Nasa's Curiosity rover on course for Mars landing

Adam Steltzner expects the new landing
 system to perform as designed 

Nasa says the big robot rover it is sending to Mars looks in excellent shape for its Monday (GMT) landing.

The vehicle, known as Curiosity, was launched from Earth in November last year and is now nearing the end of a 570-million-km journey across space.

To reach its intended touch-down zone in a deep equatorial crater, the machine must enter the atmosphere at a very precise point on the sky.

Engineers told reporters on Thursday that they were close to a bulls-eye.

A slight course correction - the fourth since launch - was instigated last Saturday, and the latest analysis indicates Curiosity will be no more than a kilometre from going straight down its planned "keyhole".

The team's confidence is such that it may pass up the opportunity to make a further correction on Friday.

"We are about to land a small compact car on the surface with a trunk-load of instruments. This is a pretty amazing feat getting ready to happen. It's exciting, it's daring - but it's fantastic," said Doug McCuistion, the head of Nasa's Mars programme.

Curiosity - also known as the Mars Science laboratory (MSL) - is the biggest, most sophisticated Mars rover yet.

It will study the rocks inside Gale Crater, one of the deepest holes on Mars, for signs that the planet may once have supported microbial life.

The $2.5bn mission is due to touch down at 05:31 GMT (06:31 BST) Monday 6 August; 22:31 PDT, Sunday 5 August.

It will be a totally automated landing.

Engineers here at the Jet Propulsion Laboratory (JPL) in Pasadena, California, can only watch and wait.

The vast distance between Mars and Earth means there is a 13-minute lag in communications, making real-time intervention impossible.

Nasa has had to abandon the bouncing airbag approach to making soft landings.

This technique was used to great effect on the three previous rovers - Sojourner, Spirit and Opportunity.

But at nearly a tonne, Curiosity is simply too heavy to be supported by inflated cushions.

Instead, the mission team has devised a rocket-powered, hovering crane to lower the rover to the surface in the final moments of its descent.   (BBC.co.uk)