The antenna phase center motion effect in space-based experiments for fundamental physics and astronomy

TL;DR

This paper analyzes the impact of antenna phase center motion on space-based experiments in physics and astronomy, demonstrating its significance and proposing configurations to mitigate its effects for precise measurements.

Contribution

It provides a detailed assessment of phase center motion effects and introduces antenna configurations that can effectively compensate for these effects in space experiments.

Findings

Phase center motion can cause several mm/s velocity correction in spacecraft.

Certain antenna configurations can fully or significantly compensate for phase center motion effects.

Results are supported by real spacecraft data and simulations for future missions.

Abstract

We consider the effect of phase center motion of mechanically steerable high-gain parabolic antennas for ground-based and spacecraft-mounted antennas. For spacecrafts on highly elliptic Earth orbits the magnitude of the effect is as large as several mm/s in terms of the required velocity correction, both for ground-based and spacecraft-mounted antennas. We illustrate this with real data from the RadioAstron spacecraft and also provide results of our simulations for the concept of a possible follow-up space very long baseline radio astronomy mission. We also consider a specific configuration of satellite communication links, with simultaneously operating one-way down link and two-way loop link, pioneered by the Gravity Probe A experiment. We find that this configuration provides for complete compensation of the phase center motion effect due to the onboard antenna and significant compensation of that due to the ground antenna. This result is important for future space-based fundamental physics experiments, primarily those concerned with studies of gravity.