NASA Shot The MESSENGER -- Into Orbit, Around The Iron Planet

And you thought hitting a thermal exhaust port was tough? Try shooting a 450kg satellite 7.8 billion kilometres across the solar system into orbit around a planet less than half the size of Earth, and just 45.8 million kilometres from the sun.

The probe launched in August 2004, but it took six-and-a-half years, six planetary flybys, 17 trajectory corrections and 15 solar circuits to get NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) to the innermost corner of the solar system and into the history books as the first man-made satellite to ever orbit Mercury. Until its successful arrival in March 2011, humans had only ever performed fly-bys of the diminutive celestial body -- first in 1975 with Mariner 10, then again in 2008 and 2009 (by MESSENGER itself).

Because it's taken up a residence so close to Mercury, the $US450 million graphite/cyanate ester composite vessel is built to withstand the planet's intense heat. A pair of adjustable 450W GaAs/Ge solar panels charge a 23-ampere-hour nickel hydrogen battery, which, in turn, powers a suite of star trackers and sun sensors to help monitor its altitude. The entire system is protected under a 2.4m x 1.8m ceramic-cloth sunshade and kept aloft via a series of thrusters.

So far, it has performed its year-long primary mission with aplomb, snapping over 100,000 images of the planet while carefully studying Mercury's chemical composition, geology and magnetic field. It is also searching for clues to Mercury's reputed molten outer core and the identity of oddly radar reflective materials discovered at the planet's poles. MESSENGER has now entered the extended portion of its mission, which will last until March of 2013. [Wikipedia - Physorg - A New Domain - NASA - Spaceflight Now]

Image: MESSENGER Project

This image is of a 40km wide section of the floor of Raditladi impact basin. "One progenitor hypothesis is that the hollows formed from the sublimation of material exposed and heated during the violent impact that created the Raditladi basin," said NASA.

MESSENGER's orbit per the MESSENGER mission page.

MESSENGER getting a pre-launch sunshade check. Image: NASA