How an $800m mission to Mars left Nasa red-faced 25 years ago today

It was a hugely ambitious project, costing more than $820m, which was designed to be the most comprehensive survey of Mars by humankind to that date. Except, of course, that the Observer never quite made it

to Mars…

SO WHAT WAS IT ALL ABOUT?

Last seen by the human eye in its launch phase high aboard the Commercial Titan III rocket, the 5,000lbs-plus Observer was clearly based on the kind of satellite that was already successfully mapping every inch of Earth.

Its aim was simple – to fly to Mars, get into orbit around the planet and find enough detail about its magnetic fields, its surface and atmosphere, and especially the climates of Mars past and present, so that future exploration could be targeted at areas that might, just might, be able to support human life.

The sub-text, as always with Martian exploration, was to see if any form of life could be found there, and the Observer was especially equipped to find any traces of water, without which life cannot be sustained – as far as we know.

The Mariner and Viking missions had suggested that water had indeed flowed on Mars at one time in its more than 4 billion year history, but liquid water as we know it cannot exist on the planet surface due to the near absence of atmospheric pressure. However, the polar ice caps appear to be frozen water, and that was why Observer was going to spend a lot of time orbiting them.

SO HOW DID IT DO?

It all went well at first. The Titan booster rocket cleared the launchpad at Cape Canaveral in Florida and put Observer into Earth orbit, where the Transfer Orbit Stage ignited to put Mars Observer into a trajectory that would take the spacecraft towards Mars in a journey that would last 11 months.

SO FAR, SO GOOD?

Apart from a mid-course correction, Observer was working well and sending back data and images from space via its powerful communication system. These included pictures of Mars as the Observer got closer and closer.

When it reached Mars orbit, the aim was for the Observer to enter an elliptical orbit and spend an entire Martian year – about 21 Earth months – collecting data that would include the first global map of the planet that is our nearest planetary neighbour.

Observer had plenty fuel on board to last out that Martian year, and it also had a solar array collecting precious power for its fuel cells. Amongst the equipment on board was one of the most accurate laser altimeters ever designed, which would give a detailed topography of a planet already well known to have mountains and canyons, plus a highly sensitive camera and a gamma ray spectrometer to measure gamma rays and neutrons emitted by radioactive decay of elements on the surface. The hope was that this would provide a real clue about how Mars developed over aeons.

It was intended that Observer would gradually attain a circular orbit around Mars from pole to pole that would see it travel around the planet every two hours. In short, the Observer would tell us much, much more about Mars than we had ever known.

SO WHAT HAPPENED?

In the mission control room at Nasa’s Jet Propulsion Laboratory in Pasadena, California, everything seemed to be going well and confidence was high that Mars Observer would at least reach its target and begin transmitting data.

On August 21, 1993, all communications were lost instantaneously. Television pictures at the time showed the shock on the Nasa scientists’ faces as the realisation sank in. The spacecraft was just three days from entering the orbit around Mars.

The flight managers tried everything they could to re-establish contact with Observer, including sending signals every 20 minutes for hours on end, but finally they had to conclude that Observer was defunct.

EMBARRASSING OR WHAT?

It was indeed a massive embarrassment for Nasa, but anyone with any idea about the vast difficulties of sending a spacecraft 40-plus million miles to another planet and getting it to send back data realised that Observer did well just to get to where it did. It was hugely disappointing, however, to the expectant space community and adversely affected Nasa’s prestige.

SO WHAT WENT WRONG?

The most probable cause of the loss of Observer, according to the final official report, was “rupture of the fuel (monomethyl hydrazine – MMH) pressurisation side of the spacecraft’s propulsion system, resulting in a pressurised leak of both helium gas and liquid MMH under the spacecraft’s thermal blanket.” Immediate doom, in other words.

WILL WE EVER SEE HUMANS ON MARS?

It is the next great challenge in space exploration, and many missions have taken place since Observer so we know much more about the planet, including the fact that water did indeed once flow there.

We also now know that putting humans on Mars is theoretically possible.

And anyway, Donald Trump says we are going, and has pledged $19.1 billion (£14bn) to Nasa for the project. So that’s it in the bag, then.