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.