The Telegraph
Sunday , August 5 , 2012
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‘Seven minutes of terror’ on Mars

- Nasa tense over landing

Aug. 4: For the fifth time in over 15 years, astronomer G. Scott Hubbard is hoping to track a US spacecraft as it attempts to land on Mars, but the entry, descent and landing (EDL) sequence on Sunday night will be trickier than ever before.

If the seven-minute EDL sequence, dubbed by one engineer as “seven minutes of terror”, is successful, and the spacecraft safely deposits a robotic rover named Curiosity on the planet’s surface, scientists will be ready for their most ambitious effort yet to explore Mars.

Hubbard will watch the EDL sequence from a room next to the mission control centre at the US National Aeronautics and Space Administration’s (Nasa) Jet Propulsion Laboratory (JPL) in southern California. Inside mission control, dozens of scientists and engineers will monitor streams of data pouring in from the spacecraft as it approaches Mars at about 6km per second.

The Mars Science Laboratory spacecraft, launched by Nasa a little more than eight months ago, is expected to lower the Curiosity rover onto the surface of the planet for a two-year mission to study Martian geology and look for the fingerprints of life.

“We’re approaching this landing with great confidence, but also some tension,” Hubbard, a Nasa veteran and a Stanford University professor, told The Telegraph in a telephone interview. “There’s a coat of tension hanging over everything.”

Among the 44 missions aimed at reaching Mars launched since the 1960s, only 12 — eleven American missions and one European orbiter called Mars Express — have been fully successful. All five Nasa missions since 2001 have been fully successful.

The multiple cameras on Curiosity. Picture credit: Nasa-JPL

An update released by Nasa-JPL said the spacecraft was about 753,000km from Mars on Friday night, travelling at 3,576m per second, and its speed was expected to increase to 5,900m per second by the time it reached the top of the Martian atmosphere. The spacecraft will begin its entry into the atmosphere at 10.31pm on Sunday California time (Monday morning in India).

“This mission will have three ways of finding organics — complex carbon compounds that could not be definitively detected earlier,” Hubbard said. “Organics produced by living systems are the fingerprints of life.”

Hubbard, who has spent about 20 years with Nasa, was its first Mars programme director and tracked the landing of four previous Mars rover missions: Pathfinder in 1997, Spirit and Opportunity in 2004, and Phoenix in 2008.

Curiosity, a car-sized rover, the first robotic vehicle designed to navigate terrain as well as scoop up and analyse samples of dust and rock, will be tasked with roaming up to 18km from its landing site, collecting soil and rock samples.

“The Curiosity rover is the next best thing to sending a geologist to Mars,” said Robert Downs, professor of geosciences at the University of Arizona, Tucson, who is among scientists assigned to identify the rocks that Curiosity picks up during its stay on Mars.

“It carries all the equipment that we would use here on Earth when we study rocks and minerals,” Downs said through a media release from the University of Arizona.

The rover is equipped with multiple cameras that will provide engineers with images of its surroundings and will be used as eyes to provide three-dimensional information that the rover will need as it roams about the Martian surface.

During the EDL sequence, as the spacecraft enters the atmosphere, it will encounter intense heat of up to 1,600C. While protected by a heat shield, it will need to be slowed down with a supersonic parachute.

As it nears the ground, however, its speed will still be too high for a gentle landing, so thruster rockets will be activated and Curiosity lowered to the ground through tethers.

In an educational documentary released by Nasa-JPL on the challenges during the EDL sequence, EDL engineer Tom Rivellini described the period as “seven minutes of terror” as all events during the sequence need to occur exactly as planned “in perfect sequence, in perfect choreography, and perfect timing”.

“There’s no room for error,” Anita Sengupta, an aerospace engineer with Nasa-JPL who had helped test the parachute designed to slow down the spacecraft, told this newspaper.

The first images from Curiosity are likely to arrive about two hours after the landing, according to Nasa-JPL. “The measurements of the analytic chemistry experiments may take months,” Hubbard said.

The earlier missions to Mars were mainly focused on understanding the history of water on the planet.

“Now there’s absolutely no doubt that Mars had abundant water flowing on its surface. We’re now moving into the next phase of searching for organics,” Hubbard said.