Today's the day Rosetta arrives at a comet!

The latest image from comet Churyumov-Gerasimenko was taken from less than 250 kilometers away. In less than a day, Rosetta will officially arrive, becoming the first spacecraft ever to orbit a comet!

Here's a lovely composite of all the approach images so far, by Phil Stooke:

ESA will be livestreaming the arrival beginning at 08:00 UTC August 6 (which is 1 in the morning my time). At 09:00 UTC, Rosetta will fire its thrusters for 6 minutes and 26 seconds. This will not be Rosetta's final burn -- in fact, in order to stay in the neighborhood of the comet, it will be turning and burning once every three or four days, performing a series of 100-kilometer arcs in a sort of triangular path around the comet.

Here is the anticipated timeline of events in Universal Time (UTC) and my local time (PDT):

• 08:00/01:00: New Norcia tracking station begins tracking Rosetta
• 08:00/01:00: Livestream begins
• 09:00/02:00: Rosetta begins 6.5-minute orbit entry maneuver
• 09:22/02:22: Start of thruster burn confirmed on the ground (one-way light time is 22.5 minutes)
• 09:29/02:29: End of thruster burn confirmed on the ground
• 11:00/04:00: Press briefing at the European Space Operations Centre (will be Livestreamed)

This arrival will be the triumph of a 10-year effort for the European Space Agency to match orbits with a comet. They posted a nice long feature on how they track a spacecraft following a comet, with a great photo of their navigation team. I may not be awake at the time of the orbit insertion, but I've asked German blogger Daniel Fischer to report from the media events for us; check his Twitter feed for updates!