees -9999.0
lunar_direct_theta Float32 AntennaScan_Tb_Array 0 180 Degrees -9999.0
lunar_specular_correction_3 Float32 AntennaScan_Tb_Array -0.2 2 Kelvin -9999.0
lunar_specular_correction_4 Float32 AntennaScan_Tb_Array -0.2 2 Kelvin -9999.0
lunar_specular_correction_h Float32 AntennaScan_Tb_Array -0.2 2 Kelvin -9999.0
lunar_specular_correction_v Float32 AntennaScan_Tb_Array -0.2 2 Kelvin -9999.0
lunar_specular_lat Float32 AntennaScan_Tb_Array -90 90 Degrees -9999.0
lunar_specular_lon Float32 AntennaScan_Tb_Array -180 179.999 Degrees -9999.0
lunar_specular_phi Float32 AntennaScan_Tb_Array 0 359.999 Degrees -9999.0
lunar_specular_reflection_coefficient_h Float32 AntennaScan_Tb_Array 0 1 N/A -9999.0
lunar_specular_reflection_coefficient_v Float32 AntennaScan_Tb_Array 0 1 N/A -9999.0
lunar_specular_theta Float32 AntennaScan_Tb_Array 0 180 Degrees -9999.0
nedt_3 Float32 AntennaScan_Tb_Array 0.5 3 Kelvin -9999.0
nedt_4 Float32 AntennaScan_Tb_Array 0.5 3 Kelvin -9999.0
nedt_h Float32 AntennaScan_Tb_Array 0.5 3 Kelvin -9999.0
nedt_v Float32 AntennaScan_Tb_Array 0.5 3 Kelvin -9999.0
polarization_rotation_angle Float32 AntennaScan_Tb_Array 0 90 Degrees -9999.0
sea_ice_fraction Float32 AntennaScan_Tb_Array 0 1.0 N/A -9999.0
solar_direct_correction_h Float32 AntennaScan_Tb_Array 0 0.6 Kelvin -9999.0
solar_direct_correction_v Float32 AntennaScan_Tb_Array 0 0.6 Kelvin -9999.0
solar_direct_phi Float32 AntennaScan_Tb_Array 0 360 Degrees -9999.0
solar_direct_theta Float32 AntennaScan_Tb_Array 0 180 Degrees -9999.0
solar_specular_correction_3 Float32 AntennaScan_Tb_Array -0.5 1 Kelvin -9999.0
solar_specular_correction_4 Float32 AntennaScan_Tb_Array -0.5 1 Kelvin -9999.0
solar_specular_correction_h Float32 AntennaScan_Tb_Array -0.5 1 Kelvin -9999.0
solar_specular_correction_v Float32 AntennaScan_Tb_Array -0.5 1 Kelvin -9999.0
solar_specular_lat Float32 AntennaScan_Tb_Array -90 90 Degrees -9999.0
solar_specular_lon Float32 AntennaScan_Tb_Array -180 179.999 Degrees -9999.0
solar_specular_phi Float32 AntennaScan_Tb_Array 0 360 Degrees -9999.0
solar_specular_reflection_coefficient_h Float32 AntennaScan_Tb_Array 0 1 N/A -9999.0
solar_specular_reflection_coefficient_v Float32 AntennaScan_Tb_Array 0 1 N/A -9999.0
solar_specular_theta Float32 AntennaScan_Tb_Array 0 180 Degrees -9999.0
specular_declination Float32 AntennaScan_Tb_Array -90 90 Degrees -9999.0
specular_right_ascension Float32 AntennaScan_Tb_Array 0 359.999 Degrees -9999.0
surface_water_fraction_mb Float32 AntennaScan_Tb_Array 0 1 N/A -9999.0
ta_3 Float32 AntennaScan_Tb_Array -50 50 Kelvin -9999.0
ta_4 Float32 AntennaScan_Tb_Array -50 50 Kelvin -9999.0
ta_filtered_3 Float32 AntennaScan_Tb_Array -50 50 Kelvin -9999.0
ta_filtered_4 Float32 AntennaScan_Tb_Array -50 50 Kelvin -9999.0
ta_filtered_h Float32 AntennaScan_Tb_Array 0 340 Kelvin -9999.0
ta_filtered_v Float32 AntennaScan_Tb_Array 0 340 Kelvin -9999.0
ta_h Float32 AntennaScan_Tb_Array -0 340 Kelvin -9999.0
ta_v Float32 AntennaScan_Tb_Array -0 340 Kelvin -9999.0
tb_3 Float32 AntennaScan_Tb_Array 0 0 Kelvin -9999.0
tb_4 Float32 AntennaScan_Tb_Array -50 -50 Kelvin -9999.0
tb_declination Float32 AntennaScan_Tb_Array -90 90 Degrees -9999.0
tb_h Float32 AntennaScan_Tb_Array 0 340 Kelvin -9999.0
tb_lat Float32 AntennaScan_Tb_Array -90 90 Degrees -9999.0
tb_lon Float32 AntennaScan_Tb_Array -180 179.999 Degrees -9999.0
tb_mode_flag Bit flag AntennaScan_Tb_Array N/A N/A N/A N/A
tb_qual_flag_3 Bit flag AntennaScan_Tb_Array N/A N/A N/A N/A
tb_qual_flag_4 Bit flag AntennaScan_Tb_Array N/A N/A N/A N/A
tb_qual_flag_h Bit flag AntennaScan_Tb_Array N/A N/A N/A N/A
tb_qual_flag_v Bit flag AntennaScan_Tb_Array N/A N/A N/A N/A
tb_right_ascension Float32 AntennaScan_Tb_Array 0 359.999 Degrees -9999.0
tb_time_seconds Float64 AntennaScan_Tb_Array N/A N/A Seconds -9999.0
tb_time_utc Char AntennaScan_Tb_Array N/A N/A N/A -9999.0
tb_upwelling Float32 AntennaScan_Tb_Array 0 4.0 Kelvin -9999.0
tb_v Float32 AntennaScan_Tb_Array 0 340 Kelvin -9999.0
toa_3 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
toa_4 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
toa_h Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0
toa_v Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0
toi_3 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
toi_4 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
toi_h Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0
toi_v Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0

Calibration_Data [top]

Table 2 lists the elements in the Calibration Data group. The Calibration Data provides information about the instrument component losses and noise temperatures which the SMAP Level-1B brightness temperature data product employs in the calibration algorithm. Included are values for the vertical and horizontal polarization for the fullband. All of the product elements in the Calibration Data group are stored in a single HDF5 Group named Calibration_Data. A distinct HDF5 Dataset stores each data element. The name of each Dataset object matches the data element that it stores. Table 2 lists the elements in the Calibration Data group.

The data elements in the Calibration Data group have varying shapes depending on whether data is stored for both the vertical and horizontal channels. TheAntennaScan_VHPol_Array shape describes a two-dimensional array. The slowest moving dimension represents a particular antenna scan. The second dimension represents the polarization. The element that represents vertical polarization always precedes the element that represents horizontal polarization.

