KEYWORDS: Imaging systems, Spectrographs, Gemini Observatory, Spectroscopes, Sensors, Imaging spectroscopy, Telescopes, Near infrared, James Webb Space Telescope, Space telescopes
OCTOCAM has been proposed to the Gemini Observatory as a workhorse imager and spectrograph that will fulfill the needs of a large number of research areas in the 2020s. It is based on the use of high-efficiency dichroics to divide the incoming light in eight different channels, four optical and four infrared, each optimized for its wavelength range. In its imaging mode, it will observe a field of 3'x3' simultaneously in g, r, i, z, Y, J, H, and KS bands. It will obtain long-slit spectroscopy covering the range from 3700 to 23500 Å with a resolution of 4000 and a slit length of 3 arcminutes. To avoid slit losses, the instrument it will be equipped with an atmospheric dispersion corrector for the complete spectral range. Thanks to the use of state of the art detectors, OCTOCAM will allow high time-resolution observations and will have negligible overheads in classical observing modes. It will be equipped with a unique integral field unit that will observe in the complete spectral range with an on-sky coverage of 9.7"x6.8", composed of 17 slitlets, 0.4" wide each. Finally, a state-of-the-art polarimetric unit will allow us to obtain simultaneous full Stokes spectropolarimetry of the range between 3700 and 22000 Å.
We report our progress toward optimizing backside-illuminated silicon P-type intrinsic N-type complementary metal oxide semiconductor devices developed by Teledyne Imaging Sensors (TIS) for far-ultraviolet (UV) planetary science applications. This project was motivated by initial measurements at Southwest Research Institute of the far-UV responsivity of backside-illuminated silicon PIN photodiode test structures, which revealed a promising QE in the 100 to 200 nm range. Our effort to advance the capabilities of thinned silicon wafers capitalizes on recent innovations in molecular beam epitaxy (MBE) doping processes. Key achievements to date include the following: (1) representative silicon test wafers were fabricated by TIS, and set up for MBE processing at MIT Lincoln Laboratory; (2) preliminary far-UV detector QE simulation runs were completed to aid MBE layer design; (3) detector fabrication was completed through the pre-MBE step; and (4) initial testing of the MBE doping process was performed on monitoring wafers, with detailed quality assessments.
We report our progress toward optimizing backside-illuminated silicon PIN CMOS devices developed by Teledyne Imaging Sensors (TIS) for far-UV planetary science applications. This project was motivated by initial measurements at Southwest Research Institute (SwRI) of the far-UV responsivity of backside-illuminated silicon PIN photodiode test structures described in Bai et al., SPIE, 2008, which revealed a promising QE in the 100-200 nm range as reported in Davis et al., SPIE, 2012. Our effort to advance the capabilities of thinned silicon wafers capitalizes on recent innovations in molecular beam epitaxy (MBE) doping processes. Key achievements to date include: 1) Representative silicon test wafers were fabricated by TIS, and set up for MBE processing at MIT Lincoln Laboratory (LL); 2) Preliminary far-UV detector QE simulation runs were completed to aid MBE layer design; 3) Detector fabrication was completed through the pre-MBE step; and 4) Initial testing of the MBE doping process was performed on monitoring wafers, with detailed quality assessments. Early results suggest that potential challenges in optimizing the UV-sensitivity of silicon PIN type CMOS devices, compared with similar UV enhancement methods established for CCDs, have been mitigated through our newly developed methods. We will discuss the potential advantages of our approach and briefly describe future development steps.
We present a description of the Juno ultraviolet spectrograph (Juno-UVS) and results from its in-flight commissioning
performed between December 5th and 13th 2011 and its first periodic maintenance between October 10th and 12th 2012.
