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photo of OSO mission
Credit: NASA

* Mission Overview

OSO-6 operated from August 1969 until January 1972. The orbital period was ~ 95 minutes, with the orbital day lasting ~ 60 minutes of each orbit. The spin rate was 0.5 rps.

* Instrumentation

The hard X-ray detector (27-189 keV) was a 5.1 cm2 NaI(Tl) scintillator, collimated to 17 deg x 23 deg FWHM. The system had 4 energy channels (separated 27-49-75-118-189 keV). The detector spun with the spacecraft on a plane containing the Sun direction within +/- 3.5 degrees. Data were read with alternate 70 ms and 30 ms integrations for 5 intervals every 320 ms.

Also on board was a NRL experiment meant primarily to monitor solar flares. This X-ray detector operated from August 1969 until January 1972. The NaI(Tl) scintillator had a frontal area of 1.3 cm2 and was 2.54 cm thick. The detector operated during daylight periods only (~ 70% of each 99.8 minute orbit). It had 6 energy channels covering 23-82 keV, and an integral channel for >82 keV (out to about 500 keV). Spectra were accumulated for 2.56 s.

* Science

Intended primarily to study bursts and flares from the Sun, the instrument was also used to search for hard X-ray coincidences with known gamma-ray bursts (primarily those seen by the Vela satellites). Three such coincidences were observed. The NRL instrument, when combined with data from the OGO-5 satellite, confirmed 5 hard X-ray bursts (they detected 12 altogether).

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