The design and characterisation of a low-cost micro-satellite thermal IR imager based on COTS technology.

The region of the optical spectrum known as the thermal infrared (TIR) has long been a waveband of interest for space-based Earth observation. By mapping thermal variations, on-orbit TIR imaging radiometers can provide a significant amount of information regarding the temperature and emissivity profiles of the ground scene. The traditional approach to space-borne TIR instrument design usually focuses on high radiometric sensitivity and hence, typically relies on expensive and bulky cryogenically-cooled detector technology. This approach yields instruments that are very precise but are cost- and/or size-limited for flight on single large-scale satellite platforms. While these systems serve the bulk of the TIR user community needs, there are numerous user groups still ill-served due to the finite data products offered by these handful of instruments. The main objective of this thesis is to advance the field of TIR instrument design by developing a novel TIR imager, affordable and compact enough for flight on multiple microsatellite platforms, therefore enabling low-cost high temporal/medium spatial resolution TIR data products. Leveraging the latest low-cost miniaturization developments in the terrestrial uncooled TIR detector industry has been the key to reducing instrument cost and size. In this thesis, a 6 kg thermal infrared (TIR) imaging radiometer, compatible with a Surrey Satellite Technology Limited (SSTL) Disaster Monitoring Constellation (DMC) micro-satellite has been designed. The flight instrument concept utilizes two commercial-off-the-shelf (COTS) un-cooled microbolometer arrays in a pushbroom configuration to collect Earth observation data in two TIR wavebands (3-5 and 8-12 mum). After the bench-top characterisation of a prototype, a computer model was created to predict the expected on-orbit performance. Analysis has shown that a flight version of this instrument flown in the DMC would yield a 0.4 K noise equivalent temperature difference (NETD) for a 300 K ground scene, a 300-metre ground sample distance (GSD), and a 1 to 7 day ground revisit time, depending on the instrument and constellation configuration. Its application in specific niche or currently ill-served mission areas, such as autonomous global thermal change detection dedicated to highly specialized user communities, is proposed