In-flight performance of the Multi-band Uncooled Radiometer Instrument (MURI) thermal sensor

Abstract

NASA's Earth Science and Technology Office (ESTO) encourages and promotes new and innovative science technologies to improve how the Earth is observed from space. Through their Instrument Incubator Program (IIP), an uncooled multispectral thermal instrument was fabricated and flight-tested to demonstrate its potential utility to support future spaceborne missions. While uncooled systems offer the attractive advantage of eliminating the need for large and expensive cryocoolers, they naturally introduce challenges that must be overcome to achieve the fidelity observed in image data acquired by existing cooled spaceborne instruments.In this work, the Multi-band Uncooled Radiometer Instrument (MURI) system, designed and built by Leonardo DRS, is fabricated using custom microbolometer detector arrays also developed by Leonardo DRS. Potential issues associated with thermal imaging using microbolometers from a spaceborne platform are discussed and innovative engineering solutions to overcome these issues are highlighted. Details of three airborne campaigns designed to assess the fidelity of MURI image data, using Landsat 8's Thermal Infrared Sensor's (TIRS) radiometric & geometric requirements as a baseline, are presented. Results of these campaigns show that the as-built MURI system significantly outperforms these requirements, as compared to ground-based reference measurements. Sustainable Land Imaging (SLI) requirements indicate that a five-band instrument is desirable to improve future Landsat science while maintaining continuity with previous thermal instruments. Considering its multiband design, temperature/emissivity separation (TES) is applied to MURI flight data and compared to ground-based spectrometer measurements for several materials. Results of this study indicate that MURI's TES performance is in-line with existing spaceborne systems. When considered in conjunction with its radiometric fidelity, the MURI uncooled system represents an intriguing option for future space-based missions.