You are here

GRACE

Launched March 17, 2002, tGravity Recovery and Climate Experiment (GRACE) twin satelliteshe Gravity Recovery and Climate Experiment (GRACE) twin satellites made detailed measurements of Earth's gravity field and improved investigations about Earth's water reservoirs, over land, ice and oceans. GRACE was a collaboration of the US and German space agencies (NASA and DLR). The key partners were the University of Texas Center for Space Research (CSR), the GeoForschungsZentrum (GFZ) Potsdam, and the Jet Propulsion Laboratory (JPL).
 
GRACE measured gravity by relating it to the distance between the twin satellites.  When there was an increase in gravity ahead of the pair, the front satellite sped up and the distance between the pair increased. When there was an increase in gravity between the pair their distance decreased. The opposite occurred when there was decreased gravity ahead of, or between the satellite pair. The satellites were separated by 220 km and could detect changes smaller than a micrometer per second in relative velocity.  These measurements, in conjunction with other data and models, provided observations of terrestrial water storage changes, ice-mass variations, ocean bottom pressure changes and sea-level variations.
 
GRACE ended its science mission in October 12, 2017.

Instruments
  • ACC – Super STAR Accelerometer is in both satellites and measures non-gravitational forces acting on the satellites, such as solar radiation pressure, air drag and attitude control activator operation.
  • GPS – Black Jack Global Positioning System Receiver is used for navigation and collects atmospheric occultation data.
  • SCA – Star Camera Assembly provides orientation references for both satellites.
  • KBR – K-Band Ranging System uses K and Ka-band to measure the separation change between the two satellites.
  • LRR – Laser Retro Reflector provides orbit verification from the terrestrial Laser tracking network.  It is also used for precise orbit determination.
Guide to Available Data

(December 2, 2014)  
Distribution of Release 05 (RL05) began March 2012.  Errors in the AOD1B de-aliasing fields from 26 June 2013 to 31 July 2014 were corrected, AOD1B data in the archive were replaced on 3 October 2014.  The CSR Level 2 RL05 fields from June 2013 to June 2014 based on these erroneous de-aliasing fields were replaced on 6 October 2014.  The GFZ Level 2 RL05 fields were replaced on 26 September 2014.  If you have downloaded any of these products before these dates, please download the replacement files.
 
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. 
 
Level-2 data refer to monthly estimates of spherical harmonic coefficients of the Earth gravity field. 

Data products from all three centers are available, as follows:

Center Release Span Remarks
UTCSR
(Operational)
05
Release
Notes
All months from 4/2002 to present

Due to errors in the AOD1B de-aliasing fields from 26 June 2013 to 31 July 2014, these AOD1B fields have been corrected and the CSR level 2 data reprocessed.  If you downloaded any Release 05 CSR data product for June 2013 through June 2014 before 6 October 2014, please download those files again.

GFZ
(Operational)
05a
Release Notes
All months from 4/2002 to present

Due to errors in the AOD1B de-aliasing fields from 26 June 2013 to 31 July 2014, these AOD1B fields have been corrected and the GFZ level 2 data reprocessed.  If you downloaded any Release 05 GFZ data product for June 2013 through June 2014 before 26 September 2014, please download those files again.

JPL
(Validation)
05.1
Release Notes
All months from 4/2002 to present Due to errors in the AOD1B de-aliasing fields from 26 June 2013 to 31 July 2014, these AOD1B fields have been corrected but the JPL level 2 data have not been reprocessed.  If you downloaded any Release 05 JPL data product for June 2013 through June 2014, please be aware that those data have known problems and have been replaced by JPL Release 05.1, which uses the corrected de-aliasing fields.

If you require gridded/mapped GRACE data or do not want to generate the gravity fields from the spherical harmonics please visit the GRACE Tellus website at http://grace.jpl.nasa.gov/