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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1987

System implications of aperture-shade design for the SIRTF Observatory

The 1-m-aperture Space Infrared Telescope Facility (SIRTF) will operate with a sensitivity limited only by the zodiacal background. This sensitivity requirement places severe restrictions on the amount of stray light which can reach the focal plane from off-axis sources such as the sun or earth limb. In addition, radiation from these sources can degrade the lifetime of the telescope and instrument cryogenic system which is now planned for two years before the first servicing. Since the aperture of the telescope represents a break in the telescope insulation system and is effectively the first element in the optical train, the aperture shade is a key system component. The mass, length, and temperature of the shade should be minimized to reduce system cost while maximizing the telescope lifetime and stray light performance. The independent geometric parameters that characterize an asymmetrical shade for a 600 km, 28 deg orbit were identified, and the system sensitivity to the three most important shade parameters were explored. Despite the higher heat loads compared to previously studied polar orbit missions, the analysis determined that passive radiators of a reasonable size are sufficient to meet the system requirements. An optimized design for the SIRTF mission, based on the sensitivity analysis, is proposed.

Lee, J. H.↗
NASA NTRS1985

BASD: SIRTF Telescope Instrument Changeout and Cryogen Replenishment (STICCR) study

The Space Infrared Telescope Facility (SIRTF) is a long-life cryogenically cooled space-based telescope for infrared astronomy from 2 micrometer to 700 miocrometers currently under study by NASA-ARC, and planned for launch in approximately the mid 90's. SIRTF will operate as a multi-user facility, initially carrying 3 instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and is currently baselined to be 2 years. The telescope changes required to allow in-space replenishment of the 2,000 liter superfluid helium tank are investigated. A preliminary design for the space services equipment is also developed. The impacts of basing the equipment and servicing on the space station are investigated. Space replenishment and changeout of instruments requires changes to the telescope design and preliminary concepts are presented.

Mord, A. J.↗
NASA NTRS1986

Space Infrared Telescope Facility (SIRTF) observatory design

The NASA Space IR Telescope Facility (SIRTF) is a 1-m aperture, cryogenically cooled IR observatory scheduled for launch into orbit in the mid-1990s. SIRTF will operate in the 2-700 micron range and yield a 1000-fold increase in sensitivity over NASA's IRAS observatory. A low inclination orbit compatible with Space Shuttle operations will be used. Results from comparisons of a system error budget allocation for the f/24 optical configuration with recent test data indicate that a figured fused silica mirror and a blade flexure mounting system can be cooled to cryogenic temperature while meeting required wavefront tolerances for substrate deformation. An all-He cooling system will be used in the low inclination orbit.

Brooks, W. F.↗
NASA NTRS1987

Study of helium transfer technology for STICCR: Fluid management

The Space Infrared Telescope Facility (SIRTF) is a long life cryogenically cooled space based telescope for infrared astronomy from 2 to 700 microns currently under study and planned for launch in the mid 90's. SIRTF will operate as a multi-user facility, initially carrying 3 instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and is currently baselined to be 2 years. Candidates are reviewed for a liquid management device to be used in the resupply of liquid helium, and for the selection of an appropriate candidate.

Frank, D. J.↗
NASA NTRS1985

SIRTF Telescope Instrument Changeout and Cryogen Replenishment (STICCR) Study

The Space Infrared Telescope Facility (SIRTF) is a long-life cryogenically cooled space-based telescope for infrared astronomy from 2 to 700 micrometers. SIRTF is currently under study by NASA-ARC (Reference AP) and planned for launch in approximately the mid 1990s. SIRTF will operate as a multiuser facility, initially carrying three instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and baseline is currently to be 2 years. The telescope changes required to allow in-space replenishment of the 4,000-L superfluid helium tank was investigated. A preliminary design for the space services equipment was also developed. The impacts of basing the equipment and servicing on the space station were investigated. Space replenishment and changeout of instruments required changes to the telescope design. Preliminary concepts are presented.

Nast, T. C.↗
NASA NTRS1991

Cosmological investigations from SIRTF

An overview is presented of the Space Infrared Telescope Facility (SIRTF), a one-meter-class cryogenically-cooled observatory for IR astronomy from space that will be the IR component of NASA's family of Great Observatories. SIRTF will operate at an altitude of 100,000 km and achieve its five year lifetime without the complication of on-orbit cryogenic replenishment and have twice the on-target efficiency that could be realized in LEO. The observations will permit the development of a direct empirical picture of the time evolution of cosmic phenomena, such as evolution of the chemical and stellar content of galaxies and the growth and decay of the quasar population.

Werner, M.↗
NASA NTRS1991

Ground systems and operations concepts for the Space Infrared Telescope Facility (SIRTF)

Key requirements and ground systems implementation strategy for SIRTF which presents a significant challenge in the operational phase of the mission are discussed. The facility is aimed at reliably integrating a guaranteed time program, requests from about 200 guest observer teams per year, and observatory maintenance. SIRFT is characterized by the five-year life time due to cryogen boil-off which means that the ground system must be fully operational at launch and must operate with an efficiency and timeliness rarely achieved in previous space missions.

