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NASA NTRS1988

Superfluid Helium Tanker (SFHT) study

Replenishment of superfluid helium (SFHe) offers the potential of extending the on-orbit life of observatories, satellite instruments, sensors and laboratories which operate in the 2 K temperature regime. A reference set of resupply customers was identified as representing realistic helium servicing requirements and interfaces for the first 10 years of superfluid helium tanker (SFHT) operations. These included the Space Infrared Telescope Facility (SIRTF), the Advanced X-ray Astrophysics Facility (AXAF), the Particle Astrophysics Magnet Facility (Astromag), and the Microgravity and Materials Processing Sciences Facility (MMPS)/Critical Point Phenomena Facility (CPPF). A mixed-fleet approach to SFHT utilization was considered. The tanker permits servicing from the Shuttle cargo bay, in situ when attached to the OMV and carried to the user spacecraft, and as a depot at the Space Station. A SFHT Dewar ground servicing concept was developed which uses a dedicated ground cooling heat exchanger to convert all the liquid, after initial fill as normal fluid, to superfluid for launch. This concept permits the tanker to be filled to a near full condition, and then cooled without any loss of fluid. The final load condition can be saturated superfluid with any desired ullage volume, or the tank can be totally filed and pressurized. The SFHT Dewar and helium plumbing system design has sufficient component redundancy to meet fail-operational, fail-safe requirements, and is designed structurally to meet a 50 mission life usage requirement. Technology development recommendations were made for the selected SFHT concept, and a Program Plan and cost estimate prepared for a phase C/D program spanning 72 months from initiation through first launch in 1997.

Eberhardt, Ralph N.↗

NASA NTRS1996

The feasibility study and evaluation of applying expert system techniques to the mission operations for the AXAF-I spacecraft

Advanced X-ray Astrophysics Facility - Imaging (AXAF-I) is a spacecraft for X-ray emitting sources observation and has been tentatively scheduled for a space shuttle launch in late 1998 at the Kennedy Space Center. Its main objectives are 'to determine the nature of astronomical objects ranging from normal stars to quasars, to understand the nature of the physical processes which take place in and between astronomical objects, and to add to our understanding of the history and evolution of the universe.' The AXAF-I will have an expected five year life time for the science mission phase. During the science mission phase, the monitoring and management operation of the flight and ground systems is personnel intensive, requiring system experts on duty around the clock. The purpose of the expert system presented in this report is intended to reduce the level of expertise, training, and personnel requirement for the mission operation. The telemetry data from the spacecraft can be divided into two categories: the science observation data and the engineering status data. The science data contains the outputs from the X-ray sensing devices and will be forwarded to the AXAF-I Science Center for interpretation; while the engineering status data will be monitored by the Operation Control Center (OCC) for the operation diagnosis of the spacecraft. The expert system is designed to assist the operation controllers at the OCC to perform the daily mission operations. Since there are hundreds of engineering telemetry data points and the interpretation of the telemetry depends on many factors, e.g., sun or eclipse, the monitoring of the AXAF-I is not a trivial task. In this phase of expert system development, the focus has been limited to the engineering data interpretation, i.e., warnings will be provided to the operation controllers to signal any anomaly. The system is hosted in a Silicon Graphics Indigo-2 workstation running the IRIX operating system. The expert system tool used is the G2 system from Gensym (Gensy).

Chang, Kai H.↗

NASA NTRSDate not supplied

AXAF Hypervelocity Impact Test Results

Composite and honeycomb panels are commonly used for spacecraft structural components. The impact test results and analysis of six different composite and honeycomb combinations for use on the advanced X-ray astrophysics facility (AXAF) are reported. The AXAF consists of an X-ray telescope and the associated detecting devices attached to an octagonal spacecraft with an internal propulsion system. The spacecraft's structural panels and optical bench are made of two different graphite fiber reinforced polyimides or composite panels bonded to either side of an aluminum honeycomb. The instrument is required to have at least a 0.92 probability of no failure of any of the critical elements due to meteoroids and debris. In relation to the no-failure probability determination in its low earth orbit environment, hypervelocity impact testing was performed to determine the ballistic limit range and the extent of damage due to impact. The test results for a power and signal cable bundle located behind a panel are presented. Tests planned for a multilayer insulation (MLI) blanket and four types of cable bundles are discussed.

