Explorer 42

  1970-107A

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The first small Explorer payload, SAS-A, carried two x-ray proportional counters provided by the American Science and Engineering team which later became the x-ray astronomy group of the Smithsonian Astrophysical Observatory. It was launched at 1053 on 1970 Dec 12 by a Scout B from the San Marco Launch Complex in the Indian Ocean off Kenya. It reached a 95.30 min, 522 x 563 km x 3.04 deg orbit and began operations on Dec 18. SAS-A was given the designations Small Astronomy Satellite 1 (SAS 1) and Explorer 42, but it is famous by the name given to it in honor of the Kenya-based launch site - Uhuru, the Swahili for `freedom'. Uhuru was the first successful x-ray astronomy satellite and made a survey of the 2-10 keV x-ray sky which was turned into a series of catalogs, the final one being the Fourth Uhuru (4U) catalog. Uhuru operations ended on 1973 Mar 18 and the satellite reentered on 1979 Apr 5.

Uhuru
Date	Time	Event	Orbit
1970 Dec 12	1053:50	Launch by Scout B S175C	SMLC
		T+1:16 St 1 burnout
		T+1:19 Stage 2 burn
		T+1:59 Stage 2 burnout
		T+2:13 Stage 3 burn
		T+2:49 Stage 3 burnout
		T+9:05 spinup
		T+9:07 Stage 3 sep
	1103:02	T+9:12 Stage 4 burn
	1103:37	T+9:47 Stage 4 burnout
	1108:17	T+14:27 Stage 4 sep
		Magnetic despin
1970 Dec 13			95.76 535 x 574 x 3.0
1971 Feb		Tape recorder failed
1971 May 25			95.63 530 x 568 x 3.0
1971 Aug		Transmitter strength weakened
1971 Sep		Degraded star sensors
1971 Dec		Transmitter recovered
1972 Mar		Battery failed, day ops only
1973 Mar 18		End of ops