A simulation study of effects of GRACE orbit decay on the gravity field recovery

Abstract

The effects of satellite ground track changes of GRACE on monthly gravity field recoveries are investigated. In the case of a gravity field recovery using a relatively short period of a month or so, the variation of ground tracks affects the precision of the gravity field solutions. It is a serious problem when the solutions are employed for detecting temporal gravity changes which are almost at their detection limits. In this study, the recoveries of four-weekly gravity fields are simulated and the relation between the recovery precision and the ground track is investigated. The result shows that the GRACE ground track of the year 2003 was in good condition for four-week gravity field recovery, but it will sometimes appear as worse cases as the orbit altitude decays. In those cases, the global standard deviations of geoid height errors will be about one order worse than the best case. From our simulation, ground tracks of around altitudes of 473, 448, 399, 350 and 337 km give insufficient spatial resolutions, even for gravity field recovery up to degree 30.

Landwater variation in four major river basins of the Indochina peninsula as revealed by GRACE

“…Figure 9 shows the derived mass variation in the combined area of the four rivers based on the three new data sets. Yamamoto et al, 2005). In this period, the resolution of the GRACE monthly field is significantly degraded to only about degree 30 (Wagner et al, 2006).…”

An improved sampling rule for mapping geopotential functions of a planet from a near polar orbit

“…On the other hand, they can cause a degradation of the overall performance due to an insufficient spatial sampling. The influence of the ground track on the quality of the solution attracted first attention for the low-low satellite-to-satellite tracking mission GRACE and has been investigated by Yamamoto et al (2005) using simulated data. Wagner et al (2006) compared the severe loss of accuracy of monthly solutions to degree and order 120 of published GRACE solutions during the 61 /4-resonance orbit in September 2004 to theoretical error estimates from linear perturbation theory.…”

“…These analytical approaches are often amended by numerical investigations, e.g. Yamamoto et al (2005); Bezděk et al (2009Bezděk et al ( , 2010 Equation (1) is generally accepted as the Nyquist ruleof-thumb for mapping geopotential functions of a planet, often also referred to as the Colombo-Nyquist rule-of-thumb, which connects the spatial resolution with the sampling. It found wide-spread application in the orbit design and recovery of the gravity field, e.g.…”

Efficient Calibration of the Non-Conservative Force Data from the Space-Borne Accelerometers of the Twin GRACE Satellites

“…Since the successful launching of the first Sputnik-1 satellite on October 4, 1957, many scholars have carried out all kinds of wide-ranging and extensive studies on satellite gravity measurement. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The Earth's static and timevarying gravitational field can reflect the spatial distribution, movement and alteration of materials on and inside the Earth, and can dominate the undulation and changes of the geoid. Accordingly, investigating the detailed configuration and time-variable characteristics of the Earth's gravitational field not only is required for satellite geodesy, space science, astronautics, geophysics, seismology, oceanography, and so on, but also provides important information for resource exploration, environmental protection and disaster monitoring.…”