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GRACE
 
MyRetrieval | Product Browser | Product Description | Document List | Newsletter | Documents | Software
 

GRACE Project

The twin GRACE satellites were launched on March 17, 2002. Since that time, the GRACE Science Data System (SDS) has produced and distributed estimates of the Earth gravity field on an ongoing basis. These estimates, in conjunction with other data and models, have provided observations of terrestrial water storage changes, ice-mass variations, ocean bottom pressure changes and sea-level variations. This portal, together with PODAAC, is responsible for the distribution of the data and documentation for the GRACE project. A brief overview of the science data flow is given at http://www.csr.utexas.edu/grace/asdp.html and more details are provided in the project documents. A complete list of relevant project documents has been made available (click here). Users are strongly urged to read these documents before proceeding with data analysis.
 
GRACE Project GFZ Homepage  

GRACE Links

 GRACE Project GFZ Homepage
 GRACE Project UTCSR Homepage
 GRACE Project JPL Homepage

 PO.DAAC Archive

 
GRACE is a joint partnership between the National Aeronautics and Space Administration (NASA) in the United States and Deutsches Zentrum Fuer Luft und Raumfahrt (DLR) in Germany. Prof. Byron Tapley of The University of Texas Center for Space Research (UTCSR) is the Principal Investigator (PI), and Dr.-Ing. Frank Flechtner of the GeoForschungsZentrum (GFZ) Potsdam is the Co-Principal Investigator (Co-PI).

News

  • May 20, 2014: The AOD1B Product Description Document (see Documents Section following the link on the left) has been updated to Version 4.2. This version includes editorial changes to chapters 3.6 and 3.7 to better describe the correct usage of various GAx Level-2 products.

  • April 7, 2014: GFZ has generated and delivered GAE and GAF Level-2 products in terms of Technical Notes TN08 and TN09. The coefficients may be used to correct discontinuities in atmospheric pressure data on January 29, 2006 and January 26, 2010, respectively. Details are described in chapter 3.7 of the AOD1B Product Description Document Version 4.1 which is, as the Technical Notes, available in the ISDC Documents Section (follow the link on the left).

  • December 17, 2013: GFZ has generated and delivered a reprocessed RL05 time series called RL05a for January 2003 till July 2013. All RL05a Level-2 products are available at ISDC and PO.DAAC. When making your request at the ISDC retrieval pages, the RL05a GSM products can be found under the same revision number (“5”) as the RL05 GSM products and are distinguishable by the string “_005a” (instead of “_0005”) at the end of the product name. At the PO.DAAC archive, the RL05a GSM products can be found in the directory “allData/grace/L2/GFZ/RL05”. Note that GAx products are not affected and need not to be replaced! Further details are described in the “Release notes for GFZ RL05 GRACE L2 products”, also available at both archives. For the missing months in 2002 (soon to be delivered) and all upcoming months starting with October 2013, only RL05a products will be generated, i.e. the GFZ RL05 time-series will not be continued.

  • March 17, 2012: At 10:46:50.875 UTC, the orbiting phase of the twin GRACE satellites has completed 10 years in orbit. In recognition of this anniversary, the project will release over the next few weeks a new gravity solution based on a complete and detailed reanalysis of the GRACE mission data set. The solution, designated the GRACE RL05 Solution, is the result of reprocessing the 10 year data set, taking advantage of improvements in modeling and data quality and adding additional data from the extended mission.
    The improved accuracy and extended data length on which the solution is based will allow more complete studies of seasonal and decadal signals involved in climate change processes. In addition to the improvements associated with an additional iteration of the mission data, the RL05 solution benefits from a significantly improved AOD1B background model for the correction of high frequency atmosphere and ocean mass variations, improved ocean tide models and improvements in the Level 1B data.
    To accommodate investigations that will be presented at the EGU in April, an initial release, covering a six year span (2005 till 2010) from the GRACE GFZ RL05 Level 2 Solution, has been placed in the archive by the anniversary epoch including the AOD1B RL05 Model, covering the period from July 2002 through December 2011. The Level 1b version 2 data and remaining Level 2 gravity solutions, along with updated documentation, will be placed in the archives during the following weeks. Further details on the RL05 release will be found in the monthly news letter as they develop.

  • Release 04 Level-2 products and documentation are still available. For details see below.

  • The GRACE Science System Monthly Report April 2014 is available now.

  • The next GRACE Science Team Meeting together with the DFG SPP1257 Final Colloquium will be held on September 17-19 (Mon-Wed), 2012 at GFZ Potsdam. Further information can be found here.

  • The GSTM 2011 and older proceedings (collection of presentations, posters and videos) are available online, at http://www.csr.utexas.edu/grace/GSTM/2011/proceedings.html and (for 2010) at http://www.gfz-potsdam.de/portal/gfz/Neuestes/Veranstaltungen/Tagungen+und+Konferenzen/2010-Conferences/GSTM-2010/proceedings

  • The following acknowledgement shall be added to any new GRACE related publication (paper, poster etc.): We would like to thank the German Space Operations Center (GSOC) of the German Aerospace Center (DLR) for providing continuously and nearly 100% of the raw telemetry data of the twin GRACE satellites.

  • Since January 2011 GRACE ground segment operations are co-funded, besides significant GFZ and DLR R&D contributions, by ESA. Therefore, ESA is supporting the continuation of the measurements of mass redistribution in the Earth system.

  • A Guide To Available Data (Januar 26, 2009)
    The newest Level-1B and Level-2 products are made available at approximately monthly intervals.

