1964-051A
The S-048 Ionosphere Explorer A, nicknamed Topsi, was a topside ionospheric sounder: it used a radio signal transmitted through the ionosphere from above (as opposed to the traditional technique with ground based stations reflecting signals from below) to study ionospheric structure. The S-48 satellite was built by Cutler-Hammer Inc.'s Airborne Instrument Lab Division for GSFC. It had a mass of 44 kg and was 0.83m long and 0.66m diameter.
S-48 was launched at 1343:17 on 1964 Aug 25 by Scout X-4 from Space Launch Complex 5 at Vandenberg (formerly PALC-D). At 1355:23 it was inserted into a 103.97 min, 871 x 1018 km x 79.9 deg orbit and became Explorer XX. It operated until 1966 Jul.
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| Explorer 20 |
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| Date | Time | Event | Orbit |
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| 1964 Aug 25 | 1343:17 | Launch by Scout X-4 | V SLC5 |
| | | T+1:04 St 1 burnout |
| | | T+1:13 St 2 burn |
| | | T+1:55 St 2 burnout |
| | | T+1:59 Fairing sep |
| | | T+2:01 St 3 burn |
| | | T+2:34 St 3 burnout |
| | | T+11:31 St 3 sep |
| | | T+11:41 St 4 burn 25s |
| | 1355:23 | T+12:06 St 4 burnout | 103.97 871 x 1018 x 79.9 |
| | | St 4 sep |
| | | Despin rockets fire |
| | 1415 | Antenna extension complete |
| 1966 Mar 30 | | Last transmission (GSFC) |
| 1966 Jul | | End of ops |
Payload:
- Topside sounder (Fixed frequency ionosonde)
- 9m sounding antennas, 4
- 18m sounding antennas, 2
- Ion mass spectrometer