Messenger still Delivering after all these years

Throughout its long journey toward the orbital phase of the mission, MESSENGER has remained quite busy. In addition to completing six planetary flybys and five deep-space maneuvers, a wide variety of tests have been conducted to characterize the performance of the science payload and the spacecraft subsystems.

The MESSENGER spacecraft has crossed the four-billion-mile mark since its launch. The probe has completed about 81 percent of its journey toward its destination to be the first spacecraft to orbit the planet Mercury.

That MESSENGER's odometer reading has reached another major milestone reminds us of the long and complex route that our spacecraft must follow. Mercury orbits deep within the Sun's gravity well.

So, even though the planet can be as close as 82 million kilometers (51 million miles) from Earth, getting the probe into orbit around Mercury depends on an innovative trajectory that uses the gravity of Earth, Venus, and Mercury itself to slow and shape the probe's descent into the inner solar system.

On its 4.9 billion-mile trek, MESSENGER has flown by Earth once, Venus twice, and Mercury three times.

"Four billion miles, more than 43 times Earth's distance from the Sun, is an impressive figure," says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington.

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