AIRWATCH: onboard readout and data handling

A basic problem in an AIRWATCH based experiment is the development of suitable trigger, read-out and data handling techniques. Considering a matrix of image elements to read- out, ideally one would like to have as many position and timing channels as pixels in the image, but for obvious practical and cost reasons, this solution is not always applicable. In fact the complexity of the electronics demanding a huge amount of channels, is not generally suitable for mission base don satellites, where stringent limitations are present for what concerns power supply, weight and telemetry. One way to deal with such a problem, in the assumption of using a fast detector capable of detecting single photoelectron, is to reduce the number of position and timing channels without significant loss of performance. We present a modular read-out electronics system called 'FIRE'. The modular hierarchical organization of FIRE allow to register X-Y position and arrival time of the single photoelectrons. To check the validity of the method, a set of simulated data was produced and analyzed. Results are illustrated both for the read-out performance and the event reconstruction efficiency.