Table 2. Calibration Data Fields
Data Field Name Type Shape Valid_Min Valid_Max Units Fill/Gap Value
cal_loss12_radome Float32 AntennaScan_Array 1 2 N/A -9999.0
cal_loss1_reflector Float32 AntennaScan_VHPol_Array 1 2 N/A -9999.0
cal_loss2_feed Float32 HighResolutionScan_Subband_Array 1 999999.9 N/A -9999.0
cal_loss3_omt Float32 HighResolutionScan_Subband_VHPol_Array  1 999999.9 N/A -9999.0
cal_loss4_coupler Float32 HighResolutionScan_Subband_VHPol_Array 1 999999.9 N/A -9999.0
cal_loss5_diplexer Float32 HighResolutionScan_Subband_VHPol_Array 1 999999.9 N/A -9999.0
cal_nd_phase Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Radians -9999.0
cal_rx_phase Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Radians -9999.0
cal_temp12_radome Float32 AntennaScan_Array 110.0 260.0 Kelvin -9999.0
cal_temp1_reflector Float32 AntennaScan_Array 330.0 400.0 Kelvin -9999.0
cal_temp2_feed Float32 AntennaScan_Array 253.15 313.15 Kelvin -9999.0
cal_temp3_omt Float32 AntennaScan_VHPol_Array 253.15 313.15 Kelvin -9999.0
cal_temp4_coupler Float32 AntennaScan_VHPol_Array 253.15 313.15 Kelvin -9999.0
cal_temp5_deplexer Float32 AntennaScan_VHPol_Array 253.15 313.15 Kelvin -9999.0
cal_temp_nd Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Kelvin -9999.0
cal_temp_ref Float32 AntennaScan_VHPol_Array 253.15 313.15 Kelvin -9999.0
cal_temp_xnd Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Kelvin -9999.0
cal_tempref_offset Float32 HighResolutionScan_Subband_VHPol_Array  999999.9 999999.9 Kelvin -9999.0
cal_tnd Float32 HighResolutionScan_Subband_VHPol_Array  999999.9 999999.9 Kelvin -9999.0
cal_tref Float32 HighResolutionScan_Subband_VHPol_Array 999999.9 999999.9 Kelvin -9999.0
cal_txnd Float32 HighResolutionScan_Subband_VHPol_Array  999999.9 999999.9 Kelvin -9999.0
cal_xnd_phase  Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Radians -9999.0

High_Resolution_Calibration_Data [top]

Table 3 lists the elements in the High Resolution Calibration Data group. The High Resolution Calibration Data provides information about the instrument component losses and noise temperatures which the SMAP Level-1B brightness temperature data product employs in the calibration algorithm. Included are values for the vertical and horizontal polarization for all 16 subbands. All of the product elements in the High Resolution Calibration Data group are stored in a single HDF5 Group named HighResolution_Calibration_Data. A distinct HDF5 data set stores each data element. The name of each data set object matches the data element that it stores. Table 3 lists the elements in the High Resolution Calibration Data group.

The data elements in the High Resolution Calibration Data group have varying shapes depending on whether data is stored for both the vertical and horizontal channels. The HighResolutionScan_Subband_VHPol_Array shape describes a three-dimensional array. The slowest moving dimension represents a particular antenna scan. The second dimension represents the 16 subbands. The third dimension represents the polarization. The element that represents vertical polarization always precedes the element that represents horizontal polarization.

Table 3. High Resolution Calibration Data Fields
Data Field Name Type Shape Valid_Min Valid_Max Units Fill/Gap Value
cal_loss2_feed16 Float32 HighResolutionScan_Subband_Array 1 999999.9 N/A -9999.0
cal_loss3_omt16  Float32 HighResolutionScan_Subband_VHPol_Array  1 999999.9 N/A -9999.0
cal_loss4_coupler16 Float32 HighResolutionScan_Subband_VHPol_Array  1 999999.9 N/A -9999.0
cal_loss5_diplexer16 Float32 HighResolutionScan_Subband_VHPol_Array 1 999999.9 N/A -9999.0
cal_nd_phase16 Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Radians -9999.0
cal_rx_phase16 Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Radians -9999.0
cal_temp_nd16  Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Kelvin -9999.0
cal_temp_xnd16 Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Kelvin -9999.0
cal_tempref_offset16 Float32 HighResolutionScan_Subband_VHPol_Array  999999.9 999999.9 Kelvin -9999.0
cal_tnd16  Float32 HighResolutionScan_Subband_VHPol_Array  999999.9 999999.9 Kelvin -9999.0
cal_tref16  Float32 HighResolutionScan_Subband_VHPol_Array 999999.9 999999.9 Kelvin -9999.0
cal_txnd16 Float32 HighResolutionScan_Subband_VHPol_Array  999999.9 999999.9 Kelvin -9999.0
cal_xnd_phase16 Float32 HighResolutionScan_Subband_Array  999999.9 999999.9 Radians -9999.0
calibration_time_seconds Float64 HighResolutionScan_Array 0 946000000 Seconds -9999.0
highresolution_scan_index Uint32 HighResolutionScan_Array 0 800 N/A -9999.0

Metadata [top]

For a description of all metadata fields for this product, refer to the Metadata Fields document. 

Spacecraft_Data [top]

Tables 4 describes the data fields within the HDF5 Group called Spacecraft_Data. All the HDF5 data sets in the Spacecraft Data group have AntennaScan_Array shape. TheAntennaScan_Array shape describes a one-dimensional array, where each array element represents one rotation of the SMAP antenna. The representative time instant for each antenna scan takes place when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The X-axis of the spacecraft coordinate system approximates the direction of motion of the SMAP spacecraft. Thus, array element x_pos(212) lists the representative spacecraft position in the x dimension, array elementyaw(212) lists the representative spacecraft yaw, and array element sc_geodetic_alt(212) lists the representative spacecraft altitude at the instant during each antenna scan when the boresight aligns with the X-axis of the spacecraft coordinate system. The time of that event appears in array element antenna_scan_time_utc (212). The precise range of time covered by each antenna scan depends on the antenna rotation rate. The mission selected one of two likely antenna rotation rates. They are either 14.6 revolutions per minute or 13 revolutions per minute.

Table 4. Spacecraft Data Fields
Data Field Name Type Shape Valid Min

Valid Max

Unit Fill/Gap Value
antenna_scan_mode_flag Uint16 AntennaScan_Array 0 65535 N/A 65534
antenna_scan_qual_flag Uint16 AntennaScan_Array N/A N/A N/A 65534
antenna_scan_time Float64 AntennaScan_Array 0 946000000 seconds -9999.0
antenna_scan_time_utc FixedLenString 
(24 characters)
AntennaScan_Array 2014-10-31T00:00:00.000Z 2030-12-31T23:59:60.999Z N/A N/A
footprints_per_scan Uint16 AntennaScan_Array 0 300 N/A 65534
pitch Float32 AntennaScan_Array -90 90 degrees -9999.0
roll Float32 AntennaScan_Array -90 90 degrees -9999.0
sc_alongtrack_velocity Float32 AntennaScan_Array -8000 8000 m/s -9999.0
sc_geodetic_alt_ellipsoid Float32 AntennaScan_Array 650000 900000 meters -9999.0
sc_nadir_angle Float32 AntennaScan_Array 0 180 degrees -9999.0
sc_nadir_lat Float32 AntennaScan_Array -90 90 degrees -9999.0
sc_nadir_lon Float32 AntennaScan_Array -180 179.999 degrees -9999.0
sc_radial_velocity Float32 AntennaScan_Array -8000 8000 m/s -9999.0
tbs_per_scan Uint16 AntennaScan_Array 0 300 N/A 65534
x_pos Float32 AntennaScan_Array -999999 9999999 m -9999.0
x_vel Float32 AntennaScan_Array -8000 8000 m/s -9999.0
y_pos Float32 AntennaScan_Array -999999 9999999 m -9999.0
y_vel Float32 AntennaScan_Array -8000 8000 m/s -9999.0
yaw Float32 AntennaScan_Array -180 180 degrees -9999.0
z_pos Float32 AntennaScan_Array -999999 9999999 m -9999.0
z_vel Float32 AntennaScan_Array -8000 8000 m/s -9999.0

