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NASA NTRS1995

Neutrons, gamma rays, and beta particles interactions with IIaO films flown on Astro I and Astro II and comparison with IIaO flown on the get-away-special STS-7

The current requirements for the Laboratory for Astronomy and Solar Physics, sends rocket satellites and in the near future will involve flights in the shuttle to the upper reaches of the Earth's atmosphere where they will be subjected to the atomic particles and electromagnetic radiation produced by the Sun and other cosmic radiation. It is therefore appropriate to examine the effect of neutrons, gamma rays, beta particles, and X-rays on the film currently being used by the Laboratory for current and future research requirements. It is also hoped by examining these particles in their effect that we will have simulated the space environment of the rockets, satellites, and shuttles. Several samples of the IIaO film were exposed to a neutron howitzer with a source energy of approximately 106 neutrons/steradians. We exposed several samples of the film to a 10 second blast of neutrons in both metal and plastic containers which exhibited higher density readings which indicated the possibility of some secondary nuclear interactions between neutrons and the aluminum container. The plastic container showed some variations at the higher densities. Exposure of the samples of IIaO film to a neutron beam of approximately 10 neutrons per steradians for eight minutes produces approximately a 13% difference in the density readings of the dark density grids. It is not noticeable that at the lighter density grid the neutrons have minimal effects, but on a whole the trend of the eight minute exposed IIaO film density grids at the darker end had a 7.1% difference than the control. Further analysis is anticipated by increasing the exposure time. Two sets of film were exposed to a beta source in a plastic container. The beta source was placed at the bottom so that the cone of rays striking the film would be conical for a period of seven days. It was observed in the films, designated 4a and 4b, a dramatic increase in the grid densities had occurred. The attenuation of beta particles due to the presence of air were observed. The darker density grids, whose positions were the furthest from the beta source, displayed minimal fluctuations as compared with the control. It is suspected that the orientation of the film in the cansister with the beta source is the key factor responsible for the dramatic increases of the lighter density grids. Emulsions 3a and 3b exposed for a period of six days with the grid orientation reserved produced substantial differences in the darker grids as shown in the graphs. There is a great deal of fluctuations in this sample between the beta exposed density grids and the control density grids. The lighter density grids whose orientations were reversed displays minimal fluctuations due to the presence of this beta source and the attenuation that is taking place.

Hammond, Ernest C., Jr.↗

NASA NTRS1992

SPIKE: Application for ASTRO-D mission planning

SPIKE is a mission planning software system developed by a team of programmers at the STScI for use with the Hubble Space Telescope (HST). SPIKE has been developed for the purpose of automating observatory scheduling to increase the effective utilization and ultimately, scientific return from orbiting telescopes. High-level scheduling strategies using both rule-based and neural network approaches have been incorporated. Graphical displays of activities, constraints, and schedules are an important feature of the system. Although SPIKE was originally developed for the HST, it can be used for other astronomy missions including ground-based observatories. One of the missions that has decided to use SPIKE is ASTRO-D, a Japanese X-ray satellite for which the U.S. is providing a part of the scientific payload. Scheduled to fly in Feb. 1993, its four telescopes will focus X-rays over a wide energy range onto CCD's and imaging gas proportional counters. ASTRO-D will be the first X-ray imaging mission operating over the 0.5-12 keV band with high energy resolution. This combination of capabilities will enable a varied and exciting program of astronomical research to be carried out. ASTRO-D is expected to observe 5 to 20 objects per day and a total of several thousands per year. This requires the implementation of an efficient planning and scheduling system which SPIKE can provide. Although the version of SPIKE that will be used for ASTRO-D mission is almost identical to that used for the HST, there are a few differences. For example, ASTRO-D will use two ground stations for data downlinks, instead of the TDRSS system for data transmission. As a consequence ASTRO-D is constrained by limited on-board data storage capacity to schedule high data-rate observations during periods of frequent high bit rate observations accordingly. We will demonstrate the ASTRO-D version of SPIKE to show what SPIKE can provide and how efficiently it creates an observational schedule.

