Satellite Attitude Determination: Digital Sensing and On-Board Processing

The determination of the aspect or orientation of spin stabilized satellites is vital for the correct interpretation of scientific measurements made on these spacecraft. Aspect information is collected optically from the sun, moon and earth. Little channel capacity is generally available for telemetry of this information. Therefore, completely digital low power aspect sensing and on-board information processing systems have been built and flown on various satellites. Some interesting results of aspect measurements on Explorer XII showed an unexpected increase in spin rate due to solar pressure, and on Explorer XIV an erratic precession history.