Search NASA⌕ Search

Engineering topics

Cruddace, R. G.

Publications and source records attributed to Cruddace, R. G..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

The Spartan 1 mission

The first Spartan mission is documented. The Spartan program, an outgrowth of a joint Naval Research Laboratory (NRL)/National Aeronautics and Space Administration (NASA)-Goddard Space Flight Center (GSFC) development effort, was instituted by NASA for launching autonomous, recoverable payloads from the Space Shuttle. These payloads have a precise pointing system and are intended to support a wide range of space-science observations and experiments. The first Spartan, carrying an NRL X-ray astronomy instrument, was launched by the orbiter Discovery (STS51G) on June 20, 1985 and recovered successfully 45 h later, on June 22. During this period, Spartan 1 conducted a preprogrammed series of observations of two X-ray sources: the Perseus cluster of galaxies and the center of our galaxy. The mission was successful from both on engineering and a scientific viewpoint. Only one problem was encountered, the attitude control system (ACS) shut down earlier than planned because of high attitude control system gas consumption. A preplanned emergency mode then placed Spartan 1 into a stable, safe condition and allowed a safe recovery. The events are described of the mission and presents X-ray maps of the two observed sources, which were produced from the flight data.

Cruddace, R. G.↗
NASA NTRS1988

X-ray observations of the Galactic center by Spartan 1

The results of Spartan 1 X-ray observations of the region within 1.25 deg of the Galactic center are presented. Four strong, hard X-ray point sources were detected: A1742-294, 1E 1740.7-2942, IE 1743.1-2843, and a new source SP 1744.2-2959 about 0.5 deg southeast of A1742-294. The new source had an intensity about 20 percent of that of A1742-294 and was relatively hard, having spectral parameters close to those of the diffuse source and of the Galactic bulge source GX 3+1. The Galactic nucleus X-ray source appears to have been a factor of four fainter during the 1985 Spartan 1 observations than during the 1979 Einstein observations. Hard, diffuse X-ray emission centered near the Galactic center, about 1 deg in extent, aligned to within 20 deg of the Galactic equator, and having a maximum 2-10 keV brightness of 1.5 x 10 to the -6th ergs/sq cm/s/sr was detected, as were two weaker point sources about 0.1 deg northeast and southeast of the Galactic nucleus, embedded in the diffuse emission.

Kawai, N.↗
NASA NTRS1986

HEAO 2 X-ray observations of clusters of galaxies

A summary of results of Einstein satellite observations of clusters of galaxies is provided, and X-ray luminosities or upper limits for 27 clusters are reported. Newly reported clusters with interesting morphologies are presented, and a brief discussion of the data in relation to theories of cluster formation and evolution is given.

Ulmer, M. P.↗
NASA NTRS1986

Experiments of opportunity pay loads revisited

The design and operation of the Spartan program are discussed. The objective of the Spartan program is to utilize the Space Shuttle for conducting exoatmospheric science research. The Spartan 1 data storage and handling, attitude control, power, and thermal control systems and structure are described. The Spartan 1 was to study the structure of two prominent cosmic X-ray sources, the Perseus cluster of galaxies, and the center of the Milky Way. Spartan 1 was launched on June 17, 1985, deployed on June 20, and retrieved on June 22. The performance of the Spartan's system, and the collected data are analyzed; it was observed that the systems performed as planned. The methods used to minimize the Spartan program costs are considered.

Shrewsberry, D. J.↗
NASA NTRS1985

X-ray observations of possible binary clusters of galaxies

Many studies of superclusters of galaxies have been conducted, taking into account also superclusters representing candidate binary cluster systems. The present investigation is concerned with further studies of potential binary cluster systems, giving attention to a sample of six cluster pairs, in which the redshifts and X-ray luminosities of each member of a pair have been measured. One of the objectives of the investigation was related to a search for X-ray evidence that the clusters interact in these potentially binary systems. A second objective was to provide a measure of the mass of hot gas in the clusters. Two new systems in which the two clusters may have a physical association were found.

