  In ultraviolet (UV) astronomical observations, photons from the sources are
very few compared to the visible or infrared (IR) wavelength ranges. Detectors
operating in the UV usually employ a photon-counting mode of operation. These
detectors usually have an image intensifier sensitive to UV photons and a
readout mechanism that employs photon counting. The development of readouts for
these detectors is resource-intensive and expensive. In this paper, we describe
the development of a low-cost UV photon-counting detector processing unit that
employs a Raspberry Pi with its in built readout to perform the photon-counting
operation. Our system can operate in both 3x3 and 5x5 window modes at 30 frames
per sec (fps), where 5x5 window mode also enables the provision of detection of
double events. The system can be built quickly from readily available
custom-off-the-shelf (COTS) components and is thus used in inexpensive CubeSats
or small satellite missions. This low-cost solution promises to broaden access
to UV observations, advancing research possibilities in space-based astronomy.
