ATL06 L3A This data set (ATL06) provides geolocated, land-ice surface heights (above the WGS 84 ellipsoid, ITRF2014 reference frame), plus ancillary parameters that can be used to interpret and assess the quality of the height estimates. The data were acquired by th CF-1.6 Thomas A Neumann (thomas.neumann@nasa.gov), Thorsten Markus (thorsten.markus@nasa.gov), Suneel Bhardwaj (suneel.bhardwaj@nasa.gov) David W Hancock III (david.w.hancock@nasa.gov) Instrument Engineer, Investigator, Principle Investigator, Data Producer, Data Producer Data within this group pertain to the granule in its entirety. UTC trajectory degrees_north degrees_east ATL06 http://dx.doi.org Data may not be reproduced or distributed without including the citation for this product included in this metadata. Data may not be distributed in an altered form without the written permission of the ICESat-2 Science Project Office at NASA/GSFC. http://dx.doi.org Horizontal CF-1.6 CCSDS UTC-A 2025-12-19T22:01:54.000000Z HDF5 1.14.4 2025-12-19T22:01:54.000000Z;fe870c8f-7533-3a33-8c17-d667ecdd83b6;Created by PGE atlas_l3a_is Version 5.1 fe870c8f-7533-3a33-8c17-d667ecdd83b6 5.1 422. 2025-09-13T14:30:26.000000Z 2025-09-13T14:23:24.000000Z 25.474481959584711 -171.42912310348692 25.51268125829365 -171.42503689992421 NSIDC DAAC > NASA National Snow and Ice Data Center Distributed Active Archive Center nsidc@nsidc.org http://nsidc.org/daac/ ATLAS/ICESat-2 L3A Land Ice Height ATL06 doi:10.5067/ATLAS/ATL06.007 National Aeronautics and Space Administration (NASA) GSFC I-SIPS > ICESat-2 Science Investigator-led Processing System ATL06 provides estimates of the ice-sheet mean surface height relative to the WGS-84 ellipsoid, and ancillary parameters needed to interpret and assess the quality of these height estimates. EARTH SCIENCE > CRYOSPHERE > GLACIERS/ICE SHEETS > GLACIER ELEVATION/ICE SHEET ELEVATION > NONE > NONE > NONE NASA/GCMD Science Keywords Cite these data in publications as follows: The data used in this study were produced by the ICESat-2 Science Project Office at NASA/GSFC. The data archive site is the NASA National Snow and Ice Data Center Distributed Active Archive Center. 3A http://nsidc.org/data/icesat2/data.html ICESat-2 > Ice, Cloud, and land Elevation Satellite-2 ATLAS > Advanced Topographic Laser Altimeter System ICESat-2 > Ice, Cloud, and land Elevation Satellite-2 Spacecraft Release Number 1 Operations auxiliaryInformation Release number of the granule. The release number is incremented when the software or ancillary data used to create the granule has been changed. Ending Geolocation Segment 1 Derived auxiliaryInformation The ending geolocation segment number associated with the data contained within this granule. ICESat granule geographic regions are further refined by geolocation segments. During the geolocation process, a geolocation segment is created approximately every 20m from the start of the orbit to the end. The geolocation segments help align the ATLAS strong a weak beams and provide a common segment length for the L2 and higher products. The geolocation segment indices differ slightly from orbit-to-orbit because of the irregular shape of the Earth. The geolocation segment indices on ATL01 and ATL02 are only approximate because beams have not been aligned at the time of their creation. Version 1 Operations auxiliaryInformation Version number of this granule within the release. It is a sequential number corresponding to the number of times the granule has been reprocessed for the current release. Ending Region 1 Derived auxiliaryInformation The ending product-specific region number associated with the data contained within this granule. ICESat-2 data products are separated by geographic regions. The data contained within a specific region are the same for ATL01 and ATL02. ATL03 regions differ slightly because of different geolocation segment locations caused by the irregular shape of the Earth. The region indices for other products are completely independent. ATLAS Epoch Offset seconds since 1980-01-06T00:00:00.000000Z Operations auxiliaryInformation Number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS Standard Data Product (SDP) epoch (2018-01-01:T00.00.00.000000 UTC). Add this value to delta time parameters to compute full gps_seconds (relative to the GPS epoch) for each data point. Ending Reference Groundtrack 1 Derived 1 1387 auxiliaryInformation The ending reference groundtrack (RGT) number associated with the data contained within this granule. There are 1387 reference groundtrack in the ICESat-2 repeat orbit. The reference groundtrack increments each time the spacecraft completes a full orbit of the Earth and resets to 1 each time the spacecraft completes a full cycle. ATLAS End Time (Actual) time seconds since 2018-01-01 Derived auxiliaryInformation Number of GPS seconds since the ATLAS SDP epoch at the last data point in the file. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. Ending Orbit Number 1 Derived auxiliaryInformation The ending orbit number associated with the data contained within this granule. The orbit number increments each time the spacecraft completes a full orbit of the Earth. Starting Cycle 1 Derived 0 99 auxiliaryInformation The starting cycle number associated with the data contained within this granule. The cycle number is the counter of the number of 91-day repeat cycles completed by the mission. End UTC Time of Granule (CCSDS-A, Actual) 1 Derived auxiliaryInformation UTC (in CCSDS-A format) of the last data point within the granule. Control File 1 Operations auxiliaryInformation PGE-specific control file used to generate this granule. To re-use, replace breaks (BR) with linefeeds. Start GPS SOW of Granule (Actual) seconds Derived auxiliaryInformation GPS seconds-of-week of the first data point in the granule. End UTC Time of Granule (CCSDS-A, Requested) 1 Derived auxiliaryInformation Requested end time (in UTC CCSDS-A) of this granule. Ending Cycle 1 Derived 0 99 auxiliaryInformation The ending cycle number associated with the data contained within this granule. The cycle number is the counter of the number of 91-day repeat cycles completed by the mission. Start UTC Time of Granule (CCSDS-A, Requested) 1 Derived auxiliaryInformation Requested start time (in UTC CCSDS-A) of this granule. ATLAS Start Time (Actual) time seconds since 2018-01-01 Derived auxiliaryInformation Number of GPS seconds since the ATLAS SDP epoch at the first data point in the file. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. Starting Geolocation Segment 1 Derived auxiliaryInformation The starting geolocation segment number associated with the data contained within this granule. ICESat granule geographic regions are further refined by geolocation segments. During the geolocation process, a geolocation segment is created approximately every 20m from the start of the orbit to the end. The geolocation segments help align the ATLAS strong a weak beams and provide a common segment length for the L2 and higher products. The geolocation segment indices differ slightly from orbit-to-orbit because of the irregular shape of the Earth. The geolocation segment indices on ATL01 and ATL02 are only approximate because beams have not been aligned at the time of their creation. Starting Orbit Number 1 Derived auxiliaryInformation The starting orbit number associated with the data contained within this granule. The orbit number increments each time the spacecraft completes a full orbit of the Earth. Start UTC Time of Granule (CCSDS-A, Actual) 1 Derived auxiliaryInformation UTC (in CCSDS-A format) of the first data point within the granule. Ending GPSWeek of Granule (Actual) auxiliaryInformation GPS week number of the last data point in the granule. weeks from 1980-01-06 Derived Starting Reference Groundtrack 1 Derived 1 1387 auxiliaryInformation The starting reference groundtrack (RGT) number associated with the data contained within this granule. There are 1387 reference groundtrack in the ICESat-2 repeat orbit. The reference groundtrack increments each time the spacecraft completes a full orbit of the Earth and resets to 1 each time the spacecraft completes a full cycle. Ending GPS SOW of Granule (Actual) seconds Derived auxiliaryInformation GPS seconds-of-week of the last data point in the granule. QA Along-Track Interval seconds/cell control auxiliaryInformation Statistics time interval for along-track QA data. Starting Region 1 Derived auxiliaryInformation The starting product-specific region number associated with the data contained within this granule. ICESat-2 data products are separated by geographic regions. The data contained within a specific region are the same for ATL01 and ATL02. ATL03 regions differ slightly because of different geolocation segment locations caused by the irregular shape of the Earth. The region indices for other products are completely independent. Start GPSWeek of Granule (Actual) weeks from 1980-01-06 Derived auxiliaryInformation GPS week number of the first data point in the granule. Data within this group pertain to the granule in its entirety. Contains information ancillary to the data product. This may include product characteristics, instrument characteristics and/or processing constants. Bin Size meters Operations auxiliaryInformation Residual histogram bin size Sigma of Gaussian Footprint meters Operations auxiliaryInformation Spatial sigma of the Gaussian footprint (m) Height Sigma QS Limit 1 Operations auxiliaryInformation atl06_quality_summary limit for testing Height Sigma. Maximum Iterations of Fit 1 Operations auxiliaryInformation Maximum number of iterations in at_seg_fit Maximum Iterations counts Operations auxiliaryInformation Maximum number of iterations in tx_shape_corr Height Robust Spread QS Limit meters Operations auxiliaryInformation atl06_quality_summary limit for testing