Juno-UVS is a modest power (9.0 W) ultraviolet spectrograph based on the Alice instruments now in flight aboard the
European Space Agency’s Rosetta spacecraft, NASA’s New Horizons spacecraft, and the LAMP instrument aboard
NASA’s Lunar Reconnaissance Orbiter. However, unlike the other Alice spectrographs, Juno-UVS sits aboard a spin
stabilized spacecraft. The Juno-UVS scan mirror allows for pointing of the slit approximately ±30° from the spacecraft
spin plane. This ability gives Juno-UVS access to half the sky at any given spacecraft orientation. The planned 2 rpm
spin rate for the primary mission results in integration times per 0.2° spatial resolution element per spin of only ~17 ms.
Thus, for calibration purposes, data were retrieved from many spins and then remapped and co-added to build up
exposure times on bright stars to measure the effective area, spatial resolution, scan mirror pointing positions, etc. The
primary job of Juno-UVS will be to characterize Jupiter’s UV auroral emissions and relate them to in-situ particle
measurements. The ability to point the slit will make operations more flexible, allowing Juno-UVS to observe the
atmospheric footprints of magnetic field lines through which Juno flies, giving a direct connection between energetic
particle measurements on the spacecraft and the far-ultraviolet emissions produced by Jupiter’s atmosphere in response
to those particles.
The Southwest Research Institute Ultraviolet Reflectance Chamber (SwURC) is a highly capable UV reflectometer
chamber and data acquisition system designed to provide bidirectional scattering data of various surfaces and
materials. The chamber provides laboratory-based UV reflectance measurements of water frost/ice, lunar soils,
simulants, and analogs to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project
(LAMP) Lunar Reconnaissance Orbiter (LRO). A deuterium lamp illuminates a monochromator with a nominal
wavelength range of 115 nm to 210 nm. The detector scans emission angles -85° to +85°in the principal plane. Liquid
nitrogen passed through the sample mount enables constant refrigeration of tray temperatures down to 78 K to form
water ice and other volatile samples. The SwURC can be configured to examine a wide range of samples and
materials through the use of custom removable sample trays, connectors, and holders. Calibration reference standard
measurements reported here include Al/MgF2 coated mirrors for specular reflection and Fluorilon for diffuse
reflectances. This calibration work is a precursor to reports of experiments measuring the far-UV reflectance of water
frost, lunar simulants, and Apollo soil sample 10084 in support of LRO-LAMP.
The Extreme Ultraviolet Imager (IMAGE/EUV) aboard NASA's IMAGE mission studied the distribution of singly
ionized helium (He+) in the Earth's plasmasphere by imaging its emission at 30.4 nm. This instrument consisted of three
separate camera heads, each with a 28° field-of-view, with 0.6°resolution. We describe an improved imaging system
that can simultaneously image a 40° field-of-view with 0.45° resolution utilizing only one compact camera head and
detector. This improved imager also increases sensitivity over the heritage EUV imager by a factor of four due to
improvements in optical coatings, detector technology, and a larger entrance aperture.
Space and launch environments demand robust, low mass, and thermally insensitive mechanisms and optical mount designs. The rotating prism mechanism (RPM), a component of the stabilized dispersive focal plane system (SDFPS), is a spectral disperser mechanism that enables the SDFPS to deliver spectroscopic or direct imaging functionality using only a single optical path. The RPM is a redundant, vacuum-compatible, self-indexing, motorized mechanism that provides robust, athermalized prism mounting for two sets of matching prisms. Each set is composed of a BK7 and a CaF2 prism, both 70 mm in diameter. With the prism sets separated by 1 mm, the RPM rotates the two sets relative to one another over a 180° range, and maintains their alignment over a wide temperature range (190-308K). The RPM design incorporates self-indexing and backlash prevention features as well as redundant motors, bearings, and drive trains. The RPM was functionally tested in a thermal vacuum chamber at 210K and <1.0x10-6 mbar, and employed in the top-level SDFPS system testing. This paper presents the mechanical design, analysis, alignment measurements, and test results from the prototype RPM development effort.
