Abstract
The OSIRIS-REx Thermal Emission Spectrometer (OTES) will provide remote measurements of mineralogy and thermophysical properties of Bennu to map its surface, help select the OSIRIS-REx sampling site, and investigate the Yarkovsky effect. OTES is a Fourier Transform spectrometer covering the spectral range 5.71–100 μm (1750mbox{--}100~mbox{cm}^{-1}) with a spectral sample interval of 8.66~mbox{cm}^{-1} and a 6.5-mrad field of view. The OTES telescope is a 15.2-cm diameter Cassegrain telescope that feeds a flat-plate Michelson moving mirror mounted on a linear voice-coil motor assembly. A single uncooled deuterated l-alanine doped triglycine sulfate (DLATGS) pyroelectric detector is used to sample the interferogram every two seconds. Redundant ∼0.855 μm laser diodes are used in a metrology interferometer to provide precise moving mirror control and IR sampling at 772 Hz. The beamsplitter is a 38-mm diameter, 1-mm thick chemical vapor deposited diamond with an antireflection microstructure to minimize surface reflection. An internal calibration cone blackbody target provides radiometric calibration. The radiometric precision in a single spectrum is leq2.2 times 10^{-8}~mbox{W},mbox{cm}^{-2},mbox{sr} ^{-1}/mbox{cm}^{-1} between 300 and 1350~mbox{cm}^{-1}. The absolute integrated radiance error is <1% for scene temperatures ranging from 150 to 380 K. The overall OTES envelope size is 37.5 times 28.9 times 52.2~mbox{cm}, and the mass is 6.27 kg. The power consumption is 10.8 W average. OTES was developed by Arizona State University with Moog Broad Reach developing the electronics. OTES was integrated, tested, and radiometrically calibrated on the Arizona State University campus in Tempe, AZ.
Highlights
The OSIRIS-REx Thermal Emission Spectrometer (OTES) instrument will aid in the characterization and sample site selection of the asteroid Bennu (101955 Bennu) for the OSIRISREx sample return mission (Lauretta et al 2017) through the determination of Bennu’s mineralogy and thermophysical properties
In this paper we present a description of the OTES as-built instrument, calibration methods and knowledge, and system performance
The interferometer moving mirror mechanism is identical to these previous instruments, the telescope size and aperture are similar to TES, and the detector is similar to both instruments
Summary
The OSIRIS-REx Thermal Emission Spectrometer (OTES) instrument will aid in the characterization and sample site selection of the asteroid Bennu (101955 Bennu) for the OSIRISREx sample return mission (Lauretta et al 2017) through the determination of Bennu’s mineralogy and thermophysical properties. Page 3 of 39 87 physical properties (e.g., grain size and subsurface layering) using diurnal temperature measurements; (4) measure thermal emission to determine properties that contribute to the Yarkovsky effect; and (5) search for and characterize volatile outgassing, satellites, and space weathering. These objectives are addressed using thermal infrared spectral observations between 1750 and 100 cm−1 (5.7 to 100 μm). We describe the basic instrument operational strategy, data processing methodology, and the plans for archiving the data through the Planetary Data System
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