Height Robust Spread. Blowing Snow Confidence QS Limit 1 Operations auxiliaryInformation atl06_quality_summary limit for testing Blowing Snow Confidence. SNR Significance QS Limit 1 Operations auxiliaryInformation atl06_quality_summary limit for testing SNR Significance. Number of Histogram Bins 1 Operations auxiliaryInformation Number of bins in a histogram Minimum Gain Threshold 1 Operations auxiliaryInformation Minimum estimated gain threshold (3.1.6) Signal Selection Source QS Limit 1 Operations auxiliaryInformation atl06_quality_summary limit for testing Signal Selection Source. Number of Sigmas 1 Operations auxiliaryInformation Multiplied by sigma_expected to get h_win Histogram Bin Size seconds Operations auxiliaryInformation Bin size for histograms (sec) Sigma Tx seconds Operations auxiliaryInformation RDE of the Tx pulse in ATLAS Spot order (1-6). Calculated as half the difference between the 84th and 16th percentiles of the signal bins. Minimum Signal Confidence 1 Operations 0 4 auxiliaryInformation Minimum signal confidence level for a photon to be considered valid. Dead Time seconds Operations auxiliaryInformation Dead time, in ATLAS spot order (1-6). Calculated as the average of the CAL42 per-channel dead times, using the appropriate channels for strong and weak spots. Multiple Scattering Warning QS Limit 1 Operations auxiliaryInformation atl06_quality_summary limit for testing Multiple Scattering Warning. Mininum Number of Photons 1 Operations auxiliaryInformation Minimum number of selected PEs in pe_select Max Segments 1 Operations auxiliaryInformation Maximum number of segment ids in each residual_histogram Processing Interval seconds Operations auxiliaryInformation Processing interval in number of geolocation segments.. Maximum Iterations for FPB 1 Operations auxiliaryInformation Maximum number of iterations in fpb_corr Minimum Photons 1 Operations auxiliaryInformation Minimum # PEs for fit Minimum Distance meters Operations auxiliaryInformation Min dist between first and last selected PEs Number of Bins 1 Operations auxiliaryInformation Number of bins in residual histogram Contains land-ice-specific information ancillary to the data product. This may include product characteristics, instrument characteristics and/or processing constants. Granule Failure Reason 1 Operations 0 5 qualityInformation Flag indicating granule failure reason. 0=no failure; 1=processing error; 2=Insufficient output data was generated; 3=TBD Failure; 4=TBD_Failure; 5=other failure. no_failure PROCESS_ERROR INSUFFICIENT_OUTPUT failure_3 failure_4 OTHER_FAILURE 0 1 2 3 4 5 Granule Pass Flag 1 Operations 0 1 qualityInformation Flag indicating granule quality. 0=granule passes automatic QA. 1=granule fails automatic QA. PASS FAIL 0 1 Contains quality assessment data. This may include QA counters, QA along-track data and/or QA summary data. Longitude Mean longitude degrees_east Section 7.2, Q/A Statistics -180. 180. physicalMeasurement Mean longitude of the 10km segment. delta_time lat_mean Latitude Mean latitude degrees_north Section 7.2, Q/A Statistics -90. 90. physicalMeasurement Mean latitude of the 10km segment. delta_time lon_mean Elapsed GPS seconds time seconds since 2018-01-01 Section 7.2, Q/A Statistics referenceInformation Mean number of GPS seconds since the ATLAS SDP epoch for the 10km segment. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Signal Selection Source Fraction 0 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to zero. delta_time lat_mean lon_mean Signal Selection Source Fraction 2 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 2. delta_time lat_mean lon_mean Signal Selection Source Fraction 1 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 1. delta_time lat_mean lon_mean Signal Selection Source Fraction 3 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 3. delta_time lat_mean lon_mean delta_time Contains quality assessment data. This may include QA counters, QA along-track data and/or QA summary data. Longitude Mean longitude degrees_east Section 7.2, Q/A Statistics -180. 180. physicalMeasurement Mean longitude of the 10km segment. delta_time lat_mean Elapsed GPS seconds time seconds since 2018-01-01 Section 7.2, Q/A Statistics referenceInformation Mean number of GPS seconds since the ATLAS SDP epoch for the 10km segment. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Latitude Mean latitude degrees_north Section 7.2, Q/A Statistics -90. 90. physicalMeasurement Mean latitude of the 10km segment. delta_time lon_mean Signal Selection Source Fraction 0 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to zero. delta_time lat_mean lon_mean Signal Selection Source Fraction 2 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 2. delta_time lat_mean lon_mean Signal Selection Source Fraction 1 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 1. delta_time lat_mean lon_mean Signal Selection Source Fraction 3 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 3. delta_time lat_mean lon_mean delta_time Contains quality assessment data. This may include QA counters, QA along-track data and/or QA summary data. Longitude Mean longitude degrees_east Section 7.2, Q/A Statistics -180. 180. physicalMeasurement Mean longitude of the 10km segment. delta_time lat_mean Latitude Mean latitude degrees_north Section 7.2, Q/A Statistics -90. 90. physicalMeasurement Mean latitude of the 10km segment. delta_time lon_mean Elapsed GPS seconds time seconds since 2018-01-01 Section 7.2, Q/A Statistics referenceInformation Mean number of GPS seconds since the ATLAS SDP epoch for the 10km segment. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Signal Selection Source Fraction 0 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to zero. delta_time lat_mean lon_mean Signal Selection Source Fraction 2 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 2. delta_time lat_mean lon_mean Signal Selection Source Fraction 1 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 1. delta_time lat_mean lon_mean Signal Selection Source Fraction 3 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 3. delta_time lat_mean lon_mean delta_time Contains quality assessment data. This may include QA counters, QA along-track data and/or QA summary data. Longitude Mean longitude degrees_east Section 7.2, Q/A Statistics -180. 180. physicalMeasurement Mean longitude of the 10km segment. delta_time lat_mean Elapsed GPS seconds time seconds since 2018-01-01 Section 7.2, Q/A Statistics referenceInformation Mean number of GPS seconds since the ATLAS SDP epoch for the 10km segment. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Latitude Mean latitude degrees_north Section 7.2, Q/A Statistics -90. 90. physicalMeasurement Mean latitude of the 10km segment. delta_time lon_mean Signal Selection Source Fraction 0 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to zero. delta_time lat_mean lon_mean Signal Selection Source Fraction 2 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 2. delta_time lat_mean lon_mean Signal Selection Source Fraction 1 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 1. delta_time lat_mean lon_mean Signal Selection Source Fraction 3 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 3. delta_time lat_mean lon_mean delta_time Contains quality assessment data. This may include QA counters, QA along-track data and/or QA summary data. Longitude Mean longitude degrees_east Section 7.2, Q/A Statistics -180. 180. physicalMeasurement Mean longitude of the 10km segment. delta_time lat_mean Elapsed GPS seconds time seconds since 2018-01-01 Section 7.2, Q/A Statistics referenceInformation Mean number of GPS seconds since the ATLAS SDP epoch for the 10km segment. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Latitude Mean latitude degrees_north Section 7.2, Q/A Statistics -90. 90. physicalMeasurement Mean latitude of the 10km segment. delta_time lon_mean Signal Selection Source Fraction 0 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to zero. delta_time lat_mean lon_mean Signal Selection Source Fraction 2 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 2. delta_time lat_mean lon_mean Signal Selection Source Fraction 1 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 1. delta_time lat_mean lon_mean Signal Selection Source Fraction 3 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 3. delta_time lat_mean lon_mean delta_time Contains quality assessment data. This may include QA counters, QA along-track data and/or QA summary data. Longitude Mean longitude degrees_east Section 7.2, Q/A Statistics -180. 180. physicalMeasurement Mean longitude of the 10km segment. delta_time lat_mean Elapsed GPS seconds time seconds since 2018-01-01 Section 7.2, Q/A Statistics referenceInformation Mean number of GPS seconds since the ATLAS SDP epoch for the 10km segment. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Latitude Mean latitude degrees_north Section 7.2, Q/A Statistics -90. 90. physicalMeasurement Mean latitude of the 10km segment. delta_time lon_mean Signal Selection Source Fraction 0 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to zero. delta_time lat_mean lon_mean Signal Selection Source Fraction 2 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 2. delta_time lat_mean lon_mean Signal Selection Source Fraction 1 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 1. delta_time lat_mean lon_mean Signal Selection Source Fraction 3 1 ATL06 ATBD - Q/A Statistics 0. 