The MESSENGER Mercury orbiter, which launched a year ago next week, is on target for its Earth flyby on August 2. This is just the first of many flybys that are necessary to get MESSENGER into orbit around Mercury: it'll be followed by two flybys of Venus (on October 24, 2006, and June 5, 2007) and three flybys of Mercury (on January 14, 2008; October 6, 2008; and September 29, 2009) before it finally settles into orbit on March 18, 2011. All those flybys are required because t's very hard to get a spacecraft from an orbit near Earth into an orbit at Mercury's distance from the Sun -- Mercury is a very small object lying very deep in the Sun's gravity well -- especially when you're a spacecraft with a relatively low mass budget.
So, anyway, MESSENGER will be flying by Earth on August 2, with its closest approach over central Asia at 20:13 UT (middle of the night, local time) at an altitude of 2,347 kilometers (1,458 miles). There have been various discussions in the past about possible science activities for the flyby; I'm asking people now to find out what exactly is planned. MESSENGER produced a picture of the Earth and moon a few months ago, and I had a conversation then with MESSENGER scientist Louise Prockter about flyby science (follow the link for the details).