Isobe, T.↗

NASA NTRS2004

The Astro-E2 Mission

The Astro-E2 observatory is a rebuild of the original Astro-E observatory that was lost during launch in February 2000. It is scheduled for launch into low earth orbit on a Japanese M-V rocket in early 2005. The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, is developing the observatory with major contributions from the US. The three instruments on the observatory are the high-resolution x-ray spectrometer (the XRS) featuring a 30-pixel x-ray microcalorimeter array, a set of four CCD cameras (the XIS) and a combination photo-diode/scintillator detector system (the HXD) that will extend the band pass up to nearly 700 keV. A significant feature of Astro-E2 is that all of the instruments are coaligned and operated simultaneously. With its high spectral resolution and collecting area for spectroscopy above 1 keV, Astro-E2 should enable major discovery space and pioneer new technology for use in space. Prime areas for investigation are supernova remnants, active galaxies and the measurement of black hole properties via relativistically-broadened Fe-K emission galaxies. A number of enhancements have been made for the Astro-E2/XRS, including a higher resolution microcalorimeter array, ii mechanical cooler for longer cryogen life, and an improved in-flight calibration system. The Astro-E2/XIS has also been improved to include two back-side-illuminated CCDs to enhance the low energy response. Improvements have also been made to the x-ray mirrors used for both the XRS and XIS to sharpen the point spread function and reduce the effects of stray light. In this talk we will present the essential features of Astro-E2, paying particular attention to the enhancements, and describe the major scientific strengths of the observatory.

Kelley, Richard L.↗

NASA NTRS1993

Shuttle PRCS plume contamination analysis for Astro-2 mission

The Astro-2 mission scheduled for Jan. 1995 flight is co-manifested with the Spartan experiment. The Astro instrument array consists of several telescopes operating in the UV spectrum. To obtain the desired 300 observations with the telescope array in a shorter time than the Astro-1 mission, it will be necessary to use the primary reaction control system (PRCS) rather than just the Vernier reaction control system. The high mass flow rate of the PRCS engines cause considerable concern about contamination due to PRCS plume return flux. Performance of these instruments depends heavily on the environment they encounter. The ability of the optical system to detect a remote signal depends not only on the intensity of the incoming signal, but also on the ensuing transmission loss through the optical train of the instrument. Performance of these instruments is thus dependent on the properties of the optical surface and the medium through which it propagates. The on-orbit contamination environment will have a strong influence on the performance of these instruments. The finding of a two-month study of the molecular contamination environment of the Astro-2 instruments due to PRCS thruster plumes during the planned Astro-2 mission are summarized.

Wang, Francis C.↗

NASA NTRS1994

Fluid-loading solutions and plasma volume: Astro-ade and salt tablets with water

Fluid loading with salt and water is a countermeasure used after space flight to restore body fluids. However, gastrointestinal side effects have been frequently reported in persons taking similar quantities of salt and water in ground-based studies. The effectiveness of the Shuttle fluid-loading countermeasure (8 gms salt, 0.97 liters of water) was compared to Astro-ade (an isotonic electrolyte solution), to maintain plasma volume (PV) during 4.5 hrs of resting fluid restriction. Three groups of healthy men (n=6) were studied: a Control Group (no drinking), an Astro-ade Group, and a Salt Tablet Group. Changes in PV after drinking were calculated from hematocrit and hemoglobin values. Both the Salt Tablet and Astro-ade Groups maintained PV at 2-3 hours after ingestion compared to the Control Group, which had a 6 percent decline. Side effects (thirst, stomach cramping, and diarrhea) were noted in at least one subject in both the Astro-ade and Salt Tablet Groups. Nausea and vomiting were reported in one subject in the Salt Tablet Group. It was concluded that Astro-ade may be offered as an alternate fluid-loading countermeasure but further work is needed to develop a solution that is more palatable and has fewer side effects.

Fortney, Suzanne M.↗

NASA NTRS1995

The Astro Edge solar array for the NASA SSTI Clark Spacecraft

The Astro Edge solar array is a new and innovative reflective low concentrator power generating system which has been selected for the CTA Incorporate/Lockheed Martin Clark spacecraft under the NASA Small Spacecraft Technology Initiative (SSTI) program. In support of this program, Astro Aerospace Corporation has produced one qualification and two flight solar array wings to support a July 1996 launch. The Astro Edge solar array was selected as a new technology to benefit future NASA, military and commercial missions by providing high specific power, high deployed stiffness, low stowed volume, low risk, and cost reduction features which meet the agency's 'better, faster, cheaper' goals. This novel array accounts for five of the thirty-six advanced technologies which the Clark spacecraft will demonstrate. A brief SSTI Astro Edge solar array program overview is presented. Completed qualification and acceptance testing is discussed. Finally, the major discriminators which make the Astro Edge solar array 'better, faster, cheaper' technology are provided.