1. qualityInformation The fraction of 20m segments with signal_selection_source equal to 3. delta_time lat_mean lon_mean delta_time Contains quality assessment data. This may include QA counters, QA along-track data and/or QA summary data. ISO 19139 Dataset XML ISO 19139 Dataset XML ISO 19139 Series XML ISO 19139 Series XML ISO19115 Structured Metadata Represented within HDF5 10000 pps 532 nm ATLAS Laser Altimeter ATLAS on ICESat-2 determines the range between the satellite and the Earth's surface by measuring the two-way time delay of short pulses of laser light that it transmits in six beams. It is different from previous operational ice-sheet altimeters in that it is a photon-counting LIDAR. ATLAS records a set of arrival times for individual photons, which are then analyzed to derive surface, vegetation, and cloud properties. ATLAS has six beams arranged in three pairs, so that it samples each of three reference pair tracks with a pair of beams; ATLAS transmits pulses at 10 kHz, giving approximately one pulse every 0.7 m along track; ATLAS's expected pointing control will be better than 90 m RMS. Pre-Release 12/31/17 A document describing the ATLAS instrument will be provided by the ICESat-2 Project Science Office. ICESat-2 Ice, Cloud, and land Elevation Satellite-2 Spacecraft 31-Dec-16 31-Dec-16 The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2): Science requirements, concept, and implementation. Thorsten Markus, Tom Neumann, Anthony Martino, Waleed Abdalati, Kelly Brunt, Beata Csatho, Sinead Farrell, Helen Fricker, Alex Gardner, David Harding, Michael Jasinski, Ron Kwok, Lori Magruder, Dan Lubin, Scott Luthcke, James Morison, Ross Nelson, Amy Neuenschwander, Stephen Palm, Sorin Popescu, CK Shum, Bob E. Schutz, Benjamin Smith, Yuekui Yang, Jay Zwally. http://dx.doi.org/10.1016/j.rse.2016.12.029 NOT_SET directInternal TBD TBD TBD NOT_SET directInternal TBD TBD TBD NOT_SET ATL06_SDP utf8 eng Feb 2020 ICESat-2-SIPS-SPEC-4260 - ATLAS Science Algorithm Standard Data Product (SDP) Volume 5 (ATL06). v4.3 asNeeded SET_BY_META 007 eng utf8 NSIDC DAAC > NASA National Snow and Ice Data Center Distributed Active Archive Center ATLAS/ICESat-2 L3A Land Ice Height ATL06 doi:10.5067/ATLAS/ATL06.007 2022-08-09 National Aeronautics and Space Administration (NASA) ATL06 provides estimates of the ice-sheet mean surface height relative to the WGS-84 ellipsoid, and ancillary parameters needed to interpret and assess the quality of these height estimates. ATL06 provides estimates of the ice-sheet mean surface height relative to the WGS-84 ellipsoid, and ancillary parameters needed to interpret and assess the quality of these height estimates. The software that generates the ATL06 product was designed and implemented at the NASA Wallops Flight Facility in Wallops Island, Virginia. onGoing HDF 5 geoscientificInformation ICESat-2 > Ice, Cloud, and land Elevation Satellite-2 along-track 2025-12-19T22:01:54.000000Z fe870c8f-7533-3a33-8c17-d667ecdd83b6 ATL06_20250913142324_13722807_007_01.h5 007 eng utf8 ATL06 GSFC I-SIPS > ICESat-2 Science Investigator-led Processing System ATL06 provides estimates of the ice-sheet mean surface height relative to the WGS-84 ellipsoid, and ancillary parameters needed to interpret and assess the quality of these height estimates. ATL06 provides estimates of the ice-sheet mean surface height relative to the WGS-84 ellipsoid, and ancillary parameters needed to interpret and assess the quality of these height estimates. The software that generates the ATL06 product was designed and implemented at the NASA Wallops Flight Facility in Wallops Island, Virginia. onGoing geoscientificInformation 25.51268125829365 -171.42503689992421 25.474481959584711 -171.42912310348692 2025-09-13T14:23:47.485874Z 2025-09-13T14:23:48.254371Z 2025-12-19T22:01:57.000000Z An ASCII product that contains statistical information on data product results. These statistics enable data producers and users to assess the quality of the data in the data product granule ATL06_20250913142324_13722807_007_01.qa ISO 19139 XML file containing Series-level metadata information. ANC36-06_20250523205141_007_01.xml ANC36-06 f486c1c2-b893-34c1-b902-1a59f2688c66 007 Text-based keyword=value file generated automatically within the ICESat-2 data system that specifies all of the conditions required for each individual run of the software. CTL_atlas_l3a_is_021426921.ctl CNTL 1 DTU Mean Sea Surface re-referenced to the WGS84 ellipsoid. dtu13_20180705_001_01.nc ANC28 56f47040-a72e-3109-99c2-bc1658e6dda4 20180705 ISO 19139 XML file containing DataSet-level metadata information. ANC38-06_20250523205142_007_01.xml ANC38-06 f8d47ee3-4f43-3070-a6b0-f05ef6bd3cb2 007 ArcticDEM 32m Digital Elevation Model reformatted into HDF5. arcticdem32m_20190611_001_01.h5 ANC06-02 ce07ef72-0bf4-353b-8475-fb568b029905 20190611 REMA Antarctica 100m Digital Elevation Model filled and reformatted into HDF5 atl06rema100m_20190628_001_01.h5 ANC06-03 3e0a81bd-bbd5-35fa-b868-3254f9355b7f 20190628 HDF5 template file that defines the organization and default content of the product. ANC25-06_20250523205529_051_01.h5 ANC25-06 45545701-8dcb-30dc-9f21-e2ee4e77fe87 051 Land Ice Height SNR Significance Table anc17_snr_f_20180626_001_01.h5 ANC17 10e264bc-139a-3737-9f92-29e64e9b858c 20180626 HDF5 template file that defines the organization and default content of the product metadata. ANC26-06_20250523205537_051_01.h5 ANC26-06 438c292c-43ce-3b04-9c33-683805c75ca5 051 ICESat-2 ATLAS L2A Global Geolocated Photon data products. ATL03_20250913142324_13722807_007_01.h5 ATL03 c48e4feb-e9c5-3553-bdfe-a1a6e367be23 007 28 28 39022 39022 1372 1372 7 7 852091 1001793 ICESat-2 ATLAS L3A atmosphere data products. ATL09_20250913134322_13722801_007_01.h5 ATL09 758cce16-d1d5-3c1c-819f-88e47f7c36e1 007 28 28 39022 39022 1372 1372 1 14 2 2007136 MERIT 3 arcsec Digital Elevation Model reformatted into HDF5 and re-referenced to the WGS-84 ellipsoid. merit_3as_20200617_001_01.h5 ANC06-01 3db8ab65-d2ac-37c7-86db-17c762268673 20200617 TAI to UTC leapsecond file retrieved from ftp://maia.usno.navy.mil/ser7/tai-utc.dat tai_utc_2017.dat ANC19 7c66d365-278a-31f7-8fe4-9c80e2f012e5 001 Browse processing is performed for each granule SIPS produces. The browse utility reads data from the granule and produces browse images as defined in the respective product ATBD. The utility then embeds each browse image into the product within the /Browse group. atlas_brw Version 3.1.3 Apr 8 2025 Creates ATLAS HDF5 browse files CTL_atlas_l3a_is_021426921.ctl 2025-12-19T22:01:57.000000Z Metadata information is processed by the metadata utility for each granule produced by SIPS. During PGE processing, dynamic metadata are written to the product. Additional static information is provided with the metadata template. The metadata utility reads ISO Dataset and Series metadata files and updates the product with static information from within those files. The utility then merges the static and dynamic metadata to creates output ISO19139 Dataset and Series XML files. Finally the utility reads the ISO19139 Dataset and Series XML files into memory and stores the textual representations as attributes attached to the /METADATA group. atlas_meta Version 5.1.3 Apr 8 2025 Creates ATLAS XML metadata files CTL_atlas_l3a_is_021426921.ctl 2025-12-19T22:02:07.000000Z 12/04/2019 Algorithm Theoretical Basis Document (ATBD) For Land-Ice Along-Track Products Part 2: Land-ice H(t)/ATL11 N/A Feb 2020 ATLAS Science Algorithm Software Design Description (SDD) - Volume 9 (atlas_l3a_is) Computes surface heights for each beam, along and across-track slopes calculated for beam pairs. atlas_l3a_is Version 5.1 Apr 8 2025 ASAS L3A Icesheet PGE CTL_atlas_l3a_is_021426921.ctl 2025-12-19T22:01:54.000000Z QA processing is performed by an external utility on each granule produced by SIPS. The utility reads the granule, performs both generic and product-specific quality-assessment calculations, and writes a text-based quality assessment report. The name and creation data of this report are identified within the QADatasetIdentification metadata atl06_qa_util Version 5.1 Apr 8 2025 ATL06 QA Utility CTL_atlas_l3a_is_021426921.ctl 2025-12-19T22:01:57.000000Z Ascending Node Crossing Time time seconds since 2018-01-01 POD/PPD referenceInformation The time, in seconds since the ATLAS SDP GPS Epoch, at which the ascending node crosses the equator. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. Time of Last Spacecraft Orientation Change time seconds since 2018-01-01 POD/PPD referenceInformation The time of the last spacecraft orientation change between forward, backward and transitional flight modes, expressed in seconds since the ATLAS SDP GPS Epoch. ICESat-2 is considered to be flying forward when the weak beams are leading the strong beams; and backward when the strong beams are leading the weak beams. ICESat-2 is considered to be in transition while it is maneuvering between the two orientations. Science quality is potentially degraded while in transition mode. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. Cycle Number counts POD/PPD 0 50 referenceInformation Tracks the number of 91-day cycles in the mission, beginning with 01. A unique orbit number can be determined by subtracting 1 from the cycle_number, multiplying by 1387 and adding the rgt value. crossing_time Reference Ground track counts POD/PPD 1 1387 referenceInformation The reference ground track (RGT) is the track on the earth at which a specified unit vector within the observatory is pointed. Under nominal operating conditions, there will be no data collected along the RGT, as the RGT is spanned by GT2L and GT2R. During slews or off-pointing, it is possible that ground tracks may intersect the RGT. The ICESat-2 mission has 1387 RGTs. crossing_time Ascending Node Longitude degrees_east POD/PPD -180. 180. referenceInformation Longitude at the ascending node crossing. crossing_time Polygon1 Latitude degrees_north geo_poly -90. 90. auxiliaryInformation Latitude values for the first out of two possible bounding polygons Orbit Number 1 POD/PPD 1 65000 referenceInformation Unique identifying number for each planned ICESat-2 orbit. crossing_time Polygon1 Longitude degrees_east geo_poly -180. 