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Peterson, L. E.

Publications and source records attributed to Peterson, L. E..

At least 55 records · Page 3
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NASA NTRS1974

A cosmic gamma ray burst measured by Apollo 16

A cosmic gamma ray burst at about 1058:21 UT on April 27, 1972, was detected with an omnidirectional scintillation counter on Apollo 16. The event whose energy was approximately 0.0002 erg/sq cm, was pulse height analyzed in 512 channels over the 0.067 less than or equal to E less than or equal to 5 MeV range, and shows a complex, multipeak structure on a 300 msec time scale. The burst was also measured by a collimated X-ray detector on Apollo 16, giving spectral data in the 2 to 8 keV range which, together with a simultaneous observation by Vela 6A, allows a directional determination.

Matteson, J. L.↗
NASA NTRS1974

Measurements of the 0.1-27 MeV cosmic gamma ray spectrum by Apollos 15 and 16

The spectrum of diffuse cosmic gamma rays over the 0.127 MeV range was measured by a 7 x 7 cm omnidirectional NaI counter on Apollo 15 and 16. Location of the spectrometer on a 7.6 m extensible boom, use of precision pulse-height analysis, and operation in several modes permitted data to be obtained from which spacecraft and other background contributions could be separated. Recent measurements verified the Apollo spectrum.

Peterson, L. E.↗
NASA NTRS1974

A new model of atmospheric gamma rays and its implications for measurement of diffuse cosmic gamma rays from within the atmosphere

A semi-empirical model is discussed which describes atmospheric gamma rays in the range 0.3 less then or equal to E less than or equal to 10 MeV based on the production per unit mass of air. The model is based on the concept of a source strength (photon/g sec MeV) which is energy- and depth-dependent, and derived from measured fluxes. Quantities such as directional fluxes, angular distributions, and growth curves are calculated directly from this model. The source function is described by four energy-dependent parameters determined empirically from fluxes measured with a 7.5 cm x 7.5 cm Nal counter over the atmospheric depth range from 3.5 to 500 g/sq cm. From S(E,x), obtained for both continuum and discrete gamma rays at lambda = 40 deg, the depth and angle dependence of directional fluxes were calculated. Growth-curve predictions needed to separate atmospheric from diffuse cosmic fluxes were determined.

Matteson, J. L.↗
NASA NTRS1974

The UCSD/MIT hard X-ray and low energy gamma ray experiment for HEAO-A

An HEAO-A spacecraft is described which is scheduled for launch in April 1977 to survey the sky in the 0.15 keV to 10 MeV range of X-rays with improved sensitivity and angular resolution. The spectral and time variations of discrete sources, and the spectrum and isotropy of the diffuse component will be measured. A hard X-ray and low energy gamma ray experiment is described which will use as an array of seven (NaI)(Tl)/CsI(Na) phoswich detectors and eight large CsI(Na) shields. Detector events are pulse-height analyzed with a selectable time resolution of 0.1, 0.005, or 0.00002 sec. The instrument background is expected to be comprised of approximately equal parts of diffuse gamma rays entering the aperture, radioactive decay of spallation products, and gamma ray leakage through the shields. Detailed background predictions are presented, and sensitivity estimates indicate that the Crab nebula should be detected up to approximately 5 MeV. Approximate 1% isotropy limits for the diffuse component of cosmic gamma rays should be achieved, and its spectrum measured with improved precision.

Matteson, J. L.↗
NASA NTRS1974

Observations of the 4.8-hour variations of Cygnus X-3 above 7 keV from the OSO-7

Results of observations made (during the period from June 30 to July 5, 1972) of Cyg X-3 with the UCSD OSO-7 X-ray telescope in the range from about 7 to 100 keV. The 4.8-hour variation was detected in the 6.6-21.2 keV range, and the ratio of high intensity to mean intensity was 1.52 plus or minus 0.16. In the 21.2-97.8 keV range no 4.8-hour variation in phase with the 6.6-21.2 keV variation could be detected, and the ratio at the phase of high intensity to the mean intensity was 0.6 plus or minus 0.4.

Ulmer, M. P.↗
NASA NTRS1974

Long-term observations of Cygnus X-2 from OSO-7

Results of observations of Cygnus X-2 are reported that were made with an X-ray telescope on board the OSO-7 satellite during the three intervals of January 9-16 and 21-26, 1972, and July 8-11, 1972. Random factor-of-two variations were found in the data. No statistically significant periodic variations were found in the range from 10 hours to 2 days.

