The star tracker used on Alphasat, called ASTRO APS (Active Pixel Sensor), has its premiere in space. Once the new technology has been verified in space and proven to function while in orbit, it will be provided to future missions for even more accurate measurements.

Active Pixel Sensor Performance

ASTRO APS is an autonomous star tracker with the most advanced radiation hard CMOS Active Pixel Sensor (APS) detector technology for long-term missions. The technical key parameters of the APS based star trackers are the low mass budget with < 2kg, the low power consumption with < 5W and the attitude quaternion accuracy of < 1arcsec (1sigma) at 10Hz update rate. These data define a new level of compactness compared to state-of-the-art CCD-based star sensors:

• Lifetime of more than 18 years
• Radiation design for 25 years GEO environment
• APS design with space qualified CMOS detectors
• Full performance with moon in the field of view
• Very robust against solar flare environment and false star objects

ESA article: "Alphasat carries new space compass"

Animation of ASTRO APS on Alphasat