180. auxiliaryInformation Longitude values for the first out of two possible bounding polygons Spacecraft Orientation 1 POD/PPD 0 2 referenceInformation This parameter tracks the spacecraft orientation between forward, backward and transitional flight modes. ICESat-2 is considered to be flying forward when the weak beams are leading the strong beams; and backward when the strong beams are leading the weak beams. ICESat-2 is considered to be in transition while it is maneuvering between the two orientations. Science quality is potentially degraded while in transition mode. sc_orient_time backward forward transition 0 1 2 crossing_time sc_orient_time Contains data that are common among all beams for the granule. These parameters are constants for a given granule. These parameters are constant for a given granule. Contains subgroups organized by Ground Track (gt1l, gt1r, gt2l, gt2r, gt3l and gt3r) pce1 weak gt3l profile_3 2 Forward Latitude latitude degrees_north ATL06 ATBD - Top Level Fitting Routine -90. 90. physicalMeasurement Latitude of segment center, WGS84, North=+, delta_time longitude Elapsed GPS seconds time seconds since 2018-01-01 ATL06 ATBD - Top Level Fitting Routine referenceInformation Number of GPS seconds since the ATLAS SDP epoch. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. latitude longitude Longitude longitude degrees_east ATL06 ATBD - Top Level Fitting Routine -180. 180. physicalMeasurement Longitude of segment center, , WGS84, East=+ delta_time latitude 3.402823466e+38 Vertical Geolocation Error meters ATL06 ATBD - Segment Geolocation qualityInformation Total vertical geolocation error due to PPD and POD, including the effects of horizontal geolocation error on the segment vertical error. delta_time latitude longitude 3.402823466e+38 Land Ice height meters ATL06 ATBD - Top Level Fitting Routine physicalMeasurement Standard land-ice segment height determined by land ice algorithm, corrected for first-photon bias, representing the median- based height of the selected PEs delta_time latitude longitude ATL06_Quality_Summary 1 ATL06 ATBD - Top Level Fitting Routine 0 1 qualityInformation The ATL06_quality_summary parameter indicates the best-quality subset of all ATL06 data. A zero in this parameter implies that no data-quality tests have found a problem with the segment, a one implies that some potential problem has been found. Users who select only segments with zero values for this flag can be relatively certain of obtaining high-quality data, but will likely miss a significant fraction of usable data, particularly in cloudy, rough, or low-surface-reflectance conditions. delta_time latitude longitude best_quality potential_problem 0 1 0 Reference Point, m 1 ATL06 ATBD - Top Level Fitting Routine referenceInformation Segment number, counting from the equator. Equal to the segment_id for the second of the two 20m ATL03 segments included in the 40m ATL06 segment delta_time latitude longitude 3.402823466e+38 Expected RMS segment misfit meters ATL06 ATBD - Top Level Fitting Routine qualityInformation Propagated error due to sampling error and FPB correction from the land ice algorithm delta_time latitude longitude fpb_warning_flag 1 ATL06 ATBD - FPB Corrections 0 1 qualityInformation To flag that segments have potentially erroneous FPB corrections, the ATL06 algorithm sets fpb_warning_flag to 1 if full_sat_fract is greater than 0.90 (strong beams) or greater than 0.40 (weak beams) for either of the two ATL03 20 m segments that are used as inputs to each ATL06 40 m segment. Otherwise, fpb_warning_flag is set to 0. latitude longitude delta_time best_quality potential_problem 0 1 delta_time The land_ice_height group contains the primary set of derived ATL06 products. This includes geolocation, height, and standard error and quality measures for each segment. This group is sparse, meaning that parameters are provided only for pairs of segments for which at least one beam has a valid surface-height measurement. Data within this group are sparse. Data values are provided only for those ICESat-2 20m segments where at least one beam has a valid land ice height measurement. 3.402823466e+38 Height Mean meters ATL06 ATBD - Iterative Least-Squares Fitting Routine modelResult Mean surface height, not corrected for first-photon bias or pulse truncation. ../delta_time ../latitude ../longitude Signal Selection Source 1 ATL06 ATBD - Signal Selection based on ATL03 flags 0 3 qualityInformation Indicates the last algorithm attempted to select the signal for ATL06 fitting. 0=Signal selection succeeded using ATL03 detected PE; 1=Signal selection failed using ATL03 detected PE but succeeded using all flagged ATL03 PE; 2=Signal selection failed using all flagged ATL03 PE, but succeeded using the backup algorithm; 3=All signal-finding strategies failed. ../delta_time ../latitude ../longitude succeeded_using_pe succeeded_using_flagged_pe succeeded_using_backup failed 0 1 2 3 3.402823466e+38 SNR 1 ATL06 ATBD - Iterative Least Squares Fitting Routine physicalMeasurement Signal-to-noise ratio in the final refined window ../delta_time ../latitude ../longitude 3.402823466e+38 Robust Spread meters ATL06 ATBD - Iterative Least-Squares Fitting Routine referenceInformation RDE of misfit between PE heights and the along-track segment fit. ../delta_time ../latitude ../longitude counts 3.402823466e+38 Number potential segment pulses ATL06 ATBD - Top-Level Fitting Routine referenceInformation The number of pulses potentially included in the segment ../delta_time ../latitude ../longitude 3.402823466e+38 Sigma of Along Track Slope meters/meters ATL06 ATBD - Iterative Least-Squares Fitting Routine qualityInformation Propagated error in the along-track segment slope ../delta_time ../latitude ../longitude 3.402823466e+38 SNR Significance 1 ATL06 ATBD - Top-Level Fitting Routine physicalMeasurement Probability that signal-finding routine would converge to at least the observed SNR for a random-noise input. Small values indicate a small likelihood of a surface-detection blunder. ../delta_time ../latitude ../longitude 3.402823466e+38 Expected RMS misfit meters ATL06 ATBD - Iterative ground-window refinement qualityInformation Expected RMS misfit between PE heights and along-track segment fit ../delta_time ../latitude ../longitude 3.402823466e+38 Across Track Slope meters/meters ATL06 ATBD - Top-Level Fitting Routine physicalMeasurement Across track slope from segment fits to weak and strong beam; the same slope is reported for both laser beams in each pair ../delta_time ../latitude ../longitude 3.402823466e+38 Height Error meters ATL06 ATBD - Propagated Height Errors qualityInformation Propagated height error due to PE-height sampling error for height from the along-track fit, not including geolocation-induced error ../delta_time ../latitude ../longitude 3.402823466e+38 RMS Misfit meters ATL06 ATBD -Iterative Least-Squares Fitting Routine qualityInformation RMS misfit between PE heights and along- track segment fit ../delta_time ../latitude ../longitude Signal Selection Source Status 1 ATL06 ATBD - Signal Selection based on ATL03 flags 0 4 qualityInformation Indicates the status of the last signal selection algorithm attempted (see signal_selection_source). The definition of flag is different for each source and are defined in each of the signal_selection_status flags. (See Land Ice ATBD Table 3-2). ../delta_time ../latitude ../longitude 3.402823466e+38 Along Track Slope meters/meters ATL06 ATBD - Iterative Least-Squares Fitting Routine physicalMeasurement Along-track slope from along-track segment fit ../delta_time ../latitude ../longitude 2147483647 Number of Photons in Fit 1 ATL06 ATBD - Iterative Least-Squares Fitting Routine physicalMeasurement Number of PEs used in determining h_li, after editing ../delta_time ../latitude ../longitude 3.402823466e+38 Surface Window Width meters ATL06 ATBD - Top-Level Fitting Routine physicalMeasurement Width of the surface window, top to bottom ../delta_time ../latitude ../longitude The fit_statistics subgroup contains a variety of parameters that might indicate the quality of the fitted segment data. Data in this group are sparse, with dimensions matching the land_ice_height group. Data within this group are stored at the land_ice_height segment rate. 3.402823466e+38 Along Track Geolocation Error meters ATL06 ATBD - Segment Geolocation qualityInformation Along-track component of the geolocation error. ../delta_time ../latitude ../longitude 3.402823466e+38 Azimuth degrees ATL03 referenceInformation The direction, eastwards from north, of the laser beam vector as seen by an observer at the laser ground spot viewing toward the spacecraft (i.e., the vector from the ground to the spacecraft). ../delta_time ../latitude ../longitude 3.402823466e+38 Radial Orbit Error meters ATL06 ATBD - Segment Geolocation qualityInformation Radial orbit component of the geolocation error. ../delta_time ../latitude ../longitude 3.402823466e+38 Segment Azimuth degrees ATL03 referenceInformation Azimuth of the pair-track, east of local north. ../delta_time ../latitude ../longitude 3.402823466e+38 Across Track Geolocation Error meters ATL06 ATBD - Segment Geolocation qualityInformation Across-track component of the geolocation error. ../delta_time ../latitude ../longitude 3.402823466e+38 Co-elevation degrees ATL03 referenceInformation Coelevation (CE) is direction from vertical of the laser beam as seen by an observer located at the laser ground spot. ../delta_time ../latitude ../longitude 1.7976931348623157e+308 X Along Track meters ATL06 ATBD - Local Coordinate Systems referenceInformation The along-track x-coordinate of the segment, measured parallel to the RGT, measured from the ascending node of the equatorial crossing of a given RGT. ../delta_time ../latitude ../longitude 3.402823466e+38 Y Along Track meters ATL06 ATBD - Local Coordinate