Data Fields - SMAP L1B Radiometer Half-Orbit Time-Ordered Brightness Temperatures, Version 4

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 0.0 359.999 Degrees -9999.0
antenna_look_angle Float32 AntennaScan_Tb_Array 0.0 180.0 Degrees -9999.0
antenna_scan_angle Float32 AntennaScan_Tb_Array 0.0 359.999 Degrees -9999.0
antenna_sideloble_correction_3 Float32 AntennaScan_Tb_Array -0.5 6.0 Kelvin -9999.0
antenna_sideloble_correction_4 Float32 AntennaScan_Tb_Array -0.5 6.0 Kelvin -9999.0
antenna_sideloble_correction_h Float32 AntennaScan_Tb_Array -0.5 6.0 Kelvin -9999.0
antenna_sideloble_correction_v Float32 AntennaScan_Tb_Array -0.5 6.0 Kelvin -9999.0
atm_correction_h Float32 AntennaScan_Tb_Array 0.0 4.0 Kelvin -9999.0
atm_correction_v Float32 AntennaScan_Tb_Array 1 4 Kelvin -9999.0
atm_loss Float32 AntennaScan_Tb_Array 1.0 1.02 Kelvin -9999.0
earth_boresight_azimuth Float32 AntennaScan_Tb_Array 0.0 359.999 Degrees -9999.0
earth_boresight_incidence Float32 AntennaScan_Tb_Array 0.0 90.0 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
footprint_surface_status Uint16 AntennaScan_Tb_Array 0 1 N/A 65534
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 4.0 Kelvin -9999.0
galactic_reflected_correction_v Float32 AntennaScan_Tb_Array -0.4 4.0 Kelvin -9999.0
lunar_direct_phi Float32 AntennaScan_Tb_Array 0.0 359.999 Degrees -9999.0
lunar_direct_theta Float32 AntennaScan_Tb_Array 0.0 180.0 Degrees -9999.0
lunar_specular_correction_3 Float32 AntennaScan_Tb_Array -0.2 2.0 Kelvin -9999.0
lunar_specular_correction_4 Float32 AntennaScan_Tb_Array -0.2 2.0 Kelvin -9999.0
lunar_specular_correction_h Float32 AntennaScan_Tb_Array -0.2 2.0 Kelvin -9999.0
lunar_specular_correction_v Float32 AntennaScan_Tb_Array -0.2 2.0 Kelvin -9999.0
lunar_specular_lat Float32 AntennaScan_Tb_Array -90 90 Degrees -9999.0
lunar_specular_lon Float32 AntennaScan_Tb_Array -180.0 179.999 Degrees -9999.0
lunar_specular_phi Float32 AntennaScan_Tb_Array 0.0 359.999 Degrees -9999.0
lunar_specular_reflection_coefficient_h Float32 AntennaScan_Tb_Array 0.0 1.0 N/A -9999.0
lunar_specular_reflection_coefficient_v Float32 AntennaScan_Tb_Array 0.0 1.0 N/A -9999.0
lunar_specular_theta Float32 AntennaScan_Tb_Array 0.0 180.0 Degrees -9999.0
nedt_3 Float32 AntennaScan_Tb_Array 0.5 3.0 Kelvin -9999.0
nedt_4 Float32 AntennaScan_Tb_Array 0.5 3.0 Kelvin -9999.0
nedt_h Float32 AntennaScan_Tb_Array 0.5 3.0 Kelvin -9999.0
nedt_v Float32 AntennaScan_Tb_Array 0.5 3.0 Kelvin -9999.0
polarization_rotation_angle Float32 AntennaScan_Tb_Array 0.0 90.0 Degrees -9999.0
sea_ice_fraction Float32 AntennaScan_Tb_Array 0.0 1.0 N/A -9999.0
solar_direct_correction_h Float32 AntennaScan_Tb_Array 0.0 0.6 Kelvin -9999.0
solar_direct_correction_v Float32 AntennaScan_Tb_Array 0.0 0.6 Kelvin -9999.0
solar_direct_phi Float32 AntennaScan_Tb_Array 0.0 359.999 Degrees -9999.0
solar_direct_theta Float32 AntennaScan_Tb_Array 0.0 180.0 Degrees -9999.0
solar_specular_correction_3 Float32 AntennaScan_Tb_Array -0.5 1.0 Kelvin -9999.0
