  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 {\mu}m (1750 - 100 cm-1) with a spectral sample
interval of 8.66 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 {\mu}m
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 <= 2.2 x 10-8 W cm-2 sr-1/cm-1 between 300 and 1350 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 x 28.9 x 52.2 cm, and
the mass is 6.27 kg. The power consumption is 10.8 W average. The 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.