Ulmer, M. P.↗
NASA NTRS1985

Space research and Spartan

For a number of years, space research has been primarily conducted with sounding rockets and orbiting satellites. The use of satellites has disadvantages related to cost and the long lead time from design to launch, while a drawback in the case of sounding rockets is the short flight time of only a few minutes. The development of the Shuttle led to the proposal to employ for space research an autonomous free-flying payload deployed and recovered by the Shuttle. The proposed payload, called SPEAR (Small Payload Ejection and Recovery), looked very much like a rocket payload. Subsequently, the payload developed into a more compact form, and its name became Spartan-1. Attention is given to the demands of space research, the Spartan-1 payload, the payload functional control system, the thermal control system, the Spartan-1 mission, and the future of Spartan.

Cruddace, R. G.↗
NASA NTRS1984

An X-ray survey of clusters of galaxies. IV - A survey of southern clusters and a compilation of upper limits for both Abell and southern clusters

The results of the HEAO 1 A-1 X-ray survey of galaxy clusters are reported. X-ray error boxes and intensities are presented for all clusters in the Abell catalog and for the catalog of southern clusters and groups compiled by Duus and Newell (1977). A correlation is derived on the basis of the X-ray luminosity function for 2-6 keV which may be used to calculate the contribution of clusters to the diffuse X-ray background at different energies. The cluster X-ray is estimated to be 9.3 percent (+ 1.9 or - 1.5 percent). Correlations between X-ray luminosity and other cluster properties are exmained, and it is found that the distribution of upper limits may be applied to obtaining a more precise estimate of the average X-ray luminosity of clusters. The Abell richness class and southern cluster concentrations were strongly correlated with X-ray luminosity. Correlations between optical x-ray luminosity and optical radius velocity dispersion, spiral fraction, and radio power are analyzed. The evidence for all these correlations was considered to be weak because of poor scatter in the data.

Kowalski, M. P.↗
NASA NTRS1984

Contact binary stars. I - An X-ray survey

X-ray emission from a contact binary star was first detected by the HEAO 1 satellite in 1977. Spectroscopic observations of 44i Boo and VW Cep by IUE established the presence of high-temperature chromospheric and transition region emission lines in the spectra of these stars. The HEAO 1 and IUE results implied that the processes causing X-ray emission from VW Cep might be similar to those energizing the solar corona, and that X-ray emission might be a common occurrence among contact binary stars. A series of observations of these stars was, therefore, conducted with the aid of the HEAO 2 (Einstein) Observatory. The present investigation is concerned with the results of these observations, giving attention to their implications with respect to the nature of contact binary stars. The results are compared with similar HEAO 2 studies of coronal X-ray sources in the local region of the Galaxy, in the Hyades, and other rapidly rotating systems.

Cruddace, R. G.↗
NASA NTRS1983

The discovery of an X-ray bright BL Lacertae object - 0414 + 009

X-ray, optical, and radio observations have been made of an X-ray source originally discovered by Ulmer et al. (1980) in a survey of Abell clusters of galaxies. The relatively flat radio spectrum, the featureless optical spectrum, and the shape of the X-ray spectrum lead to the classification of the source as a BL Lacertae object. The source has one of the highest X-ray flux density ratios to both the optical and radio flux densities, and its strength at all these wavelengths warrants further multiwavelength studies. The radio, optical, and X-ray flux densities for the observations were 100 mJy, V = 16.4 (1 mJy), and 1 UFU (1.6 micro Jy). The X-ray flux varied by a factor of 2 over a 1 year period, but no 100 s time scale variations were seen. A search of the Harvard plate stacks did not reveal any optical variations. A model for the source is presented, and the implications of this object with respect to X-ray surveys are briefly discussed.

Brown, R. L.↗
NASA NTRS1983

Redshift modifications to HEAO A-1 cluster X-ray luminosities

New redshift measurements for the 24 Abell galactic clusters are presented. The optical observations are described and applied to the cluster X-ray luminosity function, and the results are used to delimit the cluster contribution to the diffuse X-ray background (DXRB). The evolution of the X-ray luminosity function is then investigated. It is found that while simple two-parameter analytic forms do not fit this function very well, three-parameter forms such as the exponential times power law do fit it very well. Future redshift observations will probably not change the volume emissivity significantly, but they may in a statistically significant way affect the parameters of analytic fits which define the shape of the luminosity function. The contribution of rich clusters to the DXRB in the 2-6 keV range is 5.2 percent. Future redshift observations will modify this result by no more than a factor of about 1.1.

