Star Sensor Availability of Equatorial Satellite based on LAPAN-A2 Satellite Observation

Abstract

LAPAN-A2 is the first Indonesian small satellite developed by the National Institute of Aeronautics and Space of Indonesia (LAPAN) orbiting at a near-equatorial orbit. Compared to sun-synchronous orbit, the satellite's star sensor in this orbit is prone to obstruction by the sun and its stray light. It is renowned that the star sensor is the most accurate sensor for satellite attitude determination. Hence there is a need to recognize its availability to meet the satellite mission requirements. This paper objects to observe the availability of satellite star sensors in an equatorial orbit using the calculation of LAPAN-A2 satellite telemetry data. The data was obtained from the long-time telemetry (LTT) between January 2019 to December 2019 and validated by realtime telemetry reading. Unlike real-time telemetry data, the longtime telemetry data is the satellite telemetry data acquired and stored in the satellite memory for the past 86 minutes from the telemetry reading. Calculation of the star sensor availability acquired by observing the sun position relative to the satellite limited to 85% of the availability. The result revealed that the star sensor availability of the satellite varies throughout the year with a 61.2°-star sensor angle relative to the sun as the threshold, showing the lowest availability occurs when the sun position is nearing the north and south poles, while the highest availability ensues when the sun position is nearing equator. In summary, there is a high correlation between the sun position with star sensor availability of equatorial satellites.