    Level-1B data refer to the collection of ranging, accelerometry, attitude and related ancillary data. All products have been created by the NASA/JPL element of the SDS. At present, data prior to Jan 1, 2005 are labeled Release-00, and all the data, thereafter, are labeled Release-01. Please see NOTE-1 below for special remarks on AOD1B products from June 2006 to Sep 2007. Please see NOTE-4 below for special remarks on Level-1 read software suite.

    Level-2 data refer to monthly estimates of spherical harmonic coefficients of the Earth gravity field. Please see NOTE-3 below for special remarks on re-processed Level-2 products from June 2006 through September 2007. Data products from all three centers are available, as follows:

  • Center Release Span Remarks
    UTCSR (operational) 04 Release Notes
    All months from Apr '02 to present; except Jun-Jul '02 and Jun '03
    RL-01 Series is now discontinued. See NOTE-2 about July 2007 field.
    GFZ (operational) 04Release Notes
    All months from Aug '02 to present; except Sep '02, Dec '02, Jan & Jun '03, Jan '04 The RL-03 fields are not available past Jan 2007. See NOTE 1 about Jun '06 till Sep '07 fields.
    JPL (validation) 04Release Notes All months from Apr '02 to Dec '07, except Jun '03 and Jan '04

    NOTE-1 (Feb 12, 2008): If you downloaded AOD1B RL04 products for the period June 23, 2006 until September 20, 2007 prior to November 30, 2007 please be sure to download these files again because the oceanic contributions to these products are wrong (by mistake twice reduction of atmospheric S2 tide from surface pressure data used to force the OMCT model). Please also see NOTE-3 below for impact on Level-2 GSM products. The correct AOD1B RL04 products for this range of dates have to have a product creation date later than November 2007 within the header information, e.g.

    PRODUCT CREATE START TIME(UTC): 2007-11-08 10:51:24.000
    PRODUCT CREATE END TIME(UTC) : 2007-11-08 13:19:25.000


    NOTE-2 (Nov 20, 2007): If you downloaded CSR-RL04 solution for July 2007, labeled

    GSM-2_2007182-2007212_0028_UTCSR_0060_0004

    before Nov 19, 2007, please be sure to download this file again. The correct file should have the comment line:

    CMMNT Updated GSM file based on run n28b (updated on 15 November 2007)


    NOTE-3 (Feb 29, 2008): The influence of the error in AOD1B product, described in NOTE-1, on the Level-2 gravity field products, though small, is not negligible. Therefore all GSM-products between June 2006 and September 2007 have been reprocessed with the correct AOD1B. Click Here for a summary of the principal changes in the Level-2 fields in this duration.


    The previously released Level-2 products for this span have been replaced with the re-processed fields in the archives. Specifics for each SDS center are described within the Release Notes, and are summarized here:

    - UTCSR: The GSM, GAC and GAD product files between Jun 2006 and Sep 2007 have been replaced. The new files are distinguished by the comment line:
    CMMNT Solution was reprocessed using corrected AOD product


    - GFZ: The GSM product files between Jun 2006 and Sep 2007 have been replaced. The influence of the wrong AOD1B products on the GAA/B/C/D products is negligible, thus these products are only re-distributed if the number of days used to create GSM products has changed during reprocessing. Further details are given in the release notes. The new files are distinguished by the comment line:
    CMMNT Generated with correct AOD1B RL04 product (see SDS Newsletter October 2007)


    - JPL: The new GSM and GAx product files will be made available after re-processing.

    Please review this page often, as it contains timely updates and information regarding the latest product releases.

    NOTE-4 (Apr 24, 2008): The GPS satellite PRN32 (SVN23) was set "healthy" as of Feb 26, 2008.Tracking of this satellite was therefore enabled on GRACE and the Level-1B data since Feb 26, 2008 contains GPS tracking data from PRN32. Consequently, the software to convert from GRACE GPS1x format to Rinex format has been updated to handle the presence of data from PRN32. Users should download and re-install the entire Level-1 Read software suite (RELEASE_2008-03-20) from the GRACE archives. This software is backwards compatible and can process all mission data.

    The GRACE scientific products are divided in two catagories:
    - Orbit & Gravity Field Products
    - Atmosphere & Ionosphere Products.

    Within these groups the products are distinguished by different product types which are descripted by a specific nomenclature:
    SS - CC - LL - PPPPPP where
    SS = Satellite mission ('GA' for GRACE-A,'GB' for GRACE-B or 'GX' for twin GRACE related products)
    CC = product Category ('OG'  for orbit & gravity field products or 'AI'  for atmosphere & ionosphere products)
    LL = product Level ('_0' for level-0, '1A' or '1B' for level-1 or '_2'  for level-2 Products)
    PPPPPP = unique Product identifier (e.g. 'DMPSCI' for dumped science data or  'ACCDAT' for accelerometer data)

    The product filename which is provided to the user is supplemented by 3 additional information:
    SS - CC - LL - PPPPPP + FFF - OOOOOO.EXT where
    FFF = processing Facility ('GFZ', 'CSR' or 'JPL')
    OOOOOO = Original (processing facility) filename of the product
    EXT = Extension ('asc' for ASCII data, 'dat' for binary data, 'gz' for gnuzipped data or 'dif' for DIF meta information)

    Each product consists of one couple of files, the data file in a product specific format and the metadata file in the DIF format, which describes the content of the data file. The names of both files are identically except for the file name extension behind the last "." within the file name. Please refer also to the Online available documents concerning the GRACE Product release for further processing information.

    Example for a GRACE-A, Level-1B accelerometer data product of August 10, 2003 which has been produced by JPL:
    GA-OG-1B_ACCDAT+JPL-ACC1B_2003-08-10_A_00.dat (Data file)
    GA-OG-1B_ACCDAT+JPL-ACC1B_2003-08-10_A_00.dif (Metadata file)

    Detailed descriptions of the different product types are available in Product Description.

     
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