Engineering topics

Grunsfeld, John M.

Publications and source records attributed to Grunsfeld, John M..

11 records

NASA NTRS1995

Construction of the GAMCIT gamma-ray burst detector (G-056)

The GAMCIT (Gamma-ray Astrophysics Mission, California Institute of Technology) payload is a Get-Away-Special payload designed to search for high-energy gamma-ray bursts and any associated optical transients. This paper presents details on the development and construction of the GAMCIT payload. In addition, this paper will reflect upon the unique challenges involved in bringing the payload close to completion, as the project has been designed, constructed, and managed entirely by undergraduate members of the Caltech SEDS (Students for the Exploration and Development of Space). Our experience will definitely be valuable to other student groups interested in undertaking a challenge such as a Get-Away-Special payload.

Coward, Michael H.↗

NASA NTRS1994

Observations of 1E 1740.7-2942 with ROSAT and the VLA

We have observed the Galactic black hole candidate 1E 1740.7-2942 in X-rays with both the ROSAT high resolution imager (HRI) and position-sensitive proportional counter (PSPC) and at 1.5 and 4.9 GHz with the very large array (VLA). From the HRI observation we derive a position for 1E 1740.7-2942 of right ascension = 17(exp h) 43(exp m) 54.9(exp s), declination = -29 deg 44 min 45.3 sec (J2000), with a 90% confidence error circle of radius 8.5 sec. Thermal bremsstrahlung fits to the PSPC data yield a column density of 1.12 + 1.51 or -0.18 X 10(exp 23)/ sq cm, consistent with earlier X-ray measurements. The VLA observations of 4.9 GHz revealed two sources. Source A, which is the core of a double aligned radio jet source (Mirabel et al. 1992), lies within the ROSAT error circle, further confirming its identification with 1E 1740.7-2942.

Heindl, William A.↗

NASA NTRS1994

Observations of 1E 1740.7-2942 with ROSAT and the VLA

We have observed the Galactic black hole candidate 1E 1740.7-2942 in X-rays with both the ROSAT HRI and PSPC and at 1.5 and 4.9 GHz with the VLA. From the HRI observation we derive a position for 1E 1740.7-2942 of right ascension = 17 h 43 m 54.9 s, declination = -29 deg 44 min 45.3 sec (J2000), with a 90% confidence error circle of radius 8.5 min. Thermal bremsstrahlung fits to the PSPC data yield a column density of 1.12+1.51/-0.18 x 10(exp 23)/sq cm, consistent with earlier X-ray measurements. The VLA observation of 4.9 GHz revealed two sources. Source A, which is the core of a double aligned radio jet source (Mirabel et al. 1992), lies within the ROSAT error circle, further confirming its identification with 1E 1740.7-2942.

Heindl, William A.↗

NASA NTRS1993

The GAMCIT gamma ray burst detector

The GAMCIT payload is a Get-Away-Special payload designed to search for high-energy gamma-ray bursts and any associated optical transients. This paper presents details on the design of the GAMCIT payload, in the areas of battery selection, power processing, electronics design, gamma-ray detection systems, and the optical imaging of the transients. The paper discusses the progress of the construction, testing, and specific design details of the payload. In addition, this paper discusses the unique challenges involved in bringing this payload to completion, as the project has been designed, constructed, and managed entirely by undergraduate students. Our experience will certainly be valuable to other student groups interested in taking on a challenging project such as a Get-Away-Special payload.

Mccall, Benjamin J.↗

NASA NTRS1993

An observation of the Galactic center hard X-ray source, 1E 1740.7-2942, with the Caltech coded-aperture telescope

The Galactic center region hard X-ray source IE 1740.7-2942 has been observed with the Caltech Gamma-Ray Imaging Payload (GRIP) from Alice Springs, Australia, on 1988 April 12 and on 1989 April 3 and 4. We report here results from the 1989 measurements based on 14 hr of observation of the Galactic center region. The observations showed IE 1740.7-2942 to be in its normal state, having a spectrum between 35 and 200 keV characterized by a power law with an exponent of -2.2 +/- 0.3 and flux at 100 keV of (7.0 +/- 0.7) x 10 exp -5 sq cm s keV. No flux was detected above 200 keV. A search for time variability in the spectrum of IE 1740.7-2942 on one hour time scales showed no evidence for variability.