Miller, Richard B.↗
NASA NTRS1985

Cryogenic optical systems and instruments; Proceedings of the Meeting, San Diego, CA, August 23, 24, 1984

Systems considerations for the Shuttle Infrared Telescope Facility (SIRTF) are discussed, taking into account SIRTF telescope engineering and trade studies, implications of orbital inclination for SIRTF design and operations, the approaching of the natural background limit with the SIRTF, a long life feasibility study for SIRTF, and the impact of chopping on image quality in the SIRTF telescope. Cryogenic systems and coolers for space missions are considered, giving attention to the Infrared Astronomical Satellite (IRAS) hardware flight performance, the design of the superfluid helium dewar for the Cosmic Background Explorer (COBE), Infrared Telescope (IRT) system cryogenic performance, the solidification of a cryogen by pumping, the production of superfluid helium using a Joule-Thomson Expander, and open cycle He-3 cooling to 0.18 K for space operation. Other topics explored are related to cryogenic optical instruments, facilities, and components, and to supporting technology for cryogenic infrared telescopes in space.

Melugin, R. K.↗
NASA NTRS1984

Orbit and geometry constraints on the design and operation of a long-life SIRTF mission

For a long-life SIRTF mission, the ability of the telescope to observe targets everywhere in the sky is an important requirement. For low-inclination orbits, a telescope aperture shade must be designed for Sun and Earth Limb avoidance angles of 50 deg to 60 deg to prevent unwanted radiation from entering the telescope. The minimum orbit inclination depends on the Earth Limb avoidance angle. About 30 percent of the sky will be prohibited for observations during any day in orbit, with about 100 days in orbit required to observe the entire sky.

Jackson, R. W.↗
NASA NTRS1978

Infrared detector performance in the Shuttle Infrared Telescope Facility /SIRTF/

The limitations imposed on infrared detectors for SIRTF are quite different from those imposed on ground-based, balloon-borne, or aircraft-borne systems. The paper examines the limitations and provides performance predictions corresponding to SIRTF conditions. Detector parameters typical of an infrared camera are used. The detector size is taken to be of the order of the diffraction-limited spot, frequency response is taken to correspond to a fraction of a second or less time constant, and spectral definition is provided by multilayer dielectric filters, inductive or capacitive grids, intrinsic absorption, or a combination of these. A nominal 10-micron bandwidth is assumed. The discussion covers atmospheric absorption and emission, zodiacal dust radiance, Shuttle contaminants, telescope self-emission, charged particle radiation, clear environment detector performance, and trapped radiation effects. It is concluded that the SIRTF design and operating conditions will allow current and near-term state-of-the-art detectors to reach their performance limits with SIRTF at a temperature of 10-12 K.

Mccarthy, S. G.↗
NASA NTRS2002

Current Status of High Performance Large Format Si:As IBC Detectors for SOFIA-like Applications

Airborne and space telescope astronomical observations in the 5-25 micrometer wavelength region, are critical for understanding the physical conditions, composition, chemistry, and excitation of many environments in the interstellar medium, external galaxies, solar system objects, extra-solar systems, and stars. The scientific impact is particularly unique in the 5-8 micrometer and 14-25 micrometer regions which are inaccessible or poorly observed from ground-based observatories. Large-format area mid-infrared (MIR) detectors sensitive over these wavelengths and operable under moderate backgrounds (greater than 10(circumflex)6 e-/s at R=2000, 10(micrometers)) are essential for efficient large-area survey imaging and for taking moderate resolution spectra over a large spectral range. Both SOFIA and passively cooled Explorer observatories could benefit from this technology. Current first-light SOFIA instruments use small-format MIR FPA's of sizes 128x128 and 256x256, With the collaboration of Raytheon Infrared Operations (RIO), NASA-ARC has been testing the first device of this kind, a combination of 1) the ALADDIN III readout multiplexer, cryo-processed for 6K operation, with 2) SIRTF IRAC-like Sides IBC detector material. designed for higher QE and low dark current. Here we report requirements. design, and initial fabrication and testing of the first 1024x1024 Si:As IBC mid-IR detector array for these conditions. This device has exhibited low dark current, moderate noise levels, and greater than 200,000 electron linear well size at 6K operation. We conclude with suggestions for future device development for optimal performance under moderate background, SOFIA- and low Earth orbit observing conditions.

