Posts by Josef Durech
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1) Message boards : News : New models reconstructed from ATLAS photometry (Message 7074)
Posted 6 Oct 2020 by Josef Durech
Our new paper describing asteroid models reconstructed from ATLAS photometry has been accepted for publication in Astronomy and Astrophysics. The paper is available at arXiv. Thank you for your contribution!
2) Message boards : News : New models reconstructed from Gaia and Lowell photometry (Message 6358)
Posted 24 Sep 2019 by Josef Durech
We published hundreds of new asteroid models. The paper is available at arXiv and should soon appear in Astronomy and Astrophysics journal. Thanks a lot for your contribution and patience!
3) Message boards : News : New models published (Message 5909)
Posted 10 Jul 2018 by Josef Durech
A paper with new results has been accepted for publication in Astronomy and Astrophysics. The preprint is available at arXiv. The models will be available in DAMIT soon. Thanks for your contribution!
4) Message boards : Science : Aspect ratio of asteroids (Message 5761)
Posted 28 Mar 2018 by Josef Durech
Asteroid Cerberus is similarly elongated, its model is here:
http://astro.troja.mff.cuni.cz/projects/asteroids3D/web.php?page=db_asteroid_detail&asteroid_id=310
5) Message boards : Number crunching : Is the Period search Application an open source software? (Message 5222)
Posted 10 Mar 2017 by Josef Durech
Yes, the code can be downloaded here: http://astro.troja.mff.cuni.cz/projects/asteroids3D/web.php?page=download_software
6) Message boards : News : New models published in Astronomy & Astrophysics (Message 4776)
Posted 3 Feb 2016 by Josef Durech
A paper Asteroid models from the Lowell Photometric Database describing the results obtained by A@H has been accepted for publication and is now in press in Astronomy and Astrophysics. There is a link to the public version of the paper at the Scientific Results page. All published models are also available through DAMIT. We thank all volunteers, these results are based on your contribution!
7) Message boards : News : Article in Astronomy and Computing (Message 4693)
Posted 9 Nov 2015 by Josef Durech
Sorry, the correct link to the free version (until Dec 23, 2015) is here: http://authors.elsevier.com/a/1R~8l_oKY8v6uy
8) Message boards : Science : How are asteroid selected for processing? (Message 4488)
Posted 3 Jun 2015 by Josef Durech
It means that the success rate of deriving a unique model from currently available data is only ~1%.
9) Message boards : Science : The International Astronomical Union is allowing astronomical organisations (like theSkyNet) to submit potential names for 20 exoplanet systems and I was wondering if Asteroids@Home will do the same? (Message 4487)
Posted 3 Jun 2015 by Josef Durech
A@H has nothing to do with naming asteroids, this is in hands of the International Astronomical Union.
10) Message boards : Science : When will A@H use Gaia spacecraft data (Message 4230)
Posted 24 Mar 2015 by Josef Durech
The Intermediate Data Release for Gaia is scheduled for mid-2016. We will use Gaia photometry at A@H after that.
11) Message boards : Science : How are asteroid selected for processing? (Message 3959)
Posted 19 Jan 2015 by Josef Durech
The selection is based on the number of brightness measurements for an asteroid. If there are more than about 50 photometric points, we scan the parameter space with the aim to find a unique model that fits the data. In practice it means that we process the first ~300,000 numbered asteroids.
12) Message boards : Science : Are all asteroids convex? (Message 3784)
Posted 15 Nov 2014 by Josef Durech
- Strictly speaking, all asteroids are nonconvex. The reason why all our models are convex is that the difference in disk-integrated brightness between a convex and a nonconvex body is small. There is simply not enough information in the photometry to derive reliable nonconvex models.

- In some cases non-convexities can be detected from photometry when they are large compared to the size of the body and when the body is observed at high Sun-asteroid-Earth angle (when the shadowing is important). The best way to reveal non-convexities is to have some disk-resolved data (images).

- It would be slower, but more importantly, it is not needed given the type and quality of the data we process.

For an example of a non-convex model derived from photometry look at asteroids Ivar or Eger in DAMIT (http://astro.troja.mff.cuni.cz/projects/asteroids3D).
13) Message boards : Science : Why has the number of models gone down? (Message 3043)
Posted 16 May 2014 by Josef Durech
About 1 %.
14) Message boards : Science : "peanut" fly-by... (Message 2647)
Posted 4 Mar 2014 by Josef Durech
No, this one hasn't been processed yet. Even if it was, we wouldn't get any shape model because there are too few photometric data points available.
15) Message boards : News : New models of asteroids (Message 2014)
Posted 4 Nov 2013 by Josef Durech
There is a strong bias in the shapes we derive. The closer the shape is to a sphere, the lower is the variation of the reflected light caused by its rotation. In such cases, the signal is drowned in the noise and we can't derive the rotation period. Given the poor quality of the data we have now, the shape has to be elongated enough to produce a high-amplitude lightcurve - only then we can find the period and the corresponding shape.
16) Message boards : Science : NASA Announces Asteroid Grand Challenge (Message 1585)
Posted 26 Aug 2013 by Josef Durech
The A@H project can in principle deliver spin&shape of asteroids interesting for NASA if there are enough sparse photometric data (which is unlikely for small near-Earth asteroids). But if NASA selects an asteroid, the first thing they should do is to get more data, dense lightcurves in particular, to derive the rotation period. Once the rotation period is roughly known, there's no need for A@H because the parameter space we need to search is small and it can be done on a single PC.

The aim of A@H is to process sparse-in-time photometry (which means unknown rotation period and a large interval of periods that has to be scanned) of most of the known asteroids and derive period/spin/shape models when possible. Concentrating on selected asteroids usually means their rotation period is known and they are processed (with the same lightcurve inversion technique) outside the A@H project.

As regards contacting NASA, I think we formally missed the deadline for the Request for Information (July 18).
17) Message boards : Science : Advances counted in the nuber of asteroids, not credits (Message 1308)
Posted 27 May 2013 by Josef Durech
The "Scientific results" page is updated irregularly. Please be patient. The more WUs computed, the higher is the chance to get in the list - however, no amount of WUs can secure it.
18) Message boards : Number crunching : Why does it take 30 to 40 minutes before Progress begins. (Message 925)
Posted 26 Feb 2013 by Josef Durech
The reason is that every task starts with an initialization when several control parameters are tested and then set up for the rest of the computing. During this process, there is no output and no checkpointing. As it takes less than 1/100 of the total time, I thought it wouldn't cause any practical problems.
19) Message boards : Number crunching : Task Names (Message 917)
Posted 25 Feb 2013 by Josef Durech
The numbers are 'standard' asteroid numbers, so no conversion/mapping is needed.
20) Message boards : Number crunching : Task Names (Message 913)
Posted 24 Feb 2013 by Josef Durech
The first number is the date when the workunit was created (yymmdd) and the second is the number of the asteroid (1 Ceres, 2 Pallas, 3 Juno,...). Each asteroid is divided into several hundreds of workunits and that is the third number.


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