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NASA NTRS1992

AE 152 cascode readout for far-IR focal plane arrays

The Amber Engineering AE 152 readout is a 32-channel multiplexer built as part of the FIR focal plane array development effort for the Space Infrared Telescope Facility (SIRTF). The design of the device addresses a number of constraints peculiar to the operation of germanium photoconductors. In particular, the need for a very high level of bias stability is solved by a nonswitched operation of the first stage. Additionally, the readout was optimized for the detector capacitance expected of large bulk photoconductors (about 0.7 pF) and for the slow operating speeds anticipated for this astronomical application. Fabricated in a 1.25-micron C-MOS process, the circuit utilizes a cascode input stage to provide gain at the front end while avoiding the Miller effect. The AE 152 also includes an internal offset correction and a shift register multiplexer for the output. We present test data for this device at a variety of temperatures, and show read noises as low as 8 electrons at a temperature of 77 K.

Young, Erick T.↗

NASA NTRS1998

Airborne Submillimeter Spectroscopy

This is the final technical report for NASA-Ames grant NAG2-1068 to Caltech, entitled "Airborne Submillimeter Spectroscopy", which extended over the period May 1, 1996 through January 31, 1998. The grant was funded by the NASA airborne astronomy program, during a period of time after the Kuiper Airborne Observatory was no longer operational. Instead. this funding program was intended to help develop instrument concepts and technology for the upcoming SOFIA (Stratospheric Observatory for Infrared Astronomy) project. SOFIA, which is funded by NASA and is now being carried out by a consortium lead by USRA (Universities Space Research Association), will be a 747 aircraft carrying a 2.5 meter diameter telescope. The purpose of our grant was to fund the ongoing development of sensitive heterodyne receivers for the submillimeter band (500-1200 GHz), using sensitive superconducting (SIS) detectors. In 1997 July we submitted a proposal to USRA to construct a heterodyne instrument for SOFIA. Our proposal was successful [1], and we are now continuing our airborne astronomy effort with funding from USRA. A secondary purpose of the NAG2-1068 grant was to continue the anaIN'sis of astronomical data collected with an earlier instrument which was flown on the NASA Kuiper Airborne Observatory (KAO). The KAO instrument and the astronomical studies which were carried out with it were supported primarily under another grant, NAG2-744, which extended over October 1, 1991 through Januarv 31, 1997. For a complete description of the astronomical data and its anailysis, we refer the reader to the final technical report for NAG2-744, which was submitted to NASA on December 1. 1997. Here we report on the SIS detector development effort for SOFIA carried out under NAG2-1068. The main result of this effort has been the demonstration of SIS mixers using a new superconducting material niobium titanium nitride (NbTiN), which promises to deliver dramatic improvements in sensitivity in the 700-1200 GHz frequency range.

Zmuidzinas, J.↗

NASA NTRS1973

A position-sensitive X-ray detector for the HEAO-A satellite.

A position-sensitive, low-energy proportional counter system is described which will be used on the High-Energy Astronomical Observatory, Mission A, spacecraft. The associated system incorporates the capability to employ pulse-shape discrimination for background rejection and interpolation circuitry to locate the centroid of an X-ray event with an accuracy of approximately one eighth the cathode-wire spacing.

Held, D.↗

NASA NTRS1979

Wide field/planetary camera optics study

Design feasibility of the baseline optical design concept was established for the wide field/planetary camera (WF/PC) and will be used with the space telescope (ST) to obtain high angular resolution astronomical information over a wide field. The design concept employs internal optics to relay the ST image to a CCD detector system. Optical design performance predictions, sensitivity and tolerance analyses, manufacturability of the optical components, and acceptance testing of the two mirror Cassegrain relays are discussed.

