KEYWORDS: Sensors, Telescopes, Electronics, James Webb Space Telescope, Gamma radiation, Infrared telescopes, Monte Carlo methods, Electromagnetism, Control systems, Aerospace engineering
The Photo-z InfraRed Telescope (PIRT) is an instrument on the Gamow Explorer, currently proposed for a NASA Astrophysics Medium Explorer. PIRT works in tandem with a companion wide-field instrument, the Lobster Eye X-ray Telescope (LEXT), that will identify x-ray transients likely to be associated with high redshift gamma-ray bursts (GRBs) or electromagnetic counterparts to gravitational wave (GW) events. PIRT will gather the necessary data in order to identify GRB sources with redshift z >6, with an expected source localization better than 1 arcsec. A near real-time link to the ground will allow timely follow-up as a target of opportunity for large ground-based telescopes or the James Webb Space Telescope (JWST). PIRT will also allow localization and characterization of GW event counterparts. We discuss the instrument design, the on-board data processing approach, and the expected performance of the system.
The Compact Wide Swath Imaging Spectrometer (CWIS) is a pushbroom imaging spectrometer for the solar reflected spectrum (380-2510 nm) with wide swath (1600/1280 elements), fast optical speed (F/1.8), and high uniformity (≥95%). CWIS is currently being tested at the Jet Propulsion Laboratory and is intended to address the need for high signal-to-noise ratio (SNR) compact imaging spectrometer systems for the visible to short wave infrared wavelength (VSWIR) range. We give an overview of the instrument functionality, describe the spectrometer alignment and system integration and report laboratory data that include spatial, spectral and radiometric calibration.
The ultra-compact imaging spectrometer is a miniature imaging spectrometer that has been designed for compatibility with operation in a Martian environment. The spectrometer can be mated to a variety of front optics, both telescopic and microscopic. With a miniature telescope, it can serve as a rover mast instrument that surveys the surrounding area from a distance of ∼1 m to infinity and produces full spectral data (500 to 2500 nm) of a wide panoramic scene in order to find the most mineralogically promising targets for further analysis and for directing subsequent rover activities. With a microscopic front lens, it can serve as an analytical tool for determining types of minerals in a rock and their spatial relations at a scale of tens of micrometers in order to make detailed interpretations of geological history. A realization of the instrument, adapted for operation in the Earth’s atmosphere, has been produced and tested both in the laboratory and in the field. The results prove the ability of the instrument to detect and map minerals of interest in both modes of operation.
KEYWORDS: Prisms, Spectroscopy, Calibration, Radiometry, Short wave infrared radiation, Signal to noise ratio, Sensors, Electronics, Data modeling, Polarization
We report the characteristics of the Portable Remote Imaging Spectrometer, an airborne sensor specifically designed for the challenges of coastal ocean research. PRISM has high signal to noise ratio and uniformity, as well as low
polarization sensitivity. Acquisition of high quality data has been demonstrated with the first engineering flight.
The Ultra-Compact Imaging Spectrometer (UCIS) is a miniature telescope and spectrometer system intended for
mapping terrain mineralogy over distances from 1.5 m to infinity with spatial sampling of 1.35 mrad over a 30° field,
and spectral sampling of 10 nm in the 600-2500 nm range. The core of the system has been designed for operation in a
Martian environment, but can also be used in a terrestrial environment when placed inside a vacuum vessel. We report
the laboratory and field calibration data that include spatial and spectral calibration, and demonstrate the use of the
system.
We present the optical design and performance of the Ultra-Compact Imaging Spectrometer (UCIS) currently under
development at Caltech's Jet Propulsion Laboratory. The new instrument demonstrates a low optical bench mass of less
than 0.5 kg and compact size that enables Mars Rover or other in situ planetary applications. UCIS is an F/4, wide field
(30°) design, covering the spectral range 600-2600 nm and is enabled by a simple all aluminum two-mirror telescope and
Offner spectrometer. We discuss here the optical design and alignment method that enables this compact and low mass
imaging spectrometer and demonstrate successful spectrometer alignment with smile and keystone levels at 2-3% of a
pixel width.
NASA's Orbiting Carbon Observatory (OCO) was designed to make measurements of carbon dioxide concentrations
from space with the precision and accuracy required to identify sources and sinks on regions scales (~1,000 km).
Unfortunately, OCO was lost due to a failure of the launch vehicle. Since then, work has started on OCO-2, planned for
launch in early 2013. This paper will document the OCO instrument performance and discuss the changes planned for
the OCO-2 instrument.
A novel space interferometer design originating in Europe has been studied. The interferometer uses the technique of
starlight nulling to enable detection of earth-like planets orbiting nearby stars. A set of four telescope spacecraft flying in
formation with a fifth, beam-combiner spacecraft forms the interferometer. This particular concept shows potential for
reducing the mission cost when compared with previous concepts by greatly reducing the complexity of the telescope
spacecraft. These spacecraft have no major deployable systems, have simplified propulsion and a more rugged
construction. The formation flying geometry provides for greater average separation between the spacecraft with
commensurate risk reduction. Key aspects of the design have been studied at the Jet Propulsion Laboratory with a view
to collaborations between NASA and the European Space Agency. An overview of the design study is presented with
some comparisons with the TPF-FFI concept.