We designed and assembled a highly capable UV reflectometer chamber and data acquisition system to provide bidirectional scattering data of various surfaces and materials. This chamber was initially conceived to create laboratory-based UV reflectance measurements of water frost on lunar soil/regolith simulants, to support interpretation of UV reflectance data from the Lyman Alpha Mapping Project (“LAMP”) instrument on-board the NASA Lunar Reconnaissance Orbiter spacecraft. A deuterium lamp illuminates surfaces and materials at a fixed 45° incident beam angle over the 115 to 200 nm range via a monochromator, while a photomultiplier tube detector is scanned to cover emission angles -85° to +85° (with a gap from -60° to -30°, due to the detector blocking the incident beam). Liquid nitrogen cools the material/sample mount when desired. The chamber can be configured to test a wide range of samples and materials using sample trays and holders. Test surfaces to date include aluminum mirrors, water ice, reflectance standards, and frozen mixtures of water and lunar soil/regolith stimulant. Future UV measurements planned include Apollo lunar samples, meteorite samples, other ices, minerals, and optical surfaces. Since this chamber may well be able to provide useful research data for groups outside Southwest Research Institute, we plan to take requests from and collaborate with others in the UV and surface reflection research community.
We describe vacuum ultraviolet sensitivity measurements of a new high performance silicon-based CMOS sensor from
Teledyne Imaging Sensors. These sensors do not require the high voltages of MCP detectors, making them a lower mass
and power alternative to the more mature MCP technology. These devices demonstrate up to 40 percent quantum
efficiency at vacuum ultraviolet wavelengths, either meeting or greatly exceeding 10 percent quantum efficiency across
the entire 100-200 nm wavelength region. As with similar visible sensitive devices, backside illumination results in a
higher quantum efficiency than frontside illumination. Measurements of the vacuum ultraviolet sensitivity of the
Teledyne silicon PIN detectors were made by directing a known intensity of ultraviolet light at discrete wavelengths onto
the test detectors and reading out the resulting photocurrent. The sensitivity of the detector at a given wavelength was
then calculated from the intensity and wavelength of the incoming light and the relative photodiode to NIST-traceable
calibration diode active areas. A custom electromechanical interface was developed to make these measurements within
the SwRI Vacuum Radiometric Calibration Chamber. While still in the single pixel stage, full 1K × 1K focal plane
arrays are possible using existing CMOS readout electronics and hold great promise for inclusion in future spaceflight
instrument concepts.
As the costs of space missions continue to rise, the demand for compact, low mass, low-cost technologies that maintain
high reliability and facilitate high performance is increasing. One such technology is the stabilized dispersive focal plane
system (SDFPS). This technology provides image stabilization while simultaneously delivering spectroscopic or direct
imaging functionality using only a single optical path and detector. Typical systems require multiple expensive optical
trains and/or detectors, sometimes at the expense of photon throughput. The SDFPS is ideal for performing wide-field
low-resolution space-based spectroscopic and direct-imaging surveys. In preparation for a suborbital flight, we have
built and ground tested a prototype SDFPS that will concurrently eliminate unwanted image blurring due to the lack of
adequate platform stability, while producing images in both spectroscopic and direct-imaging modes. We present the
overall design, testing results, and potential scientific applications.
We describe the radiometric performance and ground calibration results of the Juno mission's Ultraviolet Spectrograph
(Juno-UVS) flight model. Juno-UVS is a modest power (9.0 W) ultraviolet spectrograph based on the Alice instruments
now in flight aboard the European Space Agency's Rosetta spacecraft, NASA's New Horizons spacecraft, and the LAMP
instrument aboard NASA's Lunar Reconnaissance Orbiter. Its primary job will be to characterize Jupiter's UV auroral
emissions and relate them to in situ particle measurements.
Traditionally, focal plane arrays require extensive external focal plane electronics (FPE) to provide clocks and biases as well as to digitize the analog output signals. The FPE has to be well-designed and is typically large, heavy and powerhungry. Most importantly, the FPE has to be placed some distance away from the FPA, which complicates maintaining low noise performance throughout the complete system. To offer an alternative to the discrete electronics, Rockwell Scientific has developed a new approach known as the SIDECAR application-specific integrated circuit (ASIC). This single chip provides all the functionality necessary to operate an infrared array with the convenience of a pure digital interface to the outside world. This paper will present performance data on the latest generation of the SIDECAR ASIC operating the JWST H2RG detector arrays at cryogenic temperature. The test results demonstrate that an ASIC based FPA system will meet or exceed all performance requirements for the JWST mission. The SIDECAR ASIC has been selected by NASA to become the FPA drive electronics for all shortwave infrared instruments on JWST.
