Contributed Talk - Splinter Compact

Friday, 16 September 2022, 17:26   (SFG 1020 / virtual Compact)

Gravitational field recovery via inter-satellite redshift measurements

Jan Hackstein, Dennis Philipp, Eva Hackmann, Claus Lämmerzahl
ZARM, University of Bremen

In relativistic gravity, a clock comparison is sensitive to the clocks' positions in the gravity field and their relative velocity, making it an ideal tool to investigate a given object's gravity field. For the Earth gravity field, orbiting satellites can be equipped with clocks and observed by terrestrial ground stations. One important obstacle for Earth-satellite gravimetry, however, is the low measurement accuracy of a satellite's velocity, which enters into the redshift via the Doppler effect. We follow an alternative approach without absolute velocity measurements based on the framework of general relativity, applicable to the Earth system and compact objects as the gravity field source. Here we consider an idealised satellite setup in the Schwarzschild spacetime where the monopole moment is recovered from pairwise redshift measurements between two satellites equipped with clocks. We investigate whether or not the redshift between two satellites can be retrieved given only relative observables between the satellites. This method promises a higher accuracy for gravity field recovery by bypassing the Doppler effect. We compare the results and error estimates of inter-satellite measurements with conventional Earth-satellite measurements and conclude with future applications of this theoretical setup.