Data Field Definitions [top]

antenna_earth_azimuth

The antenna_earth_azimuth records the clockwise rot ation from the projection of the Earth's North polar axis onto the XY plane of the SMAP Spacecraft Coordinate System to the projection of the antenna boresight vector onto the XY plane of the SMAP spacecraft coordinate system. The vertex of the angle is at the origin of the Spacecraft Coordinate System. The antenna_earth_azimuth field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

antenna_look_angle

The angle defined by the antenna boresight vector and the spacecraft nadir vector. The antenna_look_angle field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

antenna_scan_angle

The angular position of the antenna boresight projected onto the X-Y plane of the spacecraft coordinate system. The antenna_scan_angle is zero when the antenna boresight aligns with the X axis of the spacecraft coordinate system. Angular measure increases as the antenna rotates counterclockwise. The antenna_scan_angle field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

antenna_sidelobe_correction_h

The brightness temperature correction to the TA for the energy detected within the antenna pattern sidelobes to derive tb_h. The antenna_sidelobe_correction_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

antenna_sidelobe_correction_v

The brightness temperature correction to the TA for the energy detected within the antenna pattern sidelobes to derive tb_v. The antenna_sidelobe_correction_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

antenna_sidelobe_correction_3

The brightness temperature correction to the TA for the energy detected within the antenna pattern sidelobes to derive tb_3. The antenna_sidelobe_correction_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

antenna_sidelobe_correction_4

The brightness temperature correction to the TA for the energy detected within the antenna pattern sidelobes to derive tb_4. The antenna_sidelobe_correction_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

atm_correction_h

The brightness temperature correction to TA for atmospheric emission to derive tb_h. The atm_correction_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

atm_correction_v

The brightness temperature correction to TA for atmospheric emission to derive tb_v. The atm_correction_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

atm_loss

The reduction in power density of the brightness te mperature signal as it propagates through the Earth's atmosphere. The atm_loss field is a two-dimensional array. The slower moving dimensio n index represents the antenna scan. The faster moving dime nsion index represents each of the footprints in the scan.

earth_boresight_azimuth

The angle defined by the vector that extends from the intersection of the spacecraft geodetic nadir vector on the Earths surface to the geographic North and the vector that extends from the vector that extends from the intersection of the spacecraft geodetic nadir on the Earths surface to the pierce point of the boresight vector. The angle measure is clockwise from the northward vector. The earth_boresight_azimuth field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

earth_boresight_incidence

The angle defined by the antenna vector and the mean surface normal vector. The earth_boresight_incidence field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

faraday_rotation_angle

The Faraday rotation angle. The faraday_rotation_angle field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

faraday_rotation_correction_h

The brightness temperature correction to the TA for Faraday rotation to derive tb_h. The faraday_rotation_correction_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

faraday_rotation_correction_v

The brightness temperature correction to the TA for Faraday rotation to derive tb_v. The faraday_rotation_correction_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

galactic_direct_correction_h

The brightness temperature correction to the antenna temperature, TA, for direct galactic and cosmic contamination to derive tb_h. The galactic_direct_correction_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

galactic_direct_correction_v

The brightness temperature correction to the antenna temperature, TA, for direct galactic and cosmic contamination to derive tb_v. The galactic_direct_correction_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

galactic_reflected_correction_3

The brightness temperature correction to the antenna temperature, TA, for reflected galactic and cosmic contamination to derive tb_3. the galactic_reflected_correction_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

galactic_reflected_correction_4

The brightness temperature correction to the antenna temperature, TA, for reflected galactic and cosmic contamination to derive tb_4. the galactic_reflected_correction_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

galactic_reflected_correction_h

The brightness temperature correction to the antenna temperature, TA, for reflected galactic and cosmic contamination to derive tb_h. The galactic_reflected_correction_hfield is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

galactic_reflected_correction_v

The brightness temperature correction to the antenna temperature, TA, for reflected galactic and cosmic contamination to derive tb_v. The galactic_reflected_correction_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_direct_phi

The angle defined by the +X axis of the ABFCS and the vector that extends from the origin to the Mood projected onto the XY plane of the ABFCS. The lunar_direct_phi field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_direct_theta

The angle defined by the +Z axis of the ABFCS which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the ABFCS to the Moon. The lunar_direct_theta field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_correction_3

The brightness temperature correction to the antenna temperature, TA, for reflected lunar contamination to derive tb_3. The lunar_specular_correction_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_correction_4

The brightness temperature correction to the antenna temperature, TA, for reflected lunar contamination to derive tb_4. The lunar_specular_correction_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_correction_h

The brightness temperature correction to the TA for reflected lunar contamination to derive tb_h. The lunar_specular_correction_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_correction_v

The brightness temperature correction to the antenna temperature (TA), for reflected lunar contamination to derive tb_v. The lunar_specular_correction_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_lat

The geodetic latitude of the center of the lunar specular reflection point on the Earth's surface relative to the spacecraft position. The lunar_specular_lat field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_lon

The longitude of the center of the lunar specular reflection point on the Earth's surface relative to the spacecraft position. The lunar_specular_lon field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_phi

The angle defined by the +X axis of the ABFCS and the vector that extends from the origin to the lunar glint spot on the Earths surface projected onto the XY plane of the ABFCS. The lunar_specular_phi field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_reflection_coefficient_h

The quasi-specular reflection coefficient of the surface at the lunar specular point used to derive tb_h. The lunar_specular_reflection_coefficient_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_reflection_coefficient_v

The quasi-specular reflection coefficient of the surface at the lunar specular point used to derive tb_v. The lunar_specular_reflection_coefficient_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

lunar_specular_theta

The angle defined by the +Z axis of the ABFCS which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the ABFCS to the lunar glint spot on the Earth's surface. The lunar_specular_theta field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

nedt_3

The NEDT after RFI removal for the 3rd Stokes parameter value. The nedt_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

nedt_4

The NEDT after RFI removal for the 4th Stokes parameter value. The nedt_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

Table 5. Description of tb_qual_flag_v
Bits Interpretation Value Description
0 Vertical polarization quality flag 0 Vertical polarization brightness temperature measurement has acceptable quality
1 Use of vertical polarization brightness temperature not recommended
1 Vertical polarization range flag 0 Vertical polarization brightness temperature measurement falls in expected range
1 Vertical polarization brightness temperature value is out of range
2

Vertical polarization RFI detection flag 0 RFI not detected for vertical polarization brightness temperatures in the grid cell
1 If RFI was detected, the software was unable to correct the vertical polarization brightness temperature for RFI
3

Vertical polarization RFI correction flag 0 If RFI was detected, the vertical polarization brightness temperature was corrected to remove RFI
1 If RFI was detected, the software was unable to correct the vertical polarization brightness temperature for RFI
4

Vertical polarization NEDT flag 0 Vertical polarization brightness temperature measurement has acceptable NEDT
1 Use of vertical polarization brightness temperature not recommended, since NEDT exceeds pre-determined threshold
5

Vertical polarization direct sun correction 0 Correction for direct sun operated successfully on the vertical polarization brightness temperature
1 Correction for direct sun did not function or yielded poor results on the vertical polarization brightness temperature
6

Vertical polarization reflected sun correction 0 Correction for reflected sun operated successfully on the vertical polarization brightness temperature
1 Correction for reflected sun did not function or yielded poor results on the vertical polarization brightness temperature
7

Vertical polarization reflected moon correction 0 Correction for reflected moon operated successfully on the vertical polarization brightness temperature
1 Correction for reflected moon did not function or yielded poor results on the vertical polarization brightness temperature
8

Vertical polarization direct galaxy correction 0 Correction for direct galaxy operated successfully on the vertical polarization brightness temperature
1 Correction for direct galaxy did not function or yielded poor results on the vertical polarization brightness temperature
9

Vertical polarization reflected galaxy correction 0 Correction for reflected galaxy operated successfully on the vertical polarization brightness temperature
1 Correction for reflected galaxy did not function or yielded poor results on the vertical polarization brightness temperature
10 Vertical polarization correction for atmospheric conditions 0 Correction for atmospheric conditions operated successfully on the vertical polarization brightness temperature
1 Correction for atmospheric conditions did not function or yielded poor results on the vertical polarization brightness temperature
11 Vertical polarization Faraday rotation correction 0 Correction for Faraday rotation operated successfully on the vertical polarization brightness temperature
1 Correction for Faraday rotation did not function or yielded poor results on the vertical polarization brightness temperature
12 Vertical polarization null value 0 The corresponding vertical polarization brightness temperature element contains a calculated value.
1 The corresponding vertical polarization brightness temperature element is null.
13-15 Undefined N/A N/A
N/A N/A

nedt_h

The NEDT after RFI removal for horizontal polarization. The nedt_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

nedt_v

NEDT after RFI removal for vertical polarization. The nedt_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

polarization_rotation_angle

The angle between the plane of polarization and the reference plane used to calculate the Stokes vector. The polarization_rotation_angle field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

sea_ice_fraction

The Gaussian weighted average of the sea ice concentration within the main beam of the antenna pattern. Sea_ice_fraction is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_direct_correction_h

