The Thermal Earth Resource Monitoring Instrument (THERMI) has been designed to meet stringent Landsat heritage requirements with reduced size, weight and power (SWaP). The instrument design provides Earth resource monitoring through the use of two long-wave infrared bands that measure the land surface temperatures. These bands are especially valuable for monitoring water resources and water use. Instrument subsystems, including electronics, cryocooler, thermal management, optical telescope assembly, focal plane module, in-flight calibrator, and scene select mirror were studied and conceptually designed to reduce overall THERMI SWaP. Reductions in SWaP make it possible for THERMI to fit on a small satellite bus with room available for an additional optical instrument. Since mission cost historically correlates well with mass and power on-orbit, it is expected that significant cost savings will result from the predicted SWaP reductions.
Space Dynamics Laboratory (SDL), in partnership with GATS, Inc., designed and built an instrument to conduct the
Solar Occultation for Ice Experiment (SOFIE). SOFIE is an infrared sensor in the NASA Aeronomy of Ice in the
Mesosphere (AIM) instrument suite. AIM's mission is to study polar mesospheric clouds (PMCs). SOFIE will make
measurements in 16 separate spectral bands, arranged in 8 pairs between 0.29 and 5.3 μm. Each band pair will provide
differential absorption limb-path transmission profiles for an atmospheric component of interest, by observing the sun
through the limb of the atmsophere during solar occulation as AIM orbits Earth. The AIM mission was launched in
April, 2007.
SOFIE originally completed calibration and was delivered in March 2006. The design originally included a steering
mirror coaligned with the science detectors to track the sun during occultation events. During spacecraft integration, a
test anomaly resulted in damage to the steering mirror mechanism, resulting in the removal of this hardware from the
instrument. Subsequently, additional ground calibration experiments were performed to validate the sensor performance
following the change. Measurements performed in this additional phase of calibration testing included SOFIE end-to-end
relative spectral response, nonlinearity, and spatial characterization. SDL's multifunction infrared calibrator #1
(MIC1) was used to present sources to the instrument for calibration. Relative spectral response (RSR) measurements
were performed using a step-scan Fourier transform spectrometer (FTS). Out-of-band RSR was measured to
approximately 0.01% of in-band peak response using the cascaded filter Fourier transform spectrometer (CFFTS)
method. Linearity calibration was performed using a calcium fluoride attenuator in combination with a 3000K
blackbody. Spatial characterization was accomplished using a point source and the MIC1 pointing mirror. These
techniques are described in detail, and resulting SOFIE performance parameters are presented and compared to original
SOFIE calibration results.
Space Dynamics Laboratory (SDL), in partnership with GATS, Inc., designed, built, and calibrated an instrument to conduct the Solar Occultation for Ice Experiment (SOFIE). SOFIE is the primary infrared sensor in the NASA Aeronomy of Ice in the Mesosphere (AIM) instrument suite. AIM's mission is to study polar mesospheric clouds (PMCs). SOFIE will make measurements in 16 separate spectral bands, arranged in 8 pairs between 0.29 and 5.3 μm. Each band pair will provide differential absorption limb-path transmission profiles for an atmospheric component of interest, by observing the sun through the limb of the atmosphere during solar occultation as AIM orbits Earth. A fast steering mirror and imaging sun sensor coaligned with the detectors will track the sun during occultation events and maintain stable alignment of the Sun on the detectors. This paper outlines the instrument specifications and resulting design. The success of the design process followed at SDL is illustrated by comparison of instrument model calculations to calibration results, and lessons learned during the SOFIE program are discussed. Relative spectral response predictions based on component measurements are compared to end-to-end spectral response measurements. Field-of-view measurements are compared to design expectations, and radiometric predictions are compared to results from blackbody and solar measurements. Measurements of SOFIE detector response non-linearity are presented, and compared to expectations based on simple detector models.
