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.
The Multiple Kill Vehicle (MKV) system, which is being developed by the US Missile Defense Agency (MDA), is a
midcourse payload that includes a carrier vehicle and a number of small kill vehicles. During the mission, the carrier
vehicle dispenses the kill vehicles to address a complex threat environment and directs each kill vehicle toward the
intercept point for its assigned threat object. As part of the long range carrier vehicle sensor development strategy, MDA
and project leaders have developed a pathfinder sensor and are in the process of developing two subsequent
demonstration sensors to provide proof of concept and to demonstrate technology. To increase the probability of
successful development of the sensor system, detailed calibration measurements have been included as part of the sensor
development. A detailed sensor calibration can provide a thorough understanding of sensor operation and performance,
verifying that the sensor can meet the mission requirements. This approach to instrument knowledge will help ensure the
program success and reduce cost and schedule risks. The Space Dynamics Laboratory at Utah State University (SDL)
completed a calibration test campaign for the pathfinder sensor in April 2008. Similar calibration efforts are planned in
2009 for the two demonstration sensors. This paper provides an overview of calibration benefits, requirements,
approach, facility, measurements, and preliminary results of the pathfinder calibration.
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), in partnership with GATS, Inc., designed and built 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 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 atmosphere during solar occultation as AIM orbits Earth. A pointing mirror and imaging sun sensor coaligned with the detectors are used to track the sun during occultation events and maintain stable alignment of the sun on the detectors. Ground calibration experiments were performed to measure SOFIE end-to-end relative spectral response, nonlinearity, and spatial characteristics. 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. SOFIE sun sensor tracking algorithms were verified using a heliostat and relay mirrors to observe the sun from the ground. These techniques are described in detail, and resulting SOFIE performance parameters are presented.
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 Spatial Infrared Imaging Telescope (SPIRIT III) is the primary sensor aboard the Midcourse Space Experiment (MSX), which was launched 24 April 1996. SPIRIT III included a Fourier transform spectrometer that collected terrestrial and celestial background phenomenology data for the Ballistic Missile Defense Organization (BMDO). This spectrometer used a helium-neon reference laser to measure the optical path difference (OPD) in the spectrometer and to command the analog-to-digital conversion of the infrared detector signals, thereby ensuring the data were sampled at precise increments of OPD. Spectrometer data must be sampled at accurate increments of OPD to optimize the spectral resolution and spectral position of the transformed spectra. Unfortunately, a failure in the power supply preregulator at the MSX spacecraft/SPIRIT III interface early in the mission forced the spectrometer to be operated without the reference laser until a failure investigation was completed. During this time data were collected in a backup mode that used an electronic clock to sample the data. These data were sampled evenly in time, and because the scan velocity varied, at nonuniform increments of OPD. The scan velocity profile depended on scan direction and scan length, and varied over time, greatly degrading the spectral resolution and spectral and radiometric accuracy of the measurements. The Convert software used to process the SPIRIT III data was modified to resample the clock-sampled data at even increments of OPD, using scan velocity profiles determined from ground and on-orbit data, greatly improving the quality of the clock-sampled data. This paper presents the resampling algorithm, the characterization of the scan velocity profiles, and the results of applying the resampling algorithm to on-orbit data.
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