Detector Safety

The Swift mission requires the UVOT to have autonomous functionality in order to protect itself against potentially damaging bright sources. This is accomplished through the use of a bright source catalog and a real time system for monitoring the raw pixel data from the camera and automatically reducing the detector gain when a signal above a programmable threshold is seen. The bright source limit is typically triggered by sources with a magnitude of V = 5-6. A complicating factor is that brighter stars will suffer from high coincidence losses, making photometry very difficult.