SMALL PRINT:AT LUNCHTIME today, Nasa's twin Gravity Recovery And Interior Laboratory (Grail) spacecraft are expected to take off on a venture into space that promises to "unlock the mysteries of the Moon".
It has been 400 years since Galileo made the first telescopic observations of the Moon, yet there is still much we don’t know about our natural satellite. Does it really have a solid centre surrounded by a liquid core, as some theories suggest? This mission hopes to fill in the details and will help scientists find out where the Moon came from and how it formed.
The Grail project is led by Dr Maria Zuber of the Massachusetts Institute of Technology and is the 11th mission in Nasa’s Discovery Programme.
The primary job for the two Grail project spacecraft, Grail-Aand Grail-B, is to measure the gravity around the Moon. It has the lumpiest gravitational field known in our solar system, say Nasa, because of its mountains, lava tubes and craters. They are made of materials with different densities and this affects the Moon's gravity.
By making an incredibly detailed map of the Moon’s gravity, scientists can work out its structure from the crusts at the surface, right down to the very core. Finding out about gravity on the Moon “opens the door to understanding its origin and development”, says Nasa.
The Grailspacecraft will also take images and video of the surface of the Moon. The Moon's surface geology preserves the record of nearly the entirety of 4.5 billion years of solar system history, Nasa says. Scientists will be able to use this information to learn more about the planets in our solar system.
There is a one-second launch window set for 1:37pm today (Irish time) when the twin spacecraft can lift off from the Cape Canaveral Air Force Station in Florida. And about 40 minutes later there is another one-second launch opportunity, giving them two chances to get Grail into orbit.
A rocket will take a small “satellite bus” carrying the two spacecraft 152km above Earth. It will take about three months for the craft to reach the Moon and manoeuvre into the correct orbit. The craft are mirror images of each other, and will fly facing each other, so their antennae can communicate while they are orbiting the moon.
The Grail mission cost $496.2 million (€355 million), and the craft will be in space for 270 days, 82 of which are devoted to scientific exploration. During this phase, Grailwill orbit 55km above the surface of the Moon, with each orbit taking 113 minutes. It will take about a year to analyse all the data captured by the satellites.
By the end of the mission in June 2012, the two spacecraft will have travelled almost 42 million km. When the space flight is complete, they will rather unceremoniously crash onto the surface of the Moon.
If today’s launch does not go ahead, all is not lost. This is the start of a 42-day period, during which there are two opportunities every day – each just one-second long – when the launch could take place.