Cynthia L Frost↗

NASA NTRS1997

Calibration of the AXAF Observatory: Overview

The Advanced X-ray Astrophysics Facility (AXAF) will soon begin its exploration of the x-ray universe, providing unprecedented angular and spectral resolution. Also unprecedented is the ambitious goal of calibrating the AXAF observatory to an accuracy of a few percent. Toward this end, AXAF science and engineering teams undertook an extensive calibration program at component, subsystem, and system levels. This paper is an overview of the system-level calibration activities, conducted over the past year at the Marshall Space Flight Center (MSFC) X-Ray Calibration Facility (XRCF).

Weisskopf, M.C.↗

NASA NTRS1997

Calibration of the AXAF Observatory: Overview

Weisskopf, M. C.↗

NASA NTRS1997

Calibration of the AXAF Observatory: Overview

The Advanced X-ray Astrophysics Facility (AXAF) will soon begin its exploration of the X-ray universe, providing unprecedented angular and spectral resolution. Also unprecedented is the ambitious goal of calibrating the AXAF observatory to an accuracy of a few percent. Toward this end, AXAF science and engineering teams undertook an extensive calibration program at component, subsystem, and system levels. This paper is an overview of the system-level calibration activities, conducted over the past year at the Marshall Space Flight Center (MSFC) X-Ray Calibration Facility (XRCF).

Weisskopf, M. C.↗

NASA NTRS2000

Participation In The AXAF Program As Interdisciplinary Scientist

We have supported the Advanced X-ray Astrophysics Facility (AXAF) project through specific studies and research in X-ray astronomy. Our research in X-ray astronomy has been concentrated in three projects: the ROSAT Deep Survey, the ROSAT All-sky Cluster Survey, and the study of moderate to high redshift clusters discovered serendipitously in long ROSAT pointings utilizing the wavelet transform. We have continued to develop the techniques and catalogues described in the publications listed below. The PI continued to participate in the SWG and attended its meetings except where conflicts existed. The Co-I supported the PI and attended all meetings in order to provide continuity. A post-doctoral fellow (Rosati) was hired to fully develop the techniques described above and make them applicable to the AXAF program. The results are described in the publications below. We continued to provide analysis of scientific and technical issues to the project scientist as appropriate. We made detailed simulations of the AXAF deep survey program and have made this available to the project and the ASC. The principal scientific results, discussed in great detail in the publications listed below, are as follows: (1) The wavelet transform is now a fine working tool for the analysis of faint X-ray sources especially clusters. (2) The analysis of the ROSAT DEEP CLUSTER SURVEY has given important constraints on cosmology particularly on the matter content of the universe and the amplitude of the fluctuations that created the galaxies and clusters. (3) The ROSAT DEEP SURVEY in the Lockman Hole has given an important'deep survey in the X-ray band that gives vital data on the distribution and evolution of X-ray sources. It is an important and complementary data base to compare with the AXAF deep fields. (4) The Northern ROSAT All Sky Cluster Survey now has a complete catalog and is again important and complementary to AXAF/ Chandra studies of clusters which are deeper but in a narrower area. These projects have had a significant impact on the whole field and have set up some excellent experiments to be undertaken with the AXAF/Chandra telescope such as the Chandra Deep Field South.

Giacconi, Riccardo↗

NASA NTRS1983

Preliminary Designs for Modifications to the X-Ray Source and Beam Monitor of the Marshall Space Flight Center's X-Ray Calibration Facility

Preliminary designs for modifications to the X-ray source and beam monitor of the MSFC X-Ray Calibration Facility to meet requirements for the calibration of the Advanced X-Ray Astrophysics Facility are considered. A rhodium plated copper target and rhodium foil filter are proposed as a source of X-rays of approximately 2.6 keV energy. Bragg scattering of the unpolarized X-ray beam from the present source through an angle of 90 deg by a single crystal placed on the axis of the guide tube is proposed as a source of approximately monoenergetic plane polarized X-rays. A sealed xenon proportional counter with a Beryllium window is proposed as a beam monitor for use between 2.5 and 8 keV to obtain improved detection efficiency.

