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Odyssey launched into Mars orbit

Mars Odyssey

Orbiting the red planet: the 2001 Mars Odyssey spacecraft. (Illustration: NASA)

The thirty-first mission to Mars has launched into Mars's orbit.

NASA's 2001 Mars Odyssey fired its main engine and was successfully captured into orbit around the red planet on Wednesday, October 24. Flight controllers picked up the first radio signal from the spacecraft at 12.55pm, Australian EST, as it emerged from behind Mars.

It will now begin the process of slowing down to the speed necessary for scientific observations.

"The research will be used to pave the way for future human missions," said Jennifer Laing, from the Mars Society Australia.

"NASA are saying that we can have humans on Mars by 2020."

"It's a long-term approach."

Odyssey has been hurtling towards Mars in a straight line for six months. In order to curve its trajectory and enter the planet's orbit, 262.8 kilograms of propellant were burned in exactly the right direction for close to 20 minutes, forcing the craft into orbit.

Initially, Odyssey will be in a 19-hour elliptical orbit around Mars, but to make scientific observations it will need to move into a 2-hour circular orbit at an altitude of approximately 400 kilometres. To do this the spacecraft will 'aerobrake' over the next few months, by brushing against the top of the atmosphere.

The Odyssey is carrying instruments to map the chemical and mineralogical make-up of Mars including a gamma ray spectrometer, a thermal-emission imaging system and a Martian Radiation environment experiment.

These research tools will help determine if humans have a future on Mars.

"The mission is measuring the radiation dose on Mars. You don't want people to end up with huge radiation doses," said Ms Laing.

2001 Mars Odyssey has travelled 460 million kilometres since its launch on April 7 from Cape Canaveral Air Force Station in the United States.

Thirty previous missions have been sent to Mars, the first in 1960. Almost half have been American, with most of the rest from Russia or the former Soviet Union.

Many have been unsuccessful, failing at launch, not reaching Earth's orbit, or not providing any useful data.

Success was first achieved on the seventh mission, the US Mariner 4, launched in November 1964. It returned 21 photos.

Two later missions, Mariner 6 and Mariner 7, returned a further 201 photos in 1969.

Then in 1975, two orbiters called Viking 1 and Viking 2 were launched. By 1982 the Viking orbiters and landers had returned over 50,000 photos.

A further three missions failed but in 1996 the Mars Global Surveyor was launched, arriving in Mars's orbit 17 months later. This has made highly detailed maps of the planet.

The Mars Pathfinder, launched at almost the same time, sent transmissions back for nearly three months but had a limited lifespan, and sent its last transmission in September 1997.

The only Japanese mission, named Nozomi (Planet-B) was launched in April 1998. It is currently in orbit around the Sun and is expected to reach Mars in 2003.