Space imagery provides a unique resource for addressing environmental challenges associated with land cover change, land use, disaster relief, deforestation, regional planning and global change research. At Ball Aerospace, we are developing the Compact Hyperspectral Prism Spectrometer (CHPS) as a candidate imaging spectrometer technology for insertion into future Sustainable Land Imaging missions. The 2013 NRC report Landsat and Beyond: Sustaining and Enhancing the Nations Land Imaging Program recommended that the nation should “maintain a sustained, space-based, land-imaging program, while ensuring the continuity of 42-years of multispectral information.” In support of this, NASA’s Sustainable Land Imaging-Technology (SLI-T) program aims to develop technology for a new generation of smaller, more capable, less costly payloads that meet or exceed current Landsat imaging capabilities. CHPS is designed to meet these objectives, providing high-fidelity visible-to-shortwave spectroscopic information. CHPS supports continuity of legacy Landsat data products, but also, provides a path to enhanced capabilities in support of land, inland waters, and coastal waters science. CHPS features full aperture full optical path calibration, extremely low straylight, and low polarization sensitivity; all crucial performance parameters for achieving the demanding SLI measurement objectives. In support of our space-borne instrument development, we have developed an airborne instrument to provide representative spectroscopic data and data products. Now in the final year of this 3-year development program, we have completed our initial engineering airborne flights and are beginning science flights. We present initial results from laboratory characterization and calibration and from our engineering flights and close with an overview of instrument performance.
X-Ray telescopes with optics and detectors at opposite ends of semi-rigid, extendable booms can improve their imaging performance if the flexing of the boom is measured and removed in image reconstruction. This has been accomplished on previous missions with analog position detectors and highly stable laser pointing indicators. This report shows that a flight-proven digital imaging system observing LED sources, can achieve as high or higher precision measurements without extensive calibration at modest cost.
While some instrument requirements are levied on a per-pixel basis, efficiencies and economies can be gained by testing them in parallel. Furthermore, the use of detector arrays as imagers with extended targets enables the derivation of geometrical information from select pixels in each image, and its propagation to neighboring pixels. We discuss the implementation of one such test regime for the Operational Landsat Imager (OLI) at Ball Aerospace and Technologies Corp. This enabled rapid measurement of spatial parameters, including Edge Response Function and aliasing, for all of the nearly 70,000 active pixels of the focal plane assembly with reduced reliance on the precision and stability of the supporting equipment. The derived geometrical information enabled us to replace a step-stare testing of individual pixels with a continuous scan of the entire assembly, without demanding precision motion or introducing noise from variations in the scan velocity. Three complete scans were performed in under 30 hours.
We have recently demonstrated the ability to measure the absolute change in optical power (focus) of a 152 mm diameter flat mirror in vacuum between room and cryogenic temperatures (133K) with a peak-to-valley measurement error of only 22nm. Such a measurement would be crucial to the verification of the focus of a cryogenic instrument during ground testing.
The testing utilized a vibration-insensitive interferometer and a reference mirror maintained at room temperature located within the thermal vacuum chamber. Special considerations were taken to ensure that the reference mirror experienced low axial thermal gradients, since structural modeling indicated that axial thermal gradients and axial variation of substrate coefficient of thermal expansion are critical in maintaining flatness under cryogenic test conditions. This paper will discuss the testing equipment and methodology and the corresponding analysis and results.
The instrument named Ralph is a visible/NIR imager and IR hyperspectral imager that would fly as one of the core instruments on New Horizons, NASA's mission to the Pluto/Charon system and the Kuiper Belt. It is a compact, power efficient, and robust instrument with excellent imaging characteristics and sensitivity, and is well suited to this longduration flyby reconnaissance mission.
Unpolished diamond turned mirrors are common for infrared systems. We report the successful use of unpolished mirrors in a visible spectrum, all aluminum telescope for the planned New Horizons mission to Pluto. The Ralph telescope is an F/8.7 Three Mirror Anastigmat with a 75mm aperture, a 5.7° by 1.0° field of view, and a mass of only 8kg. Key to the performance of the system are a process for reducing the micro-roughness of the off-axis aspheric surfaces to below 60 Ångstroms RMS, and the fabrication of precision diamond turned mounting features on the mirrors and one-piece, thin-walled housing. The telescope achieves nearly diffraction-limited performance with minimal post-assembly alignment, and maintains that performance, including focus, over a wide range about the operating temperature of 210K.
