Advanced time-of-flight system-on-a-chip for remote sensing instruments

Abstract

Many remote sensing instruments include the detection of photon/particle events, position decoding and time-of-hit measurement. Microchannel plates (MCPs) are widely used to detect photons and particles for position sensing and relative time of impact in imaging and time-of-flight (TOF) spectrometers. Two dimensional delay lines are used for fast and accurate readout of MCPs. Instruments that use these techniques are Neutral Atom Imagers and Particle Spectrometers to study planetary magnetospheres; photon counting detectors for spectrographic imaging in the far-UV and extreme-UV to study the earth's aurora and airglow; laser range finders. In all these there is a requirement of accurate and/or fast time interval measurement. An advance TOF system-on-a-chip has been developed that includes the complete signal processing electronics for MCP readout: two channels (start- stop) of amplifiers and constant fraction discriminators (CFDs), an 11-bit Time to Digital Converter (TDC), and control/readout logic. The TOF chip is capable for a time resolution of <50ps including time walk and time jitter, the dead time is as low as 0.5us; the power dissipation is a function of counting rate and time resolution-for resolution of ~100ps the power is <20mW at rates <100K/sec and <50mW at rates <1M/sec. The TOF chip flies on the NASA/IMAGE spacecraft launched in 2000 and is part of many other science instruments such as particles and fields, and laser altimeter on MESSENGER.