MESSENGER is now on autopilot, faithfully executing a detailed set of instructions required to achieve its historic rendezvous with Mercury tomorrow night.

At 8 a.m. Tuesday, all attitude re-orientations planned to control the probe's momentum accumulation and adjust its trajectory were successfully completed. MESSENGER turned to point its high-gain antenna back to Earth for the final stretch of continuous data monitoring until just before the start of Mercury orbit insertion.

The operations team at the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., has monitored on-board commanded vehicle re-configurations and has sent pre-defined ground commands to establish configurations for the burn.

The science instrument suite has recorded the last set of data for the cruise portion of the mission, and all instruments have been turned off. Although not in an operational mode, the Gamma-Ray Spectrometer has been left in its stand-by mode to ensure thermal stability of the delicate cryogenic cooler.

The instruments will be tuned back on as part of orbital commissioning beginning on March 23.

"The navigation team is reporting that there has been little change from the previous targeting estimates, so the spacecraft is on the glide-slope for final approach to Mercury," says MESSENGER Systems Engineer Eric Finnegan.