Systems referenceInformation Along-track y coordinate of the segment, relative to the RGT, measured along the perpendicular to the RGT, positive to the right of the RGT. ../delta_time ../latitude ../longitude The ground_track group contains parameters describing the GT and RGT for each land ice segment, as well as angular information about the beams. Data within this group are stored at the land_ice_height segment rate. DEM Source Flag 1 ATL03 0 4 referenceInformation Indicates source of the DEM height. Values: 0=None, 1=Arctic, 2=Global, 3=MSS, 4=Antarctic. ../delta_time ../latitude ../longitude none arctic global mss antarctic 0 1 2 3 4 3.402823466e+38 Geoid Free-to-Mean conversion meters ATL03 modelResult Additive value to convert geoid heights from the tide-free system to the mean-tide system. (Add to geoid to get the geoid heights in the mean-tide system.) ../delta_time ../latitude ../longitude 3.402823466e+38 DEM Height meters ATL03 referenceInformation Height of the DEM, interpolated by cubic-spline interpolation in the DEM coordinate system to the PE location. (Best available DEM value in priority of Arctic/Antarctic/Global/MSS) ../delta_time ../latitude ../longitude 3.402823466e+38 Geoid Height meters ATL03 referenceInformation Geoid height above WGS-84 reference ellipsoid (range -107 to 86m) in the tide-free system. ../delta_time ../latitude ../longitude Contains reference DEM and geoid heights. Data within this group are stored at the land_ice segment rate. 127 Multiple Scattering Warning Flag 1 ATL09 -1 5 referenceInformation Multiple Scattering warning flag. The multiple scattering warning flag (ATL09 parameter msw_flag) has values from -1 to 5 where zero means no multiple scattering and 5 the greatest. If no layers were detected, then msw_flag = 0. If blowing snow is detected and its estimated optical depth is greater than or equal to 0.5, then msw_flag = 5. If the blowing snow optical depth is less than 0.5, then msw_flag = 4. If no blowing snow is detected but there are cloud or aerosol layers detected, the msw_flag assumes values of 1 to 3 based on the height of the bottom of the lowest layer: < 1 km, msw_flag = 3; 1-3 km, msw_flag = 2; > 3km, msw_flag = 1. A value of -1 indicates that the signal to noise of the data was too low to reliably ascertain the presence of cloud or blowing snow. We expect values of -1 to occur only during daylight. ../delta_time ../latitude ../longitude cannot_determine no_layers layer_gt_3km layer_between_1_and_3_km layer_lt_1km blow_snow_od_lt_0.5 blow_snow_od_gt_0.5 -1 0 1 2 3 4 5 1 ATL09 127 Consolidated cloud flag 0 1 referenceInformation This flag is a combination of multiple flags (cloud_flag_atm, cloud_flag_asr, and bsnow_con) and takes daytime/nighttime into consideration. A value of 1 means clouds or blowing snow are likely present. A value of 0 indicates the likely absence of clouds or blowing snow. ../delta_time ../latitude ../longitude likely_clear likely_cloudy 0 1 127 Blowing Snow confidence 1 ATL09 referenceInformation Confidence flag for presence of blowing snow ../delta_time ../latitude ../longitude 3.402823466e+38 Blowing Snow Layer Top Height meters ATL09 referenceInformation Blowing snow layer top height ../delta_time ../latitude ../longitude 3.402823466e+38 Ocean Tide meters ATL03 referenceInformation Ocean Tides including diurnal and semi-diurnal (harmonic analysis), and longer period tides (dynamic and self-consistent equilibrium). ../delta_time ../latitude ../longitude 3.402823466e+38 Earth Tide meters ATL03 referenceInformation Solid earth tides in the tide-free system. ../delta_time ../latitude ../longitude 3.402823466e+38 solar azimuth degrees_east ATL03 referenceInformation The direction, eastwards from north, of the sun vector as seen by an observer at the laser ground spot. ../delta_time ../latitude ../longitude 3.402823466e+38 Effective uncorrected reflectance 1 ATL06 ATBD - Top-Level Fitting Routine referenceInformation Effective reflectance, uncorrected for atmospheric effects. ../delta_time ../latitude ../longitude 3.402823466e+38 Dynamic Atmosphere Correction meters ATL03 referenceInformation Dynamic Atmospheric Correction (DAC) includes inverted barometer (IB) effect. ../delta_time ../latitude ../longitude 3.402823466e+38 Load Tide meters ATL03 referenceInformation Load Tide - Local displacement due to Ocean Loading (-6 to 0 cm). ../delta_time ../latitude ../longitude 3.402823466e+38 Earth Tide Free-to-Mean conversion meters ATL03 referenceInformation Additive value to convert solid earth tide from the tide-free system to the mean tide system. (Add to tide_earth to get solid earth tides in the mean-tide system.) ../delta_time ../latitude ../longitude 3.402823466e+38 Blowing snow OD 1 ATL09 modelResult Optical thickness of blowing snow layer. ../delta_time ../latitude ../longitude 3.402823466e+38 Equilibrium Tide meters ATL03 referenceInformation Long period equilibrium tide self-consistent with the ocean tide model (+-0.04m). ../delta_time ../latitude ../longitude 127 Cloud Flag ATM 1 ATL09 0 10 referenceInformation Number of layers found from the backscatter profile using the DDA layer finder. ../delta_time ../latitude ../longitude 3.402823466e+38 solar elevation degrees ATL03 -90. 90. referenceInformation Solar Angle above or below the plane tangent to the ellipsoid surface at the laser spot. Positive values mean the sun is above the horizon, while negative values mean it is below the horizon. The effect of atmospheric refraction is not included. This is a low-precision value, with approximately TBD degree accuracy. ../delta_time ../latitude ../longitude 3.402823466e+38 Solid Earth Pole Tide meters ATL03 referenceInformation Solid Earth Pole Tide -Rotational deformation due to polar motion (-1.5 to 1.5 cm). ../delta_time ../latitude ../longitude 3.402823466e+38 Expected background count rate hz ATL06 ATBD - Background PE Rate referenceInformation Expected background count rate based on sun angle, surface slope, for unit surface reflectance ../delta_time ../latitude ../longitude 127 Cloud Flag ASR 1 ATL09 0 5 referenceInformation Cloud flag (probability) from apparent surface reflectance. 0=clear with high confidence; 1=clear with medium confidence; 2=clear with low confidence; 3=cloudy with low confidence; 4=cloudy with medium confidence; 5=cloudy with high confidence ../delta_time ../latitude ../longitude clear_with_high_confidence clear_with_medium_confidence clear_with_low_confidence cloudy_with_low_confidence cloudy_with_medium_confidence cloudy_with_high_confidence 0 1 2 3 4 5 3.402823466e+38 Background count rate hz ATL03 referenceInformation Background count rate, derived from the ATL03 50-shot-average, interpolated to the segment center. ../delta_time ../latitude ../longitude 3.402823466e+38 Total Neutral Atmospheric Delay meters ATL03 referenceInformation Total neutral atmosphere delay correction (wet+dry). ../delta_time ../latitude ../longitude The sun_and_clouds group contains parameters related to solar background and parameters indicative of the presence or absence of clouds. Data within this group are stored at the land_ice_height segment rate. meters 3.402823466e+38 fpb mean corr sigma ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated error in fpb_mean_corr ../delta_time ../latitude ../longitude 3.402823466e+38 fpb median corr sigma meters ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated error in fpb_med_corr ../delta_time ../latitude ../longitude 3.402823466e+38 first photon bias mean correction meters ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated first-photon bias (fpb) correction to mean segment height ../delta_time ../latitude ../longitude 3.402823466e+38 mean median residual meters ATL06 ATBD - Top-Level Fitting Routine qualityInformation Difference between uncorrected mean and median of linear fit residuals ../delta_time ../latitude ../longitude 3.402823466e+38 fpb median corr meters ATL06 ATBD - First-Photon Bias Correction qualityInformation First-photon-bias correction giving the difference between the mean segment height and the corrected median height ../delta_time ../latitude ../longitude 3.402823466e+38 tx shape mean correction meters ATL06 ATBD - Transmit-pulse shape correction qualityInformation Estimate of the difference between the mean of the full-waveform transmit-pulse and the mean of a broadened, truncated waveform consistent with the received pulse ../delta_time ../latitude ../longitude 3.402823466e+38 fpb number photons corr counts ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated window photon count after first-photon-bias correction ../delta_time ../latitude ../longitude 3.402823466e+38 tx shape median correction meters ATL06 ATBD - Transmit-pulse shape correction qualityInformation Estimate of the difference between the median of the full-waveform transmit-pulse mean and the median of a broadened, truncated waveform consistent with the received pulse ../delta_time ../latitude ../longitude The bias_correction group contains information about the estimated first-photon bias, and the transmit-pulse-shape bias. Data within this group are stored at the land_ice segment rate. Segment ID Index 1 ATL06 ATBD - Residual_histogram calculation 1 10 auxiliaryInformation Relative index of each segment_id used in the derivation of the histogram. Latitude Mean latitude degrees_north ATL06 ATBD - Residual_histogram calculation -90. 90. physicalMeasurement Mean latitude of the segments included in the histogram delta_time lon_mean Longitude Mean longitude degrees_east ATL06 ATBD - Residual_histogram calculation -180. 180. physicalMeasurement Mean longitude of the segments included in the histogram delta_time lat_mean Elapsed GPS seconds time seconds since 2018-01-01 ATL06 ATBD - Residual_histogram calculation referenceInformation Number of GPS seconds since the ATLAS SDP epoch. