ADCS requirements of Lapan-A3 satellite based on image geometry analysis

Images captured by Lapan-A3 pushbroom imager will have some geometric distortions from various sources. Most of them can be ideally corrected by using a high quality ancillary data, i.e. Lapan-A3 attitude sensor must provide attitude data for each image line (2,5ms) and free from measurement error. That ideal condition is nearly impossible to achieve so this paper aims to determine the minimum performance of Lapan-A3 ADCS (Attitude Determination and Control System) so that the image captured can still be well corrected with systematic geometric correction software. Three aspects being evaluated are accuracy and sampling frequency of attitude sensor, as well as the stability mode of ACS. Simulation results show that 10 Hertz sampling frequency of attitude data is needed when ACS closed loop mode is used, while 1/3 Hertz sampling frequency is enough when ACS open loop mode is used. Accuracy of attitude sensor should be better than 0,003° for pitch/roll axis and 0,02° for yaw axis. Related with ACS stability mode, image correction is way easier if observation is done under open loop mode since in closed loop mode there will be random jitter error. If the observation is done under closed loop mode then ACS should have pointing stability of 0,002°, far from current Lapan-A3 ACS pointing stability under closed loop mode, which is 0,1°.