Ennico, Kimberly↗
NASA NTRS2004

First Solar System Results of the Spitzer Space Telescope

The Spitzer Space Telescope, formerly known as SIRTF, is now operational and delivers unprecedented sensitivity for the observation of Solar System targets. Spitzer's capabilities and first general results were presented at the January 2004 AAS meeting. In this poster, we focus on Spitzer's performance for moving targets, and the first Solar System results. Spitzer has three instruments, IRAC, IRS, and MIPS. IRAC (InfraRed Array Camera) provides simultaneous images at wavelengths of 3.6, 4.5, 5.8, and 8.0 microns. IRS (InfraRed Spectrograph) has 4 modules providing low-resolution (R=60-120) spectra from 5.3 to 40 microns, high-resolution (R=600) spectra from 10 to 37 m, and an autonomous target acquisition system (PeakUp) which includes small-field imaging at 15 m. MIPS (Multiband Imaging Photometer for SIRTF) does imaging photometry at 24, 70, and 160 m and low-resolution (R=15-25) spectroscopy (SED) between 55 and 96 microns. Guaranteed Time Observer (GTO) programs include the moons of the outer Solar System, Pluto, Centaurs, Kuiper Belt Objects, and comets

VanCleve, J.↗
NASA NTRS1990

Design of a prototype secondary mirror assembly for the Space Infrared Telescope Facility

The design of a liquid helium temperature prototype secondary mirror assembly (PSMA) under development for the NASA Space Infrared Telescope Facility (SIRTF) program is described. The SIRTF assembly must operate below 4 K and provide the functions of highly precise two-axis periodic tilting ('chopping') in addition to the conventional functions of focus and collimation adjustment. The PSMA design employs a fused quartz mirror kinematically attached at its center to an aluminum cruciform. The mirror/cruciform assembly is driven in tilt about its combined center of mass using an aluminum flexure pivot of unique design and a four-actuator control system with feedback provided by pairs of differential position sensors. The voice coil actuators are mounted on a second flexure-pivoted mass to enhance servosystem stability and isolate the telescope from vibration-induced disturbances. The mirror/cruciform and reaction mass are attached to opposite sides of an aluminum mounting plate whose position relative to the outer housing is controlled by a six-degree-of-freedom focus and centering mechanism using pivoted actuation levers driven by lead screw/harmonic drive/stepper motor assemblies.

Stier, Mark T.↗
NASA NTRS1992

Fabrication

What aspects of optical fabrication technology need to be developed so as to facilitate existing planned missions, or enable new ones? Throughout the submillimeter to UV wavelengths, the common goal is to push technology to the limits to make the largest possible apertures that are diffraction limited. At any one wavelength, the accuracy of the surface must be better than lambda/30 (rms error). The wavelength range is huge, covering four orders of magnitude from 1 mm to 100 nm. At the longer wavelengths, diffraction limited surfaces can be shaped with relatively crude techniques. The challenge in their fabrication is to make as large as possible a reflector, given the weight and volume constraints of the launch vehicle. The limited cargo diameter of the shuttle has led in the past to emphasis on deployable or erectable concepts such as the Large Deployable Reflector (LDR), which was studied by NASA for a submillimeter astrophysics mission. Replication techniques that can be used to produce light, low-cost reflecting panels are of great interest for this class of mission. At shorter wavelengths, in the optical and ultraviolet, optical fabrication will tax to the limit the most refined polishing methods. Methods of mechanical and thermal stabilization of the substrate will be severely stressed. In the thermal infrared, the need for large aperture is tempered by the even stronger need to control the telescope's thermal emission by cooled or cryogenic operation. Thus, the SIRTF mirror at 1 meter is not large and does not require unusually high accuracy, but the fabrication process must produce a mirror that is the right shape at a temperature of 4 K. Future large cooled mirrors will present more severe problems, especially if they must also be accurate enough to work at optical wavelengths. At the very shortest wavelengths accessible to reflecting optics, in the x-ray domain, the very low count fluxes of high energy photons place a premium on the collecting area. It is not necessary to reach or even approach the diffraction limit, which would demand subnanometer fabrication and figure control. Replication techniques that produce large very lightweight surfaces are of interest for x-ray optics just as they are for the submillimeter region. Optical fabrication requirements are examined in more detail for missions in each of the three spectral regions of interest in astrophysics.

Angel, Roger↗
NASA NTRS1981

Orbital operations with the Shuttle Infrared Telescope Facility /SIRTF/

The Shuttle Infrared Telescope Facility (SIRTF) is a cryogenically-cooled, 1-m-class telescope that will be operated from the Space Shuttle as an observatory for infrared astronomy. This paper discusses the scientific constraints on and the requirements for pointing and controlling SIRTF as well as several aspects of SIRTF orbital operations. The basic pointing requirement is for an rms stability of 0.25 arcsec, which is necessary to realize the full angular resolution of the 5-micron diffraction-limited SIRTF. Achieving this stability requires the use of hardware and software integral to SIRTF working interactively with the gyrostabilized Shuttle pointing-mount. The higher sensitivity of SIRTF, together with orbital and time constraints, puts a premium on rapid target acquisition and on efficient operational and observational procedures. Several possible acquisition modes are discussed, and the importance of source acquisition by maximizing the output of an infrared detector is emphasized.

Werner, M. W.↗