The BRITE Constellation Space Telescope Design and Test of a Wide Field, High Resolution, Low Noise Optical Telescope for a Nanosatellite Constellation

The BRIght Target Explorer (BRITE) Constellation is a nanosatellite-based astronomy mission tasked with measuring stellar variability of the brightest and most massive stars in the Earth’s sky. Charged with the task of capturing the stellar cycles through photometry, the payload of the BRITE nanosatellite is a wide-field, high resolution, low noise CCD-based refracting telescope capable of observing stars with apparent magnitude of +3.5 and brighter with a signal to noise of 3,000 per 1,000s cumulative exposure. A number of payload system design aspects of particular interest to the small satellite community are discussed including a low-noise CCD-driver design that respects the power limitations of a nanosatellite, a primarily passive thermal control strategy for stabilizing the CCD temperature, a software architecture that maximizes scientific output by enabling highly flexible yet automated payload operations, and a modular mechanical design that ensures maximum flexibility during assembly, focusing, and debugging. In addition, this paper discusses key aspects of instrument integration and testing including the focusing process and the challenges associated with achieving acceptable Point Spread Functions in a wide-field scientific instrument over the entire field of view, imager characterization of bias, gain, saturation level, dark current, and readout noise over temperature