Heindl, William A.↗

NASA NTRS1993

Discovery of the Orbit of the X-ray pulsar OAO 1657-415

Timing observations of the 38 s accreting X-ray pulsar OAO 1657-415 made with the BATSE large-area detectors on the Compton Gamma Ray Observatory have revealed a binary orbit with an X-ray eclipse by the stellar companion. From the pulsar mass function fx(M) = 11.7 +/- 0.2 solar masses and the measured eclipse half-angle theta(e) = 29.7 +/- 1.3 deg, we infer that the stellar companion is a supergiant of spectral class B0-B6. If the companion can be identified and its orbital velocity measured, the neutron star mass can be constrained. Both intrinsic spin-up and spin-down of the pulsar were measured during our observation.

Chakrabarty, Deepto↗

NASA NTRS1992

GAMCIT: A gamma ray burst detector

The origin of celestial gamma ray bursts remains one of the great mysteries of modern astrophysics. The GAMCIT Get-Away-Special payload is designed to provide new and unique data in the search for the sources of gamma ray bursts. GAMCIT consists of three gamma ray detectors, an optical CCD camera, and an intelligent electronics system. This paper describes the major components of the system, including the electronics and structural designs.

Surka, Derek M.↗

NASA NTRS1991

Coded-aperture imaging of the Galactic center region at gamma-ray energies

The first coded-aperture images of the Galactic center region at energies above 30 keV have revealed two strong gamma-ray sources. One source has been identified with the X-ray source IE 1740.7 - 2942, located 0.8 deg away from the nucleus. If this source is at the distance of the Galactic center, it is one of the most luminous objects in the galaxy at energies from 35 to 200 keV. The second source is consistent in location with the X-ray source GX 354 + 0 (MXB 1728-34). In addition, gamma-ray flux from the location of GX 1 + 4 was marginally detected at a level consistent with other post-1980 measurements. No significant hard X-ray or gamma-ray flux was detected from the direction of the Galactic nucleus or from the direction of the recently discovered gamma-ray source GRS 1758-258.

Cook, Walter R.↗

NASA NTRS1990

A 153 day periodicity in the occurrence of solar flares producing energetic interplanetary electrons

The occurrence times of energetic (above 10 MeV) solar flare electron events observed on board the ISEE 3 spacecraft during the years 1978-1982 have been examined; strong evidence is found for a periodicity of 153 + or - 2 days, confirming the discovery of a periodicity in the occurrence of solar flares producing X-rays and gamma rays. The Rayleigh test for periodicity is applied to obtain a probability of less than 10 to the -6th that the times of the electron flares were drawn from a uniform distribution.

Droge, Wolfgang↗

NASA NTRS1990

Relative abundances of secondary and primary cosmic rays at high energies

New results on the energy spectra of the cosmic-ray nuclei boron, carbon, nitrogen, and oxygen up to energies around 1 TeV per amu are described. The measurements were performed on the Spacelab 2 mission of the Space Shuttle in 1985. Carbon and oxygen are essentially primary cosmic rays, while boron is purely secondary, and nitrogen has secondary as well as primary contributions. Therefore, the relative abundances of these nuclei provide sensitive information on the propagation of cosmic rays through the Galaxy. It is found that the flux of the secondary cosmic rays continues to decrease relative to that of the primaries over the energy range covered with this observation, and that the mean escape length near 1 TeV per amu is about 1 g/sq cm.

Swordy, Simon P.↗

NASA NTRS1988

Energy spectra of cosmic-ray nuclei from 50 to 2000 GeV per amu

A direct measurement of the elemental composition of cosmic rays up to energies of several TeV/amu was performed during the Spacelab 2 flight of the Space Shuttle. Results on the spectral shape for the elements C, O, Ne, Mg, Si, and Fe, obtained from this experiment, are presented. It was found that the C and O energy spectra retain a power-law spectrum in energy with an exponent Gamma of about 2.65. The Fe spectrum is flatter (Gamma of about 2.55) up to a particle energy of about 10 to the 14th eV, indicating a steady increase in the relative abundance of iron in cosmic rays up to this energy. The energy spectra of Ne, Mg, and Si are steeper than anticipated. This behavior is unexpected within current models of cosmic-ray acceleration.

Grunsfeld, John M.↗