Source record↗

NASA NTRS1986

First results from Spacelab 2

Preliminary results of physical experiments carried out during the Spacelab 2 Shuttle mission are summarized. Attention is given to experiments in the fields of plasma dynamics; solar physics; high-energy astrophysics; and astronomy. Plasma experiments included an ejectable plasma diagnosics package and measurements of the passive charging of the Shuttle vehicle in the surrounding space plasma. The solar physics instrument package consisted of a solar spectral irradiance monitor; a solar optical universal polarimeter (SOUP); and a solar helium abundance high-resolution telescope and spectrograph (HRTS). Astronomical observations were performed using a scanning infrared telescope (IRT) which consisted of a highly baffled herschelian telescope and 10 detectors covering wavelengths from 2 to 120 microns. Cosmic-ray nuclei were detected and analyzed using gas Cerenkov counters and a transition radiation detector. Addition experiments included a thin film fluid dynamics payload and analysis of blood samples taken from the mission specialists. Complete data records from the experiments have now been distributed for an analysis period which will take at least a year. A table listing the Spacelab 2 experiments and their principal investigators is provided.

Urban, E. W.↗

NASA NTRS1986

A faint object spectrometer for the infrared

A cryogenic astronomical spectrometer for the NASA Infrared Telescope Facility is described. This spectrometer will employ an array of at least 20 detectors and provide a resolving power of 100 to 1500 at 1-5 microns. The resolving power will be adjustable by changing gratings.

Tokunaga, A. T.↗

NASA NTRS1986

Astronomy on a manned Mars mission

Three extra-solar-system astronomical experiments onboard a manned Mars mission are proposed. First, a modest, 50 cm aperture optical-ultraviolet-infrared telescope (or pair used as an interferometer) coupled with the Mars-Sun baseline would increase the number (by a factor of 3.4) and a volume of stars with accurately measured distances via stellar parallax and, therefore, greatly improve upon the cosmic distance scale; the darker sky at Mars would also provide nearly a full astronomical magnitude deeper images of distant and low brightness objects (limited by zodiacal light). Second, a gamma-ray burst detector coupled with similar detectors in other parts of the solar system will be used to reduce the position error boxes and to study the nature of these energetic sources. Third, the long baselines on a Mars mission radio interferometer will provide a view of the radio universe at unprescedented resolution, 4 x 10 to the minus 9th arcsec at 1 mm wavelength, which can potentially resolve the engine in nearby active galaxies. Each of these experiments is relatively inexpensive, taking advantage of the human presence for operation and maintenance, and the long Earth to Mars baseline.

Burns, Jack O.↗

NASA NTRS1992

Far-Infrared Imaging Radiometer

Inexpensive far-infrared imaging radiometer contains 128 X 128-picture-element array of AlxGa1-xAs quantum-well detectors. Potentially useful in remote sensing from airborne platforms. Industrial applications include rapid thermal imaging of heat-sensitive components. Astronomical applications include imaging of planets and Sun.

Forrest, Kathrine↗

NASA NTRS1998

Design and Specification of Optical Bandpass Filters for Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)

Advanced optical bandpass filters for the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) have been developed on a filter-by-filter basis through detailed studies which take into account the instrument's science goals, available optical filter fabrication technology, and developments in ACS's charge-coupled-device (CCD) detector technology. These filters include a subset of filters for the Sloan Digital Sky Survey (SDSS) which are optimized for astronomical photometry using today's charge-coupled-devices (CCD's). In order for ACS to be truly advanced, these filters must push the state-of-the-art in performance in a number of key areas at the same time. Important requirements for these filters include outstanding transmitted wavefront, high transmittance, uniform transmittance across each filter, spectrally structure-free bandpasses, exceptionally high out of band rejection, a high degree of parfocality, and immunity to environmental degradation. These constitute a very stringent set of requirements indeed, especially for filters which are up to 90 mm in diameter. The highly successful paradigm in which final specifications for flight filters were derived through interaction amongst the ACS Science Team, the instrument designer, the lead optical engineer, and the filter designer and vendor is described. Examples of iterative design trade studies carried out in the context of science needs and budgetary and schedule constraints are presented. An overview of the final design specifications for the ACS bandpass and ramp filters is also presented.

