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peter59
Only 78 days to Stein encounter ! I can't believe I forgot about this event.
dmuller
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
ugordan
QUOTE (peter59 @ Jun 19 2008, 08:53 AM) *
Only 78 days to Stein encounter !

Anyone wanna bet if the previous flyby data (Earth, Mars) will hit the Planetary Science Archive before or after this flyby? rolleyes.gif
peter59
QUOTE (ugordan @ Jun 19 2008, 09:05 AM) *
Anyone wanna bet if the previous flyby data (Earth, Mars) will hit the Planetary Science Archive before or after this flyby? rolleyes.gif


PSA announcements:
First release of Rosetta data - early 2008 ??
First release of Venus Express data - July 2008 !?

Planetary Science Archive
jasedm
Perhaps it's time for a dedicated 'Steins' thread...
A few details on the rock:

Main belt asteroid
Discovered: November 4th 1969
Spectral type: E
Diameter 4.6km
ugordan
QUOTE (peter59 @ Jun 19 2008, 12:01 PM) *
PSA announcements:

That's just what they are: announcements.
djellison
They had previously been announced ( both of them, iiirc ) as being earlier. I would essentially ignore the announcement dates and just wait for stuff to actually arrive.

Alice data is already available upto and including the most recent Earth flyby. No other instrument has provided anything to date.

Doug
Paolo
Some details about Steins that I collected for the third volume of my book "robotic exploration of the solar system"

Steins is a small body less than 10 km across, discovered on 4 November 1969 by Soviet astronomer N. Chernykh at the Nauchnyj Observatory in Crimea and named after Karlis Steins, former director of the Latvian University Astronomical Observatory. While the properties of Lutetia, the second asteroid target are relatively well known, being a largish and bright object discovered more than a century ago, almost nothing was known about Steins, and observational campaigns were started in 2004 to characterize it. Steins was observed by the largest astronomical observatory on Earth, including the European Very Large Telescope (VLT) in Chile, JPL's Table Mountain Observatory, the Spitzer infrared astronomy satellite and Rosetta itself.
The Rosetta orbiter observed continuously Steins (1.06 AU away) for 24 hours with its science camera on 11 March 2006 in order to collect a “light curve” at phase angles larger than ever achievable from Earth, due to observational geometry constrains and for a longer time span, uninterrupted by day and night cycles. A total of 238 images were taken, covering four rotations.
Although researchers initially catalogued Steins in the S class (like most previously-visited bodies), the observational campaigns found that its spectral and polarimetric properties placed it in the E taxonomic class of reddish bodies with high albedo believed to be thermally evolved and of igneous origin, which underwent at least a partial melting and differentiation early in their history. E asteroid spectra probably makes them related to some rare enstatite chondrite or aubrite meteorites and therefore these bodies are believed to have a surface consisting of iron-free or iron-poor silicates. Observations pinpointed Steins' rotation period at about 6.05 hours, while the measured diameter could vary between 2 and 5 km, depending on its albedo. Asymmetries in the light curve confirmed that the small body has an irregular shape, with a ratio between the main axes of about 1.3. Other researchers pointed out that some of the characteristics of Steins could hint at a young and very rough surface at most a few million years old.
While fewer than 30 members of the E class of asteroids were known, including (44) Nysa, the largest, and two near-Earth objects, (3103) Eger and (4660) Nereus (a recurrent space mission target), little is known about the evolutionary history of the type. Steins was initially placed in the same family as (64) Angelina, but other studies showed that it shared most of the same spectral characteristics as Eger, both bodies being believed to be members of an old eroded family which formed in the inner asteroid belt close to the present position of Steins, which appears to be the largest member of the family. The presence of Eger in an Earth-intersecting orbit of course provides a path for enstatite and aubrite meteorites to hit our planet.
The encounter on 5 September 2008 will be at a distance of 1745 km and a relative speed of 8.6 km/s
IM4
Even more details for Rosetta fans !!!

Flyby in a nutshell:
  1. Closest approach on 5 Sept. 2008 18:33:57 ± 30 sec
  2. Heliocentric distance 2.14 AU, geocentric distance 2.41 AU
  3. Low phase angle during approach, high phase angle after closest approach, coverage 0-140°
  4. Minimum flyby distance of 800 km
  5. Zero phase angle will be reached at a distance of 1280 km
  6. One way light travel time will be 20 min

Flyby strategy
  1. Default pointing
  2. Spacecraft flip (T-40 min -> T-20 min)
  3. Inverted pointing (> T-20 min)
  4. +Z axis points at Steins at all times

Flyby Science:
  1. Alice: point at Steins to obtain FUV spectra search for exosphere/coma around Steins
  2. COSIMA: execute normal dust collection cycle
  3. GIADA: Impact sensor operational, but cover closed
  4. MIRO: Steins observations during approach and recession. Special asteroid mode sequence at closest approach (CA)
  5. ROSINA: Pressure monitoring, single mass measurement sequence
  6. RPC: Measurements of plasma environment
  7. RSI: Attempt for mass determination (probably not feasible)
  8. OSIRIS: Light curve for 2 weeks before CA for shape reconstruction. At CA: spectrophotometry, mapping and surface properties, satellite/dust search
  9. VIRTIS: Steins light curve determination starting 7 hours before CA. At CA: mineralogy mapping

Expected data volume:
  1. 600 MiB before closest approach
  2. 2400 MiB after closest approach
tasp
Do we have any radar data indicating binary/satellite existence for any asteroid in this size range ?

