Advanced X-ray Astrophysics Facility (AXAF)
The progress of the Advanced X-ray Astrophysics Facility is summarized. A design review of the facility, hardware development, cost analysis, and listings of published reports are examined.
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The Advanced X-Ray Astrophysics Facility
The advanced X-Ray Astrophysics Facility (AXAF) will be a free-flying observatory for high-quality observations and research in the X-ray spectrum. AXAF is planned to be launched in 1991 by the Shuttle and maintained in-orbit over a period of 15 years. This paper presents a summary of the AXAF program and describes several possible configurations which resulted from Phase A studies.
Dailey, C. C.↗
A wind-type model for the generation of astrophysical jets
Wind-type solutions for the generation of astrophysical jets from active galactic nuclei and stellar sources, such as those associated with SS 433 and protostellar objects, are discussed. Acceleration, collimation, and morphology are consistently interpreted in terms of a flow starting from the galactic or stellar core inside the 'throat' of a thick accretion disk.
Ferrari, A.↗
Advanced X-ray Astrophysics Facility thermal control
A conceptual active/passive thermal control system design is presented for the Advanced X-ray Astrophysics Facility (AXAF), where the design variables considered in system optimization were vehicle orientation for environmental extremes, thermal coating properties, and insulation materials. Because power and weight are at a premium, the design was limited to one power module, resulting in a thermal control limit of 441 W of regulated power. The present study has determined that all thermal control objectives for AXAF's instruments can be met by the design considered. The thermal resistance schematics employed in this conceptual study are presented, together with simulated performance characteristics.
Fritz, C. G.↗
NASA astrophysics - Optical systems to explore the universe
Major and minor NASA astrophysical research efforts in the near-term are outlined, together with projections of direction for future projects. The Space Telescope is being readied for a 1986 launch and will feature an f/24, 2.4 m aperture, an MgF2 mirror with better than 1/60 wavelength accuracy and will be diffraction-limited in the UV. Pointing accuracy is designed to be 0.007 arcsec for 24 hr. Optical, spectrometric, and photometric equipment will be included. Around 1990, Shuttle-based missions will include an IR telescope and a subarcsec solar surface imaging device. A free-flying X-ray observatory (AXAF) is planned and will include a sensitivity that exceeds that of the HEAO-2 spacecraft by two orders of magnitude. Instruments are under development for higher resolution UV, gamma-ray, and IR studies. In-orbit interferometry is being studied and will depend on in-orbit assembly and servicing of stable structures with segmented optics.
Pellerin, C. J., Jr.↗
Natural environment design criteria for the Advanced X-ray Astrophysics Facility (AXAF) definition and preliminary design
This document provides the natural environment design criteria requirements for use in the Advanced X-Ray Astrophysics Facility (AXAF) definition and preliminary design studies. The atmospheric dynamic and thermodynamic environments, meteoroids, radiation, magnetic fields, and physical constants are all addressed. This information will enable all groups involved in the definition and preliminary design studies to proceed with a common and consistent set of natural environment criteria requirements.
Greene, W. M.↗
Nonlinear evolution of astrophysical Alfven waves
Nonlinear Alfven waves were studied using the derivative nonlinear Schrodinger equation as a model. The evolution of initial conditions, such as envelope solitons, amplitude-modulated waves, and band-limited noise was investigated. The last two furnish models for naturally occurring Alfven waves in an astrophysical plasma. A collapse instability in which a wave packet becomes more intense and of smaller spatial extent was analyzed. It is argued that this instability leads to enhanced plasma heating. In studies in which the waves are amplified by an electron beam, the instability tends to modestly inhibit wave growth.
Spangler, S. R.↗
The solar vector magnetograph of the Okayama Astrophysical Observatory
The vector magnetograph of the Okayama Astrophysical Observatory is fed to the 65 cm solar coude telescope with a 10 m Littrow spectrograph. The polarimeter put at the telescope focus analyzes the incident polarization. Photomultipliers (PMT) at the exit of the spectrograph pick up the modulated light signals and send them to the electronic controller. The controller analyzes frequency and phase of the signal. The analyzer of the polarimeter is a combination of a single wave plate rotating at 40 Hz and a Wallaston prism. Incident linear and circular polarizations are modified at four times and twice the rotation frequency, respectively. Two compensators minimize the instrumental polarization, mainly caused by the two tilt mirrors in the optical path of the telescope. The four photomultipliers placed on the wings of the FeI 5250A line give maps of intensity, longitudinal field and transverse field. The main outputs, maps of intensity, and net linear and circular polarizations in the neighboring continuum are obtained by the other two monitor PMTs.
Makita, M.↗
Monopole, astrophysics and cosmic ray observatory at Gran Sasso
A new large area detector, MACRO was approved for installation at the Gran Sasso Laboratory in Italy. The detector will be dedicated to the study of naturally penetrating radiation deep underground. It is designed with the general philosophy of covering the largest possible area with a detector having both sufficient built-in redundancy and use of complementary techniques to study very rare phenomena. The detector capabilities will include monopole investigations significantly below the Parker bound; astrophysics studies of very high energy gamma ray and neutrino point sources; cosmic ray measurements of single and multimuons; and the general observation of rare new forms of matter in the cosmic rays.
