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Moon mission set to begin in New Year

Artist's impression of the GRAIL spacecraft in lunar orbit

The twin Moon-orbiting GRAIL spacecraft will map the lunar gravitational field, which scientists will use to "peer" deep beneath the Moon's surface. (Artist's impression)

  • Twin spacecraft called GRAIL
  • Will map the Moon’s gravitational field
  • Aim is to study the Moon from core to crust

NASA’S TWIN SPACECRAFT to study the Moon from crust to core are nearing their main-engine burns to place the duo into lunar orbit.

Named the Gravity Recovery And Interior Laboratory (GRAIL), the spacecraft are scheduled to be placed in orbit beginning at 8:21am Sydney time for GRAIL-A on January 1, 2012, and 9:05am for GRAIL-B the following day.

The distance from Earth to the Moon is approximately 402,000 kilometres. NASA’s Apollo crews took about three days to travel to the Moon. Launched from Cape Canaveral Air Force Station September 10, 2011, the GRAIL spacecraft are taking about 30 times that long and covering more than 4 million kilometres to get there.

This low-energy, long-duration trajectory has given mission planners and controllers more time to assess the spacecraft’s health. The path also allowed a vital component of the spacecraft’s single science instrument, the Ultra Stable Oscillator, to be continuously powered for several months. That allowed it to reach a stable operating temperature long before science measurements from lunar orbit are to begin.

Diagram of the GRAIL trajectories to the Moon

The two GRAIL spacecraft have followed long, slow trajectories to get the Moon.

“This mission will rewrite the textbooks on the evolution of the Moon,” said Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology. “Our two spacecraft are operating so well during their journey that we have performed a full test of our science instrument and confirmed the performance required to meet our science objectives”.

A complex arrival

As of December 28, GRAIL-A was 106,000 kilometres from the Moon and closing at a speed of 1,200 kilometres per hour. GRAIL-B was 128,000 kilometres from the Moon and closing at a speed of 1,228 kilometres per hour.

During their final approaches to the Moon, both orbiters will move toward it from the south, flying nearly directly over the lunar south pole. The lunar orbit insertion burn for GRAIL-A will take approximately 40 minutes and change the spacecraft’s velocity by about 688 kilometres per hour.

GRAIL-B’s insertion burn 25 hours later will last about 39 minutes and is expected to change the probe’s velocity by 691 kilometres per hour.

The insertion manoeuvres will place each orbiter into a near-polar, elliptical orbit with a period of 11.5 hours. Over the following weeks, the GRAIL team will execute a series of burns with each spacecraft to reduce their orbital period from 11.5 hours down to just under two hours.

At the start of the science phase in March 2012, the two GRAILs will be in a near-polar, near-circular orbit with an altitude of about 55 kilometres.

GRAIL spacecraft in a white room before launch

The small GRAIL twins are almost identical.

Mapping the Moon’s gravity

When science collection begins, the spacecraft will transmit radio signals to each other as they orbit the Moon, enabling scientists to precisely define the distance between them.

As they fly over areas of greater and lesser gravity, caused both by visible features such as mountains and craters and by masses hidden beneath the lunar surface, they will move slightly toward and away from each other.

An instrument aboard each spacecraft will measure the changes in their relative velocity very precisely, and scientists will translate this information into a high-resolution map of the Moon’s gravitational field.

The data will allow mission scientists to understand what goes on below the surface. This information will increase our knowledge of how Earth and its rocky neighbours in the inner Solar System developed into the diverse worlds we see today.

For more information about GRAIL, click here.

Adapted from information issued by NASA / JPL-Caltech / LMSS / KSC.

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Moon mission soon to launch

NASA’S LUNAR-BOUND GRAIL twins are being prepared for launch at Cape Canaveral Air Force Station’s Launch Complex 17.

GRAIL-A and GRAIL-B will fly in tandem orbits around the Moon for several months to measure its gravity field in unprecedented detail. The mission will answer longstanding questions about the Moon, and provide scientists a better understanding of how Earth and other rocky planets in the Solar System formed.

GRAIL’s launch period opens September 8 and extends through to October 19. On each day, there are two separate instantaneous launch opportunities separated in time by approximately 39 minutes. On September 8, the first launch opportunity is at 10:37pm Sydney time (8:37am EDT). The second launch opportunity is 11:16pm (9:16am EDT).

Adapted from information issued by NASA/JPL-Caltech.

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2011: The year in space

Artist's impression of the Juno spacecraft at Jupiter

Artist's impression of the Juno spacecraft investigating Jupiter. Juno is set for launch later this year.

THERE ARE LOTS OF EXCITING happenings coming up in space this year. Here’s just a sample of what we can expect.

On February 14-15, NASA’s Stardust probe will do a fly-by of comet Tempel 1. It’ll be looking for damage done by the Deep Impact spacecraft, which fired a projectile into the comet back in 2005.

Also there’ll be the launch of Glory, an Earth-orbiting spacecraft that’ll make readings of black carbon and aerosols in the atmosphere, and measure the amount of incoming sunlight. Plus there’ll be the final flight of the space shuttle Discovery, on a mission to the space station.

March will see NASA’s MESSENGER spacecraft go into orbit around Mercury, the first probe to do so. A largely unknown world, the closest planet to the Sun is sure to hold some surprises. That month will also mark 25 years since Europe’s Giotto probe gave us our first close-up look at a comet, the famous Halley.

In April there’ll be a bunch of anniversaries, the 30th of the first space shuttle launch, the 40th of the first space station launch (which was the Soviet’s Salyut 1), and the biggie, the 50th anniversary of the flight of Vostok 1, carrying Yuri Gagarin, the first person to go into outer space.

Artist's impression of Salyut 1

Artist's impression of Salyut 1, the world's first space station.

April will also see the last flight of space shuttle Endeavour. And it could be the final shuttle mission of all. An extra flight by Atlantis in June has been approved but not yet funded, so we’ll just have to wait and see. Also in June, some parts of Australia will catch a short glimpse of a lunar eclipse.

July will see the second flight of the new, private Dragon spacecraft, designed to take cargo and eventually people to the International Space Station. Its first short test flight last year went perfectly. Dragon could end up being the replacement for the space shuttle.

Also in July, NASA’s Dawn spacecraft will sidle up to the 530km-wide asteroid Vesta, and go into orbit. It’ll spend a year investigating it before heading off to do the same thing with the even larger asteroid Ceres, which is actually known as a dwarf planet these days.

Artist's impression of the Dawn spacecraft

Artist's impression of the Dawn spacecraft studying asteroid Vesta

August will see the launch of Juno, NASA’s new unmanned mission to study the planet Jupiter. It’ll take about five years to get there. And the following month will see NASA launch GRAIL, a pair of satellites that’ll orbit the Moon and map its gravitational field, which will help scientists work out its inner structure.

In November, Russia will launch Fobos-Grunt, a mission to the larger of the two Martian moons, Phobos. All going well, it’ll touch down, grab some samples, and blast off back to Earth with them. The Chinese are piggybacking a small satellite too, which will orbit Mars and study its atmosphere, ionosphere and surface.

Finally, in December, there’ll be another launch of that Dragon capsule, plus the first launch of its competitor, called Cygnus. And to top it off, we’ll have another lunar eclipse.

Image credits: NASA / JPL-Caltech.

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