solar_specular_correction_4 Float32 AntennaScan_Tb_Array -0.5 1.0 Kelvin -9999.0
solar_specular_correction_h Float32 AntennaScan_Tb_Array -0.5 1.0 Kelvin -9999.0
solar_specular_correction_v Float32 AntennaScan_Tb_Array -0.5 1.0 Kelvin -9999.0
solar_specular_lat Float32 AntennaScan_Tb_Array -90.0 90.0 Degrees -9999.0
solar_specular_lon Float32 AntennaScan_Tb_Array -180.0 179.999 Degrees -9999.0
solar_specular_phi Float32 AntennaScan_Tb_Array 0.0 359.999 Degrees -9999.0
solar_specular_reflection_coefficient_h Float32 AntennaScan_Tb_Array 0.0 1.0 N/A -9999.0
solar_specular_reflection_coefficient_v Float32 AntennaScan_Tb_Array 0.0 1.0 N/A -9999.0
solar_specular_theta Float32 AntennaScan_Tb_Array 0.0 99.9 Degrees -9999.0
specular_declination Float32 AntennaScan_Tb_Array -90.0 90.0 Degrees -9999.0
specular_right_ascension Float32 AntennaScan_Tb_Array 0.0 359.999 Degrees -9999.0
surface_water_fraction_mb_h Float32 AntennaScan_Tb_Array 0.0 1.0 N/A -9999.0
surface_water_fraction_mb_v Float32 Antena_Scan_Tb_Array 0.0 1.0 N/A -9999.0
ta_3 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
ta_4 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
ta_filtered_3 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
ta_filtered_4 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
ta_filtered_h Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0
ta_filtered_v Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0
ta_h Float32 AntennaScan_Tb_Array -0.0 340.0 Kelvin -9999.0
ta_v Float32 AntennaScan_Tb_Array -0.0 340.0 Kelvin -9999.0
tb_3 Float32 AntennaScan_Tb_Array -50.0 50.0 Kelvin -9999.0
tb_4 Float32 AntennaScan_Tb_Array -50.0 -50.0 Kelvin -9999.0
tb_declination Float32 AntennaScan_Tb_Array -90.0 90.0 Degrees -9999.0
tb_h Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0
tb_h_surface_corrected Float32 AntennaScan_Tb_Array 0.0 340.0 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 0.0 359.999 Degrees -9999.0
tb_time_seconds Float64 AntennaScan_Tb_Array 0.0 9.46E8 Seconds -9999.0
tb_time_utc Char AntennaScan_Tb_Array N/A N/A N/A -9999.0
tb_upwelling Float32 AntennaScan_Tb_Array 0.0 4.0 Kelvin -9999.0
tb_v Float32 AntennaScan_Tb_Array 0.0 340.0 Kelvin -9999.0
tb_v_surface_corrected Float32 AntennaScan_Tb_Array 0.0 340.0 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
wind_direction_ancillary Float32 AntennaScan_Tb_Array 0.0 359.999 degrees -9999.0
wind_speed_ancillary Float32 AntennaScan_Tb_Array 0.0 75.0 m/s -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 1.0 2.0 N/A -9999.0
cal_loss1_reflector Float32 AntennaScan_VHPol_Array 1.0 2.0 N/A -9999.0
cal_loss2_feed Float32 HighResolutionScan_Subband_Array 1.0 2.0 N/A -9999.0
cal_loss3_omt Float32 HighResolutionScan_Subband_VHPol_Array  1.0 2.0 N/A -9999.0
cal_loss4_coupler Float32 HighResolutionScan_Subband_VHPol_Array 1.0 2.0 N/A -9999.0
cal_loss5_diplexer Float32 HighResolutionScan_Subband_VHPol_Array 1.0 2.0 N/A -9999.0