Spence, B. R.↗

NASA NTRS1992

Magnitude calibration of a fixed head star tracker using Astro-1 flight data

The Astro-1 UV astronomy mission was hampered by the failures of the automatic star acquisition procedure. The acquisition procedure depended on the Instrument Pointing Subsystem's Fixed Head Star Trackers (FHST) to acquire, track and identify guidestars of known visual magnitude. During the Astro-1 mission it was suspected that the star magnitudes measured by the FHST were much lower than predicted. A postflight investigation of the Astro-1 flight data confirmed and quantified this suspicion. Star magnitude calibration curves computed from the flight data depict the variance from the preflight calibration curves. These results are helping engineers to plan improvements to the acquisition procedure for the upcoming Astro-2 mission.

Rakoczy, John M.↗

NASA NTRS1990

Expert system for multidisciplinary analysis and optimization using ASTROS

This paper discusses the framework of a Knowledge Based Expert System (KBES) environment to design aerospace structures under structural and aerodynamic constraints using ASTROS (Automated Structural Optimization program). ASTROS is a synthesis tool built around the NASTRAN finite element program. The knowledge base capabilities are discussed for synthesizing in statics, normal mode, steady and unsteady aerodynamic disciplines. A description of the two ASTROS advisor modules the Editor/Bulk Data generator and Post-processor is included. Experiences and issues involved in hierarchical representation of knowledge as menu options at different levels of abstraction are presented. A brief overview of Knowledge Based Systems and the shell CLIPS (C Language Integrated Production System) used to develop the ASTROS Advisor are discussed. Illustrative examples of the advisor in designing airframe structures are also included.

Sarma, Hari K.↗

NASA NTRS1995

ASTRO-2 Spacelab Instrument Pointing System mission performance

This paper reports the performance of the Instrument Pointing System (IPS) that flew on the National Aeronautics and Space Administration (NASA) ASTRO-2 Spacelab mission aboard the Space Shuttle Endeavour in March 1995. The IPS provides a stabilizing platform for the ASTRO-2 instrument payload complement that consists of three main experiments (telescopes). The telescopes observe stellar targets in the universe within the ultraviolet portion of the electromagnetic spectrum that must be observed from beyond the earth's atmospheric filtering effects. The three main experiments for observation are the Hopkins Ultraviolet Telescope (HUT), the Ultraviolet Imaging Telescope (UIT), and the Wisconsin Ultraviolet Photo-Polarimetry Experiment (WUPPE). The HUT uses spectroscopy to obtain the structure and chemical makeup of ultraviolet targets. UIT is responsible for wide field photographing to capture the hidden view of the ultraviolet universe. The WUPPE gathers data on the polarization of the ultraviolet electromagnetic energy coming from the astronomical targets. The capability of IPS enables the experiments to 'see' faint celestial objects. A brief explanation of the IPS is given followed by a review of engineering efforts to improve IPS performance over the ASTRO-1 mission. The main focus of improvements was on enhancing the star acquisition capability through improved guide star selection, lab simulations, computer upgrades, data display systems improvements, and software modifications. A star simulator was developed in the lab to enable IPS to be simulated on the ground pre-mission with flight hardware and software in the loop. The paper concludes with results from the ASTRO-2 mission. The number of targets acquired and the IPS pointing accuracy/stability is reported along with recommendations for the future use of the Instrument Pointing System.

Wessling, Francis C., III↗

NASA NTRS2002

The X-ray Mirrors for the Astro-E2 Mission

The X-Ray telescopes (XRT) for the US/Japan collaborative mission Astro-E2 will be of the same basic design as those built for the original Astro-E mission which failed to reach orbit in Feb. 2000. The NASA/GSFC X-ray Astrophysics Branch will again provide the five lightweight, broad-band mirrors for the mission. X-ray calibrations of the mirrors delivered for the original Astro-E instrument showed spatial resolutions characterized by Half-Power Diameters (HPD) in the range of 1.8 - 2.2 minutes of arc, essentially independent of photon energy in the soft X-ray band. For the mission Astro-E2, both funding constraints and management decisions drastically limit any design modifications, so reflector fabrication and assembly procedures have remained largely unchanged. Nevertheless, in view of the importance in scientific return of attaining even a modest improvement in the spatial resolution of these mirrors, we have carefully considered the various sources of spatial error and, whenever possible, incorporated promising modifications. In this paper, we discuss our current understanding of the various error components as well as the small changes we have been able to implement.

