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| DOI | 10.5067/GFL20-MJ060 |
| Short Name | GRACEFO_L2_JPL_MONTHLY_0060 |
| Description | FOR EXPERT USE ONLY. This dataset contains estimates of the total month-by-month geopotential of the Earth, derived from the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission measurements, produced by the NASA Jet Propulsion Laboratory (JPL). The data are provided in spherical harmonic coefficients, averaged over approximately a month. The primary objective of the GRACE-FO mission is to obtain accurate estimates of the mean and time-variable components of the gravity field and corresponding Earth mass change variations, such as from polar ice sheets and mountain glaciers; total water storage on land (from groundwater changes in deep aquifers to changes in soil moisture and surface water); changes in deep ocean currents; and changes within the solid Earth itself, such as postglacial rebound and the impact of major earthquakes. This objective is achieved by making continuous measurements of the change in distance between twin spacecraft, co-orbiting in about 490 km altitude, near circular, polar orbit, spaced approximately 220+/-50 km apart, using a microwave ranging system. In addition to these inter-satellite range changes, the non-gravitational forces acting on each satellite are measured using a high accuracy electrostatic accelerometer. The satellite orientation and position (and timing) are precisely measured using star cameras (with three heads per satellite) and a GPS receiver. Spatial and temporal variations in the gravity field perturb the orbits (or trajectories) of the twin spacecraft differently. These differences lead to minute changes (on the order of tens of micrometers per second) in the distance between the spacecraft as they orbit the Earth. This change in distance (or range rate) is reflected in the time-of-flight of microwave signals transmitted and received nearly simultaneously between the two spacecraft. The change in this time of fight is continuously measured by tracking the phase of the microwave carrier signals. The so called dual-one-way range change measurements can be reconstructed from these phase measurements. This range change (or its numerically derived derivatives), along with other mission and ancillary data, is subsequently analyzed to extract the geopotential coefficients of an Earth gravity field model, typically on a per-month basis. |
| Version | 6 |
| Dataset Type | OPEN |
| Measurement | SOLID EARTH > GRAVITY/GRAVITATIONAL FIELD > GRAVITY |
| Processing Level | 2 |
| Coverage | Region: Global Northernmost Latitude: 89 degrees Southernmost Latitude: -89 degrees Westernmost Longitude: -180 degrees Easternmost Longitude: 180 degrees Time Span: 2018-May-22 to Present Granule Time Span: 2018-Jun-01 to 2020-May-31 |
| Resolution | Spatial Resolution: 500 km (Along) x 500 km (Across) |
| Projection | Type: Spherical Detail: N/A Ellipsoid: WGS 84 |
| Latency | hours |
| Swath Width | -1 km |
| Sample Frequency | - |
| Temporal Repeat (Nominal) | 1 Month |
| Temporal Repeat (Min) | - |
| Temporal Repeat (Max) | - |
| Platform/Sensor | GRACE-FO / Platform Name: Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) Orbit Period: -1 minutes Inclination Angle: 89 degrees Ascending Node: 1970-Jan-01 00:00:00 GRACE-FO ACC SENSOR Name: GRACE-FO SuperSTAR Accelerometer (GRACE-FO ACC) Swath Width: -1 km Description: The accelerometer, located at the center of mass of each satellite, measures all non-gravitational forces acting on each satellite. These forces include air drag, solar radiation pressure, and attitude control activator operation. GRACE-FO / Platform Name: Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) Orbit Period: -1 minutes Inclination Angle: 89 degrees Ascending Node: 1970-Jan-01 00:00:00 GRACE-FO KBR SENSOR Name: GRACE-FO K-Band Ranging System (GRACE-FO KBR) Swath Width: -1 km Description: This instrument precisely measures the changes in the separation between the two GRACE satellites using phase tracking of K- and Ka-band signals sent between the two satellites GRACE-FO / Platform Name: Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) Orbit Period: -1 minutes Inclination Angle: 89 degrees Ascending Node: 1970-Jan-01 00:00:00 GRACE-FO LRI SENSOR Name: GRACE-FO Laser Ranging Interferometer (GRACE-FO LRI) Swath Width: -1 km Description: The laser ranging interferometer (LRI) on board GRACE-FO measures the distance between the two satellites GRACE-FO / Platform Name: Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) Orbit Period: -1 minutes Inclination Angle: 89 degrees Ascending Node: 1970-Jan-01 00:00:00 GRACE-FO SCA SENSOR Name: GRACE-FO Star Camera Assembly (GRACE-FO SCA) Swath Width: -1 km Description: The SCA (Star Camera Assembly) consists of three temperature controlled CCD star cameras mounted to the accelerometer, along with the respective baffle assemblies. The STR delivers its video frames to the OBC, which then computes the attitude quaternions. The OBC also acts as the power and command/control interface to the STR. Once switched on and initialized, the STR proceeds with automatic coarse attitude acquisition and then on to fine attitude derivation. |
| Project | GRACE Follow-On (GRACE-FO) |
| Data Provider | Creator: GRACE-FO Release Place: JPL Release Date: 2019-Jun-10 Resource: https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/ |
| Keyword(s) | gravity, GRACEFO, GFO, RL06, JPL |
| Persistent ID | PODAAC-GFL20-MJ060 |
Questions related to this dataset? Contact podaac@podaac.jpl.nasa.gov
| PO.DAAC DRIVE | https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/L2/JPL/RL06 |
| Format (Compression) | ASCII (GZIP) |
| Web Service | https://podaac.jpl.nasa.gov/ws/search/granule/?datasetId=PODAAC-GFL20-MJ060 (Search Granule) |
| User's Guide | |
| L2-UserHandbook | https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/GRACE-FO_L2-UserHandbook.pdf Level-2 Gravity Field Product User Handbook |
| Project Materials | |
| Release Notes | https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/GRACE-FO_L2-ReleaseNotes_JPL_RL06.pdf GRACE-FO JPL Release Notes |
| ProStds Doc | https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/GRACE-FO_L2-JPL_ProcStds_v1.0.pdf GRACE-FO JPL Level-2 Processing Standards Document |
| Additional Sites | |
| GRACE-FO Project | https://gracefo.jpl.nasa.gov/ GRACE-FO Project |
| GRACE-FO Info | https://podaac.jpl.nasa.gov/GRACE-FO GRACE-FO Mission |
| Citation | GRACE-FO. 2019. GRACE-FO Level-2 Monthly Geopotential Spherical Harmonics JPL Release 6.0 (RL06). Ver. 6. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/GFL20-MJ060.
For more information see Data Citations and Acknowledgments.
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| Journal Reference | Dah-Ning Yuan, 2019, GRACE Follow-On Level-2 Gravity Field Product User Handbook. Jet Propulsion Laboratory, JPL D-103922. https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/GRACE-FO_L2-UserHandbook_v1.0.pdf | |||||||
