The SwissCube Telescope
SwissCube’s science objective is to measure the airglow emission in the upper atmosphere at about 100 km altitude to:
- Demonstrate the feasibility of using airglow as a basis for a low-cost earth sensor.
- Validate the established airglow model or bring additional information about airglow dependence on latitude, altitude and local solar time.
To achieve that scientific goal, a small telescope was built (length of 4.5 cm) which looks at the near-infrared (IR) product of the airglow. The airglow is seen as an emission of light in the green and near-infrared spectral regions. These emissions are due to the recombination of oxygen atoms (2 O into O2), which have been dissociated by the UV light of the Sun. The near-IR emission is actually the most intense.
SwissCube has very tight volume and mass constraints, as defined by the CubeSat standard (cubesat.calpoly.edu
). Thus the SwissCube telescope had to fit within the following physical and electrical constraints:
- Volume: 30 x 30 x 65 mm3 for the optics; 80 x 35 x 15 mm3 for the payload board
- Mass: < 50 g
- Power consumption: 8 mW when no science observations are performed; < 450 mW during science observations.
The design was performed by the academic partner HES-SO/HEIG-VD
and the EPFL/LMTS
. It consists of a triplet lens design with off-the-shelf components (see Figures 4,5,6)
, a baffle for a solar exclusion angle of 30°, with an attenuation factor of 10-4, and a filter with a central wavelength at 767 nm and a bandwidth of 20 nm. The Field of View of the telescope is 18.8° x 25°, and the resolution of each pixel is 0.16°. Each image is 188 x 120 pixels, and is around 180 kbits (22 KiB). It takes about 5 minutes to download a full image at our downlink rate of 1.2 kbps.
Figure 4. SwissCube's optical design.
Figure 5. SwissCube's telescope design.
Figure 6. SwissCube's telescope (45 mm length).