METRIC: A Dedicated Earth-Orbiting Spacecraft for Investigating Gravitational Physics and the Space Environment

Abstract

A dedicated mission in low Earth orbit is proposed to test predictions of gravitational interaction theories and to directly measure the atmospheric density in a relevant altitude range, as well as to provide a metrological platform able to tie different space geodesy techniques. The concept foresees a small spacecraft to be placed in a dawn-dusk eccentric orbit between 450 and 1200 km of altitude. The spacecraft will be tracked from the ground with high precision, and a three-axis accelerometer package on-board will measure the non-gravitational accelerations acting on its surface. Estimates of parameters related to fundamental physics and geophysics should be obtained by a precise orbit determination, while the accelerometer data will be instrumental in constraining the atmospheric density. Along with the mission scientific objectives, a conceptual configuration is described together with an analysis of the dynamical environment experienced by the spacecraft and the accelerometer.

Estimation and Error Analysis for Optomechanical Inertial Sensors

“…The results obtained from the calibration step can now be incorporated to develop procedure for the estimation of the forcing acceleration using a series of displacement measurements defined in Equation (8). Upon completion of the calibration step, it is assumed that the bias estimate (b) is itself unbiased.…”

“…The first estimator considered is a moving least squares method using a batch of N + 1 measurements obtained from the laser interferometer, which are defined in Equation (8).…”

“…Accelerometers are used in countless applications including: satellite, aircraft, robotic, and automotive inertial navigation. Particularly, in the realm of satellite design these devices are used both as navigation equipment [ 1 , 2 , 3 , 4 ] and as scientific instrumentation [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. In both cases the accuracy of the estimated acceleration directly impacts the performance of the system and its ability to meet critical mission requirements.…”