The brightness temperature correction to the antenna temperature, TA, for direct solar contamination to derive tb_h. Limits on the contribution of all error sources will be determined using the orbit simulator. The solar_direct_correction_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_direct_correction_v

The brightness temperature correction to the antenna temperature, TA, for direct solar contamination to derive tb_v. Limits on the contribution of all error sources will be determined using the orbit simulator. The solar_direct_correction_v is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_direct_phi

The angle defined by the +X axis of the Antenna Beam Frame Coordinate System (ABFCS) and the vector that extends from the origin to the Sun projected onto the XY plane of the ABFCS. The solar_direct_phi field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_direct_theta

The angle defined by the +Z axis of the ABFCS, which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the ABFCS to the Sun. Thesolar_direct_theta field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_correction_3

The brightness temperature correction to the antenna temperature, TA, for the solar specular reflection detected within range of the antenna pattern to derive tb_3. Thesolar_specular_correction_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_correction_4

The brightness temperature correction to the antenna temperature, TA, for the solar specular reflection detected within range of the antenna pattern to derive tb_4.
The solar_specular_correction_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_correction_h

The brightness temperature correction to the antenna temperature, TA, for the solar specular reflection detected within range of the antenna pattern to derive tb_h. Thesolar_specular_correction_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_correction_v

The brightness temperature correction to the antenna temperature, TA, for the solar specular reflection detected within range of the antenna pattern to derive tb_v. Thesolar_specular_correction_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_lat

The geodetic latitude of the center of the solar specular reflection point on the Earth's surface relative to the spacecraft position. The solar_specular_lat field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_lon

The longitude of the center of the solar specular reflection point on the Earth's surface relative to the spacecraft position. The solar_specular_lon field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_phi

The angle defined by the +X axis of the ABFCS and the vector that extends from the origin to the solar glint spot on the Earths surface projected onto the XY plane of the ABFCS. The solar_specular_phi field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_reflection_coefficient_h

The quasi-specular reflection coefficient of the surface at the solar specular point used to derive tb_h. The solar_specular_reflection_coefficient_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_reflection_coefficient_v

The quasi-specular reflection coefficient of the surface at the solar specular point used to derive tb_v. The solar_specular_reflection_coefficient_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

solar_specular_theta

The angle defined by the +Z axis of the ABFCS, which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the ABFCS to the solar glint spot on the Earths surface. The solar_specular_theta field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

specular_declination

The declination of the specular reflection vector relative to each footprint in the product. The specular reflection vector is in the same plane as the boresight vector and the spacecraft nadir vector. The specular_declination field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

specular_right_ascension

The right ascension of the specular reflection vector relative to each footprint in the product. The specular reflection vector is in the same plane as the boresight vector and the spacecraft nadir vector. The specular_right_ascension field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

surface_water_fraction_mb

The areal fraction of static water within the radiometer main beam. The surface_water_fraction_mb field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_3

The antenna temperature for the 3rd Stokes parameter before RFI filtering. The ta_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_4

The antenna temperature for the 4th Stokes parameter before RFI filtering. The ta_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_filtered_3

Antenna temperature for the 3rd Stokes parameter after RFI filtering. The ta_filtered_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_filtered_4

Antenna temperature for the 4th Stokes parameter after RFI filtering. The ta_filtered_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_filtered_h

The horizontally polarized antenna temperature after RFI mitigation. The ta_filtered_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_filtered_v

The vertically polarized antenna temperature after RFI mitigation. The ta_filtered_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_h

The horizontally polarized antenna temperature before RFI filtering. The ta_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

ta_v

The vertically polarized antenna temperature before RFI filtering The ta_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_3

The 3rd Stokes parameter at the surface of the Earth after RFI filtering. The Faraday Rotation Correction algorithm in the L1B_TB executable sets the third Stokes to zero and then recalculates an equivalent brightness temperature vector with non-zero vertical and horizontal brightness temperatures. Thus, this element always displays a value of 0.  Users who are interested in third Stokes measure derived from instrument data should inspect either the antenna temperatures or the top of ionosphere temperatures. Details of the Faraday Rotation Correction algorithm appear in the Algorithm Theoretical Basis Document (ATBD) for the SMAP Level-1B radiometer brightness temperatures product.

The tb_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_4

The 4th Stokes parameter at the surface of the Earth after RFI filtering. The tb_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_declination

The declination of the spacecraft boresight vector. The tb_declination field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_h

The horizontally polarized brightness temperature at the surface of the Earth after RFI filtering. The tb_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_lat

The geodetic latitude of the intersection of the antenna boresight vector and the Earth's surface. The tb_lat field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_lon

The longitude of the intersection of the antenna boresight vector and the Earth's surface. The tb_lon field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_mode_flag

Bit flags that indicate instrument and ambient conditions when the brightness temperature measurements were acquired. Table 6 specifies the meaning of individual bits in thetb_mode_flag field.

Table 6. Description of tb_mode_flag
Bits Interpretation Value Description
0 Data resolution flag (land/ocean) 0 High resolution data contribute to this scan
1 Low resolution data contribute to this scan
1 Scan view flag 0 Brightness temperature footprint is forward of spacecraft position
1 Brightness temperature footprint is aft of spacecraft position
2

Spacecraft viewing mode 0 Instrument is in normal Earth viewing mode
1 Instrument boresight does not view the Earth's surface
3

Ocean calibration region 0 Pixel views external calibration region over the ocean
1 Pixel does not view ocean calibration region over the ocean
4

Antarctic calibration region 0 Correction for reflected sun operated successfully on the 4th Stokes parameter
1 Correction for reflected sun did not function or yielded poor results on the 4th Stokes parameter
5

Lunar visible flag 0 The moon is not visible from the SMAP spacecraft.
1 The moon is visible from the SMAP spacecraft.
6

Solar visible flag 0 The sun is not visible from the SMAP spacecraft.
1 The sun is visible from the SMAP spacecraft.
7-15 Undefined N/A N/A
N/A N/A

The tb_mode_flag field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_qual_flag_3

Bit flags that indicate the quality of the 3rd Stokes parameter measurement. Table 7 specifies the meaning of individual bits in the tb_qual_flag_3.

Table 7. Description of tb_qual_flag_3
Bits Interpretation Value Description
0 3rd Stokes quality flag 0 3rd Stokes parameter measurement has acceptable quality
1 Use of 3rd Stokes parameter measurement not recommended
1 3rd Stokes range flag 0 3rd Stokes parameter measurement falls in expected range
1 3rd Stokes parameter measurement is out of range
2

3rd Stokes RFI detection flag 0 RFI not detected for 3rd Stokes brightness temperatures in the grid cell
1 RFI detected for 3rd Stokes brightness temperatures in the grid cell
3

3rd Stokes RFI correction flag 0 If RFI was detected, the 3rd Stokes brightness temperature was corrected to remove RFI
1 If RFI was detected, the software was unable to correct the 3rd Stokes brightness temperature for RFI
4

3rd Stokes NEDT flag 0 3rd Stokes has acceptable NEDT
1 Use of 3rd Stokes not recommended, since NEDT exceeds pre-determined threshold
5

3rd Stokes direct sun correction 0 Correction for direct sun operated successfully on the 3rd Stokes parameter
1 Correction for direct sun did not function or yielded poor results on the 3rd Stokes parameter
6

3rd Stokes reflected sun correction 0 Correction for reflected sun operated successfully on the 3rd Stokes parameter
1 Correction for reflected sun did not function or yielded poor results on the 3rd Stokes parameter
7

3rd Stokes reflected moon correction 0 Correction for reflected moon operated successfully on the 3rd Stokes parameter
1 Correction for reflected moon did not function or yielded poor results on the 3rd Stokes parameter
8

