Communications with Earth will be cut off for 51 minutes while the spacecraft passes behind Mercury as seen from Earth. A sunshade will need to keep Messenger's instruments at room temperature while temperatures on the sunward side reach 6,000 degrees Fahrenheit.
Window for orbit
In the 37 hours from approach to departure, scientists said, Messenger will capture 1,500 images and sock away 500 megabytes of scientific data for later rebroadcast to Earth.
But the most critical task will be for Messenger to slip through a 2,000-foot window in space, setting it on course to orbit the planet 18 months from now, said Eric J. Finnegan, systems engineer for the mission at APL. "Any shortfall will need to be corrected by the spacecraft, using the limited supply of onboard propellant."
But as long as Messenger is on course, it's the science data that scientists care most about. "We're all anxiously looking forward to the great science coming out of this flyby," said Anthony Carro, NASA's Messenger program executive.