cal_nd_phase Float32 HighResolutionScan_Subband_Array  -3.1415927 3.1415927 Radians -9999.0
cal_rx_phase Float32 HighResolutionScan_Subband_Array  -3.1415927 3.1415927 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  253.15 313.15 Kelvin -9999.0
cal_temp_ref Float32 AntennaScan_VHPol_Array 253.15 313.15 Kelvin -9999.0
cal_temp_xnd Float32 HighResolutionScan_Subband_Array  -253.15 314.15 Kelvin -9999.0
cal_tempref_offset Float32 HighResolutionScan_Subband_VHPol_Array  -1.0 1.0 Kelvin -9999.0
cal_tnd Float32 HighResolutionScan_Subband_VHPol_Array  218.0 658.0 Kelvin -9999.0
cal_tref Float32 HighResolutionScan_Subband_VHPol_Array 252.15 314.15 Kelvin -9999.0
cal_txnd Float32 HighResolutionScan_Subband_VHPol_Array  62.0 216.0 Kelvin -9999.0
cal_xnd_phase  Float32 HighResolutionScan_Subband_Array  -3.1415927 3.1415927 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 1.0 2.0 N/A -9999.0
cal_loss3_omt16  Float32 HighResolutionScan_Subband_VHPol_Array  1.0 2.0 N/A -9999.0
cal_loss4_coupler16 Float32 HighResolutionScan_Subband_VHPol_Array  1.0 2.0 N/A -9999.0
cal_loss5_diplexer16 Float32 HighResolutionScan_Subband_VHPol_Array 1.0 2.0 N/A -9999.0
cal_nd_phase16 Float32 HighResolutionScan_Subband_Array  -3.1415927 3.1415927 Radians -9999.0
cal_rx_phase16 Float32 HighResolutionScan_Subband_Array  -3.1415927 3.1415927 Radians -9999.0
cal_temp_nd16  Float32 HighResolutionScan_Subband_Array  253.15 313.15 Kelvin -9999.0
cal_temp_xnd16 Float32 HighResolutionScan_Subband_Array  253.15 313.15 Kelvin -9999.0
cal_tempref_offset16 Float32 HighResolutionScan_Subband_VHPol_Array  1.0 1.0 Kelvin -9999.0
cal_tnd16  Float32 HighResolutionScan_Subband_VHPol_Array  212.0 676.0 Kelvin -9999.0
cal_tref16  Float32 HighResolutionScan_Subband_VHPol_Array 252.15 314.15 Kelvin -9999.0
cal_txnd16 Float32 HighResolutionScan_Subband_VHPol_Array  61.0 217.1 Kelvin -9999.0
cal_xnd_phase16 Float32 HighResolutionScan_Subband_Array  -3.1415927 3.1415927 Radians -9999.0
calibration_time_seconds Float64 HighResolutionScan_Array -0.0 9.46E8 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 0.0 9.46E8 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 -90.0 90.0 degrees -9999.0
roll Float32 AntennaScan_Array -90.0 90.0 degrees -9999.0
sc_alongtrack_velocity Float32 AntennaScan_Array -8000.0 8000.0 m/s -9999.0
sc_geodetic_alt_ellipsoid Float32 AntennaScan_Array 650000.0 900000.0 meters -9999.0
sc_nadir_angle Float32 AntennaScan_Array 0.0 180.0 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 -8000.0 8000.0 m/s -9999.0
tbs_per_scan Uint16 AntennaScan_Array 0 300 N/A 65534
x_pos Float32 AntennaScan_Array -999999.0 9999999.0 m -9999.0
x_vel Float32 AntennaScan_Array -8000.0 8000.0 m/s -9999.0
y_pos Float32 AntennaScan_Array -999999.0 9999999.0 m -9999.0
y_vel Float32 AntennaScan_Array -8000.0 8000.0 m/s -9999.0
yaw Float32 AntennaScan_Array -180.0 180.0 degrees -9999.0
z_pos Float32 AntennaScan_Array -999999.0 9999999 m -9999.0
z_vel Float32 AntennaScan_Array -8000.0 8000.0 m/s -9999.0