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Bin Top Height meters ATL06 ATBD - Residual_histogram calculation physicalMeasurement Height of the top of each histogram bin, listed in increasing order. The bottom of each bin is equal to the top of the next- lowest bin. delta_time lat_mean lon_mean 2147483647 Bin Counts counts ATL06 ATBD - Residual_histogram calculation physicalMeasurement Residual count falling with each histogram bin. The top height of each histogram bin may be found in the bin_top_h dataset. delta_time lat_mean lon_mean Number of Histogram Segment Pulses counts ATL06 ATBD - Residual_histogram calculation physicalMeasurement Number of pulses potentially included in the histogram (pulses are counted if they are in the central 20 m of each segment, even if no PE from the pulse are selected). delta_time lat_mean lon_mean Along Track Coordinate Mean 1 ATL06 ATBD - Residual_histogram calculation physicalMeasurement Mean along-track coordinate of the segments included in the histogram. delta_time lat_mean lon_mean Segment ID List 1 ATL06 ATBD - Residual_histogram calculation referenceInformation Segments ids included in each column of the histogram delta_time lat_mean lon_mean 2147483647 Expected background PEs 1 ATL06 ATBD - Residual_histogram calculation physicalMeasurement Number of background PE expected for each vertical meter of the histogram based on the observed background rate (bckgrd). delta_time lat_mean lon_mean delta_time Data within this group are stored at the 200-meter along-track rate. This group contains histograms of the residuals between PE heights and the least-squares fit segment heights, at 200-meter along-track resolution. Latitude degrees_north ATL06 ATBD - segment_quality group -90. 90. referenceInformation Latitude of the reference segment location on the RPT delta_time reference_pt_lon latitude Longitude degrees_east ATL06 ATBD - segment_quality group -180. 180. referenceInformation Longitude of the reference segment location on the RPT delta_time reference_pt_lat longitude Elapsed GPS seconds time seconds since 2018-01-01 ATL06 ATBD - segment_quality group referenceInformation Number of GPS seconds since the ATLAS SDP epoch. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. reference_pt_lat reference_pt_lon Land Ice Height Index 1 ATL06 ATBD - segment_quality group referenceInformation For those segments that have adequate signal strength, this parameter gives the record for the pair within the other groups in the granule. delta_time reference_pt_lat reference_pt_lon Signal Selection Source 1 ATL06 ATBD - Signal selection base on ATL03 flags 0 3 qualityInformation Indicates the last algorithm attempted to select the signal for ATL06 fitting. 0=Signal selection succeeded using ATL03 detected PE; 1=Signal selection failed using ATL03 detected PE but succeeded using all flagged ATL03 PE; 3=All signal-finding strategies failed. delta_time reference_pt_lat reference_pt_lon succeeded_using_pe succeeded_using_flagged_pe failed 0 1 3 Reference Point, m 1 ATL06 ATBD - segment_quality group referenceInformation Segment number corresponding to the second of two ATL03 segments in the ATL06 segment, counted from the RGT equator crossing delta_time reference_pt_lat reference_pt_lon delta_time Data within this group are stored at the ICESat-2 20m segment rate. The segment_quality group contains a dense record (i.e. for every possible segment in the granule) of the success or failure of the surface-finding strategies, and gives the locations of the reference points on the RPTs. For segments with adequate data quality (i.e. with more than 10 PE) it also contains offsets into the data structures for the other groups that allow each segment to be efficiently located within the file. 1 Signal Selection Status Flag ATL06 ATBD - Signal selection base on ATL03 flags 0 3 qualityInformation Indicates confidence of the signal-selection algorithm using all ATL03-flagged PEs. 0=Signal selection succeeded using all ATL03-flagged PEs (or algorithm not attempted); 1=Signal selection using all ATL03-flagged PEs failed the 20-meter-spread test; 2=Signal selection using all ATL03-flagged PEs failed the 10-photon-count test; 3=Signal selection using all ATL03-flagged PEs failed both tests ../delta_time ../reference_pt_lat ../reference_pt_lon succeeded failed_20 failed_10 failed_both 0 1 2 3 1 Signal Selection Confident Flag ATL06 ATBD - Signal selection base on ATL03 flags 0 3 qualityInformation Indicates confidence of the signal-selection algorithm using low or better PEs. 0=Signal selection succeeded using ATL03 low-or-better confidence PEs; 1=Signal selection using ATL03 low-or-better confidence PEs failed the 20-meter-spread test; 2=Signal selection using ATL03 low-or-better confidence PEs failed the 10-photon-count test; 3=Signal selection using ATL03 low-or-better confidence PEs failed both tests ../delta_time ../reference_pt_lat ../reference_pt_lon succeeded failed_20 failed_10 failed_both 0 1 2 3 The signal selection status subgroup contains the success or failure for each surface-finding strategies Data within this group are stored at the ICESat-2 20m segment rate. Contains subgroups organized by Ground Track (gt1l, gt1r, gt2l, gt2r, gt3l and gt3r) pce1 strong gt3r profile_3 1 Forward Latitude latitude degrees_north ATL06 ATBD - Top Level Fitting Routine -90. 90. physicalMeasurement Latitude of segment center, WGS84, North=+, delta_time longitude Elapsed GPS seconds time seconds since 2018-01-01 ATL06 ATBD - Top Level Fitting Routine referenceInformation Number of GPS seconds since the ATLAS SDP epoch. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. latitude longitude Longitude longitude degrees_east ATL06 ATBD - Top Level Fitting Routine -180. 180. physicalMeasurement Longitude of segment center, , WGS84, East=+ delta_time latitude 3.402823466e+38 Vertical Geolocation Error meters ATL06 ATBD - Segment Geolocation qualityInformation Total vertical geolocation error due to PPD and POD, including the effects of horizontal geolocation error on the segment vertical error. delta_time latitude longitude 3.402823466e+38 Land Ice height meters ATL06 ATBD - Top Level Fitting Routine physicalMeasurement Standard land-ice segment height determined by land ice algorithm, corrected for first-photon bias, representing the median- based height of the selected PEs delta_time latitude longitude ATL06_Quality_Summary 1 ATL06 ATBD - Top Level Fitting Routine 0 1 qualityInformation The ATL06_quality_summary parameter indicates the best-quality subset of all ATL06 data. A zero in this parameter implies that no data-quality tests have found a problem with the segment, a one implies that some potential problem has been found. Users who select only segments with zero values for this flag can be relatively certain of obtaining high-quality data, but will likely miss a significant fraction of usable data, particularly in cloudy, rough, or low-surface-reflectance conditions. delta_time latitude longitude best_quality potential_problem 0 1 0 Reference Point, m 1 ATL06 ATBD - Top Level Fitting Routine referenceInformation Segment number, counting from the equator. Equal to the segment_id for the second of the two 20m ATL03 segments included in the 40m ATL06 segment delta_time latitude longitude 3.402823466e+38 Expected RMS segment misfit meters ATL06 ATBD - Top Level Fitting Routine qualityInformation Propagated error due to sampling error and FPB correction from the land ice algorithm delta_time latitude longitude fpb_warning_flag 1 ATL06 ATBD - FPB Corrections 0 1 qualityInformation To flag that segments have potentially erroneous FPB corrections, the ATL06 algorithm sets fpb_warning_flag to 1 if full_sat_fract is greater than 0.90 (strong beams) or greater than 0.40 (weak beams) for either of the two ATL03 20 m segments that are used as inputs to each ATL06 40 m segment. Otherwise, fpb_warning_flag is set to 0. latitude longitude delta_time best_quality potential_problem 0 1 delta_time The land_ice_height group contains the primary set of derived ATL06 products. This includes geolocation, height, and standard error and quality measures for each segment. This group is sparse, meaning that parameters are provided only for pairs of segments for which at least one beam has a valid surface-height measurement. Data within this group are sparse. Data values are provided only for those ICESat-2 20m segments where at least one beam has a valid land ice height measurement. 3.402823466e+38 Height Mean meters ATL06 ATBD - Iterative Least-Squares Fitting Routine modelResult Mean surface height, not corrected for first-photon bias or pulse truncation. ../delta_time ../latitude ../longitude Signal Selection Source 1 ATL06 ATBD - Signal Selection based on ATL03 flags 0 3 qualityInformation Indicates the last algorithm attempted to select the signal for ATL06 fitting. 