KEYWORDS: Comets, Space operations, Telescopes, Space telescopes, Mirrors, Magnetic resonance imaging, Sensors, Information technology, Image resolution, Optical filters
Deep Impact is NASA's Discovery class mission to Comet Tempel 1. The probe will separate into two spacecraft, one of which will impact the surface and excavate a large crater. Optical observations will allow the mission to determine much about the composition and structure of the comet nucleus, of which very little is known, in addition to helping the craft navigate to the target. We will discuss the mission, its goals and hardware, with emphasis on the optical instruments and the challenges of designing passive cryogenic optics for deep space operation while staying within tighter cost constraints than have been the norm for space missions.
We report on a technique to measure the surface figure of mirrors under extreme vibrational conditions. Measurements are presented of the surface figure changes of Zerodur primary mirrors with both spherical and parabolic shapes, manufactured for the NASA Deep Impact program. Conditions ranged from room temperature to 130K. The interferometer was located outside the cryogenic vacuum chamber and did not require any active or passive vibration isolation. We show measurement repeatability of better than 1/500 waves RMS at 633nm.
Deep Impact is a NASA Discovery Mission to impact and observe the nucleus of Comet Temple 1. The instrumentation includes a 300 mm aperture telescope that will operate at 130K once in deep space. It is critical that the telescope mirrors maintain their figure at the operational temperature. We report on measurements of the surface figure changes of three Zerodur primary mirrors from room temperature to 130K, using a PhaseCam interferometer from 4D Vision Technologies, Inc. Although the mirror substrates were taken from the same melt and annealing, they did not perform equally, with differential surface figures ranging from 0.014 waves RMS at 633 nm to 0.082 waves.
It is common for spectrometers to cover large spectral ranges with a single focal plane. It is difficult or impossible to strongly suppress reflections with a single coating stack. Abutting short and long wavelengths coatings is expensive, and the performance can still be insufficient. We discuss a novel structure that comprises a single layer whose thickness varies along the length of the dispersed spectrum. Such a coating has high performance, is inexpensive, and has large fabrication tolerances. We further report on measurements of the performance of one such optic. Extension of the concept are discussed.
SAGE III has been selected as part of the earth observing system for flight on the aerosol and chemistry satellites missions beginning in the year 2000. During lunar and solar occultation, SAGE III will measure vertical profiles of O3, NO2, H2O, NO3, OClO, temperature, and aerosols from cloud tops through the stratosphere, and of O3 through the mesosphere. This paper describes the lineage of SAGE III, its science objectives, current instrument design, details of phase B testing and analysis, expected performance, and its contributions to monitoring global change and to meeting other EOS objectives.
The Relay Mirror Experiment (RME) required continuous illumination of its satellite by ground-based lasers. To maintain tracking, the system relied on an array of six-inch diameter hollow retroreflectors, mounted on the lower deck of the spacecraft. The retroreflectors are tailored to the mission, including compensation for their orbital velocity. The array has a lidar cross section of up to 3,000 square kilometers. This paper describes the design, construction, testing, and use of this retroreflector array.
A third-generation SAGE instrument is about to be designed as part of the NASA Earth Observational System. Previous instruments have used individual diodes as detectors. The new instrument will use a custom design CCD to dramatically enhance the study of the gas and aerosol components of the upper atmosphere. The CCD is a 3 by 400 imaging array that has a single serial register and an exposure control drain. It will be used at the focal plane of a spectrometer covering the spectral range from 288 nm to 1.02 micron.
A third-generation SAGE instrument is about to be designed as part of the NASA Earth Observational System. Previous instruments have used individual diodes as detectors. The new instrument will use a custom design CCD to dramatically enhance the study of the gas and aerosol components of the upper atmosphere. The CCD is a 3 X 400 imaging array that has a single serial register and an exposure control drain. It will be used at the focal plane of a spectrometer covering the spectral range from 288 nm to 1.02 micrometers .
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