Data Field Definitions [top]

antenna_earth_azimuth

 The is angle from due North to the projection of the antenna scan angle onto a plane tangent to the Earth at the spacecraft nadir point.  The spacecraft nadir point serves as the vertex of this angle.

antenna_look_angle

The angle defined by the antenna boresight vector and the spacecraft nadir vector.

antenna_scan_angle

The angle in the X-Y plane of the instrument fixed coordinate system that indicates the angular position of the antenna assembly. The angle is measured in the counterclockwise direction from the X axis, which approximates the direction of motion of the spacecraft.

antenna_sidelobe_correction_3

TB correction to TA for earth sidelobe contribution for 3rd Stokes.

antenna_sidelobe_correction_4

TB correction to TA for earth sidelobe contribution for 4th Stokes.

antenna_sidelobe_correction_h

TB correction to TA for earth sidelobe contribution for horizontal polarization.

antenna_sidelobe_correction_v

TB correction to TA for earth sidelobe contribution for vertical polarization.

atm_correction_h

TB correction to TA for atmospheric emission for horizontal polarization.

atm_correction_v

TB correction to TA for atmospheric emission for vertical polarization.

atm_loss

The reduction in power density of the brightness temperature signal as it propagates through the Earth's atmosphere.

earth_boresight_azimuth

The angle defined by the vector that extends from the intersection of the spacecraft geodetic nadir vector on the Earth's surface to geographic North and the vector that extends from the intersection of the spacecraft geodetic nadir on the Earth's surface to the pierce point of the boresight vector. The angle measure is clockwise from the northward vector.

earth_boresight_incidence

The angle defined by the antenna boresight vector and the mean surface normal vector.

faraday_rotation_angle

The Faraday rotation angle. 

faraday_rotation_correction_h

TB correction to TA for Faraday Rotation for horizontal polarization.

faraday_rotation_correction_v

TB correction to TA for Faraday Rotation for vertical polarization.

footprint_surface_status

Indicates if the footprint center lies on land (0) or water (1).

galactic_direct_correction_h

TB correction to TA for direct galactic contamination for horizontal polarization.

galactic_direct_correction_v

TB correction to TA for direct galactic contamination for vertical polarization.

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

TB correction to TA for reflected galactic contamination for 4th Stokes.

galactic_reflected_correction_h

TB correction to TA for reflected galactic contamination for horizontal polarization.

galactic_reflected_correction_v

TB correction to TA for reflected galactic contamination for vertical polarization.

lunar_direct_phi

The angle defined by the +X axis of the Antenna Beam Frame Coordinate System and the vector that extends from the origin to the Moon projected onto the XY plane of the Antenna Beam Frame Coordinate System.

lunar_direct_theta

The angle defined by the +Z axis of the Antenna Beam Frame Coordinate System, which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the Antenna Bean Frame Coordinate System to the Moon.

lunar_specular_correction_3

TB correction to TA for reflected lunar contamination for 3rd Stokes.

lunar_specular_correction_4

TB correction to TA for reflected lunar contamination for 4th Stokes.

lunar_specular_correction_h

TB correction to TA for reflected lunar contamination for horizontal polarization.

lunar_specular_correction_v

TB correction to TA for reflected lunar contamination for vertical polarization.

lunar_specular_lat

 Latitude of the center of the lunar specular reflection point on the Earth's surface relative to the spacecraft position.

lunar_specular_lon

Longitude of the center of the lunar specular reflection point on the Earth's surface relative to the spacecraft position.

