Star Tracker
CCD/CMOS Star Tracker with Catalog Matching
A star tracker is an optical instrument that provides absolute attitude reference and corrects inertial measurement unit drift by imaging star fields across a 20-degree field of view and matching patterns against an onboard catalog of approximately 10,000 stars. Although the absence of a lunar atmosphere ensures constant stellar visibility, the operating environment delivers a cumulative total ionizing dose that degrades standard imaging sensors, necessitating radiation-tolerant CCD or CMOS arrays. Integrated optical baffles must also suppress bright stray light from the Sun, Moon, and permanent polar Earthrise to maintain 5-arcsecond accuracy over a 20-year operating life.
Star tracker providing absolute attitude reference via stellar pattern matching, used as primary attitude reference and IMU bias-correction source.
Purpose
Star tracker providing absolute attitude reference via stellar pattern matching, used as primary attitude reference and IMU bias-correction source.
Context
Child of L2-NAV-REF within the Lunar Ark system
Principles
- ▸CCD/CMOS sensor images star field
- ▸Pattern matching against onboard star catalog (~10000 stars)
- ▸Attitude accuracy <10 arcsec
- ▸Sun + Moon exclusion via baffle
- ▸Long-life proven (decades on numerous spacecraft)
Typical implementations
- ▸Sodern HYDRA star tracker (ESA heritage)
- ▸Ball Aerospace CT-633 / 700 family
- ▸LONEStar optical nav (arXiv 2401.12198)
Lunar considerations
- ▸Permanent earthrise visible from south pole (libration)
- ▸Stars always visible (no atmosphere)
- ▸Cumulative TID degrades CCD — rad-tolerant variants preferred
Specifications
Functional
| primary function | Star tracker providing absolute attitude reference via stellar pattern matching, used as primary attitude reference and IMU bias-correction source. |
| accuracy arcsec | 5 |
| field of view deg | 20 |
Physical
| mass kg | 3 |
| materials | Rad-tolerant CCD/CMOS, Optical baffle, DSP processor |
| vacuum compatibility | True |
Operational
| power consumption w | 10 |
| thermal range c | -40, 70 |
| lifetime years | 20 |
| mtbf hours | 100000 |
Interfaces
Provides
- Absolute attitude reference
- Bias calibration aid
Requires
- Star tracker (~10 W)
Cite this entry
Lunar Ark Codex. "Star Tracker" (L3-NAV-REF-STAR). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-NAV-REF-STAR
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.