DIRBE External Calibrator (DEC)

Under NASA Contract No. NAS5-28185, the Center for Space Engineering at Utah State University has produced a calibration instrument for the Diffuse Infrared Background Experiment (DIRBE). DIRBE is one of the instruments aboard the Cosmic Background Experiment Observatory (COBE). The calibration instrument is referred to as the DEC (Dirbe External Calibrator). DEC produces a steerable, infrared beam of controlled spectral content and intensity and with selectable point source or diffuse source characteristics, that can be directed into the DIRBE to map fields and determine response characteristics. This report discusses the design of the DEC instrument, its operation and characteristics, and provides an analysis of the systems capabilities and performance

Focus Optimization of a Cryogenic Collimater Using Interferometric Measurements and Optical Modeling

Space Dynamics Laboratory at Utah State University (SDL/IJSU) optimized the focus of an off-axis, cryogenically cooled infrared collimator for cryogenic operating temperatures. Historically, collimator focus was optimized at ambient temperatures where interactive focus adjustment and testing coulà be performed. The focus shift that occurred when the optics were cooled was minimized by collimator design, and the change was negligible compared to the spatial resolution of the IR sensor measuring the collimator\u27s simulated point source. However, the focus determined at ambient temperature does not meet the image quality requirements of state-of-the-art sensors. The method used by SDL to determine optimal focus at cryogenic temperatures applies classical optical techniques to the cryogenically cooled environment. System level interferometric measurements are first made to characterize the system wavefront error. These measurements are then applied to an aberration- free optical model to evaluate system focus for a wavelength of 12 tim. The method also uses a knife edge test to refer the interferometric measurements to the aperture located near the focal point of the collimator. This paper discusses the physical test setup, outlines the optical model and analysis procedure, and presents results before and after focus optimization of a multifunction infrared calibrator

The WFI Relative Calibration System for WFIRST

NASA’s Wide-Field Infrared Survey Telescope (WFIRST) is a space-based observatory now being designed for launch in the mid-2020s. As the U.S. astronomical community’s top-priority mission for this decade, WFIRST is designed not only as a “discovery machine” for general PI-driven science but also as a survey platform to address three fundamental problems at the forefront of modern astrophysics: the dark energy content of the Universe, the evolution of the high-redshift galaxy and quasar population, and the demographics of exoplanets in our own galaxy. WFIRST’s primary camera, the Wide-Field Instrument (WFI), is a near-IR imager under development by Ball Aerospace and NASA’s Goddard Space Flight Center that will provide a field of view over 100 times greater than that of the Hubble Space Telescope. Achieving WFIRST’s key science objectives will require WFI to obtain imagery of faint galaxies, stars, and supernovae with unprecedented photometric precision. Attaining this level of accuracy demands calibrating the data at a level never previously accomplished in space. To meet these requirements, Ball Aerospace and Utah State University’s Space Dynamics Laboratory (SDL) are collaborating to design and build the Relative Calibration System (RCS) for WFI. The RCS is a self-calibrating unit which will generate temporally and spatially stable illumination of the WFI focal plane at a variety of wavelengths over an exceptionally large range of intensity. The RCS will enable not only standard tests of pixel-to-pixel sensitivity and gain from space, but also assessments of interpixel non-linearity, charge persistence, total-count-dependent non-linearity, and count-rate-dependent non-linearity throughout the mission’s lifetime. This talk will explore novel aspects of the RCS hardware design that permit the system to meet these demanding requirements

A first-principles computational O-17 NMR investigation of metal ion-oxygen interactions in carboxylate oxygens of alkali oxalates

O-17 NMR parameters, including chemical shift (CS) and electrical-field gradient (EFG) tensors, are calculated for oxalate compounds containing various different alkali ions using a DFT infinite periodic solid approach. This DFT study allows correlations to be found between the metal ion and oxygen interaction and the O-17 NMR interaction parameters. The O-17 CS shows greater sensitivity to the local alkali ions than that shown by the C-13 CS in the same compounds. It is found that the combination of metal ion-oxygen bond strength and cation size induce a deshielding shift up to similar to 70 ppm of O-17 delta(iso). The results also show the effects of different M-O interactions and C-O bond characteristics on the orientation of O-17 CS tensor components, and suggest that the O-17 quadrupolar parameters are systematically sensitive to the local cation environments around the carboxylate oxygen

TIRS Flood Source Calibration

Part of the calibration of the Thermal Infrared Sensor (TIRS) currently on the Landsat Data Continuity Mission was performed using the TIRS Flood Source, a 16” diameter blackbody. This presentation discusses the calibration of the TIRS Flood Source for absolute radiance after the Flood Source had been used to calibrate TIRS. The Flood source calibration was performed at Space Dynamics Lab (SDL) by comparing the output of the Flood Source to the SDL Long Wave Infrared Calibration Source (LWIRCS) blackbody using the SDL transfer radiometer (SDL-XR). LWIRCS is a calibrated, high-emissivity, 2 to 100 micron blackbody and the SDL-XR is a combination radiometer and spectrometer that was used in spectrometer mode with a filter that included the 10.8 and 12 micron TIRS bands. The Flood Source radiance was measured at 10 temperatures from 240 to 345 K, and at several horizontal positions and at several incidence angles. Flood Source effective emissivity was found to be 0.992+/-0.003 at all temperatures with no variation in horizontal position or incidence angle

Optical Coating Characterization System (OCCS) Design and Qualification

The Space Dynamics Laboratory, under contract to the Missile Defense Agency, designed and built the optical coating characterization system (OCCS) cryogenic system for spectral (FTIR) measurement of optical transmittance and reflectance at temperatures of 90 K and higher. The OCCS is designed to make cryogenic transmittance measurements from normal up to a 50 degree angle-of-incidence, and reflectance measurements between 40 and 50 degrees angle-of-incidence, in a converging optical beam of F/2 or greater. The system can measure up to 20 1-inch diameter optical components in a single cold cycle, or fewer larger components with flat surfaces up to 3 inches in diameter. This presentation will provide a brief overview of the OCCS design, followed by test results showing the performance achieved during qualification measurements

Guidelines for Radiometric Calibration of Electro-Optical Instruments for Remote Sensing

Sensor calibration increases the probability of mission success by quantifying the sensor’s response to known radiometric input, characterizing the interactions between the sensor\u27s components, and allowing systematic errors to be discovered and resolved before launch. This poster provides guidelines for conducting a successful EO sensor calibration campaign. It is intended for use by managers, technical oversight personnel, scientists, and engineers as a useful reference in planning and carrying out a sensor calibration. This content of this poster is based on a publication titled Guidelines for Radiometric Calibration of Electro-Optical Instruments for Remote Sensing. The publication is based on the authors\u27 many years of combined experience planning, reviewing, preparing, conducting, analyzing, implementing, and reporting on a variety of calibration efforts. Authors involved with this publication include, in alphabetical order: Daniel Bancroft, Jim Butler, Changyong Cao, Raju Datla, Scott Hansen, Dennis Helder, Raghu Kacker, Harri Latvakoski, Martin Mlynczak, Tom Murdock, James Peterson, David Pollock, Ray Russell, Deron Scott, John Seamons, Tom Stone, Joe Tansock, Alan Thurgood, Richard Williams, Xiaoxiong (Jack) Xiong, and Howard Yoon