Tim Furniss/LONDON
Russia's Mars '96 spacecraft plunged into the Earth's atmosphere on 17 November after its Proton D2 fourth stage failed to re-ignite in low-Earth parking orbit. It was the fifteenth Russian Mars failure in 18 launches since 1960. Even the other three flights were considered to be only partial successes.
The total cost of the lost mission is estimated at $300 million, including the $180 million invested by 20 European scientific organisations and one from the USA, which provided instruments for the 1,100kg payload.
The Proton SL-12 launch from the Baikonur Cosmodrome at 2048GMT on 16 November was successful. The first three stages and one burn of the fourth stage placed the spacecraft/D2 stage combination into a circular parking orbit of about 160km. An instrument section on the Mars '96 took control of the flight from this point.
The D2 failed to re-ignite to place the spacecraft into a new apogee of about 100,000km. This may have been caused by a fault in the Mars '96 instrument section, or in the D2 propulsion system which developed a fault after the first burn, says Phillip Clark, of the Molniya Space Consultancy in London. The combination ended up in a 145 x 170km orbit, it is thought, as a result of the firing of the stage's ullage motors, to prepare for the second burn.
The Mars '96 separated from the D2 stage in the new parking orbit at the pre-programmed time, as it would have done if the stage's firing had been successful. The craft also appears to have fired its own propulsion unit, which was to have placed it en route to the Red Planet in heliocentric, solar, orbit, at escape velocity.
The 6,500kg probe is then assumed to have entered an 80 x 1,500km orbit because of its incorrect position for the burn and re-entered, and untracked on its third orbit later, at about 0130-0230 GMT on 17 November.
The location of its four thermoelectric generators, containing plutonium 238 fuel on the two Mars surface stations - which probably survived re-entry - is unknown.
The 12t stage, with an estimated 10,000 kg of propellant on board - assumed still to be attached to the Mars '96 - re-entered the Earth's atmosphere, tracked by monitors in the USA and Russia. Fragments are thought to have landed 560km South-East of Easter Island after re-entry at 0113 GMT on 18 November.
The D2 failure is not expected to affect the commercial future of the Proton K booster, since its fourth stage is a different version called the DM and has its own instrument control unit, says Clark.
The Mars '96 was to have placed an orbiter around the Red Planet and deposited four instrumented stations on the surface, along with two harpoons, which were to have penetrated the soil. It would have worked in tandem with the US Mars Global Surveyor, launched on 7 November, and the Mars Pathfinder, to be launched on 2 December.
The failure has devastated the cash-starved Russian space programme, and effectively ended hopes that Russia will launch its own Mars probe during the next launch window in 1998. The Mars '96 had already been delayed from 1994. Closer co-operation with NASA in a "Mars Together" programme seems inevitable.
Stanislav Kulikov, the organisation's general constructor, says that the failure was caused by the probe's automatic control system.
Source: Flight International