Space Dynamics Laboratory (SDL) recently designed, built, and delivered the Solar Occultation for Ice Experiment (SOFIE) instrument as the primary sensor in the NASA Aeronomy of Ice in the Mesosphere (AIM) instrument suite. AIM's mission is to study polar mesospheric clouds (PMCs). SOFIE will make measurements in 16 separate spectral bands, arranged in eight pairs between 0.29 and 5.3 μm. Each band pair will provide differential absorption limb-path transmission profiles for an atmospheric component of interest, by observing the sun through the limb of the atmsophere during solar occulation as AIM orbits Earth. A pointing mirror and imaging sun sensor coaligned with the detectors are used to track the sun during occulation events and maintain stable alignment of the sun on the detectors. This paper outlines the mission requirements and goals, gives an overview of the instrument design, fabrication, testing and calibration results, and discusses lessons learned in the process.
The Solar Occultation for Ice Experiment (SOFIE) instrument is one of three science instruments for the Aeronomy of
Ice in the Mesosphere (AIM) mission. SOFIE is used to measure solar attenuation by mesospheric ice aerosols during
each observatory sunrise and sunset using an 8-channel (16-detector) differential absorption radiometer. It directly
views the sun and compares the near UV to the mid-IR spectral response during exo-atmospheric and endo-atmospheric
measurements. Deposition of molecular films can degrade the reflectance and transmittance of SOFIE's optics. During
on-orbit performance, it may be possible for the extended solar exposure to promote photochemical deposition and
darkening effects in the UV. This paper will review the methods used to derive and verify contamination control
budgets for particulate and molecular contamination during the fabrication and testing of the SOFIE instrument.
Reported results include the molecular surface cleanliness throughout integration and test as well as outgassing
measurements using internal and external quartz crystal microbalances. This information provides important baseline
data for future correlation of instrument outgassing and potential photo-deposited contamination effects should they
occur during on-orbit solar exposure
The Space Dynamics Laboratory at Utah State University designed and constructed two identical cryogenic mid- infrared radiometers that will be used as NIST-traceable radiometric calibration transfer standards. The radiometer design is similar to the NIST BXR radiometer and thus may be calibrated at NIST using the same sources and procedures used with the BXR. Important features of these radiometers include a single element, chopped indium antimonide detector cooled by a Stirling-cycle cryocooler, two 8-position filter wheels populated with spectral and neutral density filters, and an indium antimonide focal plane array (FPA) that can be temporarily positioned at the field stop for alignment and diagnostics. This paper presents the design and results of the as-built optical and thermal performance of these radiometers. It also presents the testing set up and calibration philosophy and approach.
The SPIRIT III (spatial infrared imaging telescope) radiometer is the primary instrument aboard the midcourse space experiment (MSX), which was launched on 24 April 1997. The Space Dynamics Laboratory at Utah State University (SDL/USU) developed and implemented a ground-based procedure to optimize the focus of the SPIRIT III radiometer. The procedure used point source data acquired during ground measurements. These measurements were obtained with a calibration source consisting of an illuminated pinhole near the focus of a cryogenically cooled collimator. Simulated point source measurements were obtained at multiple focus positions by translating the pinhole along the optical axis inside and outside the optimum focus of the collimator. The radiometer was found to be slightly out of focus, and the detector focal plane arrays were moved to positions indicated by the test results. This method employed a single cryogenic cycle to measure both the distance and direction needed to adjust each array for optimal focus. The results of the SPIRIT III on- orbit stellar point source observation demonstrate the success of the technique. This paper describes the method and hardware used to achieve focus optimization.
KEYWORDS: Reflectivity, Temperature metrology, System on a chip, Humidity, Environmental sensing, Black bodies, Calibration, Cryogenics, Scanning electron microscopy, Aluminum
Martin Black and enhanced Martin Black samples were heated above 620 K and also cooled to 77 K while the directional reflectance and emittance were measured in the spectral region of 1.35 to 26 micrometer. Little emittance variation was found for both surfaces below 300 K. From 77 K to 315 K Martin Black emittance was 98.5% or greater from 7.5 to 24 micrometer. Similarly, enhanced Martin Black emittance was 96% or greater. Furthermore, these conditions apply up to 620 K. Significant reflectance variations below 7.5 micrometer were observed at ambient temperature after baking samples at 620 K both in air and vacuum environments. Reflectance variations as a function of temperature from 300 to 620 K were measured. Humidity and vacuum exposure effects on the surface reflectance properties were also investigated. Post-backed sample reflectance near 5 micrometer was extremely sensitive to ambient air exposure.
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