Chan, Kai-Wing↗

NASA NTRS2016

Mapping the Gas Turbulence in the Coma Cluster: Predictions for Astro-H

Astro-H will be able for the first time to map gas velocities and detect turbulence in galaxy clusters. One of the best targets for turbulence studies is the Coma cluster, due to its proximity, absence of a cool core, and lack of a central active galactic nucleus. To determine what constraints Astro-H will be able to place on the Coma velocity field, we construct simulated maps of the projected gas velocity and compute the second-order structure function, an analog of the velocity power spectrum. We vary the injection scale, dissipation scale, slope, and normalization of the turbulent power spectrum, and apply measurement errors and finite sampling to the velocity field. We find that even with sparse coverage of the cluster, Astro-H will be able to measure the Mach number and the injection scale of the turbulent power spectrum-the quantities determining the energy flux down the turbulent cascade and the diffusion rate for everything that is advected by the gas (metals, cosmic rays, etc.). Astro-H will not be sensitive to the dissipation scale or the slope of the power spectrum in its inertial range, unless they are outside physically motivated intervals. We give the expected confidence intervals for the injection scale and the normalization of the power spectrum for a number of possible pointing configurations, combining the structure function and velocity dispersion data. Importantly, we also determine that measurement errors on the line shift will bias the velocity structure function upward, and show how to correct this bias.

clusters: intracluster medium↗

NASA NTRS2016

System Design and Implementation of the Detector Assembly of the Astro-H Soft X-Ray Spectrometer

The soft x-ray spectrometer (SXS) onboard Astro-H presents to the science community unprecedented capability (less than 7 eV at 6 keV) for high-resolution spectral measurements in the range of 0.5-12 keV to study extended celestial sources. At the heart of this SXS is the x-ray calorimeter spectrometer (XCS) where detectors (calorimeter array and anticoincidence detector) operate at 50 mK, the bias circuit operates at nominal 1.3 K, and the first stage amplifiers operateat 130 K, all within a nominal 20 cm envelope. The design of the detector assembly in this XCS originates from the Astro-E x-ray spectrometer (XRS) and lessons learned from Astro-E and Suzaku. After the production of our engineering model, additional changes were made in order to improve our flight assembly process for better reliability and overall performance. In this poster, we present the final design and implementation of the flight detector assembly, show comparison of parameters and performance to Suzakus XRS, and list susceptibilities to other subsystems as well as our lessons learned.

soft x-ray spectrometer↗

NASA NTRS2016

The ASTRO-H SXT Performance to the Large Off-Set Angles

The X-ray astronomy satellite ASTRO-H, which is the 6th Japanese X-ray astronomy satellite and is renamed Hitomi after launch, is designed to observe celestial X-ray objects in a wide energy band from a few hundred eV to 600 keV. The Soft X-ray Telescopes (SXTs) onboard ASTRO-H play a role of collecting and imaging X-rays up to approximately 12 keV. Although the field of view of the SXT is approximately 15' (FWHM), due to the thin-foil-nested Wolter-I type optics adopted in the SXTs, X-rays out of the field of view can reach the focal plane without experiencing a normal double reflection. This component is referred to as 'stray light'. Owing to investigation of the stray light so far, 'secondary reflection' is now identified as the main component of the stray light, which is composed of X-rays reflected only by secondary reflectors. In order to cut the secondary reflections, a 'pre-collimator' is equipped on top of the SXTs. However, we cannot cut all the stray lights with the pre-collimator in some off-axis angle domain. In this study, we measure the brightness of the stray light of the SXTs at some representative off-axis angles by using the ISAS X-ray beam line. ASTRO-H is equipped with two modules of the SXT; one is for the Soft X-ray Spectrometer (SXS), an X-ray calorimeter, and the other is for the Soft X-ray Imager (SXI), an X-ray CCD camera. These SXT modules are called SXT-S and SXT-I, respectively. Of the two detector systems, the SXI has a large field of view, a square with 38' on a side. To cope with this, we have made a mosaic mapping of the stray light at a representative off-axis angle of 30' in the X-ray beam line at the Institute of Space and Astronautical Science. The effective area of the brightest secondary reflection is found of order approximately 0.1% of the on-axis effective area at the energy of 1.49 keV. The other components are not so bright (less than 5 x 10(exp -4) times smaller than the on-axis effective area). On the other hand, we have found that the effective area of the stray light in the SXS field of view (approximately 3' x 3') at large off-axis angles (greater than 15') are approximately 1(exp -4) times smaller than the on-axis effective area (approximately 590 sq cm at 1.49 keV).

