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

On-Orbit Operation Results of the World\u27s First CubeSat XI-IV – Lessons Learned from Its Successful 15-years Space Flight

In recent years, the size and cost of satellites have been reduced, and the frequent launch of satellites have been realized even by small private companies and universities. The first step of this big wave was the first successful launch of CubeSats, 1kg nano-satellites, in June 2003. One of the CubeSats was XI-IV, which was developed by Intelligent Space Systems Laboratory (ISSL) of the University of Tokyo. Its mission was the world’s first on-orbit demonstration of the CubeSat bus system. Due to the spatial, power and cost constraints, most of the bus system was composed of low-cost COTS parts, and a “cross-check” type fault redundancy system against the radiation effects was implemented to achieve as better reliability as possible within the resource constraints. Since the successful launch by the ROCKOT launch vehicle from Russia, the satellite has been in normal operation for over fifteen years since the launch (as of June 2019). The operation has been jointly conducted by the University of Tokyo and amateur radio operators in Japan. This paper reports its more-than-15-years world\u27s longest CubeSat operation results and the lessons learned from it

University of Tokyo\u27s CubeSat Project: Its Educational and Technological Significance

This paper describes outline of the University of Tokyo Intelligent Space Systems Laboratory(ISSL)\u27s CubeSat \XI for the demonstration of the pico-satellite bus technology and validation of the commercial- o_-the-shelf parts in space as well as the earth imaging mission. CubeSat project is the international joint program, which aims for developing and actually launching 10cm cubic satellites weighing less than 1kg to the earth\u27s orbit. 18 CubeSats developed by Japanese and U.S. institutes are to be launched by the Russian launch vehicle \Dnepr in May, 2002 to the Sun-synchronized orbit. The project in ISSL is conducted by 20 space engineering students as a material of education

Utilizing Commercial DSLR for High Resolution Earth Observation Satellite

CE-SAT-I, the first technology demonstration satellite from Canon Electronics Inc. has been launched on June 23, 2017 from India by PSLV-C38. Canon is to enter small satellite industry to exercise its precision manufacturing, image processing and mass production capabilities as a new business sector. In this study, commercial DSLR camera, Canon EOS 5D Mark III has been proposed as a detector of the satellite with 40cm aperture, 3720mm focal length telescope aiming to capture 0.9m GSD from LEO. The satellite size is 50 x 50 x 80cm and 65kg in weight. Advantage of area sensor by applying commercial DSLR camera brings full HD and full color video, standardization and cost deduction capabilities. The sensor resolution is 5760 x 3840 pixels and the physical size of the sensor is 36 x 24mm. Point-and-shoot camera, PowerShot S110 is also equipped as wide angle camera as a finder of main telescope. Systems of CE-SAT-I has been developed based on commercial product of Canon. For instance, OBC has been developed based on same technology of multi-function printer. During initial operation, satellite health has been fully confirmed and optical calibration has been done with resolution test chart on the ground. Focus calibration has been performed with temperature control and physically adjusted by hyper-sonic actuator equipped on secondary mirror. Advanced missions are performed including video capturing, HDR, super-resolution and reprograming of OBC after initial operation. Ground stations has been developed and operated by Canon Electronics. The antennas are located around Tokyo and remotely operated. With the heritage of CE-SAT-I, Canon electronics is aiming to build a constellation of over 100 satellites with 8K low light real time video broadcasting with laser communication

Magnetic Substance Disturbance Torque Caused by Shape Magnetic Anisotropy and its Applications in Small-Sized Satellites

This study presents the magnetic substance disturbance torque caused by shape magnetic anisotropy. This magnetic substance disturbance occurs in on-board unsymmetrical magnetic substances, even if the magnetic substance does not have a residual magnetic dipole moment. Although this magnetic substance disturbance torques has not been considered in previous small-sized satellites, in some cases, the strength of the disturbance is stronger than the effect of aerodynamic and solar radiation disturbances. First, this study presents the strength and effects of the magnetic substance disturbance torque in Cubesat satellites: XI-IV and PRISM in the University of Tokyo. Then, the study shows that the strength of the magnetic substance torque caused by an arbitrary-shaped magnetic substance can be expressed as follows: T=M_s B^2 cosθsinθ, where M_s, B, and θ are constant parameter, outer magnetic field, and direction of the outer magnetic field, respectively. Second, the study proposes a method of estimating magnetic substance disturbance using a least squared method in orbit. Finally, the study presents the application of the magnetic substance torque for passive attitude control systems for spacecraft. The proposed formulation and estimation method are indispensable to achieve the precise attitude determination and control in nano- and micro-satellite missions

Magnetic Substance Disturbance Torque Caused by Shape Magnetic Anisotropy and its Applications in Small-Sized Satellites

This study presents the magnetic substance disturbance torque caused by shape magnetic anisotropy. This magnetic substance disturbance occurs in on-board unsymmetrical magnetic substances, even if the magnetic substance does not have a residual magnetic dipole moment. Although this magnetic substance disturbance torques has not been considered in previous small-sized satellites, in some cases, the strength of the disturbance is stronger than the effect of aerodynamic and solar radiation disturbances. First, this study presents the strength and effects of the magnetic substance disturbance torque in Cubesat satellites: XI-IV and PRISM in the University of Tokyo. Then, the study shows that the strength of the magnetic substance torque caused by an arbitrary-shaped magnetic substance can be expressed as follows: T=M_s B^2 cosθsinθ, where M_s, B, and θ are constant parameter, outer magnetic field, and direction of the outer magnetic field, respectively. Second, the study proposes a method of estimating magnetic substance disturbance using a least squared method in orbit. Finally, the study presents the application of the magnetic substance torque for passive attitude control systems for spacecraft. The proposed formulation and estimation method are indispensable to achieve the precise attitude determination and control in nano- and micro-satellite missions

Nano-JASMINE: A Small Infrared Astrometry Satellite

The University of Tokyo and National Astronomical Observatory of Japan have been developing a small infrared astrometry satellite named “Nano-JASMINE”. This is about 50cm cubic and 15kg size satellite and it aims to achieve 1 milli arcsecond astrometry data for stars of magnitude of 7.5. And this is traditional large satellite scientific data class. Therefore Nano-JASMINE has advanced specification compared to past small satellites. It can achieve 1 arcsecond attitude control accuracy using customize fiber optical gyros and mission telescope and also 0.1[K] thermal stability by multilayer adiabatic structure. Also new centralized information architecture is adopted to simplify the system. Nano-JAMINE satellite system and missions are described in this paper