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Rosetta flyby of Asteroid Steins, 5th September 2008
tasp
post Jul 15 2008, 12:18 PM
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IIRC, a craft will eventually return to Tempel 1, if light curve could be worked out, perhaps encounter could be timed to observe Deep Impact crater on the dayside.

Light curves for Nix and Hydra, from as far out as possible (if made by NH) are quite desirable too. Tidal braking effects for those 2 objects (from Pluto) appear to be quite small. Rotation rates other than synchronous to Pluto would be very interesting. So would satellites of Nix and Hydra. Maybe something analogous to Mercury (3:2) would be interesting too. A debris belt (like Rhea's) ????


I was also curious if Pluto's hill sphere has objects similar to Phoebe or Nereid (but smaller) and perhaps some 500 meter to 1km objects might be looked for too when NH is close enough to 'see' them in long exposures. I am thinking the observatory phase for the NH Pluto encounter could be very interesting.

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tedstryk
post Jul 15 2008, 01:43 PM
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And that couldn't be done from earth because why?

They do seem to have the flyby pretty well planned.

http://www.astro.cornell.edu/next/noannot.mov
http://www.lpi.usra.edu/meetings/acm2008/pdf/8053.pdf


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tasp
post Jul 15 2008, 02:04 PM
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I am just trying to find activities for NH when it is further out from Pluto and less busy. The earlier anything new and unexpected is found in the Pluto system, maybe we have time to reprioritize the flyby. (not that Alan Stern needs more work laugh.gif )

Nix and Hydra are so faint, tying up HST for light curve data seems not a good use of assets, especially if NH can make similar or better observations during later cruise phase.

I just don't know effective magnitude limits for NH instruments and when various objects in Pluto system become usefully visible. That other craft in solar system are making (to me) surprising studies from great distances (159 million kilometers!!) seems to suggest useful info might be possible from other missions too, and at surprising distances. When do the orbits of Nix and Hydra subtend more than, let's say, 10 arcseconds, as seen from NH?

(Thanx for the Tempel 1 info, I didn't know they had the rotation period accurate enough to know now which hemisphere would be visible during next flyby)

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ugordan
post Jul 15 2008, 02:23 PM
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QUOTE (tasp @ Jul 15 2008, 04:04 PM) *
Nix and Hydra are so faint, tying up HST for light curve data seems not a good use of assets, especially if NH can make similar or better observations during later cruise phase.

Unless some clever data reduction scheme is implemented, NH would have to return full LORRI frames for lightcurves, AFAIK. Is that really feasible/worth it given the immense distances by then and consequently low bitrates?


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plasmatorus
post Jul 28 2008, 04:45 PM
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QUOTE (dmuller @ Jun 19 2008, 02:00 AM) *
Indeed, almost there ... 78 days and 121 million km to fly. Currently 61 million km away from Steins: Rosetta Real-Time Simulation

Does anybody have more details on the flyby trajectory? I currently have it nailed down to minute precision with closest approach being on 05 Sep 2008 18:35 spacecraft event time at a distance of 712 km


The nominal time for Rosetta's closest approach to Steins is 2008-09-05 18:37:48 +/- 20s. Flyby distance will be 800 km.
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dmuller
post Jul 29 2008, 10:49 AM
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Thanks plasmatorus for the flyby time and Emily for the forwarded timeline which I have incorporated into the realtime simulation at http://www.dmuller.net/rosetta ... and yes, I have fixed the problem I had with the database at least for the Rosetta mission


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Paolo
post Aug 2 2008, 05:51 PM
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Note that there are three papers on Steins for publication in Astronomy & Astrophysics:

Asteroid 2867 Steins.I. Photometric properties from OSIRIS/Rosetta and ground-based visible observations
L. Jorda, P. Lamy, G. Faury, P. Weissman, M. A. Barucci, S. Fornasier, S. Lowry, I. Toth, and M. Kuppers

Asteroid 2867 Steins.II. Multi-telescope visible observations, shape reconstruction, and rotational state
P. L. Lamy, M. Kaasalainen, S. Lowry, P. Weissman, M. A. Barucci, J. Carvano, Y.-J. Choi, F. Colas, G. Faury, S. Fornasier, O. Groussin, M. D. Hicks, L. Jorda, S., A. Kryszczynska, Larson, I. Toth, and B. Warner

Asteroid 2867 Steins.III. Spitzer Space Telescope observations, size determination and, thermal properties
P. L. Lamy, L. Jorda, S. Fornasier, O. Groussin, M. A. Barucci, J. Carvano, E. Dotto, M. Fulchignoni, and I. Toth


