Development and Flight Results of Microsatellite Bus System for RISING-2

The RISING-2 microsatellite was launched in May 2014 into a sun-synchronous circular orbit at a height of 628 km. This paper describes the operation results and the flight evaluation of bus system. The satellite was successful in obtaining images of Earth using a high-resolution multi-spectral telescope system with a 5-m spatial resolution in red–green–blue (RGB) observations and 10-m resolution in spectral observations. The weight of the satellite is 43.2 kg, and the shape is almost cubic, with sides 50 cm in length. The satellite has an attitude control system that uses three-axis reaction wheels, which enables a nadir-pointing mode and a target-pointing mode in tracking a specified ground location. The attitude actuators and sensors are magnetic coils, star sensors, gyro sensors, sun sensors, magnetometers, and a global positioning system (GPS) receiver. The satellite attitude could be determined with an error of less than 0.005° from observation images. Using coarse determination methods employing magnetometers, sun sensors, and gyro sensors, the pointing angle error was determined to be 1.9 deg in root mean square (RMS), and the direct distance error was determined to be 21.5 km in RMS.