Near Earth Objects - Dynamic Site
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NEODyS provides information and services for all Near Earth Asteroids. Each NEA has its own dynamically generated home page providing information and services, and a search facility puts the information in easy reach.

Starting from 1 September 2011 NEODyS is sponsored by ESA, which pays a portion of the operating costs, both for the background orbit and risk computations and for the database and web interface; the rest of the cost is covered, as before, by the Department of Mathematics, University of Pisa, with the running research grants of the Celestial Mechanics Group, and by IASF-INAF (Rome), with a PRIN-INAF grant.

The ESA participation is through a contract with SpaceDyS srl, a company of Cascina (Pisa, Italy), which is a startup promoted by same research group which has built and operated NEODyS for the past 12 years.

This is the beginning of a transition phase, in which ESA should progressively assume larger responsibility for the operations of NEODyS, under the programmatic envelope of the Space Situational Awareness (SSA) initiative, NEO segment. The NEODyS service is expected to be federated, together with others including the Spaceguard Central Node and the EARN Asteroid Database, in a new comprehensive SSA-NEO information service.

The University and Research groups will in the near future continue to share the work and the responsibility, and are in any case committed to continue for a long period of time to contribute with research, innovation and certification functions.


This is the new version NEODyS-2, implementing the new error model based upon Chesley, Baer and Monet (Icarus 2010). The orbits have all been recomputed by using star catalog debiasing and an error model with assumed astrometric errors RMS deduced from the tests of the paper cited above. Risk files have bene recomputed for all PHAs, scanning for possible impacts up to the year 2090; as a result, many objects do not have anymore a risk file, because the orbit has improved. A few NEAs have a risk file in NEODYS-2, while they had none in the old version, but this is in most cases due to the increase of the final time of the scan from 2080 (which had been in use previoulsy) to 2090.

The software used for this version of NEODyS is OrbFit version 5.0; the free distribution can be obtained on request, but needs to be used by users which do understand the new error model. We have not yet implemented the correlation model for the astrometric errors, see Baer et al. (Icarus, in press 2011); a compensating increase of the RMS has been used as a safety margin. We plan to complete this additional step towards a fully consistent statistical error model soon (but no fixed date yet).

The NEODyS service is in some circumstances time critical (e.g., during special observation campaigns for asteroids at risk of being lost and/or with Virtual Impactors). At the moment we cannot provide a duplicate service to guarantee against network failures, but we are working to restore the hot redundancy.

We are doing an effort to provide NEODyS with online help and captions. However, it is obviously not possible to explain all the technicalities involved in such a complex information system. The Tumbling Stone site had been created precisely to provide more user friendly information, including an illustrated dictionary of technical terms, and comments on the most relevant events and discoveries about Near Earth Asteroids. Unfortunately this site is not currently maintained.

The same services for other asteroids, including all numbered and multiopposition orbit objects, can be accessed at AstDyS.

How does it work?

These important buttons and links are at the top and bottom of every page:

To browse the list of objects in the NEODyS database.
To browse the list of observing stations. (You can get a listing of the NEA observations and residuals for any station.)
To search for a specific object or for objects with particular characteristics.
Risk page
Details known possibilities of Earth-asteroid collision. We operate the impact risk monitoring system CLOMON2, providing an estimate of the urgency of the problem based upon the Palermo Technical scale .
NEA elements
Catalogs of all NEA orbital elements in OrbFit format, updated daily.
Related sites
Links to related WWW sites.
Info & Credits
Information page: about Neodys, frequently asked questions, MJD conversion tables and other infos.
Help window.
This is the Tools icon (on the right in the top banner). Clicking repeatedly on it shows the following tools: Go to nea, Current date-time, MJD-calendar conversor and, finally, color and font-size selectors. When all the tools are displayed the icon changes to  ▼ . Clicking on  ▼  hides the tools and sets the icon again to  ▲ .
Expands the main content area, hiding the banners and menus, to increase the available on-screen surface for data browsing. The same icon lets you restore the initial layout.
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Send feedback to the NEODyS team.

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