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The Solar Ultraviolet Imaging Telescope (SUIT) is one of the payloads onboard the Aditya-L1 mission. It will perform full disk imaging of the Sun in the near-Ultraviolet wavelength range of 200-400 nm. This provides near-simultaneous observations of the Sun from the photosphere and chromosphere. A back-illuminated, enhanced UV Charge Coupled Device (CCD) of size 4096 (H) × 4136 (V) pixels, with a pixel size of 12 μm, is used as an imaging element in SUIT. The CCD characterization and the readout electronics development and testing were performed in-house at the Space Astronomy Group (SAG), UR Rao Satellite centre, ISRO. The test setup and procedures are explained and the measured values of various parameters including noise, dark current, gain, linearity, and cross-talk are presented in this paper. The results show a satisfactory performance from the CCD as well as the readout electronics to meet the specifications required by the SUIT payload.

Aditya-L1 is India’s first observatory class Solar space mission to study the Sun from Lagrangian 1 position. The Solar Ultra-Violet Imaging Telescope (SUIT) is one of the payloads on-board Aditya-L1. SUIT is an off-axis Ritchey-Chretien (RC) telescope, which images the Sun on to a 4k x 4k CCD covering a field-of-view of 1.5Ro with a plate scale of 0.7'/pixel. One of the primary objectives of SUIT is to study the early evolution of solar flares with high time cadence in Near UV wavelength (200 nm – 400 nm). The SUIT on-board intelligence is developed to achieve this objective. The complete intelligence algorithm is divided into several sub-modules each working on a specific aspect of intelligence. These are, HEL1OS flare trigger module: generates flare trigger using HEL1OS hard X-ray data, flare localization module: locates flare on the SUIT full-disc images, Region of Interest (RoI) tracking module: accounts for shift in RoI coordinates caused due to rotation of the Sun, auto-exposure control module: adjusts the exposure time depending upon the flare intensity for better contrast. In this paper, these on-board intelligence modules are explained in detail. The working principles of these modules are tested using available data from various existing missions and also using synthesized data and the obtained results are presented. The modules are implemented in hardware using Actel RTAX 2000S FPGA and are tested using laboratory setup. From the testing, it is found that, flares are successfully localized in a mean time of 40 seconds from the GOES soft X-ray catalog start time. Also, a time cadence of under 3 seconds for a single filter flare RoI images is achieved.