Mission instruments

The mission instruments for science observations are shown in Fig.5. The 5 lens or mirros are exposed to outside of bottom panel. The apperance photos of instruments are shown in Fig.6. The high precision telescop (HPT) and bolometer array sensor (BOL) are newly developed. The two mid-field CMOS cameras (LSI-N,W), the wide-field CCD camera (WFC), the VLF antenna and receiver have been already used in SPRITE-SAT.

The exposure time of LSI is 34.5ms, and space resolution is selectable from 600m, 1.2km, and 2.4km. The mass of unit is 583g. The field view of WFC is 134 x 180 deg, the exposure time 16.7ms, and the mass 223g.

Fig.1 System diagram of mission instruments
Fig.2 Mission instruments: a) High Precision Telescope, b) bolometer array camera, c) Lightning and Sprite CMOS Imager, d) Wide Field CCD Camera

High precision telescope (HPT)

The specification of HPT is as follows:

  • Size: Casegren telescope with about 100-mm diameter (F10) and about 1-m focal length
  • Mass: about 3 kg
  • Targets: earth surface, cumulonimbus clouds, and planets
  • Sensors: Total 4 CCD sensors with the wavelength of 400-650nm (by RGB) and 650-1000nm (by LCTF)
  • Sensitivity: High sensitivity of ISO 8000
  • Resolution: 659 x 494 pixels, which is 5 m/pixel at 700-km altitude, and 3.3 x 2.5-km field of view
  • Space Resolution: 5-50m in LCTF mode with 10-nm band range
  • Exposure time: minimum 1/4000 sec in RGB mode

The main and sub mirrors are made from Zero-expansion Pore-Free (ZPF) ceramics. They have light weight and high strength adopting brand-new grinding technology, and they have superior performance in anti-vibration at launch compared to conventional mirrors.

The liquid crystal tunable filter (LCTF) is modified to space use from the instrument for ground use in development phase. It has liquid crystal multi-layer plates and the wavelength is variable with 5-nm narrow band. The central wavelength can be changed in the range of more than 300 nm with 10 milliseconds.

Bolometer array camera (BOL)

The bolometer array is mid infrared (MIR) sensor of 8-14 micro meters with the field of view of 48 x 36 degrees. At the 700-km altitude, the space resolution is about 1 km, which is 0.076 deg/pixel. The images of temperature distribution of cumulonimbus clouds, ground surface, and sea surface can be created. The following three phenomena can be recognized:

  • From the temperature of the top of cumulonimbus, the altitude can be estimated. With the simultaneous observations by LSI and WFC, the relationship of transient luminous events and cumulonimbus is analyzed.
  • Observing the temperature distribution of ground surface, buildings, and sea, the generation of cumulonimbus can be monitored, which is resource of guerrilla heavy rain.
  • The natural disasters such as mountain fire and volcano eruption are observed and the method of rapid detection is researched.

The bolometer camera for commercial use is slightly modified to space use with low cost. The consumption power is 8.4 W, and the mass is 554 g.

When images are taken by BOL, the noises will be heavy in single image. In general use, it becomes clear image to subtract the image of closed shutter. The image of deep space without earth surface is used as shutter image, and the moving shutter parts are removed.

(C) The Space Robotics Lab (Space Exploration Lab), Tohoku University
Last-modified: 2011-06-16 (Thu) 08:26:15 (3395d)