1961-013
The 38 kg S-015 payload carried a Cerenkov detector to study gamma rays from space. Launched by a Juno II (AM-19E) from Cape Canaveral at 1416:38 on 1961 Apr 27, it reached a 487 x 1779 km x 28.8 deg orbit; the orbit was very close to the one planned. The satellite was a cylinder topped by a box, and remained attached to the stage 4 motor. Orbit mass was 43 kg including a 3 kg nutation damper weight. RTV motor is 0.15m dia 1.1m long with 5.8 kg empty mass, payload is 0.29m dia 1.1m long with 37 kg mass.
The telescope was tipped with a thin aluminium shield for micrometeorite protection which could be ejected on command. This shield is possibly the object 1961 nu 2 which was cataloged in Feb 1969.
S-15 was built by NASA MSFC; the gamma ray telescope was built at MIT. Management was by NASA GSFC.
Explorer XI, as it was now designated, transmitted until Dec 6. It did not detect significant gamma ray flux (about 22 photons were observed), and the true birth of orbital gamma ray astronomy had to wait until the COS-B mission in 1975. Explorer XI set an upper limit to the 50 MeV gamma ray background of 3x 10-4 photons/cm2/s/sr.
| Explorer 11 (S-15) | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1961 Apr 27 | 1416:38 | Launch by Juno II AM-19E | CC LC26B |
| T+2:58 MECO | |||
| 1419:05 | T+3:05 Jupiter sep | ||
| 1419:34 | Fairing sep | ||
| 1424:26 | T+8:26 Stage 2 burn, 495 km | ||
| Stage 3 burn | |||
| Stage 4 burn | |||
| 1424:56 | Orbit insertion, 496 km | 491 x 1799 x 28.8 | |
| Telescope cover sep? | |||
| 1961 Dec 6 | End of ops | ||
Payload:
- Cerenkov counter, 50-100 MeV (MIT/Kraushaar)
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