Feasibility study of a UV photometer on-board a 3 CubeSat for the study of bright massive stars

Following the amazing progresses in miniaturizing essential components of spacecraft, the last decade has witnessed an important development of nano- and micro-satellites. Beyond the mere technological experiment, these small satellites are now considered as important complements of much larger and more sophisticated probes to do scientific research.
In this context we are conducting a feasibility study of a UV photometer on-board a 3U CubeSat. The scientific purpose of this payload will be to collect time series of photometric measurements of bright massive stars. These massive stars are very hot and luminous objects emitting copious amounts of UV radiation. The properties of these stars during their life and their death in gigantic supernova explosions make them key players for the evolution of the Universe.
The UV photometer will be used for imaging photometric observations of massive stars in the spectral range from 250 to 350 nm. The strength of space photometry is the absence of signal perturbation by the Earth’s atmosphere and the continuity of the time-series. Precisely measuring photometric variations allows studying radial and non-radial pulsations of stars. This discipline, called asteroseismology, is currently the most powerful technique for probing the physical conditions in the interiors of stars. An important problem in asteroseismology of massive stars is the mode identification. Simultaneous observations in the near UV (250-350 nm) and in the visible (600 nm) provide the best combination for precise and accurate mode identification based on amplitude ratios in massive stars. Data in the latter pass-band are currently covered by the satellites of the BRITE constellation. Combining the observations of our instrument with those of BRITE will hence result in unprecedented results for pulsating massive stars.
The baseline for the UV photometer is a Ritchey-Chrétien telescope composed of two reflective hyperbolic mirrors that focalize the light coming from space onto a focal plane protected by an optical filter.
We will present the optimized optical design of the payload and its associated optical sensor. A photometric budget taking into account the characteristics of the target’s stars and the payload performances will also be presented. We will further discuss the observation strategy. Finally, the accommodation of the payload in the spacecraft and its sub-units will be shown as well as mission and preliminary thermal analyses of the whole system obtained after accommodation.