3rd Stokes direct galaxy correction 0 Correction for direct galaxy operated successfully on the 3rd Stokes parameter
1 Correction for direct galaxy did not function or yielded poor results on the 3rd Stokes parameter
9

3rd Stokes reflected galaxy correction 0 Correction for reflected galaxy operated successfully on the 3rd Stokes parameter
1 Correction for reflected galaxy did not function or yielded poor results on the 3rd Stokes parameter
10 3rd Stokes correction for atmospheric conditions 0 Correction for atmospheric conditions operated successfully on the 3rd Stokes parameter
1 Correction for atmospheric conditions did not function or yielded poor results on the 3rd Stokes parameter
11 Undefined N/A N/A
N/A N/A
12 3rd Stokes null value 0 The corresponding 3rd Stokes parameter element contains a calculated value.
1 The corresponding 3rd Stokes parameter element is null.
13-15 Undefined N/A N/A
N/A N/A

The tb_qual_flag_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_qual_flag_4

Bit flags that indicate the quality of the 4th Stokes parameter measurement. Table 8 specifies the meaning of individual bits in the tb_qual_flag_4 field.

Table 8. Description of tb_qual_flag_4
Bits Interpretation Value Description
0 4th Stokes quality flag 0 4th Stokes parameter measurement has acceptable quality
1 Use of 4th Stokes parameter measurement not recommended
1 4th Stokes range flag 0 4th Stokes parameter measurement falls in expected range
1 4th Stokes parameter measurement is out of range
2

4th Stokes RFI detection flag 0 RFI not detected for 4th Stokes brightness temperatures in the grid cell
1 RFI detected for 4th Stokes brightness temperatures in the grid cell
3

4th Stokes RFI correction flag 0 If RFI was detected, the 4th Stokes brightness temperature was corrected to remove RFI
1 If RFI was detected, the software was unable to correct the 4th Stokes brightness temperature for RFI
4

4th Stokes NEDT flag 0 4th Stokes has acceptable NEDT
1 Use of 4th Stokes not recommended, since NEDT exceeds pre-determined threshold
5

4th Stokes direct sun correction 0 Correction for direct sun operated successfully on the 4th Stokes parameter
1 Correction for direct sun did not function or yielded poor results on the 4th Stokes parameter
6

4th Stokes reflected sun correction 0 Correction for reflected sun operated successfully on the 4th Stokes parameter
1 Correction for reflected sun did not function or yielded poor results on the 4th Stokes parameter
7

4th Stokes reflected moon correction 0 Correction for reflected moon operated successfully on the 4th Stokes parameter
1 Correction for reflected moon did not function or yielded poor results on the 4th Stokes parameter
8

4th Stokes direct galaxy correction 0 Correction for direct galaxy operated successfully on the 4th Stokes parameter
1 Correction for direct galaxy did not function or yielded poor results on the 4th Stokes parameter
9

4th Stokes reflected galaxy correction 0 Correction for reflected galaxy operated successfully on the 4th Stokes parameter
1 Correction for reflected galaxy did not function or yielded poor results on the 4th Stokes parameter
10 4th Stokes correction for atmospheric conditions 0 Correction for atmospheric conditions operated successfully on the 4th Stokes parameter
1 Correction for atmospheric conditions did not function or yielded poor results on the 4th Stokes parameter
11 Undefined N/A N/A
N/A N/A
12 4th Stokes null value 0 The corresponding 4th Stokes parameter element contains a calculated value.
1 The corresponding 4th Stokes parameter element is null.
13-15 Undefined N/A N/A
N/A N/A

The tb_qual_flag_4 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_qual_flag_h

Bit flags that indicate the quality of the horizontally polarized brightness temperature. Table 9 specifies the meaning of individual bits in the tb_qual_flag_h field. 

Table 9. Description of tb_qual_flag_h
Bits Interpretation Value Description
0 Horizontal polarization quality flag 0 Horizontal polarization brightness temperature measurement has acceptable quality
1 Use of horizontal polarization brightness temperature not recommended
1 Horizontal polarization range flag 0 Horizontal polarization brightness temperature measurement falls in expected range
1 Horizontal polarization brightness temperature value is out of range
2

Horizontal polarization RFI detection flag 0 RFI not detected for Horizontal polarization brightness temperatures in the grid cell
1 If RFI was detected, the software was unable to correct the horizontal polarization brightness temperature for RFI
3

Horizontal polarization RFI correction flag 0 If RFI was detected, the horizontal polarization brightness temperature was corrected to remove RFI
1 If RFI was detected, the software was unable to correct the horizontal polarization brightness temperature for RFI
4

Horizontal polarization NEDT flag 0 Horizontal polarization brightness temperature measurement has acceptable NEDT
1 Use of horizontal polarization brightness temperature not recommended, since NEDT exceeds pre-determined threshold
5

Horizontal polarization direct sun correction 0 Correction for direct sun operated successfully on the horizontal polarization brightness temperature
1 Correction for direct sun did not function or yielded poor results on the horizontal polarization brightness temperature
6

Horizontal polarization reflected sun correction 0 Correction for reflected sun operated successfully on the horizontal polarization brightness temperature
1 Correction for reflected sun did not function or yielded poor results on the horizontal polarization brightness temperature
7

Horizontal polarization reflected moon correction 0 Correction for reflected moon operated successfully on the horizontal polarization brightness temperature
1 Correction for reflected moon did not function or yielded poor results on the horizontal polarization brightness temperature
8

Horizontal polarization direct galaxy correction 0 Correction for direct galaxy operated successfully on the horizontal polarization brightness temperature
1 Correction for direct galaxy did not function or yielded poor results on the horizontal polarization brightness temperature
9

Horizontal polarization reflected galaxy correction 0 Correction for reflected galaxy operated successfully on the horizontal polarization brightness temperature
1 Correction for reflected galaxy did not function or yielded poor results on the horizontal polarization brightness temperature
10 Horizontal polarization correction for atmospheric conditions 0 Correction for atmospheric conditions operated successfully on the horizontal polarization brightness temperature
1 Correction for atmospheric conditions did not function or yielded poor results on the horizontal polarization brightness temperature
11 Horizontal polarization Faraday rotation correction 0 Correction for Faraday rotation operated successfully on the horizontal polarization brightness temperature
1 Correction for Faraday rotation did not function or yielded poor results on the horizontal polarization brightness temperature
12 Horizontal polarization null value 0 The corresponding horizontal polarization brightness temperature element contains a calculated value.
1 The corresponding horizontal polarization brightness temperature element is null.
13-15 Undefined N/A N/A
N/A N/A

The tb_qual_flag_h field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_qual_flag_v

Bit flags that indicate the quality of the vertically polarized brightness temperature. The tb_qual_flag_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan. Table 5 specifies the meaning of individual bits in thetb_qual_flag_v field.

tb_right_ascension

The right ascension of the spacecraft boresight vector. The tb_right_ascension field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

tb_time_seconds

The time when each brightness temperature footprint within the antenna scan was recorded in seconds. Time is recorded for the middle of the footprint. Time values are counts of SI seconds based on the J2000 epoch in Ephemeris Time (ET). The J2000 epoch starting point is 01 January 2000 at 12:00 ET, which translates to 01 January 2000 at 11:58:55.816 UTC. The tb_time_seconds field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension is the number of footprints within the scan.

tb_time_utc

The UTC for each brightness temperature footprint within the antenna scan. Time is recorded for the middle of the footprint. For each antenna scan, the tb_time_utc field records the same footprint times as the tb_time_seconds field. The tb_time_utc field appears as an easily interpretable character string.

