Mercury Probe Delayed by Ten Weeks, and Two Years

Gogo Dodo writes "Spaceflight Now reports that NASA's MESSENGER probe launch has been delayed by 10 weeks. Unfortunately, this means MESSENGER will not arrive at Mercury until 2011, a two year delay."

Comments

Relativistic effects on the craft & orbit

[RobertB-DC]

To what extent does the "warping" of space near an object as massive as the sun affect this little spacecraft's orbital calculations? I know (but don't fully understand) that there are relativistic effects on Mercury's orbit that aren't described by pure Newtonian physics.

To what extent do the mission planners have to account for this effect? Can they even know for sure until they see what happens as they pass by Mercury those three times before orbital insertion? Or will the effect be negligible compared to the solar wind and other "normal" forces? The link above notes that Newton is only off by 43 arcseconds out of 5600, but it seems like even 0.77% could add up pretty quick.