Cruddace, R. G.↗
NASA NTRS1983

A survey by HEAO 1 of clusters of galaxies. III - The complete Abell catalog

A catalog of 128 X-ray emitting clusters, including the Virgo Cluster, is presented. Ninety-one of these are new identifications. The catalog was obtained by searching the HEAO 1 survey observations for coincidences of X-ray sources with Abell clusters. The distribution of these sources in the sky has been examined in search of associations with other Abell clusters, with a null result. The X-ray luminosity has been correlated with cluster richness, but no association with Bautz-Morgan class has been found. The cluster luminosity function has been evaluated, and using this function the contribution of clusters to the diffuse X-ray background radiation has been estimated. It amounts to less than 15% at 2 keV and 3% at 6 keV.

Johnson, M. W.↗
NASA NTRS1982

Three rich clusters of galaxies with bimodal or clumpy X-ray morphologies

X-ray images of the rich clusters of galaxies A1560, A2356, and A2384 show that the individual X-ray features correspond to hot gas of between one and 10 billion solar masses. These results are consistent with the formation of clusters by subcluster coalescence and merging. Clusters can be observed in almost any stage of coalescence, and it is recommended that galaxy motions and distributions be correlated with X-ray brightness distributions.

Ulmer, M. P.↗
NASA NTRS1981

Einstein observations of the region between the Abell clusters of galaxies A401 and A399

Results of Einstein (HEAO 2) observations of the region between the Abell clusters A401 and A399 are presented. It is shown that each cluster has X-ray emission that extends about 2 Mpc from their respective centers. All of the emission between the two clusters can be explained as the simple superposition of foreground and background extended emission.

Ulmer, M. P.↗
NASA NTRS1981

A survey of rich clusters of galaxies with HEAO 1. II

Results are presented of an X-ray survey of approximately 1900 Abell clusters of galaxies performed with the NRL large-area X-ray detectors on HEAO 1. The cluster luminosity function derived from the observations made at ecliptic longitudes between 80 and 180 deg and 260 and 360 deg is fit with both power law and exponential relations, and used to estimate a total contribution of Abell clusters to the volume emissivity of the diffuse X-ray background of between 3 and 10%. No strong correlation is found between X-ray luminosity and Bautz-Morgan class, richness class or 26-MHz radio power, although B-M type I and Abell richness class 3 appear more likely to be strong X-ray sources. A correlation is suggested between optical radius and X-ray luminosity.

Ulmer, M. P.↗
NASA NTRS1980

Soft X-ray sources in the bar of the Large Magellanic Cloud

X-ray observations of the Large Magellanic Cloud were made with two collimated proportional counters having high angular resolution, a wide spectral dynamic range and a large aperture. Counting rates in the two detectors during the entire rocket flight are presented, and a number of soft X-ray (0.5-2 keV) sources were found in the bar of the LMC, having luminosities between 10 to the 37th and 10 to the 38th ergs/s. Emission in the 0.15-0.28 keV band from LMC X-3 was also detected.

Mckee, J. D.↗
NASA NTRS1980

A search for extended halos of hot gas in the Perseus, Virgo, and Coma Clusters

Observations of the Perseus cluster by the HEAO 1 satellite have revealed a faint X-ray halo extending at least 2.5 deg from the center and contributing between 5% and 20% to the total luminosity. This may be of nonthermal origin, but it also may be explained in terms of hot gas bound by the gravitational field of the cluster. Statistical uncertainties made it impossible to detect any such halo in the Coma cluster. Observations of the Virgo cluster confirmed the detection by the Ariel 5 satellite of a broad region of faint X-ray emission (core radius 60 arcmin). If the very extended X-ray emission from Virgo is due to hot intracluster gas, the density of this gas is lower than expected from a consideration of gas and galaxy densities in the Perseus cluster.

Ulmer, M. P.↗
NASA NTRS1980

Identification of a faint X-ray source with the W Ursae Majoris star VW Cephei

The NRL instrument aboard the HEAO 1 satellite has detected a faint X-ray source, which has been identified tentatively with the contact binary star (W UMa variable) VW Cephei. Its luminosity is between 3 x 10 to the 30th and 4 x 10 to the 31st ergs/sec (0.1-10 keV), and the results suggest some variation of the X-ray flux with phase.

Carroll, R. W.↗