Leviton, Douglas B.↗

NASA NTRS1988

Ground based infrared astronomy

Infrared spectroscopic instrumentation has been developed for ground-based measurements of astrophysical objects in the intermediate infrared. A conventional Michelson interferometer is limited for astronomical applications in the intermediate infrared by quantum noise fluctuations in the radiation form the source and/or background incident on the detector, and the multiplex advantage is no longer available. One feasible approach to recovering the multiplex advantage is post-dispersion. The infrared signal after passing through telescope and interferometer, is dispersed by a low resolution grating spectrometer onto an array of detectors. The feasibility of the post-dispersion system has been demonstrated with observations of astrophysical objects in the 5 and 10 micrometer atmospheric windows from ground-based telescopes. During FY87/88 the post-disperser was used at the Kitt Peak 4-meter telescope and McMath telescope with facility Fourier transform spectrometers. Jupiter, Saturn, Mars, and Venus were observed. On Jupiter, the resolution at 12 micrometer was 0.01/cm, considerably higher than had been acheived previously. The spectrum contains Jovian ethane and acetylene emission. Construction was begun on the large cryogenic grating spectrometer.

Jennings, D. E.↗

NASA NTRS2015

Teledyne H1RG, H2RG, and H4RG Noise Generator

This paper describes the near-infrared detector system noise generator (NG) that we wrote for the James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec). NG simulates many important noise components including; (1) white "read noise", (2) residual bias drifts, (3) pink 1/f noise, (4) alternating column noise, and (5) picture frame noise. By adjusting the input parameters, NG can simulate noise for Teledyne's H1RG, H2RG, and H4RG detectors with and without Teledyne's SIDECAR ASIC IR array controller. NG can be used as a starting point for simulating astronomical scenes by adding dark current, scattered light, and astronomical sources into the results from NG. NG is written in Python-3.4.

H2RG↗

NASA NTRS2004

Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) Mission Concept

The AstroBiology Explorer (ABE) mission concept consists of a dedicated space observatory having a 60 cm class primary mirror cooled to T < 50 K equipped with medium resolution cross-dispersed spectrometers having cooled large format near- and mid-infrared detector arrays. Such a system would be capable of addressing outstanding problems in Astrochemistry and Astrophysics that are particularly relevant to Astrobiology and addressable via astronomical observation. The mission s observational program would make fundamental scientific progress in establishing the nature, distribution, formation and evolution of organic and other molecular materials in the following extra-terrestrial environments: 1) The Outflow of Dying Stars, 2) The Diffuse Interstellar Medium, 3) Dense Molecular Clouds, Star Formation Regions, and Young StellarPlanetary Systems, 4) Planets, Satellites, and Small Bodies within the Solar System, and 5 ) The Interstellar Media of Other Galaxies. ABE could make fundamental progress in all of these areas by conducting a 1 to 2 year mission to obtain a coordinated set of infrared spectroscopic observations over the 2.5-20 micron spectral range at a spectral resolution of R > 2000 of about 1500 objects including galaxies, stars, planetary nebulae, young stellar objects, and solar system objects. Keywords: Astrobiology, infrared, Explorers, interstellar organics, telescope, spectrometer, space, infrared detectors

Ennico, K. A.↗

NASA NTRS1984

Algorithm for astronomical, point source, signal to noise ratio calculations

An algorithm was developed to simulate the expected signal to noise ratios as a function of observation time in the charge coupled device detector plane of an optical telescope located outside the Earth's atmosphere for a signal star, and an optional secondary star, embedded in a uniform cosmic background. By choosing the appropriate input values, the expected point source signal to noise ratio can be computed for the Hubble Space Telescope using the Wide Field/Planetary Camera science instrument.

Jayroe, R. R.↗

NASA NTRS1974

A Ge/Li/ spectrometer for gamma ray astronomy

A space-borne instrument to measure the spectral and temporal characteristics of astronomical gamma rays in the .05 to 10 Mev energy range is described. The spectrometer consists of four 60 cc Ge(Li) detectors with an energy resolution of 2.5 Kev (FWHM) at 1.33 Mev. The Ge(Li) detectors are actively shielded with CsI(Na) for angular collimation and background reduction. Cooling of the Ge(Li) detectors to 88 K for orbital lifetimes of up to two years is provided by a two-stage solid subliming refrigerator.

