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Canberra to get first glimpse of Mercury


messenger and mercury

Artist's concept of the Messenger spacecraft in Mercury's orbit(Source: Image: NASA/John Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

NASA will return to Mercury for the first time in almost 33 years tomorrow when a robotic probe makes its first fly-by of the Sun's nearest neighbour.

The Messenger spacecraft is expected to make its closest approach to Mercury sometime after 6am (AEST) tomorrow, flying just 200km above the rocky surface.

The Canberra Deep Space Communications Complex, part of NASA's Deep Space Network, is tracking Messenger's approach to the planet until about 9.30pm today (AEST).

It is already receiving the first images of Mercury on approach and according to complex spokesperson Glen Nagle will receive the first detailed images from the fly-by about 7.30am tomorrow (AEST).

Scientists expect to harvest some 1200 images and other data from instruments aboard the NASA probe that could shake up the study of the solar system, according to researchers.

"I think we're in for some big surprises," says Dr Faith Vilas, director of the MMT Observatory in Arizona and a Messenger participating scientist.

"We are about to enjoy our first close-up view of Mercury in more than three decades," Messenger team principal investigator Dr Sean Solomon, of the Carnegie Institution of Washington says.

"And a successful gravity assist will ensure that Messenger remains on the trajectory needed to place it into orbit around the innermost planet for the first time."

Historic

"When the Mariner 10 spacecraft did its fly-bys in the mid-1970s, it saw a little less than half the planet," says Dr. L. M. Prockter, of Johns Hopkins University Applied Physics Laboratory.

"During this fly-by we will begin to image the hemisphere that has never been seen by a spacecraft and at resolutions that are comparable to or better than those acquired by Mariner 10 and in a number of different colour filters so that we can start to get an idea of the composition of the surface."

The fly-by will be the first since the Mariner 10's March 1975 visit, when that spacecraft conducted three flights over the planet closest to the Sun.

Mariner surveyed only one hemisphere of Mercury, using weaker observational tools.

Messenger will measure the mineral and chemical composition of Mercury's surface, study its atmosphere and magnetosphere and collect data about the magnetic tail that sweeps behind it.

The spacecraft will fly as low 200km above Mercury's surface.

It will use the planet's gravitational pull, in this flyover and two others planned this year and in 2009, to position itself to enter the planet's orbit.

Messenger is scheduled to fly over Mercury again in October 2008 and September 2009, then return for a final sweep in 2011 when it will enter Mercury's orbit for a year-long study of the planet.

The spacecraft has already flown once past Earth and twice past Venus since its August 2004 launch.

It will have travelled 7.8 billion kilometres when it completes its six-and-a-half-year odyssey.

The mission can be tracked online at http://messenger.jhuapl.edu

Tags: astronomy-space, planets-and-asteroids, space-exploration, spacecraft