HEASARC Staff Scientist Position - Applications are now being accepted for a Staff Scientist with significant experience and interest in the technical aspects of astrophysics research, to work in the High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD. Refer to the AAS Job register for full details.
The IMP-6 satellite was launched 14 March 1971. It was placed in an
elliptical orbit with an apogee of more than 200,000 km. The 16-sided
spacecraft was 182 cm high and 135 cm in diameter. The spin axis was normal
to the ecliptic, with a spin period of 10.5 seconds. The satellite was
powered by solar cells and chemical batteries. The spacecraft reentered the
Earth's atmosphere on 2 October 1974. However, the gamma-ray instrument
failed on 26 September 1972.
The gamma-ray monitor instrument consisted of a 2.25 inch diameter x 1.5
inch thick CsI(Tl) crystal surrounded by a plastic scintillator. The
plastic served as a particle rejector. The crystal was viewed by a single
photomultiplier. The monitor was on continuously except for the passage
through the magnetotail, which occurred every 4.14 days. It operated from
launch until 2 May 1971, and then again during the period 9 June 1971 - 27
September 1972. In addition to monitoring the rates of total intensity,
particle intensity, and gamma-ray intensity, energy spectra of the incident
gamma-rays were measured in 14 channels. Spectra were accumulated
for 50% of the time, with data being collected only during the sunward half
of each satellite rotation. The spectral accumulation times were fixed at
~5.1 s. The gain of the system was cycled through 4 positions, with changes
being made roughly every week for purposes of in-flight calibration. Thus,
some data were taken with a 69-1150 keV energy range, while other data were
taken with a 53-88 keV range.
The primary purpose of the instrument was as a coincident
annihilation spectrometer incorporated in a positron detector. The
secondary objective was as a solar flare monitor, and it was in this mode
of operation that gamma-ray bursts (quite unexpectedly!) were observed.
Detailed spectra of six cosmic gamma-ray bursts were gathered, confirming
the hard X-ray or gamma-ray nature of the bursts. The maximum energy release
was seen to be at several hundred keV.
HEASARC Staff Scientist Position - Applications are now being accepted for a Staff Scientist with significant experience and interest in the technical aspects of astrophysics research, to work in the High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA Goddard Space Flight Center (GSFC) in Greenbelt, MD. Refer to the AAS Job register for full details.