Just wondering what the odds are for 'nother Dactyl type discovery. Would 200+ images for albedo study yield enough light curve data to rule out a satellite? Particularly one that was in an orbit inclined enough so that the satellite was never eclipsed or transited the primary.

gpurcell
These sort of encounters always fascinate me...this is likely to be the only close approach data humanity collects on this particular hunk of rock for hundreds of years. Some time in the distant future an asteroid miner will pull up these old images on his way to this asteroid and wonder at the folks who sent a barbaric robot out to it....
centsworth_II
QUOTE (gpurcell @ Jun 21 2008, 11:31 AM) *
Some time in the distant future an asteroid miner...

I'm assuming this will be an AI robotic miner. laugh.gif
nprev
QUOTE (tasp @ Jun 21 2008, 03:35 AM) *
Do we have any radar data indicating binary/satellite existence for any asteroid in this size range ?


Wasn't there an NEO radar-imaged by Aricebo that was a small binary object? It's certainly possible that Steins is binary or has a small satellite, but if so I suspect it would have to have been the product of a weak, recent impact event. There's not a lot of gravitation exerted by a 4.6 km body.
tedstryk
QUOTE (nprev @ Jun 21 2008, 05:00 PM) *
Wasn't there an NEO radar-imaged by Aricebo that was a small binary object? It's certainly possible that Steins is binary or has a small satellite, but if so I suspect it would have to have been the product of a weak, recent impact event. There's not a lot of gravitation exerted by a 4.6 km body.


There has been a multitude of such objects. Castalia was the first one. Arecibo and Goldstone will be observing the upcoming flyby of 2008 BT18 (July 6 and 7 for Arecibo, July 11 for Goldstone]. It will pass about 2.3 million kilometers away and is 700 to 800 meters across, so we should get some nice images and, with some luck, maybe another binary.
jasedm
QUOTE (tasp @ Jun 21 2008, 12:35 PM) *
Do we have any radar data indicating binary/satellite existence for any asteroid in this size range ?

I couldn't find any relevant radar data, but it appears see here that a moon has been likely ruled out for Steins.
tasp
Thanx for the article!

An idea springs to mind:

How far out from Pluto can New Horizons be and get good light curve data for Nix and Hydra? If we are lucky, perhaps so far out when nothing much else is going on ??

(I just love it when missions can 'cross pollinate' each other)

(If such observations for New Horizons are already scheduled, never mind)


tty
Certainly there are earth-crossing binaries. There are several cases of multiple craters of equal age. Steinheim and Ries is the best example, but there are several other more or less certain cases. Even Chicxulub may be linked with Boltysh in Ukraine.
cosmo
Around 15% or even more of the NEAs are suspected to be binary. Up to now more than 30 are confirmed out of 5000+ NEAs and most of them are less than 1500m in diameter. It seems the smaller the asteroid the better the chance it is a double.

The YORP effect is maybe the main forming mechanism of binary NEAs as most of them are very tiny. Other more uncommon forming mechanisms are collisions and tidal disruptions due to planetary close-encounter.
Rakhir
Rosetta awakes from hibernation for asteroid encounter
http://www.esa.int/esaSC/SEMQPDSHKHF_index_0.html
charborob
I've been doing some calculations. Rosetta's narrow angle camera has a field of view of 2,35 x 2,35 degrees. The image size is 2048 x 2048 pixels. At a distance of 800 km, if Steins is about 5 km wide, it will subtend an angle of about 20 arc minutes. At closest approach, Steins' image should then be about 300 pixels wide. That's not much, is it?
For comparison, here's an image of the asteroid Gaspra scaled to 300 pixels wide. That's about what we should expect from the Steins flyby. I didn't take motion blur into account. I don't know if it will be an issue.
Click to view attachment
If I made some errors, thanks for correcting me.
tedstryk
To be fair, Gaspra is a much bigger asteroid - 18.2×10.5×8.9 km - and these are the best Galileo images at their original size. The larger image is a mosaic of two frames, but it just happened that the asteroid was imaged on the edge of the CCD - it could have easily fit in one frame. The smaller image is the next best shot at its original size (it is part of a color sequence). We often see the larger image in greatly enlarged forms and with a false color overlay from infrared data.

charborob
In my post, I was just trying to give an idea of what kind of detail we might expect to see on the surface of Stein during the flyby. By the way, the best resolution will be around 16 meters per pixel, if my data on the camera are correct.
Ken90000
The Cool thing about 2867 Steins is its type. We have never seen an “E” type asteroid at close range. Unfortunately, as you know, Steins is a tiny asteroid only 4.6 km in diameter.