Hicks, D. B.↗

NASA NTRS1992

Submillimeter wave detection with superconducting tunnel diodes

Superconductor-Insulator-Superconductor (SIS) diodes are the detector elements in the most sensitive heterodyne receivers available from 100 to 500 GHz. SIS mixers are the front end of radio astronomical systems around the world. SIS mixer technology is being extended to 1 THz and higher frequencies for eventual use on spaceborne astronomical experiments. Here is a short review of submillimeter SIS mixers. The role of impedance matching in the proper design of an SIS mixer is described. A variety of methods for achieving good impedance match at submillimeter frequencies are presented. The experimental state of the submillimeter SIS mixer art is described and summarized.

Wengler, Michael J.↗

NASA NTRSDate not supplied

Trajectory Optimization for the Virtual Telescope for X-Ray Observations

The Virtual Telescope for X-Ray Observations (VTXO) is a long focal length telescope which promises to provide orders of magnitude improvement in angular resolution in the X-ray band. VTXO will include a Phased Fresnel Lens (PFL), which provides nearly diffraction-limited imaging, with a 1 km focal length. The PFL is carried by the Optics Spacecraft, which flies in a formation with the Detector Spacecraft, approximating a rigid telescope body. In order to maintain the formation requirements, while pointing the telescope axis at the desired astronomical targets, one spacecraft will be traveling on a non-natural trajectory, requiring the vehicle to maneuver regularly to maintain the telescope pointing. If care is not taken in the trajectory design, these paths result in large propellant consumption. However, there is an opportunity to optimize trajectories when re-arranging the formation between different astronomical targets. This paper presents an optimization scheme for re-pointing the telescope, utilizing a non-traditional path-based cost function to solve the propellant optimal trajectory. The resulting trajectories show a factor of four improvement in propellant consumption compared to the baseline. The optimization techniques developed for VTXO are applicable to orbits ranging from low-Earth orbit, to highly eccentric Earth orbits, and Lagrange point orbits.

Kyle Rankin↗

NASA NTRS1975

Self-scanned Digicon - A digital image tube for astronomical spectroscopy

We have successfully fabricated, tested, and operated a digital image tube consisting of a magnetically focused image intensifier tube in which a self-scanned linear array of 1024 silicon photodiodes operating in the EBS mode serves as the photoelectron image detector, amplifier, and intermediate image storage device. Integral on-chip MOS shift registers driven by an external clock sequentially interrogate the photodiodes through MOS FET multiplex switch arrays. Each output frame is a sequence of 256 analog pulses on each of four video lines. Laboratory and observing tests show that the output signal is photoelectron shot noise limited over at least a range of 1-100,000 detected photoelectrons per picture element, indicating that single photon detection is achieved. High-resolution astronomical spectroscopy has been carried out in the coude spectrograph of the 2.7-m telescope at McDonald Observatory. Examples are shown.

Tull, R. G.↗

NASA NTRS2004

TES Detector Noise Limited Readout Using SQUID Multiplexers

The availability of superconducting Transition Edge Sensors (TES) with large numbers of individual detector pixels requires multiplexers for efficient readout. The use of multiplexers reduces the number of wires needed between the cryogenic electronics and the room temperature electronics and cuts the number of required cryogenic amplifiers. We are using an 8 channel SQUID multiplexer to read out one-dimensional TES arrays which are used for submillimeter astronomical observations. We present results from test measurements which show that the low noise level of the SQUID multiplexers allows accurate measurements of the TES Johnson noise, and that in operation, the readout noise is dominated by the detector noise. Multiplexers for large number of channels require a large bandwidth for the multiplexed readout signal. We discuss the resulting implications for the noise performance of these multiplexers which will be used for the readout of two dimensional TES arrays in next generation instruments.

Staguhn, J. G.↗