1. Rosetta’s first view of CG
Colin Snodgrass

3. Observations Part of delayed PC13 ops.
25th March Start 22:55, end 11:48 (26th)
163 million km from target (> 1 AU).
24.01 deg phase angle
comet at 5.1 AU from Sun.
52*900s exposures. Clear filter. 512x512 pix (~0.5 deg)
predicted R=20.9

4. Crowded field Observation towards galactic centre. Very crowded field.
2 x full frame NAC and 2 x full frame WAC also taken.
Makes nice PR pic (next time remember to take colours!)
Background subtraction required to reveal comet.

5. Crowded field 512x512 NAC window on comet (data volume).
Median frame aligned on stars, no comet.
Red circle marks position that comet was found.
This frame subtracted from each individual frame, leaves comet (not seen) and cosmics (many).

6. Comet Shift images based on comet motion, median combine.
Comet is revealed.
Centre of field
Rosetta apparently knows where it is going.
Away from Horizons predicted position, but probably as Horizons hadn’t yet updated Rosetta orbit after RVM.
Profile shows reasonable detection above background.

7. Something else… In combined frame there is another object.
Rate of motion almost the same as CG.
~ 0.1 degree away.
Rosetta already outside of MB, so unlikely to be a “common” asteroid.
Similar brightness as CG.