1992-063A
Mars Observer was built by GE Astro Space and based on the Series 4000 communications satellite, using subsystems from the Tiros N satellite bus. Mars Observer was launched at 1725:01 on 1992 Sep 25 by a Commercial Titan 3 (CT-4) from Cape Canaveral. The Titan core ignited at 1706:49, with the depleted SRMs falling away at 1706:57. By 1708 the stack was at 85km altitude. Stage 1 separated at 1709:29 as stage 2 ignited, burning until 1713:06. A stage 2 velocity trim burn at 1714:23 to 1714:59 left the rocket in a 161 x 542 km x 29.3 deg parking orbit. The CT-4 second stage separated at 1720 from its payload, the Mars Observer and the Transfer Orbit Stage (TOS). The Orbital Sciences Corp. TOS stage was named the USS Thomas O. Paine. TOS ignited at 1744:52 for a 2 min 37 sec burn. It separated at 1758:32, leaving Mars Observer in solar orbit. TOS made an avoidance maneuver at 1802:32, and at 1825 the Titan stage made a perigee-lowering burn to 138 x 429 km x 29.4 deg to ensure rapid reentry. Telemetry coverage had been lost during the TOS flight, so there was considerable relief when Mars Observer telemetry was acquired at 1829:01 on Sep 25.
TOS end velocity was 11.43 km/s. The initial MO aimpoint may have been biased about 1 M km away from Mars; (a 2 Mkm bias was planned for the original expected launch date). The further avoidance manuever by the TOS would have put it beyond the planet's gravitational sphere.
A 50 m/s TCM-1 burn was made at 2202 on Oct 10, followed by a 10 m/s TCM-2 burn at 2200 on 1993 Feb 8 and the TCM-3 burn at 1900 on Mar 18. The flight plan called for a Mars orbit insertion burn at 2042 on 1993 Aug 24, resulting in a 75 hr orbit with a periapsis of 500 km. An orbit change on Sep 15 to a 1-day orbit would have been followed by burns on Oct 17 and Oct 28 to a Mars Sun Synchronous 2pm orbit at 378 x 430 km x 92.8 deg. However, when the propellant tanks were pressurized on Aug 21, all contact with Mars Observer was lost. An engine system intended for short duration missions was later found to be inadequate for the long interplanetary cruise, and mixing of fuel and oxidizer which had leaked into the wrong part of the system probably caused the spacecraft to shed debris.
| Mars Observer | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1992 Sep 25 | 1705:01 | Launch by Titan 3 | |
| 1706:49 | St 1 burn | ||
| 1706:57 | SRM sep | ||
| 1708:52 | T+3:51 Fairing | ||
| 1709:29 | St 1 sep | ||
| 1713:12 | St 2 MECO | ||
| 1714:23 | St 2 vel trim | ||
| 1714:59 | St 2 VECO | 163 x 541 x 29.38 | |
| 1720:01 | St 2 sep | ||
| 1744:52 | TOS burn 2:24? | ||
| 1747:29 | TOS burnout | 350 x -79540 ? | |
| 1758:32 | TOS sep | ||
| 1802:32 | TOS avoidance | ||
| 1825:01 | St 2 depletion | 138 x 429 x 29.3 | |
| 1829:01 | MO telem acq | ||
| 1992 Sep 26 | 0216 | Pass EL1:4 | |
| 1992 Sep 30 | 0850? | Solar orbit | |
| 1992 Oct 1 | 0945 | Stage 2 reentry over 13S 150W | |
| 1992 Oct 9 | 4.5 Mkm range, 10.8 km/s E-rel | ||
| 1992 Oct 10 | 2200 | TCM-1 50m/s 2:13 R=5Mkm | |
| 1993 Feb 8 | 2200 | TCM-2 9.6 m/s 35s | |
| 1993 Mar 18 | 1900 | TCM-3 | |
| 1993 Aug 19 | 2330? | Enter Mars sphere | |
| 1993 Aug 22 | 0021 | Last telemetry sent | |
| 0031 | Pyros fired | ||
| 0035 | LOS | ||
| 1993 Aug 24 | 2010? | Flyby Mars | |
| 2027? | 1730 km alt, MOI burn begins, 29 min (planned) | ||
| 2040 | Planned MOI? (arrival press kit) | ||
| 2042 | Planned periapsis | ||
| Would reduce V(Mars) from 5.28 km/s to 4.56 km/s | |||
| 1993 Aug 29 | 1750? | MO leaves Mars sphere | |
| 1993 Sep 1 | 586d 1.13 x 1.61 AU x 6.67 | ||
Payload:
- MOC Mars Observer Camera (MSSS/Malin)
- GRS Gamma ray spectrometer (Arizona/Boynton)
- TES Thermal emission spectrometer (ASU/Christensen)
- PMIRR Pressure modulated IR radiometer (JPL/McCleese)
- MOLA Laser altimeter (GSFC/Smith)
- MAG/ER Magnetometer/Electron reflectometer (GSFC/Acuna)
- RS Radio science, Stable radio oscillator (Stanford/Tyler)
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