0=Signal selection succeeded using ATL03 detected PE; 1=Signal selection failed using ATL03 detected PE but succeeded using all flagged ATL03 PE; 2=Signal selection failed using all flagged ATL03 PE, but succeeded using the backup algorithm; 3=All signal-finding strategies failed. ../delta_time ../latitude ../longitude succeeded_using_pe succeeded_using_flagged_pe succeeded_using_backup failed 0 1 2 3 3.402823466e+38 SNR 1 ATL06 ATBD - Iterative Least Squares Fitting Routine physicalMeasurement Signal-to-noise ratio in the final refined window ../delta_time ../latitude ../longitude 3.402823466e+38 Robust Spread meters ATL06 ATBD - Iterative Least-Squares Fitting Routine referenceInformation RDE of misfit between PE heights and the along-track segment fit. ../delta_time ../latitude ../longitude counts 3.402823466e+38 Number potential segment pulses ATL06 ATBD - Top-Level Fitting Routine referenceInformation The number of pulses potentially included in the segment ../delta_time ../latitude ../longitude 3.402823466e+38 Sigma of Along Track Slope meters/meters ATL06 ATBD - Iterative Least-Squares Fitting Routine qualityInformation Propagated error in the along-track segment slope ../delta_time ../latitude ../longitude 3.402823466e+38 SNR Significance 1 ATL06 ATBD - Top-Level Fitting Routine physicalMeasurement Probability that signal-finding routine would converge to at least the observed SNR for a random-noise input. Small values indicate a small likelihood of a surface-detection blunder. ../delta_time ../latitude ../longitude 3.402823466e+38 Expected RMS misfit meters ATL06 ATBD - Iterative ground-window refinement qualityInformation Expected RMS misfit between PE heights and along-track segment fit ../delta_time ../latitude ../longitude 3.402823466e+38 Across Track Slope meters/meters ATL06 ATBD - Top-Level Fitting Routine physicalMeasurement Across track slope from segment fits to weak and strong beam; the same slope is reported for both laser beams in each pair ../delta_time ../latitude ../longitude 3.402823466e+38 Height Error meters ATL06 ATBD - Propagated Height Errors qualityInformation Propagated height error due to PE-height sampling error for height from the along-track fit, not including geolocation-induced error ../delta_time ../latitude ../longitude 3.402823466e+38 RMS Misfit meters ATL06 ATBD -Iterative Least-Squares Fitting Routine qualityInformation RMS misfit between PE heights and along- track segment fit ../delta_time ../latitude ../longitude Signal Selection Source Status 1 ATL06 ATBD - Signal Selection based on ATL03 flags 0 4 qualityInformation Indicates the status of the last signal selection algorithm attempted (see signal_selection_source). The definition of flag is different for each source and are defined in each of the signal_selection_status flags. (See Land Ice ATBD Table 3-2). ../delta_time ../latitude ../longitude 3.402823466e+38 Along Track Slope meters/meters ATL06 ATBD - Iterative Least-Squares Fitting Routine physicalMeasurement Along-track slope from along-track segment fit ../delta_time ../latitude ../longitude 2147483647 Number of Photons in Fit 1 ATL06 ATBD - Iterative Least-Squares Fitting Routine physicalMeasurement Number of PEs used in determining h_li, after editing ../delta_time ../latitude ../longitude 3.402823466e+38 Surface Window Width meters ATL06 ATBD - Top-Level Fitting Routine physicalMeasurement Width of the surface window, top to bottom ../delta_time ../latitude ../longitude The fit_statistics subgroup contains a variety of parameters that might indicate the quality of the fitted segment data. Data in this group are sparse, with dimensions matching the land_ice_height group. Data within this group are stored at the land_ice_height segment rate. 3.402823466e+38 Along Track Geolocation Error meters ATL06 ATBD - Segment Geolocation qualityInformation Along-track component of the geolocation error. ../delta_time ../latitude ../longitude 3.402823466e+38 Co-elevation degrees ATL03 referenceInformation Coelevation (CE) is direction from vertical of the laser beam as seen by an observer located at the laser ground spot. ../delta_time ../latitude ../longitude 3.402823466e+38 Radial Orbit Error meters ATL06 ATBD - Segment Geolocation qualityInformation Radial orbit component of the geolocation error. ../delta_time ../latitude ../longitude 3.402823466e+38 Segment Azimuth degrees ATL03 referenceInformation Azimuth of the pair-track, east of local north. ../delta_time ../latitude ../longitude 3.402823466e+38 Across Track Geolocation Error meters ATL06 ATBD - Segment Geolocation qualityInformation Across-track component of the geolocation error. ../delta_time ../latitude ../longitude 3.402823466e+38 Azimuth degrees ATL03 referenceInformation The direction, eastwards from north, of the laser beam vector as seen by an observer at the laser ground spot viewing toward the spacecraft (i.e., the vector from the ground to the spacecraft). ../delta_time ../latitude ../longitude 1.7976931348623157e+308 X Along Track meters ATL06 ATBD - Local Coordinate Systems referenceInformation The along-track x-coordinate of the segment, measured parallel to the RGT, measured from the ascending node of the equatorial crossing of a given RGT. ../delta_time ../latitude ../longitude 3.402823466e+38 Y Along Track meters ATL06 ATBD - Local Coordinate Systems referenceInformation Along-track y coordinate of the segment, relative to the RGT, measured along the perpendicular to the RGT, positive to the right of the RGT. ../delta_time ../latitude ../longitude The ground_track group contains parameters describing the GT and RGT for each land ice segment, as well as angular information about the beams. Data within this group are stored at the land_ice_height segment rate. DEM Source Flag 1 ATL03 0 4 referenceInformation Indicates source of the DEM height. Values: 0=None, 1=Arctic, 2=Global, 3=MSS, 4=Antarctic. ../delta_time ../latitude ../longitude none arctic global mss antarctic 0 1 2 3 4 3.402823466e+38 Geoid Free-to-Mean conversion meters ATL03 modelResult Additive value to convert geoid heights from the tide-free system to the mean-tide system. (Add to geoid to get the geoid heights in the mean-tide system.) ../delta_time ../latitude ../longitude 3.402823466e+38 DEM Height meters ATL03 referenceInformation Height of the DEM, interpolated by cubic-spline interpolation in the DEM coordinate system to the PE location. (Best available DEM value in priority of Arctic/Antarctic/Global/MSS) ../delta_time ../latitude ../longitude 3.402823466e+38 Geoid Height meters ATL03 referenceInformation Geoid height above WGS-84 reference ellipsoid (range -107 to 86m) in the tide-free system. ../delta_time ../latitude ../longitude Contains reference DEM and geoid heights. Data within this group are stored at the land_ice segment rate. 127 Multiple Scattering Warning Flag 1 ATL09 -1 5 referenceInformation Multiple Scattering warning flag. The multiple scattering warning flag (ATL09 parameter msw_flag) has values from -1 to 5 where zero means no multiple scattering and 5 the greatest. If no layers were detected, then msw_flag = 0. If blowing snow is detected and its estimated optical depth is greater than or equal to 0.5, then msw_flag = 5. If the blowing snow optical depth is less than 0.5, then msw_flag = 4. If no blowing snow is detected but there are cloud or aerosol layers detected, the msw_flag assumes values of 1 to 3 based on the height of the bottom of the lowest layer: < 1 km, msw_flag = 3; 1-3 km, msw_flag = 2; > 3km, msw_flag = 1. A value of -1 indicates that the signal to noise of the data was too low to reliably ascertain the presence of cloud or blowing snow. We expect values of -1 to occur only during daylight. ../delta_time ../latitude ../longitude cannot_determine no_layers layer_gt_3km layer_between_1_and_3_km layer_lt_1km blow_snow_od_lt_0.5 blow_snow_od_gt_0.5 -1 0 1 2 3 4 5 1 ATL09 127 Consolidated cloud flag 0 1 referenceInformation This flag is a combination of multiple flags (cloud_flag_atm, cloud_flag_asr, and bsnow_con) and takes daytime/nighttime into consideration. A value of 1 means clouds or blowing snow are likely present. A value of 0 indicates the likely absence of clouds or blowing snow. ../delta_time ../latitude ../longitude likely_clear likely_cloudy 0 1 127 Blowing Snow confidence 1 ATL09 referenceInformation Confidence flag for presence of blowing snow ../delta_time ../latitude ../longitude 3.402823466e+38 Blowing Snow Layer Top Height meters ATL09 referenceInformation Blowing snow layer top height ../delta_time ../latitude ../longitude 3.402823466e+38 Ocean Tide meters ATL03 referenceInformation Ocean Tides including diurnal and semi-diurnal (harmonic analysis), and longer period tides (dynamic and self-consistent equilibrium). ../delta_time ../latitude ../longitude 3.402823466e+38 Earth Tide meters ATL03 referenceInformation Solid earth tides in the tide-free system. ../delta_time ../latitude ../longitude 3.402823466e+38 solar azimuth degrees_east ATL03 referenceInformation The direction, eastwards from north, of the sun vector as seen by an observer at the laser ground spot. ../delta_time ../latitude ../longitude 3.402823466e+38 Effective uncorrected reflectance 1 ATL06 ATBD - Top-Level Fitting Routine referenceInformation Effective reflectance, uncorrected for atmospheric effects. ../delta_time ../latitude ../longitude 3.402823466e+38 Dynamic Atmosphere Correction meters ATL03 referenceInformation Dynamic Atmospheric Correction (DAC) includes inverted barometer (IB) effect. ../delta_time ../latitude ../longitude 3.402823466e+38 Load Tide meters ATL03 referenceInformation Load Tide - Local displacement due to Ocean Loading (-6 to 0 cm). ../delta_time ../latitude ../longitude 3.402823466e+38 Earth Tide Free-to-Mean conversion meters ATL03 referenceInformation Additive value to convert solid earth tide from the tide-free system to the mean tide system. (Add to tide_earth to get solid earth tides in the mean-tide system.) ../delta_time ../latitude ../longitude 3.402823466e+38 Blowing snow OD 1 ATL09 modelResult Optical thickness of blowing snow layer. ../delta_time ../latitude ../longitude 3.402823466e+38 Equilibrium Tide meters ATL03 referenceInformation Long period equilibrium tide self-consistent with the ocean tide model (+-0.04m). ../delta_time ../latitude ../longitude 127 Cloud Flag ATM 1 ATL09 0 10 referenceInformation Number of layers found from the backscatter profile using the DDA layer finder. ../delta_time ../latitude ../longitude 3.402823466e+38 solar elevation degrees ATL03 -90. 