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GLAS Ancillary Products

The following ancillary products are required to produce GLAS standard products. They are delivered to NSIDC and are available upon special request from NSIDC User Services. NSIDC only distributes the first versions of ancillary files from the beginning of the ICESat/GLAS mission. When the mission ends, NSIDC will distribute the last versions of ancillary files.

ID Name Description
ANC04 ICRF to ITRF Transformation

This file contains polynomial coefficients that represent the corresponding transformation matrix quaternions.

ANC08 Precision Orbit

The Precision Orbit Data (POD) file provides the time-referenced precision latitude, longitude, and altitude for the center of mass of the spacecraft. Data from this file are used to georeference the Level-1B GLAS standard data products, using a specially-tuned orbit interpolator. The contents of this file include:

  • Time-ordered spacecraft Earth-fixed state vector, at 30-second intervals (sufficient for GLAS due to lower altitude of spacecraft)

  • The date and time of each state vector

ANC09 Precision Attitude

The Precision Attitude Data (PAD) file provides the off-nadir component of the laser measurement's footprint. The contents of this file include:

  • Time-ordered pointing vectors (deviations from nadir) of the laser, in decimal degrees and direction, from the external laser pointing monitor on the spacecraft

  • Uncertainties associated with the pointing vectors

ANC20 Predicted Orbit

Predicted orbit file from the Center for Space Research, University of Texas

ANC25 GPS-UTC Conversion

GPS to J2000 UTC time conversion table. Contains leap seconds to add to GPS seconds which will be eventually be converted into UTC J2000 time.

ANC26 Reference Orbit Ephemeredes

This is a multi-file granule. Each file represents a different reference orbit (8-day, 91-day) with ephemeredes.

ANC33 GLAS ISF/GLAS I-SIPS Interface file

This file is delivered to ISIPS from the ISF.

  • "d_shdr_count" is the counter value in the secondary header on most APIDS

  • "d_shdr_count_prap" is the counter value in the secondary header of PRAP

  • "d_utc" is the UTC time to which the counter values are converted

  • "d_glas_osc_rate" is the GLAS oscillator rate

  • "d_sc_osc_rate" is the Spacecraft oscillator rate

  • "i_trkr_subject(1)" is the subject indicater for LRS tracker 0

  • "i_trkr_subject(2)" is the subject indicater for LRS tracker 1

  • "i_trkr_subject(3)" is the subject indicater for LRS tracker 2

  • "d_implement_time" is the UTC time where the data are first valid

  • "Implement_time" is the UTC time at which this conversion was valid. GLAS_L0proc uses the designated start time of an APID (which is specified in the control file entry) to find the correct position within the ANC33 file based on the Implement_time field.

ANC37 Spacecraft CG file

Spacecraft center of gravity file, from the Center for Space Research, University of Texas.

ANC39 GPS Data File

Converted GPS file

ANC47 PDS and EDS Construction Record The PDS/EDS construction record is delivered with the GLA00 APIDs from EDOS. The construction record contains associated information, including the number and locations of records that were filled by EDOS. Each 'xxxx' within the filename corresponds to a GLA00 APID of identical type.

The following ancillary products are included with products' Delivered Algorithm Packages (DAPs), and are available upon special request from NSIDC User Services.

ID Name Description
ANC07-00 Constants-Error

ANC07 files are in standard GSAS "KEYWORD=VALUE" format. The keyword is not case sensitive. Spaces are allowed, but not required. Comment lines must be preceded by a "#" character. The keyword is limited to 25 characters; the value is limited to 229 characters. ANC07 files contain sections for errors messages, status messages, global constants, and subsystem-specific constants. Sections may be combined into a single file or separated into multiple files. Not all sections are present in each ANC07 file.

The Constants-Error file contains the following sections.

