Abstract
CIRiS (Compact Infrared Radiometer in Space) is a radiometric imaging instrument on a 6U CubeSat bus designed for earth imaging in the thermal infrared (7.5 to 13. 5 um) spectral region. The instrument features a versatile calibration system for optimizing on-orbit radiometric calibration performance, and a modular design facilitating modifications for specialized missions. The objective of the upcoming CIRiS mission is to demonstrate technologies for high calibration performance within 6U CubeSat constraints. These include an uncooled microbolometer imaging focal plane array (FPA) that makes a cryocooler unnecessary, and high-emissivity (e > 0.996) carbon nanotube (CNT) blackbody sources on 1/8 inch-thick solid substrates, the latter replacing bulkier cavity blackbodies.
Instrument on-orbit operation utilizes up to three calibration views to deep space and to two CNT sources, one of which is heated and temperature controlled. A CIRiS radiometric uncertainty budget now under development employs ground measurement and space effect calculations. Thermal drift over the orbit potentially generates radiometric error via the FPA and other instrument components and is therefore the subject of ground measurement. Careful thermal control of the CNT sources and other critical hardware is an integral part of the calibration strategy.
The F/1.8 refractive optical system includes a butcher block filter over the 640 x 480 format FPA. This configuration enables simultaneous imaging in three infrared wavelength bands as the instrument scans the earth from low earth orbit (LEO). Assuming launch from the International Space Station into a 400 km altitude LEO the CIRiS ground sampling distance is 130 m with 83 km swath. On-orbit frame co-adding at the nominal 30 fps frame rate improves imaging and calibration SNR.
CIRiS’ calibration capabilities implemented from CubeSat constellations will enable accurate surface temperature and soil moisture data collection across much of the earth with short, potentially daily, revisit times. Variants on the CIRiS design could also provide an inexpensive and focused complement to more extensive earth radiation imbalance measurements.
CIRiS: Compact Infrared Radiometer in Space
CIRiS (Compact Infrared Radiometer in Space) is a radiometric imaging instrument on a 6U CubeSat bus designed for earth imaging in the thermal infrared (7.5 to 13. 5 um) spectral region. The instrument features a versatile calibration system for optimizing on-orbit radiometric calibration performance, and a modular design facilitating modifications for specialized missions. The objective of the upcoming CIRiS mission is to demonstrate technologies for high calibration performance within 6U CubeSat constraints. These include an uncooled microbolometer imaging focal plane array (FPA) that makes a cryocooler unnecessary, and high-emissivity (e > 0.996) carbon nanotube (CNT) blackbody sources on 1/8 inch-thick solid substrates, the latter replacing bulkier cavity blackbodies.
Instrument on-orbit operation utilizes up to three calibration views to deep space and to two CNT sources, one of which is heated and temperature controlled. A CIRiS radiometric uncertainty budget now under development employs ground measurement and space effect calculations. Thermal drift over the orbit potentially generates radiometric error via the FPA and other instrument components and is therefore the subject of ground measurement. Careful thermal control of the CNT sources and other critical hardware is an integral part of the calibration strategy.
The F/1.8 refractive optical system includes a butcher block filter over the 640 x 480 format FPA. This configuration enables simultaneous imaging in three infrared wavelength bands as the instrument scans the earth from low earth orbit (LEO). Assuming launch from the International Space Station into a 400 km altitude LEO the CIRiS ground sampling distance is 130 m with 83 km swath. On-orbit frame co-adding at the nominal 30 fps frame rate improves imaging and calibration SNR.
CIRiS’ calibration capabilities implemented from CubeSat constellations will enable accurate surface temperature and soil moisture data collection across much of the earth with short, potentially daily, revisit times. Variants on the CIRiS design could also provide an inexpensive and focused complement to more extensive earth radiation imbalance measurements.