Development of a high performance detector readout for astrophysical and planetary instrumentation

There are opportunities in space science for UV imaging instruments with photon counting sensitivity that can accommodate scenes with large dynamic range whilst maintaining the ability for very high spatial resolution imaging when desired. Current UV imaging space instruments have limitations that reduce the performance in meeting this challenge. The microchannel plate detector has an established heritage in UV astronomy and provides low noise single photon counting imaging with high spatial resolution, high dynamic range, solar-blind capability and radiation hardness. To fully complement this performance requires a new detector readout system with great flexibility in processing individual photon events, achieving high spatial resolution and with high count rate capability. An image readout system has been developed that utilises a new, low-noise capacitive division readout and has the potential to meet these high performance requirements. Unlike traditional centroiding image readout schemes that use a fixed pulse shaping time, this system has the capability to adapt to the luminosity conditions and the flexibility to optimise the image spatial resolution against the photon event rate. The design employs a low-noise front-end electronics system that uses a pulse digitisation approach to transfer the signal filtering capability into the digital signal processing domain, enabling the flexibility to select the optimum shaping scheme for the required resolution and count rate. The development progress of the instrument and imaging software is described for both a fixed shaping time readout design and an adaptable shaping solution and new performance results for the capacitive division readout are presented.