First On-orbit Results from CIRiS, a Cubesat Infrared Imaging Radiometer with On-orbit Calibration System

Abstract:

CIRiS (Compact Infrared Radiometer in Space) is a multispectral infrared, radiometric imaging instrument integrated to a 6U Cubesat spacecraft, and designed for a variety of Earth Science and operational applications. Developed and built by Ball Aerospace, the instrument carries an on-board calibration system and implements on-board image processing for SNR improvement. System architecture, including entirely uncooled operation, and technology choices enable a simple, low size, weight and power implementation suitable for constellations of Earth-observing spacecraft. CIRiS was inserted into low Earth orbit on Feb 1, 2020 on board its Cubesat spacecraft.

The CIRiS calibration system features multiple on-orbit parameter selections for performance optimization. These include three options for calibration views: a view to deep space, and to two on-board, flat panel calibration sources coated with high emissivity (e> 0.9965) carbon nanotube films. The instrument images simultaneously in three thermal infrared bands between 7.5 um and 13.5 um.

CIRiS is now in an orbit with 52 deg inclination and 470 km altitude. Pixel footprint on the ground is 160 m. Scans of the field of view through 360 deg by rotation of the scene select mirror demonstrate all four viewing modes: nadir-viewing science mode, zenith-viewing of deep space for calibration, and calibration views of the two on-board sources. Ground images have been acquired in all three bands and have been calibrated with the on-orbit calibration system. Temperature telemetry from 12 locations around the instrument provides a means to correct for thermal drift between calibrations. New images and characterization results will be discussed.

Earth Science applications of CIRiS include evapotranspiration measurement for crop irrigation sufficiency and Earth system studies, prediction of drought conditions, studies of cloud radiance and cloud microphysics, limb measurements of atmospheric trace gases, and land and sea surface temperature measurements for global climate model validation. Development of a second version of the instrument, Lunar CIRiS or L-CIRiS, is under way for studies of the mineralogical composition and thermophysics of the lunar surface.