SpaceEye-1 earth observation satellite, developed by Satrec Initiative Co. Ltd., is a 300 kg scale spacecraft with high resolution electro-optical payload (EOS-D) which performs 1 m GSD, 12 km swath in low earth orbit. Metering structure of EOS-D is manufactured with Carbon Fiber Reinforced Plastic (CFRP). Due to the moisture emission from CFRP metering structure, this spaceborne electro-optical payload undergoes shrinkage after orbit insertion. The shrinkage of metering structure causes change of the distance between primary and secondary mirror. In order to compensate the moisture shrinkage effect, two types of thermal refocusing mechanism were developed, analyzed and applied to EOS-D. Thermal analysis simulating in-orbit thermal condition and thermo-elastic displacement analysis was conducted to calculate the performance of refocusing mechanism. For each EOS-D telescope, analytical refocusing range (displacement change between primary and secondary mirror) was 2.5 um and 3.6 um. Thus, the refocusing mechanism can compensate the dimensional instability of metering structure caused by moisture emission. Furthermore, modal, static and wavefront error analysis was conducted in order to evaluate natural frequency, structural stability and optical performance. As a result, it can be concluded that the refocusing system of EOS-D payload can perform its function in orbit.
Pre-launch performance has been characterized on the EOS-C camera: capable of Earth observation at 2.5 m resolution
and 20 km swath width. Topics discussed in this paper include measurements of system modulation transfer function
(MTF) and pixel lines-of-sight (LOS); radiometric and spectral calibration; end-to-end imaging.
The mission of DIOS program is to provide the function of large-swathwidth or in-track stereo imaging with compact
electro-optical cameras. Optimized from its predecessor SAC (Small-sized Aperture Camera), DIOS consists of two
cameras, each with an aperture of 120 mm diameter, 10 m GSD, and 50 km swath width in the spectral range of 520 ~
890 nm. DIOS is developed to produce high quality images: MTF of more than 12 %; SNR of more than 100. DIOS can
be configured to have cameras side-by-side, providing a swathwidth up to 100 km for a mission of large swathwidth.
DIOS will be configured with installation of slanted two cameras for the mission of in-track stereo imaging to produce
digital elevation model. In this paper, Dual Imaging Optical Sensor (DIOS) will be introduced with design approach and
performance measure. Even though developed for micro satellites, the presentation of development status and test
results will demonstrate the potential capability that DISO can provide for world-wide remote sensing groups: short
development period, cost-effectiveness, wide application ranges, and high performance.
Pre-flight performance has been characterized on the Medium-sized Aperture Camera (MAC) of the RazakSAT: capable of Earth observation at 2.5 m resolution and 20 km swath width. Topics discussed in this paper include measurements of system modulation transfer function (MTF) and pixel lines-of-sight (LOS); characterization of focal plane assembly (FPA) and signal processing electronics; end-to-end imaging. The MTF was obtained with knife-edge scanning technique, which is also used to align the FPA. For band-to-band registration, relative pixel LOS was measured using theodolite and effective focal length of the telescope was derived from the measurement. For the FPA and signal processing module, dark reference, pixel-to-pixel response variation and response linearity have been quantified. The end-to-end imaging tests were done to check the imaging function before the launch, by scanning a slide target at the focus of the collimator.
SAC is a compact camera for imaging in visible-NIR spectral ranges. SAC provides high-resolution images over the wide geometric and spectral ranges: 10 m GSD and 50 km swath-width in the spectral ranges of 520 ~ 890 nm. The missions incorporate various imaging operations: multi-spectral imaging; super swath-width imaging with cameras in parallel; along-track stereo imaging with slanted 2 cameras. In this paper, SAC is introduced with design and performance. Though developed for small satellites, presenting development status and test results will demonstrate the potential capability for worldwide remote sensing groups: short development period, cost-effectiveness, and high performance.