The format of the tb_time_utc field is YYYY-MM-DDThh:mm:ss.dddZ, where YYYY represents the calendar year, MM represents the month of the year and DD represents the day of the month. The character T demarcates the date from the time. hh represents the hour in twenty-four hour time, mm represents the minutes, ss represents the seconds, and ddd represents thousandths of a second. The character Z designates Greenwich Mean Time. All numerical fields must occupy the allotted space. If any numerical value does not require the allotted space to represent the appropriate number, the field that specifies the number must contain leading zeroes. The tb_time_utc field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension represents each of the footprints within the scan.

tb_upwelling

The component of the top of the atmosphere apparent brightness temperature that is due to upwelling thermal radiation of the atmosphere. The tb_upwelling field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dime nsion index represents each of the footprints in the scan.

tb_v

The vertically polarized brightness temperature at the surface of the Earth after RFI filtering. The tb_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toa_3

The apparent 3 rd Stokes parameter at the top of the atmosphere. The top of atmosphere is equivalent to the bottom of the ionos phere. The Faraday Rotation Correction algorithm in the L1 B_TB executable sets the 3rd Stokes to zero and then recalculates the apparent t op of atmosphere temperature vector with non-zero vertical and horizontal brightness temperatures. Thus, this element always displays a value of 0. Users who are interested in 3rd Stokes measure derived from instrument data should inspect either the antenna temperatures or the top of ionos phere temperatures. Details of the Faraday Rotation Correction algorithm appear in the Algorithm Theoretical Basis Document for the SMAP Level 1B Radiometer Data Product. The toa_3 field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toa_4

The apparent 4th Stokes parameter at the top of the atmosphere. The top of atmosphere is equivalent to the bottom of the ionos phere. The toa_4 field is a two-dimensional array. The slower moving dimens ion index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toa_h

Vertically polarized apparent brightness temperatur e at the top of the ionosphere. The toi_v is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toa_v

The vertically polarized apparent brightness temper ature at the top of the atmosphere. The top of atmosphere is equivalent to the bottom of the ionosphere. The toa_v field is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toi_3

Apparent 3rd Stokes parameter at the top of the ionosphere. The toi_3 is a two-dimensional array. The slower moving dimension index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toi_4

Apparent 4th Stokes parameter at the top of the ionosphere. The toi_4 field is a two-dimensional array. The slower moving dimens ion index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toi_h

Horizontally polarized apparent brightness temperature at the top of the ionosphere. The toi_h field is a two-dimensional array. The slower moving dimens ion index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

toi_v

Vertically polarized apparent brightness temperatur e at the top of the ionosphere. The toi_v field is a two-dimensional array. The slower moving dimens ion index represents the antenna scan. The faster moving dimension index represents each of the footprints in the scan.

cal_loss12_radome

The loss factor attributed to the radome applied in the calibration of fullband data to obtain antenna temperature referenced to the fee dhorn. This loss factor is also used to obtain antenna temperatures for each o f the 16 frequency bands in the subband data. The cal_loss1_radome field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, then horizontal.

cal_loss1_reflector

The loss factor attributed to the reflector applied in the calibration of fullband data to obtain antenna temperature referenced to the feedhorn. This loss factor is also used to obtain antenna temperatures for each of the 16 frequency bands in the subband data. The cal_loss1_reflector field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_loss2_feed

The loss factor attributed to the feedhorn applied in the calibration of fullband data to obtain antenna temperature referenced to the feedhorn. The cal_loss2_feed field is a one-dimensional array with one value for each antenna scan.

cal_loss3_omt

The loss factor attributed to the OMT (orthomode transducer) applied in the calibration of fullband data to obtain antenna temperature referenced to the feedhorn. Thecal_loss3_omt field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_loss4_coupler

The loss factor attributed to the coupler applied in the calibration of fullband data to obtain antenna temperature referenced to the feedhorn. The cal_loss4_coupler field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_nd_phase

The calibration model noise diode phase applied in the calibration of fullband data. The cal_nd_phase field is a one dimensional array with one value for each antenna scan.

cal_rx_phase

The calibration model receiver phase for calibration of radiometer fullband data. The cal_rx_phase16 field is a one dimensional array with one value for each antenna scan.

cal_loss5_diplexer

The loss factor attributed to the diplexer applied in the calibration of fullband data to obtain antenna temperature referenced to the feedhorn. The cal_loss5_diplexer field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_temp12_radome

The loss factor attributed to the reflector applied in the calibration of fullband data to obtain antenna temperature referenced to the feedhorn.

cal_temp1_reflector

The calibration model physical temperature of the reflector applied in the calibration of fullband data. This temperature is used for each of the 16 frequency bands for calibration of subband data. The cal_temp1_reflector field is a one dimensional array with a value for each antenna scan.

cal_temp2_feed

The calibration model physical temperature of the feedhorn applied in the calibration of fullband data. This temperature is used for each of the 16 frequency bands for calibration of subband data. The cal_temp2_feed field is a one dimensional array with a value for each antenna scan.

cal_temp3_omt

The calibration model physical temperature of the OMT (orthomode transducer) applied in the calibration of fullband data. This temperature is used for each of the 16 frequency bands for calibration of subband data. The cal_temp3_feed field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan and the second dimension index represents the polarization. The order of storage is vertical, horizontal.

cal_temp4_coupler

The calibration model physical temperature of the coupler applied in the calibration of fullband data. This temperature is used for each of the 16 frequency bands for calibration of subband data. The cal_temp4_coupler field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan and the second dimension index represents the polarization. The order of storage is vertical, horizontal.

cal_temp5_deplexer

The loss factor attributed to the reflector applied in the calibration of fullband data to obtain antenna temperature referenced to the feedhorn.

cal_temp_nd

The calibration model physical temperature of the internal noise diode applied in the calibration of fullband data. The cal_temp_nd field is a one dimensional array with one value for each antenna scan.

cal_temp_ref

The calibration model physical temperature of the reference load applied in the calibration of fullband data. The brightness temperature of the reference load is the sum of this physical temperature and its offset. The cal_temp_ref field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_temp_xnd

The calibration model physical temperature of the external noise diode applied in the calibration of fullband data. The cal_temp_xnd field is a one dimensional with one value for each antenna scan.

cal_tempref_offset

The calibration model physical temperature offset of the reference load applied in the calibration of fullband data. The brightness temperature of the reference load is the sum of its physical temperature and this offset. The cal_tempref_offset field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_tnd

The calibration model brightness temperature of the internal noise diode applied in the calibration of fullband data. The cal_tnd field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal. 

cal_tref

The calibration model brightness temperature of the reference load applied in the calibration offullband data. The brightness temperature of the reference load is the sum of its physical temperature and its offset. The cal_tref field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_txnd

The calibration model brightness temperature of the external noise diode applied in the calibration of fullband data. The cal_txnd field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents polarization. The order of storage is vertical, horizontal.

cal_xnd_phase

The calibration model receiver external noise diode phase applied in the calibration of fullband data. The cal_xnd_phase field is a one dimensional array with a value for each antenna scan.

cal_loss2_feed16

The loss factor attributed to the feedhorn applied in the calibration of subband data to obtain antenna temperature referenced to the feedhorn.
The cal_loss2_feed16 field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands.

cal_loss3_omt16

The loss factor attributed to the OMT (orthomode transducer) applied in the calibration of subband data to obtain antenna temperature referenced to the feedhorn. Thecal_loss3_omt16 field is a three-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands and the third is polarization. The order of storage is vertical, horizontal.

cal_loss4_coupler16

The loss factor attributed to the coupler applied in the calibration of subband data to obtain antenna temperature referenced to the feedhorn. The cal_loss4_coupler16 field is a three-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands and the third is polarization. The order of storage is vertical, horizontal.

cal_loss5_diplexer16

The loss factor attributed to the diplexer applied in the calibration of subband data to obtain antenna temperature referenced to the feedhorn.
The cal_loss5_diplexer16 field is a three-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands and the third is polarization. The order of storage is vertical, horizontal.

cal_nd_phase16

The calibration model noise diode phase applied in the calibration of subband data. The cal_nd_phase16 field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands.

cal_rx_phase16

The calibration model receiver phase applied in the calibration of subband data. The cal_rx_phase16 field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands.