Croft, W. L.↗

NASA NTRS1988

Performance characteristics of CCDs for the ACIS experiment

The search for the optimum CCD to be used at the focal surface of the Advanced X-ray Astrophysics Facility (AXAF) is described. The physics of the interaction of X-rays in silicon through the photoelectric effect is reviewed. CCD technology at the beginning of the AXAF definition phase is summarized, and the results of the CCD enhancement program are discussed. Other sources of optimum CCDs are examined, and CCD enhancements made at MIT Lincoln Laboratory are addressed.

Garmire, Gordon P.↗

NASA NTRS1992

Multilayer and grazing incidence X-ray/EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991

The present conference discusses the Advanced X-ray Astrophysics Facility (AXAF) calibration by means of synchrotron radiation and its X-ray reflectivity, X-ray scattering measurements from thin-foil X-ray mirrors, lobster-eye X-ray optics using microchannel plates, space-based interferometry at EUV and soft X-ray wavelengths, a water-window imaging X-ray telescope, a graded d-spacing multilayer telescope for high energy X-ray astronomy, photographic films for the multispectral solar telescope array, a soft X-ray ion chamber, and the development of hard X-ray optics. Also discussed are X-ray spectroscopy with multilayered optics, a slit aperture for monitoring X-ray experiments, an objective double-crystal spectrometer, a Ly-alpha coronagraph/polarimeter, tungsten/boron nitride multilayers for XUV optical applications, the evaluation of reflectors for soft X-ray optics, the manufacture of elastically bent crystals and multilayer mirrors, and selective photodevices for the VUV.

Hoover, Richard B.↗

NASA NTRS1991

High energy from space

The following subject areas are covered: (1) important scientific problems for high energy astrophysics (stellar activity, the interstellar medium in galaxies, supernovae and endpoints of stellar evolution, nucleosynthesis, relativistic plasmas and matter under extreme conditions, nature of gamma-bursts, identification of black holes, active nuclei, accretion physics, large-scale structures, intracluster medium, nature of dark matter, and the X- and gamma-ray background); (2) the existing experimental programs (Advanced X-Ray Astrophysics Facility (AXAF), Gamma Ray Observatory (GRO), X-Ray Timing Explorer (XTE), High Energy Transient Experiment (HETE), U.S. participation in foreign missions, and attached Shuttle and Space Station Freedom payloads); (3) major missions for the 1990's; (4) a new program of moderate missions; (5) new opportunities for small missions; (6) technology development issues; and (7) policy issues.

Margon, Bruce↗

NASA NTRS1982

AXAF, a permanent orbiting X-ray observatory - Telescope and instrumentation plans

The Advanced X-ray Astrophysics Facility (AXAF) now under study is to be a long-lived X-ray observatory in space. It is to be launched by the Space Shuttle, maintainable on-orbit, and retrievable for ground re-furbishment. The AXAF is conceived as an X-ray telescope with 6 nested grazing incidence X-ray mirrors (with a maximum aperture of 1.2 m) and interchangeable and replaceable focal plane instruments. The optics will provide 0.5 arcsecond imagery over a several arcminute field and somewhat reduced resolution over 1 degree in the X-ray band from 0.1 to 10 keV (1.2 to 120 A). The characteristics and expected performance of the observatory are described.

Zombeck, M. V.↗

NASA NTRS1982

AXAF, a permanent orbiting X-ray observatory - Telescope and instrumentation plans

The Advanced X-ray Astrophysics Facility (AXAF) now under study is to be a long-lived X-ray observatory in space. It is to be launched by the Space Shuttle, maintainable on-orbit, and retrievable for ground re-furbishment. The AXAF is conceived as an X-ray telescope with 6 nested grazing incidence X-ray mirrors (with a maximum aperture of 1.2 microns) and interchangeable and repleceable focal plane instruments. The optics will provide 0.5 arcsecond imagery over a several arcminute field and somewhat reduced resolution over 1 degree in the X-ray band from 0.1 to 10 keV (1.2 to 120 A). The characteristics and expected performance of the observatory are described.