lunar_specular_phi

The angle defined by the +X axis of the Antenna Beam Frame Coordinate System and the vector that extends from the origin to the lunar glint spot on the Earth's surface projected onto the XY plane of the Antenna Beam Frame Coordinate System.

lunar_specular_reflection_coefficient_h

Reflection coefficient of surface at lunar specular point for horizontal polarization.

lunar_specular_reflection_coefficient_v

Reflection coefficient of surface at lunar specular point for vertical polarization.

lunar_specular_theta

The angle defined by the +Z axis of the Antenna Beam Frame Coordinate System, which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the Antenna Bean Frame Coordinate System to the lunar glint spot on the Earth's surface.

nedt_3

NEDT after RFI removal for third Stokes.

nedt_4

NEDT after RFI removal for fourth Stokes.

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

NEDT after RFI removal for horizontal polarization.

nedt_v

NEDT after RFI removal for vertical polarization

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 angle between the plane of polarization and the reference plane used to calculate the Stokes vector.

solar_direct_correction_h

TB correction to TA for direct solar contamination for horizontal polarization.  Limits for all error sources contributions will be determined with the orbit simulator

solar_direct_correction_v

TB correction to TA for direct solar contamination for vertical polarization.  Limits for all error sources contributions will be determined with the orbit simulator

solar_direct_phi

The angle defined by the +X axis of the Antenna Beam Frame Coordinate System and the vector that extends from the origin to the Sun projected onto the XY plane of the Antenna Beam Frame Coordinate System.

solar_direct_theta

The angle defined by the +Z axis of the Antenna Beam Frame Coordinate System, which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the Antenna Bean Frame Coordinate System to the Sun.

solar_specular_correction_3

TB correction to TA for reflected solar contamination for 3rd Stokes.

solar_specular_correction_4

TB correction to TA for reflected solar contamination for 4th Stokes.

solar_specular_correction_h

TB correction to TA for reflected solar contamination for horizontal polarization.

solar_specular_correction_v

TB correction to TA for reflected solar contamination for vertical polarization.

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 Earth's 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

Reflection coefficient of surface at solar specular point for horizontal polarization.

solar_specular_reflection_coefficient_v

Reflection coefficient of surface at solar specular point for vertical polarization.

solar_specular_theta

The angle defined by the +Z axis of the Antenna Beam Frame Coordinate System, which is equivalent to the electrical boresight vector, and the vector that extends from the origin of the Antenna Bean Frame Coordinate System to the solar glint spot on the Earth's surface.

specular_declination

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.

specular_right_ascension

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.

surface_water_fraction_mb_h

Areal fraction of static water within the radiometer H pol antenna pattern.

surface_water_fraction_mb_v

Areal fraction of static water within the radiometer V pol antenna pattern.

ta_3

The antenna temperature for the 3rd Stokes parameter before RFI filtering. 

ta_4

The antenna temperature for the 4th Stokes parameter before RFI filtering.

ta_filtered_3

Antenna temperature for the 3rd Stokes parameter after RFI filtering. 

ta_filtered_4

Antenna temperature for the 4th Stokes parameter after RFI filtering. 

ta_filtered_h

Horizontally polarized antenna temperature after RFI filtering

ta_filtered_v

Vertically polarized antenna temperature after RFI filtering.

ta_h

The horizontally polarized antenna temperature before RFI filtering. 

ta_v

The vertically polarized antenna temperature before RFI filtering.

tb_3

The 3rd 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_4

The 4th Stokes parameter at the surface of the Earth after RFI filtering. 

tb_declination

The declination of the spacecraft boresight vector. 

tb_h

The horizontally polarized brightness temperature at the surface of the Earth after RFI filtering. 

tb_h_surface_corrected

The horizontally polarized water/land contamination corrected brightness temperature at the surface of the Earth after RFI filtering. This value represents the corrected land brightness temperature if footprint_surface_status is “0” or represents the corrected water brightness temperature if footprint_surface_status is “1”.

tb_lat

 Latitude of the intersection of the antenna boresight vector and the Earth's surface.

tb_lon

Longitude of the intersection of the antenna boresight vector and the Earth's surface.

tb_mode_flag

Bit flags that indicate instrument and ambient conditions when the brightness temperature measurements were acquired.