Ulmer, M. P.↗
NASA NTRS1974

Observations of solar X-ray bursts in the energy range 5-15 keV

Bursts of solar X-rays in the energy range 5-15 keV are associated with flares and are due to thermal emission from a hot coronal plasma. The results of the first study of a large sample of separate bursts, 197 events associated with subflares, and of a few events of importance 1 are presented. The observations were made by a proportional counter on the satellite OSO-7 from October, 1971 to June, 1972. In most cases, the temperature characterizing the X-ray spectrum rises impulsively at the onset of the burst and then declines slowly throughout the remainder of the burst. The emission measure rises exponentially with a time scale of 30-100 sec and then declines slowly on a time scale of the order of 1,000 sec. It is shown that the growth of the thermal energy in the flare plasma throughout the burst can be due to the heating of new cool material.

Datlowe, D. W.↗
NASA NTRS1974

Extended observations of higher than 7-keV X-rays from Centaurus X-3 by the OSO-7 satellite

The UCSD X-ray telescope on board OSO-7 provided 43 days of continuous coverage of the variable X-ray source Cen X-3 at energies above 7 keV during December 1971 and January 1972. We detected the 4.8-sec pulsation period, the 2.087-day eclipse cycle, and an apparently nonperiodic, low-intensity state lasting more than 12 days. Spectra obtained over the 7-30 keV range during noneclipsed high-intensity states are steeper than those previously reported. Large changes, which may be characterized by a number spectral index alpha varying between 3.0 plus or minus 0.2 and 2.0 plus or minus 0.3, or by exponential spectra with kT varying from 6 plus or minus 2 to 13 plus or minus 3 keV, occur at different high-intensity states.

Baity, W. A.↗
NASA NTRS1974

The Apollo gamma-ray spectrometer

A gamma-ray spectrometer has been flown on the Apollo 15 and 16 spacecraft to determine the lunar-surface composition and measure the cosmic gamma-ray flux. The instrument included a NaI(Tl) scintillation crystal coupled to a 7.6-cm photomultiplier tube, a plastic mantle for anti-coincidence rejection of charged particles, and 511 channels of analysis. Boom-mounted operation permitted a significant reduction in the background. The data were transmitted on an event-by-event basis. About 22% of the lunar surface was mapped and spectra of the cosmic gamma-ray flux over an energy range of 0.065-27.5 MeV have been obtained.

Harrington, T. M.↗
NASA NTRS1973

Spectrum of atmospheric gamma rays to 10 MeV at lambda = 40 deg

Results of measurements of the differential counting rate spectra due to atmospheric gamma rays as a function of altitude to 3.6 g/sq cm over Texas. Two gain settings and a 128-channel pulse height analyzer were used to cover the range from 0.2 to 10 MeV. The detector was a 7.6 x 7.6 cm NaI crystal, which was surrounded on five sides by a 2-cm-thick plastic anticoincidence shield for charged particle rejection. The system had a nearly isotropic response to photons above 0.2 MeV. The spectrum at ceiling appeared as a steep continuum with a power-law index of about 1.4. The only obvious feature was the 0.51-MeV positron annihilation line. The spectral shape was independent for depths less than 20 g/sq cm, the absolute intensity varying in proportion to the intensity of the cosmic ray secondary charged particles. Also, at depths less than 30 g/sq cm the observed flux variation with altitude can be described in terms of an empirical depth-dependent source function.

Peterson, L. E.↗
NASA NTRS1973

The direction and spectral variability of a cosmic gamma-ray burst

Description of the simultaneous observations of a gamma-ray event by five different satellites on May 14, 1972 in widely differing geomagnetic environments. The direction of the source was unambiguously determined, and it is concluded that the event was real and not caused by some unexplained spurious or instrumental effects. Since the obtained direction is far from the earth and the sun, the conclusion is that this gamma-ray event was almost certainly of cosmic origin. The total energy at the earth in this event was about .0005 ergs/sq cm from 11 to 1500 keV.

Wheaton, W. A.↗
NASA NTRS1973

New transient source, Cepheus X-4, observed by OSO-7.

A new, apparently transient, X-ray source, Cep X-4, was observed from June 20 to July 7, 1972, by the UCSD X-ray telescope on OSO-7. Subsequent observations by the lower-energy MIT X-ray telescope on the same satellite confirmed the source and provided an improved position of alpha = 21 hr 37 min, delta = 56.78 deg (1950 coordinates) with an error circle radius of about 0.4 deg. Best fits to the UCSD data in the 7- to 37-keV range were obtained on June 20 to 28 and June 29 to July 6, 1972, respectively.

Ulmer, M. P.↗