We've got an expanded version of the Rosetta fly-by timeline that is in the main ESA website. At the time of closest approach (5 Sep 2008 20:58 CEST), Rosetta is planned to be 800 km from the asteroid, passing by at a speed of 8.6 km/s relative to Steins. Both Rosetta and Steins will be illuminated by the Sun, providing an excellent opportunity for scientific observations (full timeline after the jump). -- Daniel
Between 40 and 20 minutes before closest approach, Rosetta will be 'flipped over' (there's no up or down in space...) and the spacecraft will be switched into a specially designed 'asteroid fly-by mode', an optimal configuration that supports the intensive observation and tracking activity of the on-board instruments (we'll try and get more details on AFM for you later this week).
Although most scientific observations will take place in the few hours around closest approach, several instruments will be switched on for a longer time around the event.
For tracking, ESA's Cebreros deep space antenna (DSA 2), in Spain, will be used for communications with Rosetta in the two days preceding closest approach. When the spacecraft is not visible from Cebreros or New Norcia, NASA's DSN (Deep Space Network) ground stations at Goldstone, Canberra and Madrid will provide support for tracking and for science operations.
Timeline of nominal fly-by events
(All event times stated in ground time, CEST)
02:20 Instruments switched on (except OSIRIS which was already on for the
07:20-11:20 Slot for possible trajectory correction manoeuvre (36 hours before
13:20-18:20 Last opportunity to acquire images for optical navigation campaign
07:20-10:20 Slot for possible trajectory correction manoeuvre (12 hours before
then use CAM 'A' only (to be decided)
11:00 Uplink fly-by commands for asteroid fly-by mode (AFM)
Includes an update to the command profile already on board & the
final updated AFM commands
20:18-20:38 Spacecraft 'flip over'
20:39 Spacecraft switches automatically to asteroid fly-by mode
20:48 High-gain antenna on hold
From 10 minutes before to about 1 hour after closest approach, the
high-gain antenna will not point to Earth. No telemetry will be received
until the spacecraft exits the asteroid fly-by mode.
20:56 Sun illuminates Rosetta from the back and the asteroid fully
20:58 Closest approach, at a planned distance of 800 km from the asteroid
21:58 Rosetta automatically exits asteroid fly-by mode, high-gain antenna
rotated to Earth pointing (until 22:05)
22:27 First post-fly-by acquisition of signal (AOS) - telemetry received via
NASA's Goldstone ground station
22:30 Start of science data download via Goldstone
04:06-16:01 Ground station pass via ESA's New Norcia station - science data
download continues. During the first 5 hrs, OSIRIS data will be
downloaded, followed by 3:30 hrs of VIRTIS only, and then the
rest of the science data
12:00 Live streaming of Rosetta Steins fly-by press conference from
13:00 Images from fly-by published on ESA web
15:00 End of press conference streaming
16:01 End of reception of first set of science data
After 6 September
Daily ground station passes until 5 October, including 8 hrs via New Norcia & one 4-hr DSN pass daily until 14 September - then daily passes via New Norcia only until 5 October.