On 6 August, NASA employees will anxiously wait to receive news at 13 seconds past 6.30am GMT that the Curiosity rover has touched down safely on Mars, with the help of an innovative ‘sky crane,’ according to Dr Charles Elachi, Director of NASA ‘s Jet Propulsion Laboratory.
Speaking at The Royal Academy of Engineering’s ERA Foundation International Lecture on 5 March, Dr Elachi gave a unique and personal insight into the challenges of the future landing. He said: “We will be very nervous. Landing on another planet is not a walk in the park…we have about 3 tonnes of mass coming in at a speed of almost 12,000mph and we have to land softly within six minutes”.
Navigating the rover to Mars, some 450 million kilometres away, to within 80m of the planet’s atmosphere, is challenging. “The accuracy with which we have to point, to be at the right angle and the right location, is equivalent to me being in LA and hitting a golf ball to St Andrews here in the UK – and the ball landing in a cup that is moving at around 60,000mph, because Mars is moving.”
Fortunately, however, he said the team are now so good at navigation that Curiosity is well on its way to Mars and there has been little need for correction manoeuvres.
Describing the landing process as “six minutes of terror,” the touch-down of Curiosity on Mars will be dramatically different from that of its predecessors, Spirit and Opportunity. Spirit was surrounded by giant airbags and bounced onto the red planet’s surface, the first bounce measuring approximately 10 storeys.
Curiosity is around eight times larger and is the size of a small car. Dr Elachi said: "When I first saw the designs for the sky crane I thought 'are you guys kidding me?' but the best approach is for the rover to land directly on the surface of Mars with that weight."
When the craft begins the entry, descent and landing phase it will weigh around three tonnes including the heat shield, carrier and rover. “To give you an idea about the energy when you are coming at 12,000mph with that kind of mass, it’s the equivalent of 25 high speed trains. That’s the amount of energy we have to dissipate in those six minutes to land softly on the surface,” he said.
It will be slowed by the friction of Mars’ atmosphere before a parachute is deployed and the carrier and rover separated from the shield. The rover will then be lowered towards the surface, attached by three nylon cords to the ‘sky crane’ carrier, eventually hovering at around 10 metres above Mars’ surface. “As soon as the rover touches the surface of Mars, the umbilical cords will be cut and the sky crane will fly off and crash at a safe distance away from Curiosity,” Dr Elachi said.
The rover will land in the Gale crater near an “alluvial fan” of sediments, which may have been formed by running water and is well equipped to carry out research that might help prove if there was life on Mars.
Dr Elachi described the rover as “a robotic chemist” as it has a powerful laser to “zap rocks from a distance” and then analyse the vapour. It can also drill rock with its arm and take samples of the dust, which it analyses with an on-board mass spectrometer and x-ray equipment to determine the composition of rocks. Curiosity can travel about 100 metres a day and has an ingenious suspension system to negotiate rocks up to a metre high. It also has distinctive holes in its wheels which leave tracks enabling NASA to measure the distance travelled as well as print “JPL” in Morse code on Mars.
Looking to the future, Dr Elachi pinpointed two of Saturn’s moons, Titan and Enceledus, as “intriguing targets for future exploration”. As the rings of Saturn are composed of dust, he likened them to “prebiotic planets” and said he is particularly interested by Enceledus’ ‘tiger stripes’ and geysers that spout 50km high jets of salty ice water, suggesting there may be an ocean beneath the moon’s surface.
He said that NASA is looking at collaborative missions with Europe to explore Jupiter’s moons, with NASA focusing on Europa and the prospect of one day drilling the ice to see if there is an ocean.
Getting a sample back from Mars is one of NASA’s key goals and “the highest priority of the decade – now probably next decade,” said Dr Elachi. He believes that this will happen in the 2020s, despite recent budget cuts.
Notes for editors
A video of the lecture is available on raeng.tv
Charles Elachi has been the Director of the Jet Propulsion Laboratory since May 2001. Prior to becoming Director, Dr Elachi was the Jet Propulsion Laboratory’s Director for Space and Earth Science Programs (beginning in 1982) where he was responsible for the development of numerous flight missions and instruments for Earth observation, planetary exploration and astrophysics.
He has been a principal investigator on a number of NASA-sponsored studies and flight projects including the Shuttle Imaging Radar series (Science Team Leader), the Magellan Imaging Radar (Team Member), and the Cassini Titan Radar (Team Leader). He is the author of over 230 publications in the fields of active microwave remote sensing and electromagnetic theory, and he holds several patents in those fields.
Dr Elachi received his BSc in physics from University of Grenoble, France; the Dipl Ing in engineering from the Polytechnic Institute, Grenoble, and both a MSc and PhD degree in electrical sciences from the California Institute of Technology. He also has a MSc degree in geology from the University of California, Los Angeles, and a MBA from the University of Southern California.
Over his career Dr Elachi has received numerous awards, including the National Academy of Engineering Arthur M. Bueche Award, the Chevalier de la Légion d’Honneur, France, and the Lebanon Order of Cedars. In 1989, Dr Elachi was elected to the US National Academy of Engineering.
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