cal_temp_nd16

The calibration model physical temperature of the internal noise diode applied in the calibration of subband data.
The cal_temp_nd16 field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands.

cal_temp_xnd16

The calibration model physical temperature of the external noise diode applied in the calibration of subband data. The cal_temp_xnd16 field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands.

cal_tempref_offset16

The calibration model physical temperature offset of the reference load applied in the calibration of subband data. The brightness temperature of the reference load is the sum of its physical temperature and this offset. The cal_tempref_offset16 field is a three-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands and the third is polarization. The order of storage is vertical, horizontal.

cal_tnd16

The calibration model brightness temperature of the internal noise diode applied in the calibration of subband data.
The cal_tnd16 field is a three-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands and the third is polarization. The order of storage is vertical, horizontal. 

cal_tref16

The calibration model brightness temperature of the reference load applied in the calibration of subband data. This is the sum of the physical temperature of the reference load and its offset. The physical temperature of the reference load is stored in the Calibration Data group since the same value is used for calibrating both fullband and subband data.
The cal_tref16 field is a three-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands and the third is polarization. The order of storage is vertical, horizontal.

cal_txnd16

The calibration model brightness temperature of the external noise diode applied in the calibration of subband data. The cal_txnd16 field is a three-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands and the third is polarization. The order of storage is vertical, horizontal. 

cal_xnd_phase16

The calibration model receiver external noise diode phase applied in the calibration of subband data. The cal_xnd_phase16 field is a two-dimensional array. The first dimension or the slowest moving dimension index represents the antenna scan. The second dimension index represents the 16 subbands.

calibration_time_seconds

The time for each antenna rotation containing high resolution calibration data interpolated to antenna boresight azimuth of 0 degrees. Time values are counts of SI seconds based on the J2000 epoch in Ephemeris Time (ET). The J2000 epoch begins on January 1, 2000 at 12:00 ET, which translates to 01 January 2000 at 11:58:55.816 UTC. Thecalibration_time_seconds field is a one-dimensional array. Each array index is representative of a specific antenna scan.

highresolution_scan_index

The highresolution_scan_index field correlates the HighResolutionScan index of data elements in the High Resolution Calibration Data group with the AntennaScan index of data elements in the Spacecraft Data group, Calibration Data group, and Brightness Temperature Data group of the L1B_TB Product. Thus, if highresolution_scan_index[215] = 450, then elements with a HighResolutionScan index of 215 in the High Resolution Calibration Data group correlate to elements with an AntennaScan index of 450 in the other data groups of the L1B_TB product. The highresolution_scan_index field is a one-dimensional array. Each array index is representative of a specific high resolution antenn a scan.

antenna_scan_mode_flag

Bit flags that indicate operational conditions of the attitude and ephemeris telemetry and associated calculations at each instance when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The antenna_scan_mode_flag field is a one-dimensional array. Each array index is representative of a specific antenna scan. Table 10 specifies the meaning of individual bits in the antenna_scan_mode_flag field.

Bits Interpretation Value Description
Table 10. Description of antenna_scan_mode_flag
0 Instrument viewing mode 0 Spacecraft antenna is positioned so that the SMAP instrument views locations on the Earth’s surface.
1 Spacecraft antenna is positioned so that the SMAP instrument does not view the Earth. SMAP spacecraft is either in maneuver, running a cold sky calibration for the radiometer or in transition state.
1 Ephemeris Usage Flag 0 Processing employed reconstructed ephemeris
1 Processing employed predicted ephemeris
2 Data Resolution Flag 0 High resolution data contribute to this scan
1 Low resolution data contribute to this scan
3 Eclipse Flag 0 The SMAP spacecraft is not in eclipse. The Sun is visible from the SMAP spacecraft.
1 The SMAP spacecraft is in eclipse. The Sun is not visible from the SMAP spacecraft.
4-15 Undefined N/A N/A
N/A N/A

antenna_scan_qual_flag

Bit flags that indicate the quality of the attitude, the ephemeris and the antenna pointing telemetry. The Level-1B brightness temperature product contains calculated values for these measures at each instance when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. Table 11 specifies the meaning of individual bits in the antenna_scan_qual_flag field.

Table 11. Description of antenna_scan_qual_flag
Bits Interpretation Value Description
0 Ephemeris Quality 0 Quality and frequency of the ephemeris data is within acceptable range.
1 Quality or frequency of the ephemeris data may not be adequate to yield an accurate measure of spacecraft location.
1 Attitude Quality 0 Quality and frequency of the attitude data is within acceptable range.
1 Quality or frequency of the attitude data may not be adequate to yield an acceptable measure of spacecraft orientation.
2

Antenna Pointing Quality 0 Quality and frequency of the antenna pointing data is within acceptable range.
1 Quality or frequency of the antenna pointing data may not be adequate to yield an acceptable measure of antenna position.
3 Spacecraft half orbit location 0 All of the footprints associated with this spacecraft orbit location lie within the half orbit specified in the file name.
1 Some or all of the footprints associated with this spacecraft orbit location lie outside of the half orbit specified in the file name.
4-15 Undefined N/A N/A
N/A N/A

The antenna_scan_qual_flag is a one-dimensional array. Each array index is representative of a specific antenna scan.

antenna_scan_time

The time for each antenna rotation interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. Time values are counts of International System of Units (SI) seconds based on the J2000 epoch in Ephemeris Time (ET). The J2000 epoch begins on 01 January 2000 at 12:00 ET, which translates to 01 January 2000 at 11:58:55.816 Universal Coordinated Time (UTC). The antenna_scan_time field is a one-dimensional array. Each array index is representative of a specific cross antenna scan.

antenna_scan_time_utc

The UTC for each antenna rotation. The representative time for each scan takes place when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. For each antenna scan, the antenna_scan_time_utc records the same time instant as the antenna_scan_time. The antenna_scan_time_utc appears as an easily interpretable character string. The format of the antenna_scan_time_utc is YYYY-MM-DDThh:mm:ss.dddZ, where YYYY represents the calendar year, MM represents the month of the year and DD represents the day of the month. The character T demarcates the date from the time, hh represents the hour in twenty-four hour time, mm represents the minutes, ss represents the seconds, and ddd represents thousandths of a second. The character Z designates Greenwich Mean Time. All numerical fields must occupy the allotted space. If any numerical value does not require the allotted space to represent the appropriate number, the field that specifies the number must contain leading zeroes. The antenna_scan_time_utc field is a one-dimensional array. Each array index is representative of a specific antenna scan.

footprints_per_scan

The number of brightness temperature footprints based on the instrument pulse repetition interval (PRI) and the antenna rotation rate. For any given antenna scan, if the index of a particular footprint is greater than footprints_per_scan for that scan, then the contents of those array elements with that index should contain null values. Thefootprints_per_scan field is a one-dimensional array. Each array index is representative of a specific antenna scan.

pitch

The angular rotation of the spacecraft body about the Y axis of the SMAP Science Orbit Reference Frame (SRF). The Y axis of the SRF is normal to the spacecraft orbital plane. Pitch values are interpolated to the corresponding antenna_scan_time, which is equivalent to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The pitch field is a one-dimensional array. Each array index is representative of a specific antenna scan.

roll

The angular rotation of the spacecraft body about the X axis of the SMAP Science Orbit Reference Frame (SRF) coordinate system. The X axis of the SRF approximates the direction of spacecraft motion. Roll values are interpolated to the corresponding antenna_scan_time, which is equivalent to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The roll field is a one-dimensional array. Each array index is representative of a specific antenna scan.

sc_alongtrack_velocity

The instantaneous velocity of the SMAP spacecraft that is tangent to the spacecraft path within the orbital plane interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The sc_alongtrack_velocity field is a one-dimensional array. Each array index is representative of a specific antenna scan.

sc_geodetic_alt_ellipsoid

The geodetic altitude of the spacecraft above the Earths reference ellipsoid interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The sc_geodetic_alt_ellipsoid field is a one-dimensional array. Each array index is representative of a specific antenna scan. 

