Space Exploration Timeline

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OSO 6 telescope

Aug 9, 1969 – Mar 7, 1981

Observed three instances of hard X-ray coincidences with gamma ray bursts.

https://en.wikipedia.org/wiki/Orbiting_Solar_Observatory

Includes events (2):
Aug 9, 1969
Launch of OSO 6 (OSO G)
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Mar 7, 1981
Re-entry date of OSO 6 (OSO G)
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