Demarzo, C.↗
Positron-electron pairs in astrophysics; Proceedings of the Workshop, Greenbelt, MD, January 6-8, 1983
Astrophysical sources of positron-electron-pair annihilation radiation are characterized in reviews and reports of observational and theoretical investigations. Topics examined include gamma-ray lines from solar flares, gamma-ray bursts, pulsars, the Galactic center, active galaxies, and physical processes in relativistic and magnetized plasmas. Spectra, historgrams, graphs, and diagrams are provided.
Burns, M. L.↗
Simulations of high-Mach-number collisionless perpendicular shocks in astrophysical plasmas
A problem of critical importance to space physics and astrophysics is the existence and properties of high-Mach-number shocks. Preliminary results of a simulation of a perpendicular shock with Alfven Mach number 22 are reported. It is shown that for sufficiently small electron resistivity the dissipation for this shock is provided by a periodic rather than time-stationary reflection of ions. The problem of electron heating and the extension to higher Mach numbers are discussed.
Quest, K. B.↗
Theoretical study of the X-ray emission from astrophysical shock waves
Theoretical X-ray emission spectra are needed to interpret the X-ray emission observed by many low and moderate resolution X-ray instruments, and to provide diagnosis of physical conditions for high resolution spectra. Over the past decade, a set of model codes which compute the X-ray and XUV emission for a wide set of physical conditions, including high or low densities, photoionized gas, and time-dependent ionization balance was developed. In the past year, the atomic rate coefficients in the code was improved. Further capabilities were added, and applied to several astrophysical problems.
Raymond, J.↗
The Advanced X-ray Astrophysics Facility instrument interface requirements
A variety of instruments will be placed at the focus of the Advanced X-ray Astrophysics Facility (AXAF) telescope, either by moving them into focus through the use of an instrument carousel or by moving the telescope assembly. Focal plane instrument categories under consideration for AXAF encompass high and moderate resolution X-ray cameras, X-ray spectrometers, and polarimeters; some of these instruments may require such consumables as a cryogen, in the case of solid state device cooling, or a gas, as in the case of proportional counters. Attention is presently given to interface requirements impacting on the maintenance that must be conducted over the 15-year service life of AXAF, and, especially, on the 'aspect solution' criteria that must be met to minimize stiffness stability criteria.
Weisskopf, M. C.↗
Advanced X-ray Astrophysics Facility (AXAF) instrumentation
The instrumentation planned for the Advanced X-ray Astrophysics Facility (AXAF), a space-based observation platform for the 1990s, is described. The AXAF will feature a grazing incidence telescope at the end of the observatory and four independently selected instruments at the other end, including: a CCD imaging spectrometer; a Bragg crystal spectrometer; and two transmission grating spectrometers located directly behind the telescope to detect first order spectral images. The instruments are currently in the definition phase to be followed by design and development starting in the late 1980s. A detailed schematic diagram of the Bragg crystal imaging spectrometer is provided.
Winkler, C. E.↗
Nonlinear astrophysical Alfven waves - Onset and outcome of the modulational instability
The nonlinear development of Alfven waves is numerically studied, with applications to Alfven waves in astrophysical plasmas. It is found that amplitude-modulated Alfven wave packets undergo a collapse instability in which the wave packets become more intense and of smaller spatial extent. The wave packet steepening is eventually halted in a process most aptly described as soliton formation. A simple analytic model based on the method of characteristics can account for many of the results of the numerical calculations. The instability probably cannot prevent particle pitch angle isotropization due to self-generated Alfven waves. Nonlinear effects of the collapse may modify the process by which energetic electrons are reaccelerated by plasma turbulence. The model calculations can semiquantitatively account for properties of shock-associated Alfven waves in the solar system.
Spangler, S. R.↗
Advanced X-ray Astrophysics Facility (AXAF) science instrumentation
AXAF is to be equipped with a high performance X-ray telescope for the conduction of detailed astrophysics research. The observatory is to be serviced by the Space Station or the Shuttle, depending on capabilities during the AXAF operational period. The AXAF is to utilize the wavelength band from 1.2 A to 120 A. Attention is given to the AXAF science team, the AXAF observatory characteristics, the AXAF science instrument definition program, the Advanced Charge Coupled Device (CCD) Imaging Spectrometer (ACIS), the High Resolution Camera (HRC), the Bragg Crystal Spectrometer (BCS), the X-ray Spectrometer (XRS), the transmission gratings, and the program schedule.
Dailey, C. C.↗
Confidence limits for small numbers of events in astrophysical data
The calculation of limits for small numbers of astronomical counts is based on standard equations derived from Poisson and binomial statistics; although the equations are straightforward, their direct use is cumbersome and involves both table-interpolations and several mathematical operations. Convenient tables and approximate formulae are here presented for confidence limits which are based on such Poisson and binomial statistics. The limits in the tables are given for all confidence levels commonly used in astrophysics.
Gehrels, N.↗
Saturation and beaming in astrophysical masers. III - Asymmetrically pumped masers
There is reason to believe that the physical conditions in many astrophysical masers are far from homogeneous. In particular, if the maser pump involves the absorption of infrared photons, the pump rate may vary rapidly (perhaps exponentially) across the cloud. The consequences of such variation of the pump rate for the maser radiation are calculated, and it is shown that there are substantial asymmetries in the output of the maser. A general result is that the maser radiation is preferentially emitted back toward the source of pump radiation. The implication of this result for the interpretation of the circumstellar 1612 MHz OH masers is briefly discussed.
Alcock, C.↗