ESA GNC Conference Papers Repository
High-Accuracy Star Tracker ASTRO XP
Jena-Optronik GmbH, located in Jena/Germany, has profound experience in designing and manufacturing star trackers since the early 80ties. Today, the company has a worldwide leading position in supplying satellites and other spacecraft for telecom, earth observation, science and all kind of missions in various orbits with versatile and reliable star tracker systems. The future ESA science missions require high accuracy star trackers in the 0.1arcsec accuracy class to achieve the envisaged pointing budgets. Jena-Optronik received a pre-development contract (ESA Contract No. 4000112514/14/NL/BW) from the European Space Agency in order to demonstrate the feasibility of such a high accuracy star tracker within the challenging performance, mass and envelope requirements. The here identified key-enabling optics technology in terms of a compact 4-times folded fully reflective optical system opened the way forward to a second contract (ESA Contract No. 4000126831/19/NL/GLC/hh) to establish an engineering model optical head in form, fit and function, able to undergo pre-qualification tests. The star tracker optics consists of a full catoptric design and is therefore free of any chromatic aberration. This is essential for a high accuracy star tracker, which uses guide stars from a wide range of different spectral classes. The only four optics main parts are made from fused silica and build in the final assembly a self-sustaining optical system with a total lack of CTE mismatches. The high performance imaging system is completed with a FaintStar2 CMOS APS based focal plane. The FaintStar2 is the most advanced and space-qualified APS star tracker imager as a result of the ESA detector development roadmap. This detector comprises a complete system-on- chip including a space-wire interface. This minimizes the power consumption of the ASTRO XP optical head ensuring an excellent thermal-mechanical stability. The ASTRO XP EM optical head was integrated in Q4/2022 so that the test readiness review with the agency could be successfully performed. The paper presents insights in the optics and focal plane technology and design. In addition, the first test results from the engineering model test campaign will be published and discussed. The ASTRO XP optical head manufactured is the most innovative star tracker ever designed at Jena-Optronik GmbH and beyond. This design applies novel technologies and utilizes the most innovative high-technology assembly processes.