Design and characterisation of a highly miniaturised radiation monitor HMRM

Abstract Reliable data on the ionising radiation environment is regarded as very important to ensure an efficient design and operation of spacecraft. Here we present a novel Highly Miniaturised Radiation Monitor (HMRM) that aims to greatly reduce costs and complexity of radiation detectors. At the core of the current design is a CMOS Image Sensor. Size and mass are considerably reduced thanks to this approach and there is also scope for a reduction in power consumption. This makes the HMRM much easier to integrate on a spacecraft. The innovative architecture of the proposed radiation monitor will also make particle identification possible. The image sensor is based on a 50 by 51 pixel array. The selected pixel is a 4T, to reduce the noise. The array is read out in snapshot mode at a frame-rate of 10,000 fps. Biasing currents and voltages are generated on-chip to reduce the number of signals required to control the sensor. The sensor is designed to work on a large range of temperatures, from −40 °C to +80 °C; hence a temperature sensor has been integrated. The digital output data is obtained with a three-bit column parallel ADC with programmable thresholds. An analogue readout has been also designed to characterise and debug the ASIC. In this following paper we also want to present the results obtained from the measurements on the prototype. Preliminary PTC plots show a gain of 60 µV/e − with CDS and a noise of 17 e − rms, which includes the noise from the external board.