Abstract
Thanks to the unprecedented success of Gravity Recovery and Climate Experiment (GRACE), its successive mission GRACE Follow-On (GFO) has been in orbit since May 2018 to continue measuring the Earth’s mass transport. In order to possibly enhance GFO in terms of mass transport estimates, four orbit configurations of future polar-type gravity mission (FPG) (with the same payload accuracy and orbit parameters as GRACE, but differing in orbit inclination) are investigated by full-scale simulations in both standalone and jointly with GFO. The results demonstrate that the retrograde orbit modes used in FPG are generally superior to prograde in terms of gravity field estimation in the case of a joint GFO configuration. Considering the FPG’s independent capability, the orbit configurations with 89- and 91-degree inclinations (namely FPG-89 and FPG-91) are further analyzed by joint GFO monthly gravity field models over the period of one-year. Our analyses show that the FPG-91 basically outperforms the FPG-89 in mass change estimates, especially at the medium- and low-latitude regions. Compared to GFO & FPG-89, about 22% noise reduction over the ocean area and 17% over land areas are achieved by the GFO & FPG-91 combined model. Therefore, the FPG-91 is worthy to be recommended for the further orbit design of FPGs.
Highlights
The Earth is undergoing complicated and continuous mass transport [1]
We investigate the orbit configurations for Future Polar-type Gravity missions (FPG) with emphasis on orbit inclination selection via full-scale simulations based on both standalone and joint GRACE Follow-On (GFO) constellations
Four monthly models in January 2006 under future polar-type gravity mission (FPG) configurations with varying inclinations (87, 89, 91, and 93 degrees) show similar performances except that FPG-87 and FPG-93 suffer from relatively serious deficiencies in the zonal Spherical Harmonic Coefficients (SHC) estimation
Summary
The Earth is undergoing complicated and continuous mass transport [1]. To better quantify the mass changes, the Gravity Recovery and Climate Experiment (GRACE) mission was launched in 2002, which consists of the twin satellites flying in the same near-polar orbit at about 500-km altitude and separated by 220 km [2]. Based on the precise data collected by the above sensors, many scientific institutions have produced high-quality static and temporal gravity field models [7,8,9,10,11], which are successfully adopted for quantitative researches concerning the Earth’s mass changes, such as global mean sea-level variations [12,13], continental water balance [14,15], and the Tibetan Plateau and Antarctic regional ice losses [16,17] In view of such a great success achieved by GRACE in terms of the Earth’s mass change exploration, its successor GRACE Follow-On (GFO) was launched on 22 May 2018 to continue providing the geodetic observation records [18,19]. The dominant barrier to further improvement on gravity field determination by GFO is the temporal aliasing issue, which is more intractable than other limiting factors in the GFO error budget [18,21]
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