High Energy Astrophysics Group

OSO-1

Orbiting Solar Observatory-1

Gamma-Ray Experiments

Three detector systems were provided as the University of Minnesota Gamma-Ray Telescopes, and together they monitored the intensity and direction properties of gamma-rays between 50 keV and 3 MeV.

The 50-150 keV telescope consists of a NaI(Tl) crystal scintillation counter in a lead pipe shield, which looks outward through the wall of the satellite. The NaI(Tl) crystal is 2.54 cm in diameter and 1.27 cm thick. The 31 cm long lead collimator had 0.5 cm thick walls and provided a limited field of view for directional studies.

A 5.1 cm diameter by 5.7 cm thick NaI crystal within an NE-102 plastic scintillator of thickness 0.3 cm formed a phoswich detector which had nearly isotropic response. This detector was sensitive to gamma-rays in the 0.33-1 MeV and 1 -3 MeV ranges.

A third NaI crystal with 3.18 cm diameter and 3.18 cm height was placed in conjunction with the phoswich detector and operated in the Compton telescope mode. By proper energy selection of the event in the NaI crystal in coincidence with the phoswich, one gained insight into the incident direction of the gamma-ray. These two telescopes also provided information on the cosmic-ray rates experienced by the Gamma-Ray telescopes.

Detector	Function	Omni Directional	Point Source	Extended Source	Efficiency	Shielding
Pb Pipe Telescope	50-150 keV photons	5.06 cm 2	5.06 cm 2	0.283 cm 2 -sr	~1.0	1.2 gm.cm 2 Al 5.0 gm/cm 2 Pb
NaI/NE-102 Counter	0.3-1.0 MeV 1.0-3.0 MeV photons	33 cm 2	---	---	0.75 @ 0.66 MeV 0.62 @ 1.28 MeV	~5 gm/cm 2
Compton Telescope	0.3-1.0 MeV 1.0-3.0 MeV photons	---	7.9 cm 2	1.3 cm 2 -sr	0.3x10-2 @ 1.28 MeV	0.8 gm/cm 2 Al
Cosmic Ray Singles	All events >1 MeV	46 cm 2	---	---	1.0 for cosmic rays	~5 gm/cm 2 Al
Cosmic Ray Telescope	All Coincident events	---	---	1.7 cm 2 -sr	1.0 for cosmic rays	0.8 gm/cm 2 Al

OSO-1 Information

Mission Objectives
Spacecraft
Gamma-ray Experiment
Results
Publications