The probes will lift off in an unmanned Delta II Heavy Rocket and will start its three month journey to the moon. NASA’s Apollo Astronauts used the Saturn V Rocket and covered the approximately 386,242 kilometres to the moon in a mere three days. The ‘more economical’ rocket launch brings the cost of the mission from start to finish to US$ 496 million dollars.
Shortly after lift off the probes will separate from each other and travel independently to the moon. Grail-A will arrive at the moon on New Year’s Eve with Grail-B arriving on New Year’s Day. They will go into orbit around the lunar poles and effectively chase one another around the moon. The probes will range in distance apart from each other from 64 kilometres to 225 kilometres. They will be bouncing radio signals between them providing their exact locations, even on the far side of the moon.
When the mission ends in late spring (northern hemisphere), Grail-A and Grail-B will be within 16 kilometres of the moon’s surface. Barring any changes, they will then eventually crash into the moon.
The mission aims to create the most precise lunar gravity map ever. Scientists are hoping to figure out what is beneath the lunar surface, all the way to the core. The moon actually has the most uneven gravitational field in the solar system, according to NASA. The moon’s gravity is about one-sixth or Earth’s pull.
Scientists will be able to measure even the slightest variations in the gap between the orbiting probes every single second. These changes as subtle as they may be will indicate shifting masses below the lunar surface: mountains in some places, lava tubes and craters in others. The probes will also help pinpoint the best landing sites for future explorers, whether human or mechanical.
A plan to put man back on the moon was scratched off in favour of an asteroid and Mars. There are three spacecraft currently orbiting the moon, making science observations. Since the Space Age began in 1957, 109 missions have targeted the moon. 12 men have walked on its surface in six separate landings. 342 kilograms of rock and soil has been brought back to earth and are still being analysed.
The launch of the GRAIL probes will be NASA’s second robotic mission since the end of the shuttle programme in July. A probe names Juno is headed for Jupiter following a successful launch on August 5. If the GRAIL is not launched on September 8, the mission’s launch period lasts until October 19.