Telescope Reviews: Timeline of Rosetta's Flyby of 2867 Steins

"At the time of closest approach, 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 science observations.

Between 40 and 20 minutes before closest approach, Rosetta will be flipped and the spacecraft will switch to a specially designed asteroid fly-by mode, an optimal configuration that supports the intensive observation and tracking activity of the on-board instruments."

Timeline of nominal fly-by events
(All event times stated in ground time, CEST)

1 September
02:20 Instruments switched on (except OSIRIS which was already on for the
navigation campaign)

4 September
07:20-11:20 Slot for possible trajectory correction manoeuvre (36 hours before
closest approach)
13:20-18:20 Last opportunity to acquire images for optical navigation campaign

5 September
07:20-10:20 Slot for possible trajectory correction manoeuvre (12 hours before
closest approach)
10:20 Navigation cameras switch to tracking mode - initially both used,
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

6 September

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
ESOC begins
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.

Rosetta Blog

--------------------
"I do not know what I may appear to the world, but to myself I seem to have been only a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me." -- Sir Isaac Newton