OSIRIS-REx Thermal Emission Spectrometer (OTES)

OSIRIS-REx Thermal Emission Spectrometer (OTES)
Name	OSIRIS-REx Thermal Emission Spectrometer (OTES)
Operator	NASA / University of Arizona / Lockheed Martin
Mission	OSIRIS-REx
Type	Infrared spectrometer
Mass	7 kg (approx.)
Power	~10 W (operational)
Wavelength	5–50 µm (approx.)
Resolution	~8 cm−1 (approx.)
Status	Completed (sample return 2023)

OSIRIS-REx Thermal Emission Spectrometer (OTES) OTES was a flight instrument aboard the OSIRIS-REx spacecraft designed to measure thermal infrared emission from the surface of the asteroid 101955 Bennu. Developed through collaborations among the University of Arizona, NASA, and industry partners, OTES provided compositional and thermophysical data to support sampling operations and scientific investigation during the mission led by Dante Lauretta. The instrument's datasets complemented other payloads including OCAMS, OLA, OCS, REXIS, and OTES counterparts.

Overview

OTES operated as a Fourier-transform infrared spectrometer on the OSIRIS-REx mission to 101955 Bennu, delivering spatially resolved spectra of surface thermal emission across mid-infrared wavelengths. The instrument contributed to hazard assessment during the TAG maneuver and informed selection of the final sampling site near Nightingale. OTES measurements supported investigations into mineralogy, thermal inertia, and surface heterogeneity relevant to planetary science objectives outlined by NASA Headquarters, the Planetary Science Division, and the Small Body Node of the Planetary Data System.

Instrument Design and Specifications

The OTES design combined heritage from instruments developed for Mars Global Surveyor, Mars Odyssey, and Moon Mineralogy Mapper teams with innovations by the University of Arizona and industrial partners including Santa Barbara Research Center and Lockheed Martin Space Systems. Key components included a Michelson interferometer, a deuterated triglycine sulfate detector, and a telescope assembly. The instrument architecture balanced mass and power constraints set by Lockheed Martin, thermal control considerations overseen by NASA Glenn Research Center teams, and calibration needs influenced by lessons from VIR (VIR) and TES (Thermal Emission Spectrometer). OTES was designed to achieve spectral coverage roughly spanning 5–50 micrometers with spectral sampling enabling identification of silicates, carbonates, sulfates, and organics analogous to materials studied at Lunar Reconnaissance Orbiter, Hayabusa2, and Rosetta missions.

Operation and Calibration

OTES operation integrated spacecraft pointing managed by Lockheed Martin Space and navigation inputs from the OSIRIS-REx Navigation Team led by Dante Lauretta collaborators. In-flight calibration used space viewpoints, internal blackbody sources, and observations of cold sky to track instrument responsivity and detector performance, with calibration procedures informed by heritage from Mars Climate Sounder and TES campaigns. Ground calibration prior to launch involved facilities at the University of Arizona and coordination with the Jet Propulsion Laboratory calibration labs. Operational sequences were planned in coordination with the Science Operations Center and the Mission Operations Center to acquire global mapping, site-specific targeted observations, and low-altitude scans during approach and proximity operations.

Science Objectives and Measurements

OTES targeted science objectives aligned with OSIRIS-REx goals: characterize the mineralogical and thermophysical properties of 101955 Bennu to provide context for returned samples and to constrain models of primitive solar system materials. Measurements emphasized identification of silicate reststrahlen features, emissivity minima and maxima diagnostic of olivine and pyroxene, and spectral signatures indicative of hydrated minerals or carbonates analogous to finds at Itokawa and Ryugu. OTES-derived thermal inertia maps informed interpretations of particle size distribution, cohesion, and regolith porosity relevant to sampleability and matched investigations by OCAMS imaging, OLA lidar topography, and REXIS X-ray fluorescence compositional constraints. The instrument also contributed to studies of diurnal temperature variations, Yarkovsky-related thermal effects referenced in Yarkovsky effect literature, and comparisons with meteorite classes curated at institutions like the Smithsonian Institution and Natural History Museum, London.

Data Processing and Products

Raw interferograms from OTES were processed by the Planetary Data System pipeline and by teams at the University of Arizona to produce calibrated radiance and emissivity spectra, thermal inertia maps, and georeferenced data cubes compatible with tools used at the Jet Propulsion Laboratory and the NASA Planetary Science Data archives. Level 1 products included instrument-corrected radiance; Level 2 produced emissivity and brightness temperature; Level 3 delivered mosaicked maps and derived thermophysical parameter fields used by investigators at Brown University, University of California, Berkeley, Massachusetts Institute of Technology, and international partners such as University College London and University of Tokyo. Data release schedules followed policies coordinated with NASA and the OSIRIS-REx Science Team; datasets contributed to publications in journals like Science (journal), Nature (journal), and Icarus (journal).

Mission Contributions and Results

OTES played a critical role in characterizing candidate sampling sites, confirming the presence of fine-grained regolith at Nightingale and aiding the selection process that led to successful TAG in 2020 and sample return to Earth in 2023. Scientific results from OTES revealed spatial variability in mineralogy and thermal properties across Bennu consistent with a primitive, carbon-rich assemblage and provided constraints on surface alteration processes comparable to analyses from Hayabusa and Hayabusa2. OTES-derived thermophysical models informed studies of Yarkovsky effect forces on Bennu's orbit and supported risk assessments by teams at NASA Jet Propulsion Laboratory. The instrument's legacy includes high-value datasets archived in the Planetary Data System and a body of peer-reviewed literature advancing understanding of near-Earth asteroids, primitive solar system materials, and sample-return science investigations conducted by institutions such as University of Arizona, NASA, Lockheed Martin, and global research partners.

Category:Spacecraft instruments Category:Spectrometers Category:OSIRIS-REx