We describe the test approaches and results for the Multiband Imaging Photometer for SIRTF. To verify the performance within a `faster, better, cheaper' budget required innovations in the test plan, such as heavy reliance on measurements with optical photons to determine instrument alignment, and use of an integrating sphere rather than a telescope to feed the completed instrument at its operating temperature. The tests of the completed instrument were conducted in a cryostat of unique design that allowed us to achieve the ultra-low background levels the instrument will encounter in space. We controlled the instrument through simulators of the mission operations control system and the SIRTF spacecraft electronics, and used cabling virtually identical to that which will be used in SIRTF. This realistic environment led to confidence in the ultimate operability of the instrument. The test philosophy allowed complete verification of the instrument performance and showed it to be similar to pre-integration predictions and to meet the instrument requirements.
We describe the design, construction, and performance of the 32 X 32 Ge:Ga imaging array being built at the University of Arizona for the Multiband Imaging Photometer for SIRTF (MIPS). The array will support a number of operational modes in the MIPS instrument including natural background-limited mapping at 70 micrometers , super-resolution observations at 70 micrometers , and spectral energy distribution measurements between 50 and 100 micrometers . The array is constructed in a modular manner using eight 4 X 32 pixel building blocks. To meet the sensitivity and stability requirements, the array must have excellent photometric repeatability, low noise, and robustness to the effects of the ionizing radiation environment in space. Key elements in attaining this level of performance are the Ge:Ga detectors materials and the cryogenic CRC-696 readout electronics. We present laboratory data for a 16 X 32 prototype of the array, and describe the plans for the construction of the qualification and flight units.
This paper discusses the mechanical design and assembly of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) focal plane assembly (FPA). The FPA consists of a mercury-cadmium-telluride (MCT) detector array hybridized to a silicon multiplexer (MUX), a sapphire carrier, an alumina ceramic multi-layer board (CMLB) including electrical components, a base plate, and flex cables. The FPA is designed for the following conditions; (1) shock and vibration during launch, (2) Coefficient of Thermal Expansion (CTE) of dissimilar materials at cryogenic temperature, (3) outgassing limitations to meet NASA's specifications, and (4) optical assembly tolerances. Also, the FPA is designed to be easily integrated into its dewar with provisions for mechanical as well as optical alignment. The FPA is assembled by building up two subassemblies in a parallel path, and then integrating the two subassemblies with the flex cables for the final assembly. These procedures are described in this paper, including alignment tolerances required and measured.
A program is currently in process at Rockwell for the production of focal plane assemblies (FPA) for use on the University of Arizona Near Infrared Camera, Multi-Object Spectrometer (NICMOS) instrument which is to be installed in the Hubble Space Telescope (HST) during a Space Shuttle mission in 1997. This paper describes the testing approach for the production of the FPA's, the tests to be performed, the test equipment, and facilities used in the built of two prototype FPA's used as engineering evaluation units (EEU). A sample of the data output from the various tests will be discussed for one of the EEU FPA's, both in the intermediate screen tests which will be described, and for the final performance tests.
The NICMOS camera to be used on the Hubble Space Telescope will acquire near-infrared images with extremely high spatial resolution. To extract scientifically useful data from these images will require a complete understanding of the arrays used to produce the images. The NICMOS team has developed a program for characterizing arrays which will lead to this understanding and which will also allow selection of optimum devices for each section of the NICMOS instrument. The overall plan will be described and related to the scientific goals of NICMOS. The characterization plan includes standard infrared array testing such as electrical properties, read noise, dark current, and quantum efficiency, and will be expanded to include testing such as crosstalk measurements, hysteresis testing, and radiation testing.
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