Attitude Control Systems for Imaging the Moonlit Ground: Development and On-Orbit Updating Results of CE-SAT-IIB

Canon Electronics Inc. (CEI) is developing optical micro satellites “CE-SAT” for demonstrating in-house attitude determination and control systems (ADCS) and optical systems in order to achieve high-resolution and high-sensitivity imaging. CEI is now operating two satellites on orbit. The second satellite CE-SAT-IIB has the ability to take images of the ground surface with 5m GSD in the night using an Ultra High Sensitivity Camera (UHSC) and a highly accurate ADCS. The satellite has ability to track the ground with 20 arcsec/s or better of pointing stability, and this makes 100 milliseconds or longer exposure time possible. As the result, the satellite can get images of the moonlit ground surface clearly. To realize such high stability of pointing, CEI developed most components for ADCS in-house and updated software of the satellite and components on orbit. Now CE-SAT-IIB can get the ground images with 1800 milliseconds exposure time and get color images of night deserts like imaging in daylight. Additionally, this ADCS enables the satellite to get various images of the ground with changing area, sensitivity, and temporal resolution of imaging by selecting a target of pointing, exposure time, and imaging interval. Furthermore, high-speed moving objects including satellites and space debris can be photographed utilizing the high sensitivity of the UHSC

Night-Time Color Imaging with High Resolution from a 35 kg Microsatellite

Canon Electronics Inc. developed its third microsatellite to demonstrate optical systems and in-house developed components in orbit. The 35 kg microsatellite CE-SAT-IIB can capture night-time color images of moon lit earth surface as well as city lights with a newly-designed camera using an ultra-high sensitivity image sensor developed by Canon. CE-SAT-IIB was launched in October 2020 as a payload on the Rocket LabsElectron15and has been performing experiments to validate optical systems and the bus using in-house components. CE-SAT-IIB has three types of cameras. The first camera is a 20 cm Cassegrain telescope with the ultra-high sensitivity detector previously described. Exposure is controllable through shutter speed, CMOS gain, and ND filters. The sensitivity is equivalent to approximately 4 million in ISO by maximizing the gain and detaching all the ND filters. Focus can be adjusted via a stepper motor on the detector, and observable area is approximately 3.5 km x 2.3 km on the ground with theoretical ground sampling distance (GSD) 5m from a 500 km orbit. The second camera is 8.7 cm Cassegrain telescope with a commercial off-the-shelf (COTS)detector using24.2 MP CMOS sensor. Exposure is controllable through shutter speed and ISO, and focus can be adjusted by controlling the temperature of the telescope. The Effective focal length of this camera is809 mm, which enables to capture ground images of approximately 5.6 km x 3.7kmwith theoretical GSD2.3m. The third camera is also a COTS compact digital camera. Exposure is controllable through shutter speed, ISO, and F-number. In addition, adjustable focal length provides wide range of images from approximately 215 km x 145 km to 645 km x 435km in ground distance. The bus of CE-SAT-IIB mainly consists of in-house components such as sun aspect sensors, a geomagnetic aspect sensor, an inertial reference unit, a star tracker, magnetorquers, and reaction wheels to shorten the delivery time and guarantee quality for mass-manufacturing. All of these components have worked as designed in orbit, and the satellite has achieved 3-axis attitude control such as ground tracking, and inertial pointing. Canon Electronics has demonstrated three sizes of Cassegrain telescopes and validated two size of bus systems by CE-SAT-I and CE-SAT-IIB. We are going to start providing high quality telescopes, detectors, bus systems, components, and integrated satellite systemin a short delivery time