A 1.5u size 350-950nm Hyper-Spectral Camera Optical and Mechanical Design Without MTF Degradation in the Temperature Range -100 to 300 ℃

A 1.5u size 350-950nm Hyper-Spectral Camera Optical and Mechanical Design Without MTF Degradation in the Temperature Range -100 to 300 ℃

Utah State University, Logan, UT

1.5U sized hyper-spectral camera has been developed to be equipped in three-unit sized CubeSat. Even though this payload is developed for Cubesat, the optical and mechanical structure is designed for harsh environmental conditions to be equipped in the other satellite types. The optical performance of the payload is assessed using Modulation Transfer Function (MTF) in 350–950nm. The MTF is optimized with volume and MTF requirement constraints by CODE-V in the wavelength range. The constraints are 1.5U volume, the curvature ranges of fabricable aspheric design, fabrication errors, and the temperature variation in space. The 1.5U size constraint is defined to 100mm✕100mm✕145mm which includes 1U for inside and 0.5U for outside of the satellite, and the diameter of the primary mirror is 80 mm. The 0.5U space is offered in a Poly-Picosatellite Orbital Deployer (P-POD). In order to shorten the camera tube length, the lens and mirrors should be asphere and the fabricability of the optical elements with acceptable errors should be checked. The temperature range for describing harsh space environments is assumed as –100℃ to 300℃, and the maximum invar tube length expansion by the 400℃ difference is 304㎛. The temperature variation degrades the MTF and tolerance range of the drawing, so the degradation is compensated with the other length variations of mechanical elements in the optical system.