First Rosetta/OSIRIS images of asteroid Steins
6 September 2008
Images of asteroid Steins, taken by the OSIRIS Wide Angle Camera during the fly-by, were presented at a press conference on 6 September. | ||
| Images of asteroid (2867) Steins taken by the OSIRIS Wide Angle Camera on Rosetta during the fly-by of 5 September 2008. The effective diameter of the asteroid is 5 km, approximately as predicted. At the top of the asteroid (as shown in these images), a large crater, approximately 2 km in size, can be seen. | ||
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After the press conference provisional estimates (*) of the distance and phase angle for these images have been provided (from top-left to bottom-right): | ||
| Distance= 1340 km phase angle= 2° |
Distance= 1140 km phase angle= 6° |
Distance= 960 km phase angle= 17° |
| Distance= 810 km phase angle= 43° |
Distance= 800 km phase angle= 55° |
Distance= 950 km phase angle= 84° |
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(*)The estimates are based on the predicted time of closest approach (20:38:16 CEST - spacecraft event time). Some changes to these distance and phase angle estimates may be introduced when the actual time of closest approach has been confirmed. These are expected to be no more than 50 km for the larger distances and no more than 10 km at closest approach. The phase angles are expected to change by no more than 2 degrees. | ||
| Credits: ESA ©2008 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA | ||
| Preliminary results (from OSIRIS)* | |
| Size | 5.9 x 4 km (equivalent effective diameter of 5 km) |
| Shape | diamond shaped |
| Albedo | 0.35 ± 0.05 |
| Craters | Dominated by a large crater on the north with diameter of ~ 2 km; a second large crater lies in the shadowed region; a chain of 7 craters is seen; a total of 23 craters have been counted with diameter greater than 200 m |
| For OSIRIS there is a remarkable agreement between the pre-fly-by predictions and the actual observations. | |
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First impression is that this asteroid has had a complex collision history. | |
| * as reported at the press conference on 6 September. See also the link to "Asteroid (2867) Steins -first results" on the right-hand menu | |
| Preliminary results (from GIADA)* | |
| GIADA confirms a clean environment (i.e. no detection of very small particles) around Steins | |
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GIADA worked well; first results look good; housekeeping data was as expected; the team consider this to be good news for the comet encounter later. | |
| * as reported at the press conference on 6 September 2008 |
