1978-051A
The Pioneer Venus Orbiter was launched at 1313 on 1978 May 20 by Atlas Centaur from Cape Canaveral. The Atlas stage separated at 1317:16 and the Centaur ignited at T+4:26. Centaur MECO at 1322 (T+9:36) left PVO in a 170 km parking orbit. At 1331 the Centaur reignited for a 2 min 17 s solar orbit insertion burn. When it separated at 1336, PVO was on a Type 2 Venus transfer trajectory with an aphelion of 1.08 AU. Control was transferred to the PMOCC at Ames on May 22. Correction burns TCM1 and TCM2 were made on Jun 1 and Nov 2.
The onboard solid insertion motor fired at 1558:05 on 1978 Dec 4 and placed PVO in a 23h 11m, 378 x 66900 km x 105.6 deg orbit around Venus. At 0527 Dec 6 it lowered periapsis to 233 km, and on Dec 9 the periapsis was lowered further to 180 km. By Dec 20 the orbit was synchronized to the Earth day, 1436 min 150 x 66900 km x 105 deg, when the last of 7 trim burns was made.
In 1979 Jan-Feb the periapsis was varied from 142 km to 175 km. On Feb 14 the OIR instrument failed. In August the PVO was turned off temporarily while the Deep Space Network supported the Pioneer Saturn encounter. The nominal mission was over on 1979 Aug 4, and was followed by EM1, the Pioneer Venus Extended Mission. By 1979 Sep periapsis had risen to 253 km and was lowered to 142 km. Extended Mission 2 ran from 1980 Apr 3 to Dec 2. In 1980 Jul the RCS gas ran low; the periapsis was allowed to rise. The period remains constant as the inclination, now at 17 degrees, would drift to 0 degrees by 1986, and back up to 17 deg in 1992. In 1981 the periapsis was too high for the ORM and it was turned off.
The Approach Phase began in 1991 Jan when periapsis began to drop from 1000 to 200 km. This was followed by the Entry Phase, starting in 1992 Jun. A periapsis raising burn (the 6th) was carried out on 1992 Oct 2, raising closest approach from 132.9 km to 141.7 km. On Oct 3 the propellant ran dry and the satellite had to be spun up on Oct 5. A final orbit raise of 1 km was made at 0525 on Oct 8 (apoapsis). After the next periapsis passage, 128 km at 1922 on Oct 8, no further transmissions were heard from PVO and the end of mission was declared.
| PVO | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1978 May 20 | 1313:00 | Launch by Atlas Centaur | |
| T+2:19 BECO 57 km | |||
| T+2:22 Booster sep 61 km | |||
| T+3:04 Insulation panels sep 98 km | |||
| 1316:44 | T+3:44 Fairing sep | ||
| T+4:14 SECO | |||
| 1317:16 | T+4:16 Atlas sep | ||
| 1317:26 | T+4:25 Centaur MES-1 | ||
| 1322:36 | T+9:35 Centaur MECO-1 | 166 x 170 x | |
| 1332 | Centaur MES-2 2:17 | ||
| 1334 | Centaur MECO-2 | ||
| 1337:46 | T+24:46 Centaur sep (MECO2+2:15) | 0.72 x 1.08 AU | |
| 1337:49 | T+24:49 Spinup to 6.5 rpm | ||
| 1650:30 | MAG deploy | ||
| 2056? | Pass EL1:4 | ||
| 1978 May 21 | 1700? | HGA despin | |
| 1978 May 24 | 0544 | Exit Earth sphere (L1) | 0.72 x 1.08 AU |
| 1978 Jun 1 | 1001 | TCM-1 axial 0.5m/s | |
| 1916 | TCM-1 radial-1 1.6m/s | ||
| 2146 | Spin rate trim | ||
| 1978 Jun 2 | 0006 | TCM1 radial-2 1.6m/s | |
| 1978 Nov 2 | TCM-2 | ||
| 1978 Dec 1 | 1900? | Enter Venus sphere/L1 | |
| 1978 Dec 4 | 1558:17 | VOI burn 1108.7 m/s | |
| VOI burnout | 1391.43 378.7 x 66900 x 105.0210 | ||
| HGA spinup 30 rpm | |||
| SC bus despin to 15 rpm | |||
| Inversion, spin axis to NEP at apo 1 | |||
| HGA despin | |||
| ORAD antenna released | |||
| ONMS cap jettison (VOI+36h?) | |||
| OETP radial sensor deploy | |||
| 1978 Dec 5 | OTM-1 | 248 x 66900? x 105.6 | |
| 1978 Dec 6 | OTM-2 | 233 x 66900? x 105.6 | |
| 1978 Dec 9 | OTM-3 | 180 x 66900? x 105.6 | |
| 1978 Dec 20 | OTM-7? | 1436.0 150 x 66900 x 105 | |
| Spacecraft despin to 5 rpm | |||
| 1979 Jan-Feb | Periapsis (km) | 142-175 | |
| 1979 Mar-Apr | 150-170 | ||
| 1979 May-Jul | 150-190 | ||
| 1979 Aug 4 | End primary mission | ||
| 1979 Aug 4 | Start Extended Mission 1 | ||
| 1979 Sep | 253 | ||
| 1979 Sep | Orbit lower | 170 | |
| 1979 Oct | 142 | ||
| 1979 Oct | 160 | ||
| 1979 Nov | 145-160 | ||
| 1979 Dec | 150-185 | ||
| 1980 Jan | 150-185 | ||
| 1980 Feb-Mar | 150-175 | ||
| 1980 Apr 3 | Start Extended Mission 2 | ||
| 1980 Apr-Jun | 150-180 | ||
| 1980 Jul | end of orbit maintenance | ||
| 1980 Dec 2 | End EM2 | ||
| 1981 | 400-800 | ||
| 1982 | 800-1500 | ||
| 1983 | 1500-1800 | ||
| 1984 | 1800-2000 | ||
| 1985 | 2000-2100 | ||
| 1986 Jun 30 | 2270 | ||
| 1987 | 2000-2100 | ||
| 1988 | 1600-2000 | ||
| 1989 | 1200-1600 | ||
| 1990 | 1000-1200 | ||
| 1991 Jan | Approach Phase | ||
| 1991 Mar 3 | 1000 | ||
| 1991 Dec | 200 ? | ||
| 1992 Jun | Entry Phase | ||
| 1992 Oct | 132.9 | ||
| 1992 Oct 2 | PRM-6 | 141.7 | |
| 1992 Oct 3 | Fuel low | ||
| 1992 Oct 5 | spinup | ||
| 1992 Oct 6 | 130.8 (orbit 5054) | ||
| 1992 Oct 7 | 128.9 (orbit 5055) | ||
| 1992 Oct 8 | 0525 | PRM-7? 1km | 128 |
| 1992 Oct 8 | 1922 | Perapsis | 128 x |
| End of transmissions | |||
| 1992 Oct | Entry | ||
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