In this report, Phase A of the SPIRou CubeSat project has been discussed. The purpose of this study was to take the project from its initial study of Phase 0 into the feasibility Phase A. As per the specifications, the CubeSat needed to have a photometric payload that would work in near infrared, JH bands (1 to 1.8um) for the detection and characterisation of potential transiting exoplanets. The platform of the CubeSat is under the supervision of ISAE/CSUT within the 12U CubeSat standards. The total allowable weight and volume of the Payload is about 8 kg and 6U (352x207x105 mm) respectively.

The aim of this study was to design a preliminary CAD model of the payload and to do thermal analysis on the designed model in order to determine the feasibility of the payload. At first, 3U payload was designed but the task was later on updated to have twin 2 x 3U payload within the 6U specified volume of the payload in the platform. The twin payloads could work as redundant elements to each other for better detection of the number of stars. The individual design layout of the twin payloads comprised of baffles, optics (5 lenses, spacers), barrel, integration foot and a SWIR detector. The current design allowed payload(s) to integrate comfortably within the 6U allocated volume of the platform.

By first approximation, the internal power dissipation of the platform subsystems and orbital environment flux faced by the platform was taken as envelope boundary condition between temperature ranges of -20 to 50^oC in order to concentrate on the steady state thermal analysis of the payload. The analysis aimed to know the temperature range that the subsystems of the payload would be subject to during the worst cold and worst hot cases. This analysis proved helpful in determining the feasibility of the proposed payload design. The need for implementation of heaters and switching off the detector have been detailed in the discussion of results.

At the end, the conclusion and necessary future ideas for the next study phase of the payload have been discussed.