This paper describes two cryogenic thermal switches (CTSWs) under development for instruments on the James Webb Space Telescope (JWST). The first thermal switch was designed to extend the life of the solid H2 dewar for the 6 K Mid Infrared Instrument (MIRI) while the second thermal switch is needed for contamination and over-temperature control of three 35 K instruments on the Integrated Science Instrument Module (ISIM). In both cases, differential thermal expansion (DTE) between two materials having differing CTE values is the process that underpins the thermal switching. The patented DTE-CTSW design utilizes two metallic end-pieces, one cup-shaped and the other disc-shaped (both MIRI end-pieces are Al while ISIM uses an Al/Invar cup and an Al disc), joined by an axially centered Ultem rod, which creates a narrow, flat gap between the cup (rim) and disc. A heater is bonded to the rod center. Upon cooling one or both end-pieces, the rod contracts relative to the end-pieces and the gap closes, turning the CTSW ON. When the rod heater is turned on, the rod expands relative to the end-pieces and the gap opens, turning the CTSW OFF. During testing from 6-35 K, ON conductances of 0.3-12 W/K and OFF resistances greater than 2500 K/W were measured. Of particular importance at 6 K was the Al oxide layer, which was found to significantly decrease DTE-CTSW ON conductance when the mating surfaces were bare Al. When the mating surfaces were gold-plated, the adverse impact of the oxide layer was mitigated. This paper will describe both efforts from design through model correlation.
The Mid-Infrared Instrument (MIRI) is the coldest and longest wavelength (5-28 micron) science instrument on-board the James Webb Space Telescope observatory and provides imaging, coronography and high and low resolution spectroscopy. The MIRI thermal design is driven by a requirement to cool the detectors to a temperature below 7.1 Kelvin. The MIRI Optics Module (OM) is accommodated within the JWST Integrated Science Instrument Module (ISIM) which is passively cooled to between 32 and 40 K. Thermal isolation between the OM and the ISIM is therefore required, with active cooling of the OM provided by a dedicated cryostat, the MIRI Dewar. Heat transfer to the Dewar must be minimised to achieve the five year mission life with an acceptable system mass.
Stringent cleanliness levels are necessary in order to maintain the optical throughput and the performance of thermal control surfaces. The ISIM (and MIRI OM) is launched warm, therefore care must be taken during the on-orbit cooldown phase, when outgassing of water and other contaminants is anticipated from composite structures within the ISIM. Given the strong link between surface temperature and contamination levels, it is essential that the MIRI thermal and contamination control philosophies are developed concurrently.
The Atmospheric Infrared Sounder (AIRS) is one instrument in a suite of six instruments currently flying onboard NASA’s Earth Observing System (EOS) Aqua spacecraft. NASA’s Aqua spacecraft was launched successfully on May 4, 2002 from Vandenberg Air Force Base in California. AIRS is a cryogenic instrument developed under a Jet Propulsion Laboratory contract by BAe Systems formely Lockheed Martin Infrared Imaging Systems, for NASA. AIRS will provide new and more accurate data about the atmosphere, land and oceans, which provides a powerful new tool for climate studies and enables the advancement of weather prediction models. AIRS observations permit the measurement of the atmospheric temperature with an accuracy of 1 K in 1 km thick-layers in the troposphere and surface temperatures with an accuracy of 0.5 K. The Aqua spacecraft was placed in a sun-synchronous near-circular polar orbit with an inclination of 98.2 degrees, mean altitude of 705 km, 98.72 minute orbit period and 1:30 pm ascending node. The nominal on-orbit mission lifetime for the instrument is 6 years. AIRS measurements are based on passive infrared remote sensing using a precisely calibrated, high spectral resolution grating spectrometer with an infrared coverage from 3.7 to 15.4 μm. To achieve this high performance over this broad wavelength range, the spectrometer is cooled to 155 K and the Mercury Cadmium Telluride (HgCdTe) focal plane is cooled to 58 K. The detectors are cooled by a pair of long-life, low vibration, pulse tube mechanical coolers to 58 K, and a two-stage passive cooler with a deployable Earth shield provides cooling for the spectrometer to achieve a stable temperature near 155 K. This paper provides a general overview of the cryogenic system design and presents its on-orbit performance for the first year of operation.
The MIRI is the mid-IR (5-28μm) instrument for NGST and provides for imaging, cororographic, high- and low-resolution spectroscopic capabilities. Unlike to the other instruments on NGST, the MIRI must be cooled - to reduce the thermal background from the optics and because the detectors require an operating temperature of about 7k.. In this paper we summarise the science goals, the proposed overall opto-mechanical concept, the thermal design aspects, the detectors and the expected sensitivity of the instrument.
A thermally conductive, dimensionally stable optical bench has been fabricated from advanced composite materials for use at temperatures below 180 K (-93 degree(s)C). The optical bench comprises the main structure of the interferometer for the TES (Tropospheric Emission Spectrometer) instrument which will be part of the EOS CHEM satellite scheduled for launch in late 2002.
Patricia Beauchamp, Robert Brown, Carl Bruce, Gun-Shing Chen, Michael Chrisp, George Fraschetti, Timothy Krabach, Stanley Petrick, David Rodgers, J. Rodriguez, Stanley Soll, Arthur Vaughan, Laurence Soderblom, Bill Sandel, Roger Yelle
We describe an integrated instrument that will perform the functions of three optical instruments required by a Pluto Fast Flyby mission: a near-IR spectrometer (256 spectral channels, 1300 - 2600 nm), a two-channel imaging camera (300 - 500 nm, 500 - 1000 nm), and a UV spectrometer (160 spectral channels, 70 - 150 nm). A separate port, aligned in a direction compatible with radio occultation experiments, is provided for measurement of a UV solar occultation and for spectral radiance calibration of the IR and visible subsystems. Our integrated approach minimizes mass and power use, and promotes the adoption of integrated observational sequences and power management to ensure compatible duty cycles for data acquisition, compression, and storage. From flight mission experience, we believe the integrated approach will yield substantial cost savings in design, integration, and sequence planning. The integrated payload inherently provides a cohesive mission data set, optimized for correlative analysis. A breadboard version of the instrument is currently being built and is expected to be fully functional be late summer.
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