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.

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.

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. 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.

tb_right_ascension

Right ascension of the spacecraft boresight vector.

tb_time_seconds

J2000 time when brightness temperatures were recorded in seconds.

tb_time_utc

UTC time when brightness temperatures were recorded.

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.

tb_v_surface_corrected

The vertically polarized water/land contamination corrected brightness temperature at the surface of the Earth after RFI filtering. This value represents the corrected land brightness temperature if footprint_surface_status is “0” or represents the corrected water brightness temperature if footprint_surface_status is “1”.

toa_3

The apparent 3rd Stokes parameter at the top of the atmosphere.  The top of atmosphere is equivalent to the bottom of the ionosphere.

toa_4

 The apparent 4th Stokes parameter at the top of the atmosphere.  The top of atmosphere is equivalent to the bottom of the ionosphere.

toa_h

The horizontally polarized apparent brightness temperature at the top of the atmosphere.  The top of atmosphere is equivalent to the bottom of the ionosphere.

toa_v

The vertically polarized apparent brightness temperature at the top of the atmosphere.  The top of atmosphere is equivalent to the bottom of the ionosphere.

toi_3

Apparent 3rd Stokes parameter at the top of the ionosphere.

toi_4

Apparent 4th Stokes parameter at the top of the ionosphere. .

toi_h

 Horizontally polarized apparent brightness temperature at the top of the ionosphere.

toi_v

 Vertically polarized apparent brightness temperature at the top of the ionosphere.

wind_direction_ancillary

The interpolated direction of sea surface winds at the center of the corresponding Tb.  Wind direction is measured as the clockwise rotation from local North (meteorological convention). Wind measurements are based on data provided by the National Centers for Environmental Prediction (NCEP) of the National Oceanographic and Atmospheric Administration (NOAA). 

wind_speed_ancillary

The interpolated speed of sea surface winds at the center of the corresponding Tb.  Wind measurements are based on data provided by the National Centers for Environmental Prediction (NCEP) of the National Oceanographic and Atmospheric Administration (NOAA).

cal_loss12_radome

Calibration model lumped loss factor of radome (stored V then H)

cal_loss1_reflector

Calibration model lumped loss factor of reflector (stored V then H)

cal_loss2_feed

Calibration model lumped loss factor of feed

cal_loss3_omt

Calibration model lumped loss factor of OMT (stored V then H)

cal_loss4_coupler

Calibration model lumped loss factor of coupler (stored V then H)

cal_loss5_diplexer

Calibration model lumped loss factor of the diplexer (stored V then H)

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_temp12_radome

Calibration model, physical temperature, radome (same for V and H as the radome temp will most likely act on the 2 polarizations in the same way)

cal_temp1_reflector

 Calibration model, physical temperature, reflector (same for V and H as the reflector temp will most likely act on the 2 polarizations in the same way)

cal_temp2_feed

Calibration model, physical temperature, feed.

cal_temp3_omt

Calibration model, physical temperature, OMT (stored V then H).

cal_temp4_coupler

Calibration model, physical temperature, coupler (stored V then H).

cal_temp5_deplexer

Calibration model, physical temperature, diplexer (stored V then H)

cal_temp_nd

Calibration model, physical temperature, noise diode.

cal_temp_ref

Calibration model, physical temperature, reference (stored V then H)

cal_temp_xnd

Calibration model, physical temperature, external noise diode.

