SPIRIT III Radiometer Saturation Effect

The Space Dynamics Laboratory at Utah State University (SDL/USU) calibrated the spatial infrared imaging telescope (SPIRIT) radiometer as part of its contract with the Ballistic Missile Defense Organization (BMDO). During the calibration effort, SDL/USU discovered and characterized a phenomenon that reduces the detector dark offset and responsivity after saturation, which results in increased calibration uncertainties directly following a saturation event. The magnitude and recovery duration for the dark offset and responsivity depend on several variables, including saturation flux level, saturation integration mode, integration mode, focal plane temperature, and saturation duration. Detector-to-detector variations in the magnitude of the saturation effect were also observed for detectors within an array. This phenomenon and the methods used to characterize it are described

Focus Optimization of the SPIRIT III Radiometer

The spatial infrared imaging telescope (SPIRIT III) radiometer is the primary instrument aboard the Midcourse Space Experiment (MSX), which was launched on April 24, 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. The method and hardware used to achieve focus optimization are described

Component Level Prediction Versus System Level Measurement of SABER Relative Spectral Response

A 10-channel infrared (1.25–17.24 mm wavelength) radiometer known as SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) is one of four experiments that will fly on the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics) mission that was successfully launched on 7 December 2001. Theoretical models of the relative spectral response (RSR) for each SABER channel were developed during the design and build of the instrument. The RSR calculations were then refined using a component level technique where theoretical predictions of filter transmittance were replaced with measurements from filter witness samples. During SABER ground calibration, full system measurements of RSR were performed using a Michelson step-scan interferometer to present an interferometrically modulated infrared source to the instrument with the resultant interferogram recorded by the instrument detectors. Fourier transform of this interferogram and correction of the resulting spectrum for the spectral output of the interferometer and the transmittance of any intervening optics provide a measurement of the system level RSR. We compare the full system level measurements with the theoretical and component level RSR predictions for both in-band and out-of-band spectral regions. Our results show that the system level method for determining RSR provides the clearest picture of the instrument’s spectral properties

Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS): Imaging and Tracking Capability

The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 128 detector arrays with a spectral resolution of 0.57/cm with a scan duration of approx. 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept

Ground-Based Measurement Experiment and First Results with Geosynchronous-Imaging Fourier Transform Spectrometer Engineering Demonstration Unit

The geosynchronous-imaging Fourier transform spectrometer (GIFTS) engineering demonstration unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. It measures the infrared spectrum in two spectral bands (14.6 to 8.8 microns, 6.0 to 4.4 microns) using two 128 x 128 detector arrays with a spectral resolution of 0.57 cm(exp -1) with a scan duration of approximately 11 seconds. From a geosynchronous orbit, the instrument will have the capability of taking successive measurements of such data to scan desired regions of the globe, from which atmospheric status, cloud parameters, wind field profiles, and other derived products can be retrieved. The GIFTS EDU provides a flexible and accurate testbed for the new challenges of the emerging hyperspectral era. The EDU ground-based measurement experiment, held in Logan, Utah during September 2006, demonstrated its extensive capabilities and potential for geosynchronous and other applications (e.g., Earth observing environmental measurements). This paper addresses the experiment objectives and overall performance of the sensor system with a focus on the GIFTS EDU imaging capability and proof of the GIFTS measurement concept

GIFTS EDU Ground-based Measurement Experiment

Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) Engineering Demonstration Unit (EDU) is an imaging infrared spectrometer designed for atmospheric soundings. The EDU groundbased measurement experiment was held in Logan, Utah during September 2006 to demonstrate its extensive capabilities for geosynchronous and other applications

An Update of Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) Calibration

The sounding of the atmosphere using broadband emission radiometry (SABER) instrument is a 10-channel infrared (1.27–16.9μm) radiometer launched on the TIMED (Thermosphere, Ionosphere, Mesosphere Energetics, and Dynamics) satellite in December 2001 from Vandenburg Air Force Base. SABER measures earthlimb emissions and characterizes infrared radiation, allowing calculation of atmospheric temperature and composition (ozone, water vapor, and carbon dioxide), as well as solar and chemical heating rates and infrared cooling rates. Although SABER focuses on the unexplored 60-180km region, it makes measurements covering the 10-350km altitude region. Ground calibration testing was completed in September 1999. Subsequent data analyses and report generation were completed in June, 2000. This paper provides a brief overview of instrument design, calibration planning, ground calibration testing, and results. Also included is an assessment of nearly five years of post launch validation and calibration maintenance. Using SABER as an example, conclusions are given regarding the benefit of a detailed calibration approach and how it enhances the quality of science data and mission success

Radiometric Stability of the SABER Instrument

The SABER instrument on the National Aeronautics and Space Administration Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics satellite continues to provide a long‐term record of Earth\u27s stratosphere, mesosphere, and lower thermosphere. The SABER data are being used to examine long‐term changes and trends in temperature, water vapor, and carbon dioxide. A tacit, central assumption of these analyses is that the SABER instrument radiometric calibration is not changing with time; that is, the instrument is stable. SABER stratospheric temperatures and those derived from Global Positioning System Radio Occultation measurements are compared to examine SABER\u27s stability. Global Positioning System Radio Occultation measurements are inherently stable due to the accuracy and traceability of the measured phase delay rate to the Système Internationale definition of the second. Differences in global annual mean SABER and COSMIC lower stratospheric temperatures show little significant change with time in the 11 years spanning 2007–2017. From this analysis we infer that SABER temperatures are stable to better than 0.1 to 0.2 K per decade

Force Measurement with a Piezoelectric Cantilever in a Scanning Force Microscope

Detection of surface forces between a tip and sample has been demonstrated with a piezoelectric cantilever in a scanning force microscope (SFM). The use of piezoelectric force sensing is particularly advantageous in semiconductor applications where stray light from conventional optical force-sensing methods can significantly modify the local carrier density. Additionally, the piezoelectric sensors are simple, provide good sensitivity to force, and can be batch fabricated. Our piezoelectric force sensors will be described, the theoretical sensitivity and performance of piezoelectric sensors will be discussed and experimental measurements of sensitivity and imaging results will be presented

Focusing Optimization of the SPIRIT III Radiometer

The spatial infrared imaging telescope (SPIRIT III) radiometer is the primary instrument aboard the Midcourse Space Experiment (MSX), which was launched on April 24, 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. The method and hardware used to achieve focus optimization are described