Zombeck, M. V.↗

NASA NTRS1982

Astronomy and astrophysics for the 1980's, volume 1

The programs recommended address the most significant questions that confront contemporary astronomy and fall into three general categories: prerequisites for research initiatives, including instrumentation and detectors, theory and data analysis, computational facilities, laboratory astrophysics, and technical support at ground-based observatories; programs including an Advanced X-ray Astrophysics Facility, a Very-Long Baseline Array, a Technology Telescope and a Large Deployable Reflector; and programs for study and development, including X-ray observatories in space, instruments for the detection of gravitational waves from astronomical objects, and long duration spaceflights of infrared telescopes. Estimated costs of these programs are provided.

Source record↗

NASA NTRS1991

The AXAF/XRS ADR - Engineering model

A spaceworthy Adiabatic Demagnetization Refrigerator is under development at Goddard Space Flight Center as part of the X-Ray Spectrometer (XRS), an instrument on the Advanced X-ray Astrophysics Facility (AXAF). XRS will employ an array of 32 microcalorimeters capable of detecting X-rays in the energy range of 0.3 - 10 keV. In order to achieve a desired resolution of 12 eV, these detectors must be operated at a temperature of 0.065 - 0.100 K. An ADR must be used to cool these detectors in space. A breadboard model was designed and built less than two years ago, and provided excellent results. We are presently at the development stage of the engineering model. Several changes have been made to the original design in order to improve the efficiency of the ADR, to reduce its weight, and to strengthen the salt pill suspension system so that the ADR can survive launch loads and have low sensitivity to microphonic inputs. We shall report on the results of these changes; what worked and what did not.

Serlemitsos, Aristides T.↗

NASA NTRS1987

X-ray astronomical spectroscopy

The contributions of the Goddard group to the history of X-ray astronomy are numerous and varied. One role that the group has continued to play involves the pursuit of techniques for the measurement and interpretation of the X-ray spectra of cosmic sources. The latest development is the selection of the X-ray microcalorimeter for the Advanced X-ray Astrophysics Facility (AXAF) study payload. This technology is likely to revolutionize the study of cosmic X-ray spectra.

Holt, Stephen S.↗

NASA NTRS1986

The Bragg crystal spectrometer for AXAF

The goal of MIT's high resolution X-ray spectrometry investigation on the Advanced X-ray Astrophysics Facility is to study the physical conditions in celestial sources by means of detailed measurements of their X-ray spectra. The investigation involves two complimentary dispersive instruments, a Bragg crystal spectrometer (BCS) and a high energy transmission grating spectrometer. Particular attention is given to the BCS which will be used to measure the strengths of individual lines from both point and extended objects in order to apply plasma diagnostic techniques to the study of cosmic X-ray sources.

Canizares, C. R.↗

NASA NTRS1998

Calibration Results for the AXAF Flux Contamination Monitor

The Flux Contamination Monitor (FCM) on the Advanced X-ray Astrophysics Facility (AXAF) serves the purposes of transfering the absolute flux calibration from the ground calibration at the X-Ray Calibration Facility (XRCF) at Marshall Space Flight Center to operation on orbit and of detecting any changes in molecular contamination of the High Resolution Mirror Assembly (HRMA) between ground calibration and the post-launch activation phase. we describe the design, construction, and characterization of the FCM radioactive sources, and their placement on the Forward Contamination Cover (FCC). We present results from FCM measurements with the AXAF focal plane instruments, particularly the AXAF CCD Imaging Spectrometer (ACIS), during the ground calibration phase at XRCF in 1997. Finally, we describe the plans for FCM on-orbit measurements during observatory activation and the subsequent analysis.

Elsner, Ronald F.↗