Mass sensitivity of gravimetric satellites

TL;DR

This paper derives frequency-domain expressions for gravimetric satellite measurements, assesses their sensitivity to detect small surface masses, and explores how improved instrument sensitivity and orbital parameters enhance detection capabilities.

Contribution

It provides new analytical expressions for satellite measurement signals and evaluates the impact of instrument improvements on mass detection sensitivity.

Findings

A 100 Gt mass yields a signal-to-noise ratio of 3 for a GOCE-like gradiometer.

Future missions could detect masses as small as 7 Mt with improved accelerometers.

Optimal satellite separation enhances the detection of point-like surface masses.

Abstract

Frequency-domain expressions are found for gradiometer and satellite-to-satellite tracking measurements of a point source on the surface of the Earth. The maximum signal-to-noise ratio as a function of noise in the measurement apparatus is computed, and from that the minimum detectable point mass is inferred. A point mass of magnitude M_3=100 Gt gives a signal-to-noise ratio of 3 when a GOCE-like gradiometer passes directly over the mass. On the satellite-to-satellite tracking mission GRACE-FO M_3=1.3 Gt for the microwave instrument and M_3=0.5 Gt for the laser ranging interferometer. The sensitivity of future GRACE-like missions with different orbital parameters and improved accelerometer sensitivity is explored, and the optimum spacecraft separation for detecting point-like sources is found. The future-mission benefit of improving the accelerometer sensitivity for measurement of non-gravitational disturbances is shown by the resulting reduction of M_3 to as small as 7 Mt for 500 km orbital altitude and optimized satellite separation of 900 km.