X-rays↗

NASA NTRS1972

The geocentric orientation vector from limited Astro-geodetic data

Test computations using the comprehensive sets of both astro-geodetic and gravimetric data indicate that the accuracy of the geocentric orientation vector determined from incomplete representations of the earth's gravitational fields, is dependent on the overall extent of the datum. The lack of an astro-geodetic determination of the geoid due to an inadequate density of astro-geodetic stations over certain parts of the datum does not materially affect these determinations. The effect is only marginal if the station density of the area referred to does not markedly differ from the average for the region.

Mather, R. S.↗

NASA NTRS1986

ASTROS - High-performance CCD tracker for spacecraft

The architecture, capabilities, and testing of the Advanced Star and Target Reference Optical Sensor (ASTROS) I and II are described. The ASTROS I tracker is to be utilized for a UV telescope experiment on a Shuttle flight and is capable of measuring pointing errors of 1.5 microrad, and the ASTROS II tracker is being developed for the Mariner Mark II spacecraft to perform tracking, guiding, and optical navigation functions. The requirements for the two trackers are compared. Consideration is given to star and target tracking, optical navigation, and mass and power constraints. The compositions of the trackers, in particular the sensor, electrode drives, amplifiers and signal clamp, video signal processor, control and timing generator, memories, microprocessor, and interface, are examined.

Dennison, E. W.↗

NASA NTRS1987

Ultraviolet observations of starburst systems with Astro and the Hubble Space Telescope

The capabilities of the Astro observatory and the Hubble Space Telescope (HST) for UV astronomical observations are discussed. The advantages of using UV for studying extragalactic problems are reviewed, including sensitivity to hot sources, the rich UV line spectra, sensitivity to interstellar dust, and dark UV sky background. The HST and Astro instrumentation and plans for launching the systems are described. Possibile uses of HST and Astro include the study of massive stars in the Galaxy and nearby galaxies, interstellar medium, the UV excess component in old stellar populations, deep UV surveys (filter imaging and slitless spectroscopy), active galactic nuclei, quasars, and starburst systems.

O'Connell, Robert W.↗

NASA NTRS1991

Astro - Science in the fast lane

The Space Shuttle mission devoted to astronomy (Astro) is described and data obtained during the nine-day flight are briefly reviewed. The Wisconsin Ultraviolet Photo-Polarimeter Experiment reveals a trough at 2200 A in the spectrum of Alpha Camelopardalis. It is suggested that the 2200-A feature is caused by absorption by graphite-rich interstellar dust. The Broad Band X-ray Telescope made it possible to study the NGC 1399 X-ray spectrum, the spectrum of the BL Lacertae object PKS 2155-304, and a cooling flow in a cluster of galaxies. The Astro mission's search for the missing mass in the form of neutrinos is discussed. Attention is also given to the effect of delays on the Astro activity, and to equipment problems and how they were solved.

Maran, Stephen P.↗

NASA NTRS1993

Wide-field direct CCD observations supporting the Astro-1 Space Shuttle mission's Ultraviolet Imaging Telescope

Wide field direct CCD observations are being obtained to support and complement the vacuum-ultraviolet (VUV) images provided by Astro's Ultraviolet Imaging Telescope (UIT) during a Space Shuttle flight in December 1990. Because of the wide variety of projects addressed by UIT, the fields observed include (1) galactic supernova remnants such as the Cygnus Loop and globular clusters such as Omega Cen and M79; (2) the Magellanic Clouds, M33, M81, and other galaxies in the Local Group; and (3) rich clusters of galaxies, principally the Perseus cluster and Abell 1367. Ground-based observations have been obtained for virtually all of the Astro-1 UIT fields. The optical images allow identification of individual UV sources in each field and provide the long baseline in wavelength necessary for accurate analysis of UV-bright sources. To facilitate use of our optical images for analysis of UIT data and other projects, we plan to archive them, with the UIT images, at the National Space Science Data Center (NSSDC), where they will be universally accessible via anonymous FTP. The UIT, one of three telescopes comprising the Astro spacecraft, is a 38-cm f/9 Ritchey-Chretien telescope on which high quantum efficiency, solar-blind image tubes are used to record VUV images on photographic film. Five filters with passbands centered between 1250A and 2500A provide both VUV colors and a measurement of extinction via the 2200A dust feature. The resulting calibrated VUV pictures are 40 arcminutes in diameter at 2.5 arcseconds resolution. The capabilities of UIT, therefore, complement HST's WFPC: the latter has 40 times greater collecting area, while UIT's usable field has 170 times WFPC's field area.

Hintzen, Paul↗