Design For A Permanent Earth Gravitational Observatory
Abstract
Our team has developed, under NASA sponsorship, a baseline design for a permanent Earth Gravitational Observatory (EGO) comprising clusters of low-cost nanosatellites. Building on modern cubesat technology we have introduced innovations that will improve gravity mapping at a fraction of the cost of more traditional, larger-platform missions. The power of EGO arises from its cluster architecture in which cells mutually exchange high-frequency radio crosslinks. With traditional gravity satellite pairs, 10 cells would yield 5 pairs, and thus 5 concurrent links. A 10-cell EGO cluster yields 45 independent links spanning baselines from 200 to 1,000 km. Two five-cell clusters in complementary orbit planes would yield 20 total links.
The baseline spacecraft design features a long-lived propulsion system with high ISP, capable of many orbit re-boosts. Analysis shows that EGO cells can maintain an altitude of 240-280 km for on the order of 10 years, improving spatial resolution compared with higher altitude systems. The cubesat/nanosat revolution now allows cells to be produced in quantity at low cost. The ordinary mission operations budget would provide for the replenishment of cells as needed to maintain the system indefinitely. As costs decline we expect to expand to multiple orbit planes. Compared with current single-pair designs employing radio crosslinks, EGO offers: - Greater single-link precision resulting from a 60 GHz top frequency and wider frequency separation - Reduction of random measurement error through multi-link averaging - Physics-based reduction of sensitivity to certain systematic errors from internal closure loops - Improved spatial and temporal resolution - High inherent system redundancy - Low overall cost Simulation studies show that a single-orbit EGO system of nine cells can surpass traditional single-pair performance in the accuracy of geoid recovery by about a factor of 50. When combined with the current GRACE-FO mission, a 3-cell EGO system in a complementary orbit can offer a large performance boost at a small incremental cost. We have completed an end-to-end system design and hope, with community support, to launch a pilot system in the next few years.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G13C0556Y
- Keywords:
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- 1217 Time variable gravity;
- GEODESY AND GRAVITYDE: 1218 Mass balance;
- GEODESY AND GRAVITYDE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions;
- GEODESY AND GRAVITYDE: 1240 Satellite geodesy: results;
- GEODESY AND GRAVITY