BEG_OF_STATUS=
...Status section contents...
END_OF_STATUS=
BEG_OF_ERROR=
...Error section contents...
END_OF_ERROR

ANC07-01 Constants-Globals

ANC07 files are in a standard "KEYWORD=VALUE" format. The keyword is not case sensitive. Spaces are allowed, but not required. Comment lines must be preceded by a "#" character. The keyword is limited to 25 characters; the value is limited to 229 characters. ANC07 files contain sections for errors messages, status messages, global constants, and subsystem-specific constants. Sections may be combined into a single file or separated into multiple files. Not all sections are present in each ANC07 file.

The Constants-Globals file contains the following sections.

BEG_OF_GLOBALS=
...Global constants section contents...
END_OF_GLOBALS

ANC07-02 Constants-Atm

ANC07 files are in standard GSAS "KEYWORD=VALUE" format. The keyword is not case sensitive. Spaces are allowed, but not required. Comment lines must be preceded by a "#" character. The keyword is limited to 25 characters; the value is limited to 229 characters. ANC07 files contain sections for errors messages, status messages, global constants, and subsystem-specific constants. Sections may be combined into a single file or separated into multiple files. Not all sections are present in each ANC07 file.

The Constants-Atm file contains the following sections.

BEG_OF_ATM=
...Atmosphere constants section contents...
END_OF_ATM

ANC07-03 Constants-Elevation

ANC07 files are in standard GSAS "KEYWORD=VALUE" format. The keyword is not case sensitive. Spaces are allowed, but not required. Comment lines must be preceded by a "#" character. The keyword is limited to 25 characters; the value is limited to 229 characters. ANC07 files contain sections for errors messages, status messages, global constants, and subsystem-specific constants. Sections may be combined into a single file or separated into multiple files. Not all sections are present in each ANC07 file.

The Constants-Elevation file contains the following sections.

BEG_OF_ELEV=
...Elevation constants section contents...
END_OF_ELEV

ANC07-04 Constants-Waveforms

ANC07 files are in standard GSAS "KEYWORD=VALUE" format. The keyword is not case sensitive. Spaces are allowed, but not required. Comment lines must be preceded by a "#" character. The keyword is limited to 25 characters; the value is limited to 229 characters. ANC07 files contain sections for errors messages, status messages, global constants, and subsystem-specific constants. Sections may be combined into a single file or separated into multiple files. Not all sections are present in each ANC07 file.

The Constants-Waveforms file contains the following sections.

BEG_OF_WF=
...WF constants section contents...
END_OF_WF

ANC07-05 Constants-L1A

ANC07 files are in standard GSAS "KEYWORD=VALUE" format. The keyword is not case sensitive. Spaces are allowed, but not required. Comment lines must be preceded by a "#" character. The keyword is limited to 25 characters; the value is limited to 229 characters. ANC07 files contain sections for errors messages, status messages, global constants, and subsystem-specific constants. Sections may be combined into a single file or separated into multiple files. Not all sections are present in each ANC07 file.

The Constants-L1A file contains the following sections.

BEG_OF_L1A=
...L1A constants section contents...
END_OF_L1A

ANC27 Regional mask

ANC27 is a multi-file granule. 00=coarse regional mask, 01=fine regional mask. This granule provides the regional mask definitions used to determine what data goes on each elevation level-2 product at the 2-min x 2-min resolution. The coarse file contains the type of regions (ice sheet, sea ice, land, or ocean) contained at the 1° x 1° coarse resolution. If at the coarse resolution more than one region type is contained in that grid block, then a fine resolution block exists that defines each 2-min x 2-min block within the large block. More than one region type may exist in any block.

ANC30 Global aerosol categorization map ANC30 is a global aerosol categorization map file provided by the GLAS science team.
ANC31 Aerosol tropospheric classification map ANC31 is an aerosol tropospheric classification map file provided by the GLAS science team.
ANC38 Multiple-scattering table ANC38 is a multiple-scattering table for Level-2 Atmosphere