Equivariant Filter Cascade for Relative Attitude, Target's Angular Velocity, and Gyroscope Bias Estimation

TL;DR

This paper introduces a cascade of Equivariant Filters for estimating relative attitude, target's angular velocity, and gyroscope bias during spacecraft rendezvous, with theoretical stability analysis and simulation validation.

Contribution

It presents a novel cascade of Equivariant Filters that jointly estimate spacecraft attitude, target angular velocity, and sensor bias, improving accuracy in uncooperative rendezvous scenarios.

Findings

The filter cascade accurately estimates relative attitude and angular velocity.

Theoretical stability of the filter cascade is established.

Simulation results confirm the effectiveness of the proposed method.

Abstract

Rendezvous and docking between a chaser spacecraft and an uncooperative target, such as an inoperative satellite, require synchronization between the chaser spacecraft and the target. In these scenarios, the chaser must estimate the relative attitude and angular velocity of the target using onboard sensors, in the presence of gyroscope bias. In this work, we propose a cascade of Equivariant Filters (EqF) to address this problem. The first stage of the cascade estimates the chaser's attitude and the bias, using measurements from a star tracker, while the second stage of the cascade estimates the relative attitude and the target's angular velocity, using observations of two known, non-collinear vectors fixed in the target frame. The stability of the EqF cascade is theoretically analyzed and simulation results demonstrate the filter cascade's performance.