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remcook
post Aug 4 2008, 12:20 PM
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Optical tracking has started (includes image of Steins, but doesn't seem real from the description...confusing)
http://www.esa.int/esaCP/SEMF0B8N9JF_index_0.html
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cotopaxi
post Aug 4 2008, 01:09 PM
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I am not sure what exactly is unclear, but let me try to be a bit more quantitative:
Today OSIRIS and the NAVCAM start to look at Steins for navigation purposes, twice a week for the first 3 weeks, than daily until and including Sept.4
Currently the astrometric accuracy from OSIRIS is about the same as the current knowledge of the position of the asteroid, the NAVCAM will reach that accuracy in about 3 weeks.
The asteroid will be unresolved in both OSIRIS and NAVCAM during the whole navigation campaign.
The hope is that after the last slot, the absolute position of Steins, perpendicular to the flight direction, will be known to about 2 km (compared to of the order of 100 km now).
There are four slots for trajectory correction maneuovers, one mid-august, the others in the last days before closest approach. The slots will be used if at that point the flyby geometry can be significantly improved (predicted vs. planned flyby geometry). The parameters are the closest approach distance of 800 km and the passage through 0 phase angle.
The astrometry will not much improve the knowledge of the position of the asteroid in flight direction (in other words distance). This corresponds to an uncertainty in the time of closest approach of roughly 10 seconds.
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remcook
post Aug 4 2008, 01:25 PM
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thanks for the explanation.
sorry, my confusion was with the origin of the image of Steins. Is it an artist impression? It looks pretty realistic!
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cotopaxi
post Aug 5 2008, 08:26 AM
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Ah, ok, yes, that's confusing. It guess it is some sort of simulated image or artist impression. Apart from the fact that there is no image of Steins yet, the stars are much too bright compared to the asteroid for the image to be real.
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remcook
post Aug 5 2008, 08:37 AM
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Thanks again, much appreciated! Looking forward to the real images of Steins smile.gif
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Paolo
post Aug 12 2008, 12:01 PM
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the three papers are now available. I guess this is the best we can hope to know about Steins for a few weeks more...

Asteroid 2867 Steins.I. Photometric properties from OSIRIS/Rosetta and ground-based visible observations

Asteroid 2867 Steins.II. Multi-telescope visible observations, shape reconstruction, and rotational state

Asteroid 2867 Steins.III. Spitzer Space Telescope observations, size determination and, thermal properties


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jasedm
post Aug 12 2008, 12:32 PM
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The discoverer of Steins died a few years back, but his widow Lyudmila Chernyk is still alive (according to Wikipedia), and working for the Crimean Astrophysical Laboratory. The coming flyby must be of extra special interest to her.

It would be nice to think that the IAU in the fullness of time named a crater each in their honour.


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cndwrld
post Aug 13 2008, 08:57 AM
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Here is some information on the flyby. I tried to include the timeline, but I'm not familiar with the BB code so I don't know if it will show up. The timeline is in Word table format, and I couldn't figure out how to show it. So I just created a JPG of it and tried to attach it.


Fly-by operations

Rosetta will be closest to Steins on 5 September 2008 at 20:58 CEST (= 18:58 UT, ground time). The minimum distance from the asteroid will be 800 km. This is the minimum distance from which Rosetta is able to track the asteroid continuously.

Rosetta will pass by Steins very fast, at a speed of 8.6 km/s relative to the asteroid. This means that the distance between Rosetta and the asteroid will change very rapidly (by a factor of 10 within 15 minutes before and after the fly-by), and the asteroid will quickly diminish in the cameras’ field of view.

Between 40 and 20 minutes before closest approach, Rosetta will be flipped and readied to enter the asteroid fly-by mode (AFM). During this mode, the orientation of the spacecraft is automatically driven by the navigation cameras to continuously keep the asteroid in the field of view of the imaging instruments.

Although most scientific observations will be performed in the few hours around closest approach, several instruments will be on for a few days around closest approach.

Communication with Earth will take place through ESA’s New Norcia Deep Space antenna as the main station. NASA’s DSN Goldstone, Canberra and Madrid stations will provide support for tracking before closest approach and for science operations, filling the gap in visibility between Cebreros and New Norcia after closest approach. ESA’s Cebreros Deep Space antenna will be used in the 2 days preceding closest approach. Radio signals to and from Rosetta (located at 2.41 Astronomical Units, or about 360 million km from Earth at the time of fly-by) will take 20 minutes to travel to their destination.

A timeline of the main fly-by operations is given below:

CA = Closest Approach;
TCM = Trajectory Correction Manoeuvre;
AFM = Asteroid Fly-By Mode
HGA = High Gain Antenna
Spacecraft time = UT ground time – 20’

Attached Image


There will be material released in the run-up to the flyby, including video- and pod-casts and a web blog. Media activities start at ESOC, Darmstadt at 18:00 CET on Friday, 05 Sept. On Saturday, 06 Sept from 12:00 - 13:00 CET, the results of the flyby will be presented at ESOC and placed on the web pages.


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