Although nano/microsatellites have great potential as remote sensing platforms, the spatial and spectral resolutions of an optical payload instrument are limited. In this study, a high spatial resolution multispectral sensor, the High-Precision Telescope (HPT), was developed for the RISING-2 microsatellite. The HPT has four image sensors: three in the visible region of the spectrum used for the composition of true color images, and a fourth in the near-infrared region, which employs liquid crystal tunable filter (LCTF) technology for wavelength scanning. Band-to-band image registration methods have also been developed for the HPT and implemented in the image processing procedure. The processed images were compared with other satellite images, and proven to be useful in various remote sensing applications. Thus, LCTF technology can be considered an innovative tool that is suitable for future multi/hyperspectral remote sensing by nano/microsatellites.
The Space Robotics Laboratory of Tohoku University has three 50kg Micro-satellite projects. The first satellite "SPRITE-SAT" has been successfully launched into Earth orbit, and also been operated. The flight model of the second satellite "RISING-2" has been assembled and its software development is now finalized, being ready for the launch planned in the next year. The third satellite "RISESAT" project is during the Engineering Model (EM) development phase at the time of writing. Some micro-satellites can repair its software by batch file on orbit however most of it is not able to repair its basic software and system-configuration after launch. Therefore, it needs to be evaluated about its system that includes software and hardware in detail. The Space Robotics Laboratory (SRL) of Tohoku University aims to establish a verification environment for micro-satellites system through the RISESAT project. SRL named it as MEVIµS: Model-based Environment for Verification and Integration of µ-Satellite. MEVIµS system has some software and hardware. Its software simulates orbit and satellite environment such as solar power, thermal environment, attitude information and operation of equipment. Its hardware establishes interfaces between simulator and equipment of real-satellite. SRL is planning to establish an environment of hardware-in-the-loop-simulation (HILS) for RISESAT by MEVIµS and RISESAT-EM. RISESAT-EM will be evaluated by its HILS system and its software and hardware of equipment will update continuously until flight model development phase. The paper will show detail of MEVIµS configuration and result of application to RISESAT-EM.
Tohoku University is now finishing the development of its second 50-kg class Earth observation microsatellite RISING-2. RISING-2 is equipped with four camera systems with eight different imaging sensors, including a 5-m ground resolution cassegrain mirror telescope with three fixed wavelength filters in red, green, and blue, as well as a liquid crystal tunable filter. RISING-2 aims to achieve agile high resolution multi-spectral Earth observations. For this mission, Tohoku University has been developing a precise and agile attitude control system including multiple sensors and actuators. The pointing error is required to be less than 0.1 deg and the pointing knowledge shall be better than 0.06 deg. The designed star sensor is based on CCD image sensor which has a flight heritage by the university's first satellite RISING. This system utilizes a pyramid algorithm for secure constellation identification and works with a maximum update frequency of 2 Hz. Its availability is also very high in terms of the satellite's operating angular velocity. In this paper, the system integration of the star sensor as well as the results of its ground based performance evaluation is described in detail.
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