# Gravitational redshift test with the future ACES mission

## TL;DR

This paper evaluates the ACES space mission's ability to test gravitational redshift, demonstrating that with realistic noise and data conditions, the mission can achieve its precision goals within a few measurement sessions.

## Contribution

The authors develop simulation tools and analysis methods to assess ACES's gravitational redshift test performance under realistic conditions.

## Key findings

- Target uncertainty of 2-3 ppm is achievable within a few measurement sessions.
- Achieving the test precision requires orbit determination accuracy of about 300 meters.
- Realistic noise and data gaps do not significantly hinder the test's success.

## Abstract

We investigate the performance of the upcoming ACES (Atomic Clock Ensemble in Space) space mission in terms of its primary scientific objective, the test of the gravitational redshift. Whilst the ultimate performance of that test is determined by the systematic uncertainty of the on-board clock at 2-3 ppm, we determine whether, and under which conditions, that limit can be reached in the presence of colored realistic noise, data gaps and orbit determination uncertainties. To do so we have developed several methods and software tools to simulate and analyse ACES data. Using those we find that the target uncertainty of 2-3 ppm can be reached after only a few measurement sessions of 10-20 days each, with a relatively modest requirement on orbit determination of around 300 m.