MiniCAS – A Novel Type of Constellation Acquisition System

Abstract

Precise relative attitude control between two or more spacecraft is essential in satellite gravimetry missions. Missions such as GRACE-FO, or NGGM require highly accurate initial alignment to establish an interferometric laser link. Current solutions, like those used on GRACE-FO, involve acquisition scans lasting up to nine hours. To reduce this time to almost instantaneous operation, we propose MiniCAS, a compact optical system that enables attitude acquisition with microradian sensitivity.

MiniCAS (Miniaturized Constellation Acquisition System) comprises an optical receiver paired with a dedicated light source. Identical sensor systems are installed on both spacecraft. By detecting the light emitted by its counterpart, the receiver determines the misalignment relative to the connecting line between the two satellites, known as the Line of Sight (LOS). This measurement directly reflects the relative tilt of each spacecraft with respect to the LOS.

True to its name, MiniCAS focuses on a compact, lightweight and cost-efficient design, that increases MiniCAS’s application areas. The receiver integrates a lens assembly with a suitable focal plane array, resulting in a total system length of approximately 12 cm plus the sensor thickness. It is paired with a dedicated light source serving as the emitter. The current optical layout achieves a spot size of two pixels and a Field of View of approximately ± 5 mrad with additional margins.

In this presentation, we introduce the main concept of MiniCAS. We outline system requirements and present current simulation results of the sensor. In addition, we provide an overview of the current design status, including optical simulations of different lens configurations. The system is currently under active development and is expected to reach TRL 5 by the end of 2026.