90. referenceInformation Solar Angle above or below the plane tangent to the ellipsoid surface at the laser spot. Positive values mean the sun is above the horizon, while negative values mean it is below the horizon. The effect of atmospheric refraction is not included. This is a low-precision value, with approximately TBD degree accuracy. ../delta_time ../latitude ../longitude 3.402823466e+38 Solid Earth Pole Tide meters ATL03 referenceInformation Solid Earth Pole Tide -Rotational deformation due to polar motion (-1.5 to 1.5 cm). ../delta_time ../latitude ../longitude 3.402823466e+38 Expected background count rate hz ATL06 ATBD - Background PE Rate referenceInformation Expected background count rate based on sun angle, surface slope, for unit surface reflectance ../delta_time ../latitude ../longitude 127 Cloud Flag ASR 1 ATL09 0 5 referenceInformation Cloud flag (probability) from apparent surface reflectance. 0=clear with high confidence; 1=clear with medium confidence; 2=clear with low confidence; 3=cloudy with low confidence; 4=cloudy with medium confidence; 5=cloudy with high confidence ../delta_time ../latitude ../longitude clear_with_high_confidence clear_with_medium_confidence clear_with_low_confidence cloudy_with_low_confidence cloudy_with_medium_confidence cloudy_with_high_confidence 0 1 2 3 4 5 3.402823466e+38 Background count rate hz ATL03 referenceInformation Background count rate, derived from the ATL03 50-shot-average, interpolated to the segment center. ../delta_time ../latitude ../longitude 3.402823466e+38 Total Neutral Atmospheric Delay meters ATL03 referenceInformation Total neutral atmosphere delay correction (wet+dry). ../delta_time ../latitude ../longitude The sun_and_clouds group contains parameters related to solar background and parameters indicative of the presence or absence of clouds. Data within this group are stored at the land_ice_height segment rate. meters 3.402823466e+38 fpb mean corr sigma ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated error in fpb_mean_corr ../delta_time ../latitude ../longitude 3.402823466e+38 fpb median corr sigma meters ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated error in fpb_med_corr ../delta_time ../latitude ../longitude 3.402823466e+38 first photon bias mean correction meters ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated first-photon bias (fpb) correction to mean segment height ../delta_time ../latitude ../longitude 3.402823466e+38 mean median residual meters ATL06 ATBD - Top-Level Fitting Routine qualityInformation Difference between uncorrected mean and median of linear fit residuals ../delta_time ../latitude ../longitude 3.402823466e+38 fpb median corr meters ATL06 ATBD - First-Photon Bias Correction qualityInformation First-photon-bias correction giving the difference between the mean segment height and the corrected median height ../delta_time ../latitude ../longitude 3.402823466e+38 tx shape mean correction meters ATL06 ATBD - Transmit-pulse shape correction qualityInformation Estimate of the difference between the mean of the full-waveform transmit-pulse and the mean of a broadened, truncated waveform consistent with the received pulse ../delta_time ../latitude ../longitude 3.402823466e+38 fpb number photons corr counts ATL06 ATBD - First-Photon Bias Correction qualityInformation Estimated window photon count after first-photon-bias correction ../delta_time ../latitude ../longitude 3.402823466e+38 tx shape median correction meters ATL06 ATBD - Transmit-pulse shape correction qualityInformation Estimate of the difference between the median of the full-waveform transmit-pulse mean and the median of a broadened, truncated waveform consistent with the received pulse ../delta_time ../latitude ../longitude The bias_correction group contains information about the estimated first-photon bias, and the transmit-pulse-shape bias. Data within this group are stored at the land_ice segment rate. Segment ID Index 1 ATL06 ATBD - Residual_histogram calculation 1 10 auxiliaryInformation Relative index of each segment_id used in the derivation of the histogram. Latitude Mean latitude degrees_north ATL06 ATBD - Residual_histogram calculation -90. 90. physicalMeasurement Mean latitude of the segments included in the histogram delta_time lon_mean Longitude Mean longitude degrees_east ATL06 ATBD - Residual_histogram calculation -180. 180. physicalMeasurement Mean longitude of the segments included in the histogram delta_time lat_mean Elapsed GPS seconds time seconds since 2018-01-01 ATL06 ATBD - Residual_histogram calculation referenceInformation Number of GPS seconds since the ATLAS SDP epoch. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. lat_mean lon_mean Bin Top Height meters ATL06 ATBD - Residual_histogram calculation physicalMeasurement Height of the top of each histogram bin, listed in increasing order. The bottom of each bin is equal to the top of the next- lowest bin. delta_time lat_mean lon_mean 2147483647 Bin Counts counts ATL06 ATBD - Residual_histogram calculation physicalMeasurement Residual count falling with each histogram bin. The top height of each histogram bin may be found in the bin_top_h dataset. delta_time lat_mean lon_mean Number of Histogram Segment Pulses counts ATL06 ATBD - Residual_histogram calculation physicalMeasurement Number of pulses potentially included in the histogram (pulses are counted if they are in the central 20 m of each segment, even if no PE from the pulse are selected). delta_time lat_mean lon_mean Along Track Coordinate Mean 1 ATL06 ATBD - Residual_histogram calculation physicalMeasurement Mean along-track coordinate of the segments included in the histogram. delta_time lat_mean lon_mean Segment ID List 1 ATL06 ATBD - Residual_histogram calculation referenceInformation Segments ids included in each column of the histogram delta_time lat_mean lon_mean 2147483647 Expected background PEs 1 ATL06 ATBD - Residual_histogram calculation physicalMeasurement Number of background PE expected for each vertical meter of the histogram based on the observed background rate (bckgrd). delta_time lat_mean lon_mean delta_time Data within this group are stored at the 200-meter along-track rate. This group contains histograms of the residuals between PE heights and the least-squares fit segment heights, at 200-meter along-track resolution. Latitude degrees_north ATL06 ATBD - segment_quality group -90. 90. referenceInformation Latitude of the reference segment location on the RPT delta_time reference_pt_lon latitude Longitude degrees_east ATL06 ATBD - segment_quality group -180. 180. referenceInformation Longitude of the reference segment location on the RPT delta_time reference_pt_lat longitude Elapsed GPS seconds time seconds since 2018-01-01 ATL06 ATBD - segment_quality group referenceInformation Number of GPS seconds since the ATLAS SDP epoch. The ATLAS Standard Data Products (SDP) epoch offset is defined within /ancillary_data/atlas_sdp_gps_epoch as the number of GPS seconds between the GPS epoch (1980-01-06T00:00:00.000000Z UTC) and the ATLAS SDP epoch. By adding the offset contained within atlas_sdp_gps_epoch to delta time parameters, the time in gps_seconds relative to the GPS epoch can be computed. reference_pt_lat reference_pt_lon Land Ice Height Index 1 ATL06 ATBD - segment_quality group referenceInformation For those segments that have adequate signal strength, this parameter gives the record for the pair within the other groups in the granule. delta_time reference_pt_lat reference_pt_lon Signal Selection Source 1 ATL06 ATBD - Signal selection base on ATL03 flags 0 3 qualityInformation Indicates the last algorithm attempted to select the signal for ATL06 fitting. 0=Signal selection succeeded using ATL03 detected PE; 1=Signal selection failed using ATL03 detected PE but succeeded using all flagged ATL03 PE; 3=All signal-finding strategies failed. delta_time reference_pt_lat reference_pt_lon succeeded_using_pe succeeded_using_flagged_pe failed 0 1 3 Reference Point, m 1 ATL06 ATBD - segment_quality group referenceInformation Segment number corresponding to the second of two ATL03 segments in the ATL06 segment, counted from the RGT equator crossing delta_time reference_pt_lat reference_pt_lon delta_time Data within this group are stored at the ICESat-2 20m segment rate. The segment_quality group contains a dense record (i.e. for every possible segment in the granule) of the success or failure of the surface-finding strategies, and gives the locations of the reference points on the RPTs. For segments with adequate data quality (i.e. with more than 10 PE) it also contains offsets into the data structures for the other groups that allow each segment to be efficiently located within the file. 1 Signal Selection Status Flag ATL06 ATBD - Signal selection base on ATL03 flags 0 3 qualityInformation Indicates confidence of the signal-selection algorithm using all ATL03-flagged PEs. 0=Signal selection succeeded using all ATL03-flagged PEs (or algorithm not attempted); 1=Signal selection using all ATL03-flagged PEs failed the 20-meter-spread test; 2=Signal selection using all ATL03-flagged PEs failed the 10-photon-count test; 3=Signal selection using all ATL03-flagged PEs failed both tests ../delta_time ../reference_pt_lat ../reference_pt_lon succeeded failed_20 failed_10 failed_both 0 1 2 3 1 Signal Selection Confident Flag ATL06 ATBD - Signal selection base on ATL03 flags 0 3 qualityInformation Indicates confidence of the signal-selection algorithm using low or better PEs. 0=Signal selection succeeded using ATL03 low-or-better confidence PEs; 1=Signal selection using ATL03 low-or-better confidence PEs failed the 20-meter-spread test; 2=Signal selection using ATL03 low-or-better confidence PEs failed the 10-photon-count test; 3=Signal selection using ATL03 low-or-better confidence PEs failed both tests ../delta_time ../reference_pt_lat ../reference_pt_lon succeeded failed_20 failed_10 failed_both 0 1 2 3 The signal selection status subgroup contains the success or failure for each surface-finding strategies Data within this group are stored at the ICESat-2 20m segment rate.