There would be no point in approaching closer than the planned 800 km. Rosetta simply cannot track a body passing by so quickly. Remember, the spacecraft was designed to explore a comet while slowly orbiting the body.

I look forward to seeing what this body looks like even if the images are only a few hundred pixels across. Likewise, the data from spectrometers and other instruments should keep us occupied until the next flyby.

But, if you are looking for multi-image mosaics, you will have to wait for the 2010 flyby of 21 Lutetia.
dvandorn
Let us hope that ESA doesn't do the same thing with Rosetta's Steins images as it did with the crescent Mars images that Rosetta supposedly acquired... *heavy sigh*...

-the other Doug
ugordan
QUOTE (dvandorn @ Jul 8 2008, 06:11 AM) *
Let us hope that ESA doesn't do the same thing with Rosetta's Steins images as it did with the crescent Mars images that Rosetta supposedly acquired...

I'm actually willing to let that one pass for them. Reportedly, the images were saturated and not very useful for release so we're probably not missing as much as you think (think CCD charge bleed for example).
djellison
Crime 1. Not sequencing a normal RGB sequence during that phase in between the long exposures for dust obs.
Crime 2. Not releasing whatever they did take, either for press release at the time, or via the PDS to date.

But let's not have that debate again - the E2 flyby was quite well 'blogged' - and I expect the Steins flyby will be as well. If I hadn't taken all my time off for Europlanet and IAC - I'd be asking to visit ESOC during the flyby.

Doug
ugordan
Crime 2 definitely stands. It's ironic that the comment on the PSA site doesn't even mention OSIRIS data as pending for review, unlike a few of other instruments. I'm keeping my eye on this as no doubt others are, but somehow this doesn't instill confidence we'll be seeing OSIRIS data any time soon.

Second the E2 flyby comment, it was pretty nice. Although, as an imaging kind of person I was left wanting more than 3 images. Not sure if they've been taken at all, though.
cotopaxi
QUOTE (jasedm @ Jun 25 2008, 05:21 PM) *
I couldn't find any relevant radar data, but it appears see here that a moon has been likely ruled out for Steins.

Well, it depends on the size of the moon. A moon of a size comparable to that of Steins is probably ruled out, but for example a 100 m sized satellite would create only 1/2500 of the signal from Steins (assuming 5 km diameter for Steins and equal albedo), and that would not be detectable in the Rosetta lightcurve (and I suspect in no other data set).
tasp
The article indicates light curve data was taken from 159 million kilometers out!

Seems like looking for opportunities to observe Tempel 1 might be useful. (yes I know it's a comet and light curve data might be harder to interpret)

Are there instruments comparable to OSIRIS on other spacecraft ?

cotopaxi
Full quote of previous post removed - mods

OSIRIS observed Tempel 1 for two weeks around Deep Impact. See http://www.esa.int/SPECIALS/Rosetta/SEMUSK5Y3EE_0.html and http://www.esa.int/SPECIALS/Rosetta/SEMSJ06DIAE_0.html

What would we learn from observing Tempel 1 with OSIRIS now?

The High resolution camera on Deep Impact may be comparable with OSIRIS. Bigger telescope on one hand, focus problem and inferior CCD on the other hand. I don't know how SSI on Cassini compares.

Somewhat off topic here: OSIRIS is going to look for the parallax effect in gravitational microlensing in September, after the Steins flyby.
tasp
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.

tedstryk
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
tasp
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)

ugordan
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?
plasmatorus
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.
dmuller
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
Paolo
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
remcook
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
cotopaxi
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.
remcook
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!
cotopaxi
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.
remcook
Thanks again, much appreciated! Looking forward to the real images of Steins smile.gif
jasedm
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.


cndwrld
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’

Click to view attachment

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.
mchan
Thanks for posting this description.

QUOTE (cndwrld @ Aug 13 2008, 01:57 AM) *
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.

Hope to see lots of images then. smile.gif
cndwrld
QUOTE
Hope to see lots of images then.


Ahhh, don't we all...... But as in the past, I expect we'll see a handful of press conference pictures. Still, they should be very cool pictures.
cndwrld
nth Asteroid Flyby

I was wondering about this question, and searches didn't give me an answer. As Rosetta gears up for the flyby of Steins, how often has an asteroid flyby been done before? Is this the second time, or the fifth? It would be great if one of you space historians could put this into focus.
djellison
Ones I can think of

Galileo did Gaspera, then Ida & Dactly (that's only one flyby though - Dactyl was just gravy )

NEAR did Maltide then EROS, then orbited Eros

Stardust did Annefrank

DS1 did Braille ( although that didn't go well )

6 proper planned ones then I think.

Technically, NH did 132524_APL, and Cassini did Masursky - but they're more of a distant encounter rather than flybys.
PhilCo126
Don't forget Hayabusa... and the cometary fly-bys smile.gif
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