This article describes the development of a space-based near-Ultraviolet (NUV) spectrograph, focusing on the intricate fabrication and meticulous evaluation of an optical slit employing advanced techniques such as optical lithography and deep reactive ion etching (DRIE). The fabrication process entails a precise definition of the slit pattern on silicon wafer substrates through optical lithography, followed by the transfer of the pattern into the substrate material using DRIE. The resultant optical slit boasts sub-angstrom surface roughness and nanometer-scale slit width uniformity, essential for achieving superior spectrographic performance. Through comprehensive evaluation methodologies, including interferometry and spectrophotometry, the optical slit’s spectral resolution, throughput, and stray light rejection are rigorously examined. These breakthroughs promise to elevate the sensitivity, resolution, and dependability of space-based NUV spectrographic instruments, enabling deeper exploration of celestial phenomena and cosmic evolution.
KEYWORDS: Data transmission, Star sensors, Data processing, Satellites, Power consumption, Spectrographs, Data conversion, Engineering, Logic, Data communications
We present here an STM32 microcontroller based on-board computer designed for use in small satellites and CubeSat missions that was developed using commercial-off-the-shelf (COTS) electronics components. An onboard computer (OBC) is one of the important subsystems of any CubeSat mission. An on-board computer is the central brain of a CubeSat or small satellite, responsible for coordinating and controlling various subsystems to achieve mission objectives efficiently and autonomously. It performs crucial tasks such as power management, communication, command and data handling, on-board data processing and on-board software execution. This paper discusses the development of one such OBC designed for a spectroscopic mission called Spectroscopic Investigator of Nebular Gas (SING).
The Spectroscopic Investigation of Nebular Gas (SING), a near-ultraviolet (NUV) spectrograph, operates from 1400 Å to 2700 Å with a 3.7 Å spectral resolution and 1.33′ spatial resolution. Its primary objective is to study various sky regions such as interstellar medium (ISM), hot gas in supernova remnants (SNR), warm gas in planetary nebulae, and cold gas in molecular clouds. It has a 298-mm aperture telescope feeding a long slit UV spectrograph with a dumbbell slit and holographic grating. SING is designed to be mounted on a stable space platform for scanning mode of observation. This article summarizes SING’s design, calibration, and initial performance.
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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