sc_nadir_angle

The angle defined by the spacecraft geodetic nadir vector and the negative Z axis of the spacecraft coordinate system at each instance when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The sc_nadir_angle field is a one-dimensional array. Each array index is representative of a specific antenna scan.

sc_nadir_lat

The geodetic latitude of the ground track position interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. Thesc_nadir_lat field is a one-dimensional array. Each array index is representative of a specific antenna scan.

sc_nadir_lon

The longitude of the ground track position interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. 
The sc_nadir_lon field is a one-dimensional array. Each array index is representative of a specific antenna scan.

sc_radial_velocity

The velocity of the SMAP spacecraft in the direction of the vector that runs from the instantaneous spacecraft position to the center of the Earth interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The sc_radial_velocity field is a one-dimensional array. Each array index is representative of a specific antenna scan.

tbs_per_scan

The number of brightness temperature footprints output within each antenna scan. The number of footprints that provide valid brightness temperatures may be fewer than the value represented in footprints_per_scan. The variable tbs_per_scan provides the number that are deemed valid in each antenna scan. The tbs_per_scan field is a one-dimensional array. Each array index is representative of a specific antenna scan.

x_pos

The spacecraft position in the X direction of the Earth Centered Rotating (ECR) system interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The x_pos field is a one-dimensional array. Each array index is representative of a specific antenna scan.

x_vel

The spacecraft velocity in the X direction of the ECR system interpolated to when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. Thex_vel field is a one-dimensional array. Each array index is representative of a specific antenna scan.

y_pos

The spacecraft position in the Y direction of the ECR system interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The y_pos field is a one-dimensional array. Each array index is representative of a specific antenna scan.

y_vel

The spacecraft velocity in the Y direction of the ECR system interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The y_vel field is a one-dimensional array. Each array index is representative of a specific antenna scan.

yaw

The angular rotation of the spacecraft body about the Z axis of the SMAP Science Orbit Reference Frame (SRF) coordinate system. The Z axis of the SRF runs from the center of mass of the spacecraft toward geodetic nadir. Yaw values are interpolated to the corresponding antenna_scan_time, which is equivalent to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The yaw field is a one-dimensional array. Each array index is representative of a specific antenna scan.

z_pos

The spacecraft position in the Z direction of the ECR system interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The z_pos field is a one-dimensional array. Each array index is representative of a specific antenna scan.

z_vel

The spacecraft velocity in the Z direction of the ECR system interpolated to the instant when the antenna boresight aligns with the X-axis of the SMAP spacecraft coordinate system. The z_vel field is a one-dimensional array. Each array index is representative of a specific antenna scan.

Fill/Gap Values [top]

Fill values appear in the SMAP Level-1B brightness temperature product in any of the following circumstances:

  • No measured data for the maximum possible number of footprints. The total number of radiometer science packets per antenna scan varies depending on the antenna rotation rate and integration time of the instrument. The resulting number of antenna footprints per scan is therefore variable. To preserve the shape of stored data elements, the size of certain dimensions is assigned a maximum value. Thus, fill values appear in the SMAP Level-1B brightness temperature product when a particular scan does not contain the maximum possible number of footprints.
  • RFI detection algorithms flag all pixels which make up a footprint. High resolution radiometer instrument data contains radiometer counts which are integrated every approximately 300 µs per PRI and every 1 ms per packet. These radiometer counts are calibrated to produce antenna temperatures referenced to the feedhorn. The antenna temperatures are then processed by RFI detection and mitigation algorithms where the pixels for a footprint that are flagged for RFI are removed and the remaining clean pixels are averaged to form an RFI free antenna footprint. If all pixels for a particular footprint are flagged for RFI, then the footprint TA is assigned the null value. The corresponding footprint brightness temperature, brightness temperature value will also be assigned the null value since the RFI-free antenna footprint TAs are used to produce the time-ordered brightness temperature product. Subsequently, after pixels with RFI are flagged and dropped, the remaining clean pixels are used to compute the NEDT for that footprint. If all pixels are removed the null value is assigned to the NEDT for that footprint.
  • The NEDT for the footprint after RFI removal is 0. A single pixel may be left after RFI removal. The product will contain an associated footprint TA and TB value; however the NEDT will be 0. The null value will be assigned to the NEDT value in this case but the corresponding TA and TB values will be reported.

SMAP data products employ a specific set of data values to connote that an element is fill. The selected values that represent fill are dependent on the data type.

No valid value in the Level-1B brightness temperature product is equal to the values that represent fill. If any exceptions should exist in the future, the Level-1B brightness temperature content will provide a means for users to discern between elements that contain fill and elements that contain genuine data values. This document will also contain a description of the method used to ascertain which elements are fill and which elements are genuine. 

The Level-1B brightness temperature product records gaps when entire frames within the time span of a particular data granule do not appear. Gaps can occur under one of two conditions:

  • One or more complete frames of data are missing from all data streams.
  • The subset of input data that is available for a particular frame is not sufficient to process any frame output.

The Level-1B brightness temperature product records gaps in the product-level metadata. The following conditions will indicate that no gaps appear in the data product:

  • Only one instance of the attributes Extent/rangeBeginningDateTime and Extent/rangeEndingDateTime will appear in the product metadata.
  • The character string stored in metadata element Extent/rangeBeginningDateTime will match the character string stored in metadata elementOrbitMeasuredLocation/halfOrbitStartDateTime.
  • The character string stored in metadata element Extent/rangeEndingDateTime will match the character string stored in metadata elementOrbitMeasuredLocation/halfOrbitStopDateTime.

One of two conditions will indicate that gaps appear in the data product:

  • The time period covered between Extent/rangeBeginningDateTime and Extent/RangeEndingDateTime does not cover the entire half orbit as specified inOrbitMeasuredLocation/halfOrbitStartDateTime and OrbitMeasuredLocation/halfOrbitStartDateTime.
  • More than one pair of Extent/rangeBeginningDateTime and Extent/rangeEndingDateTime appears in the data product. Time periods within the time span of the half orbit that do not fall within the sets of Extent/rangeBeginningDateTime and Extent/rangeEndingDateTime constitute data gaps.

Bit flag elements in the Level-1B brightness temperature product often provide additional information about missing data. For example, the data element tb_v in the Level-1B brightness temperature product contains bit flags that indicate the quality of data for each footprint. Each of the tb_qual_flag_v variables indicates the quality of the data in each footprint. When a data frame is deemed unusable, the appropriate bits in the tb_qual_flag_v should indicate the rationale.

If data values associated with any particular look of the radiometer instrument creates untenable algorithmic conditions, the Level-1B brightness temperature Science Production Software (SPS) may curtail processing for that look. When these conditions take place, the Level-1B brightness temperature product displays whatever values the SPS was able to calculate. When a tb_v measure for a particular footprint has been deemed unusable, the appropriate bits in the tb_qual_flag_v will provide users with a rationale for the missing data.

Acronyms and Abbreviations [top]

Table 12 defines the acronyms and abbreviations used in this document.

Table 12. Acronyms and Abbreviations
Abbreviation Definition
ABFCS Antenna Beam Frame Coordinate System
ATBD Algorithm Theoretical Basis Document
Char 8-bit character
Int8 8-bit (1-byte) signed integer
Int16 16-bit (2-byte) signed integer
Int32 32-bit (4-byte) signed integer
ECR Earth Centered Rotating
ET Ephemeris Time
Float32 32-bit (4-byte) floating-point integer
Float64 64-bit (8-byte) floating-point integer
H-pol Horizontally polarized
N/A Not Applicable
NEDT Noise Equivalent Delta Temperature
PRI Pulse Repetition Interval
RFI Radio Frequency Interference
SI International System of Units
SPS Science Production Software
SRF Science Orbit Reference Frame
TA Antenna Temperature
TB Brightness Temperature
Uint8 8-bit (1-byte) unsigned integer
Uint16 16-bit (2-byte) unsigned integer
UTC Universal Coordinated Time
V-pol Vertically polarized