For a list of known issues with this product, see the Known Issues document under the Technical References tab.
Selected granules for ATL03 and associated products (ATL04, ATL06, ATL07, ATL08, ATL09, ATL10, ATL12, ATL13) have been recalled and will be released at a later time. For a list of recalled data, see the 'Retracted Data File List' document under Technical References.
Data Set ID:

ATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics, Version 3

This data set (ATL09) contains calibrated, attenuated backscatter profiles, layer integrated attenuated backscatter, and other parameters including cloud layer height and atmospheric characteristics obtained from the data. The data were acquired by the Advanced Topographic Laser Altimeter System (ATLAS) instrument on board the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) observatory.

This is the most recent version of these data.

Version Summary:

Changes for this version include:

  • A new parameter was added to the equation used to compute blowing snow. The algorithm detects blowing snow at two rates -- high (25 Hz) and low (1 Hz) -- however, the optimal threshold for low rate detection was found to be different (lower) than for high rate detection. The new parameter (ancillary_data/atmosphere/lr_bsnow_fac) adjusts the low rate detection threshold and improves retrievals. The new parameter's nominal value of 0.5 is adjustable.
  • Low-rate blowing snow height (profile_[x]/low_rate/bsnow_h) is now computed as defined in the ATBD for ATL04 (section 4.5.1 | Blowing Snow layer Height).
  • The value for the high rate blowing snow threshold constant (ancillary_data/atmosphere/bs_thresh_scale) was changed from 10.0 to 20.0 to reduce blowing snow detections.
  • A new parameter for blowing snow intensity (profile_[x]/high_rate/bsnow_intensity) was added to the product; it is defined as the average scattering ratio within the blowing snow layer multiplied by the 10 m level wind speed.
  • ATL09 was updated to accommodate the new pass-through constant (alpha) added to ATL04.
  • The single scaling constant phi, used to define a threshold in the apparent surface reflectance (ASR) cloud detection algorithm, was replaced by two constants, phi_land and phi_ocean. These new scaling parameters allow for different thresholds over land and ocean to address analyses that indicate the algorithm was reporting too many clouds over land and too few over ocean.
  • Areas masked out in ATL04 due to dense clouds were not being properly masked out in ATL09. This bug was corrected.
  • The ancillary_data/atmosphere/cloud_det_layer_thick parameter was no longer needed and removed.

COMPREHENSIVE Level of Service

Data: Data integrity and usability verified; data customization services available for select data

Documentation: Key metadata and comprehensive user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools and data customization services

See All Level of Service Details

Data Format(s):
  • HDF5
Spatial Coverage:
N: 90, 
S: -90, 
E: 180, 
W: -180
Spatial Resolution:
  • 280 m
Temporal Coverage:
  • 13 October 2018
Temporal Resolution91 dayMetadata XML:View Metadata Record
Data Contributor(s):Steve Palm, Yeukui Yang, Ute Herzfeld, David Hancock, Kristine Barbieri, et al

Geographic Coverage

Other Access Options

Other Access Options


As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Palm, S. P., Y. Yang, U. C. Herzfeld, D. Hancock, K. A. Barbieri, J. Wimert, and the ICESat-2 Science Team. 2020. ATLAS/ICESat-2 L3A Calibrated Backscatter Profiles and Atmospheric Layer Characteristics, Version 3. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].

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How To

Programmatic Data Access Guide
Data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) can be accessed directly from our HTTPS file system or through our Application Programming Interface (API). Our API offers you the ability to order data using specific temporal and spatial filters... read more
ICESat, IceBridge, and ICESat-2: A primer on data access across the three missions
This guide will provide an overview of the altimetry measurements and data sets across the missions, as well as a guide for accessing the data through NASA Earthdata Search and programmatically using an Application Programming Interface (API). Overview  The NASA ICESat, Operation IceBridge,... read more
Explore, Access, and Customize ICESat-2 data at the NASA NSIDC DAAC
This webinar introduces the ICESat-2 mission and shows you how to explore, access and customize ICESat-2 data with the OpenAltimetry application, using NSIDC DAAC tools, and shows you how to subset, reformat and analyze the data using Python. This webinar was originally presented on July 23, 2019... read more
Search, order, and customize NSIDC DAAC data with NASA Earthdata Search
NASA Earthdata Search is a map-based interface where a user can search for Earth science data, filter results based on spatial and temporal constraints, and order data with customizations including re-formatting, re-projecting, and spatial and parameter subsetting. Thousands of Earth science data... read more
Filter and order from a data set web page
Many NSIDC data set web pages provide the ability to search and filter data with spatial and temporal contstraints using a map-based interface. This article outlines how to order NSIDC DAAC data using advanced searching and filtering.  Step 1: Go to a data set web page This article will use the... read more


What subsetting and reformatting services are available for ICESat-2 data?
The following table describes the subsetting and reformatting services that are currently available for ICESat-2 data via the NASA Earthdata Search tool, along with ... read more
How do I convert an HDF5/HDF-EOS5 file into binary format?
To convert HDF5 files into binary format you will need to use the h5dump utility, which is part of the HDF5 distribution available from the HDF Group. How you install HDF5 depends on your operating system. Full instructions for installing and using h5dump on Mac/Unix and... read more