The Indian Institute of Astrophysics is developing a Multi-Conjugate Adaptive Optics system for the Kodaikanal Tower Telescope. In this context, we measured the daytime turbulence strength profile at the Kodaikanal Observatory. The first method based on wavefront sensor images, called solar differential image motion monitor+, was used to estimate the higher altitude turbulence up to a height of 5 to 6 km. The second method used balloon-borne temperature sensors to measure the near-Earth turbulence up to 350 m. We also carried out simulations to validate the performance of our system. We report the first-ever daytime turbulence strength profile measurements at the observatory. We identified the presence of a strong turbulence layer ∼3 km above the observatory. The measured near-Earth turbulence matches the trend that is expected from the model for a daytime component of turbulence and gives an integrated r0 of ∼4 cm at 500 nm. This is consistent with earlier seeing measurements. This shows that a low-cost setup with a small telescope and a simple array of temperature sensors can be used for estimating the turbulence strength profile at the site.
Star sensors are an essential instrument used to determine the attitude of satellites by identifying the stars in the field of view. The high cost and large sizes of commercially available star sensors pose challenges for small satellite missions. We at the Indian Institute of Astrophysics have developed a low-cost star sensor, StarberrySense, based on the Raspberry Pi as the main controller and built from commercial off-the-shelf components. The StarberrySense was flown on the PS4 experimental orbital platform module of the Polar Satellite Launch Vehicle C-55 by the Indian Space Research Organization. This work describes the flight hardware, environmental tests in preparation for the flight, and in-orbit performance of our StarberrySense.
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