cal_tempref_offset

Calibration model, physical temperature offset, reference (stored V then H)

cal_tnd

Calibration model, brightness temperature, noise diode (stored V then H)

cal_tref

Calibration model, brightness temperature, reference (stored V then H)

cal_txnd

Calibration model, brightness temperature, external noise diode (stored V then H)

cal_xnd_phase

Calibration model, external noise diode phase

cal_loss2_feed16

Calibration model lumped loss factor of feed, 16 subbands

cal_loss3_omt16

Calibration model lumped loss factor of OMT (stored V then H), 16 subbands

cal_loss4_coupler16

Calibration model lumped loss factor of coupler (stored V then H), 16 subbands

cal_loss5_diplexer16

Calibration model lumped loss factor of the diplexer (stored V then H), 16 subbands

cal_nd_phase16

 Calibration model, noise diode phase, 16 subbands

cal_rx_phase16

 Calibration model, receiver phase, 16 subbands

cal_temp_nd16

Calibration model, physical temperature, noise diode, 16 subbands

cal_temp_xnd16

Calibration model, physical temperature, external noise diode, 16 subbands

cal_tempref_offset16

Calibration model, physical temperature offset, reference (stored V then H), 16 subbands

cal_tnd16

Calibration model, brightness temperature, reference (stored V then H), 16 subbands

cal_tref16

Calibration model, brightness temperature, external noise diode (stored V then H), 16 subbands

cal_txnd16

Calibration model, brightness temperature, external noise diode (stored V then H), 16 subbands

cal_xnd_phase16

Calibration model, external noise diode phase, 16 subbands

calibration_time_seconds

Number of seconds since midnight on 1/1/1993 for each antenna rotation interpolated to antenna boresight azimuth of 0 degrees

highresolution_scan_index

An array of indices of the high resolution antenna scan rotations in the current granule.  The value in this array references in the matching index in the Antenna Scan array.

antenna_scan_mode_flag

Operational mode of attitude/ephemeris telemetry and associated calculations at each instance when antenna boresight azimuth is 0 degrees.

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

Quality of attitude/ephemeris telemetry and associated calculations at each instance when antenna boresight azimuth is 0 degrees

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

Number of seconds in the J2000 epoch for each antenna rotation interpolated to antenna scan angle of 0 degrees.

antenna_scan_time_utc

UTC time stamp for each antenna rotation when antenna scan angle is 0 degrees.

footprints_per_scan

Number of brightness temperature footprints acquired in the current scan.

pitch

SC pitch interpolated to antenna scan angle of 0 degrees.

roll

SC roll interpolated to antenna scan angle of 0 degrees.

sc_alongtrack_velocity

Spacecraft velocity in the direction of the spacecraft orbital track interpolated to antenna scan angle of 0 degrees.

sc_geodetic_alt_ellipsoid

Spacecraft altitude above Earth WGS84 reference ellipsoid along the nadir track interpolated to antenna scan angle of 0 degrees.

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 scan angle is 0 degrees.

sc_nadir_lat

Spacecraft latitude along nadir track interpolated to antenna scan angle of 0 degrees.

sc_nadir_lon

Spacecraft longitude along nadir track interpolated to antenna scan angle of 0 degrees.

sc_radial_velocity

Spacecraft velocity in the direction of the radius of the orbital track. Velocity that records change in altitude.

tbs_per_scan

Number of brightness temperature footprints acquired in the current scan.

x_pos

SC position in x direction of Earth Centered Rotating system interpolated to antenna scan angle of 0 degrees.

x_vel

SC velocity in x direction  of Earth Centered Rotating system interpolated to antenna scan angle of 0 degrees.

y_pos

SC position in y direction  of Earth Centered Rotating system interpolated to antenna scan angle of 0 degrees.

y_vel

SC velocity in y direction  of Earth Centered Rotating system interpolated to antenna scan angle of 0 degrees.

yaw

SC yaw interpolated to antenna scan angle of 0 degrees.

z_pos

SC position in z direction  of Earth Centered Rotating system interpolated to antenna scan angle of 0 degrees.

z_vel

SC velocity in z direction  of Earth Centered Rotating system interpolated to antenna scan angle of 0 degrees.

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