Orbit determination with very short arcsII. Identifications

Milani, Andrea; Gronchi, Giovanni F.; Knežević, Ž.; Sansaturio, M. E.; Arratia, Oscar

doi:10.1016/j.icarus.2005.07.004

Cited by 63 publications

(46 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The NEO model is based on the orbit element and absolute magnitude distributions of Bottke et al 2002 (for H < 24) and the H distribution of Rabinowitz et al (2000) for H 24. IEOs are included as a consequence of the transport model generating the known NEO population.…”

Section: The Pan-starrs Solar System Modelmentioning

confidence: 99%

Unbiased orbit determination for the next generation asteroid/comet surveys

et al. 2005

View full text Add to dashboard Cite

In the next generation surveys, the discovery of moving objects can be successful only if an observation strategy and the identification/orbit determination procedure are appropriate for the diverse apparent motions of the target sub-populations. The observations must accurately measure the displacement over a short interval of time; observations believed to belong to the same object have to be connected into tracklets. Information contained in tracklets is in most cases not sufficient to compute an orbit: two or more of them must be identified to provide an orbit. We have developed a method for recursive identification of tracklets allowing an unbiased orbit determination for all sub-populations and efficient enough to cope with the data flow expected from the next generation surveys. The success of the new algorithms can be easily measured only in a simulation, by consulting a posteriori some "ground truth".We present here the results of a simulation of the orbit determination for one month of operations of the future Pan-STARRS survey, based upon a Solar System Model with a downsized population of Main Belt asteroids and a full size populations of Trojans, NEO, Centaurs, Comets and TNO. The results indicate that the method already developed and tested to find identifications of NEO and Main Belt asteroids are directly applicable to Trojans. The more distant objects often require modified algorithms, fitting orbits with only 4 parameters in a coordinate system specially adapted to handle very short arcs of observations. These orbits are mostly used as intermediate results, allowing to find full solutions as more tracklets are identified.When the number density of detections is as large as expected from the next generation surveys, both joining observations into tracklets and identifying tracklets can produce some false results. The only reliable way to remove them is a procedure of tracklet/identification management. It compares the tracklets and the identifications with a complex logic, allowing to discard almost all the false tracklets and all the false identifications. However, the distant objects still present a challenge for orbit determination: they require three tracklets in separate nights. If this requirement is met we have found no problem in achieving an unbiased orbit determination for all populations. Further work will lead to more advanced simulations, in particular by introducing a realistic model for astrometric and photometric errors.

show abstract

Section: The Pan-starrs Solar System Modelmentioning

confidence: 99%

Unbiased orbit determination for the next generation asteroid/comet surveys

et al. 2005

View full text Add to dashboard Cite

show abstract

“…Of course, new algorithms could be implemented in successive iterations over the tracklet data set. e.g., [Milani et al 2005b] and [Boattini et al 2007]. There are only practical limits to how clever an algorithm might be and how many iterations could take place.…”

Section: Insert Tablementioning

confidence: 99%

“…show that the normalized Efficiency values from Table 7 are not a problem we have run an improved version of the recursive attribution algorithms of [Milani et al 2005b] on the leftover tracklets. To control the false identifications we have used even tighter quality controls.…”

Section: Insert Tablementioning

confidence: 99%

“…We have used the algorithms from [Kubica et al 2007] as the first step or tracklet and track identification followed by the techniques introduced in this paper as the second step. We have mentioned the possibility of using the algorithms of [Milani et al 2005b] as the third step. Even more complicated pipelines can be conceived but the discussion of pipeline design is beyond the scope of this paper and will be the subject of future work.…”

mentioning

confidence: 99%

“…In a series of three papers ( [Milani et al 2005b], [Kubica et al 2007] and the present one) we have defined a set of algorithms that may be used to process astrometric data for Solar System objects when the sky-plane density is much larger than it is for contemporary surveys. This will very soon be the case with Pan-STARRS [Hodapp et al(2004)] and LSST [Ivezić et al 2007].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Topocentric orbit determination: Algorithms for the next generation surveys

Milani¹,

Gronchi²,

Farnocchia³

et al. 2008

Icarus

View full text Add to dashboard Cite

The process of calculating a good orbit from astrometric observations of the same object involves three main steps: preliminary orbit determination, least squares orbit fitting, and quality control assessing the orbit's uncertainty and reliability. For the next generation sky surveys, with much larger number density of observations, new algorithms, or at least substantial revisions of the classical ones, are needed. The classical theory of preliminary orbit algorithms was incomplete in that the consequences of the topocentric correction had not been fully studied. We show that it is possible to rigorously account for topocentric observations and that this correction may increase the number of alternate preliminary orbits without impairing the overall performance. We have developed modified least squares algorithms including the capability of fitting the orbit to a reduced number of parameters. The restricted fitting techniques can be used to improve the reliability of the orbit computing procedure when the observed arcs have small curvature.False identification (where observations of different objects are incorrectly linked together) can be discarded with a quality control on the residuals and a 'normalization' procedure removing duplications and contradictions. We have tested our algorithms on two simulations based on the expected performance of Pan-STARRS -one of the next generation all-sky surveys. The results confirm that large sets of discoveries can be handled very efficiently resulting in good quality orbits. In these test we lost only 0.6 to 1.3% of the possible objects with a false identification rate in the range 0.02 to 0.06%.

show abstract

From Astrometry to Celestial Mechanics: Orbit Determination with Very Short Arcs

Milani

Knežević

2005

A Comparison of the Dynamical Evolution of Planetary Systems

View full text Add to dashboard Cite

Abstract.Contemporary surveys provide a huge number of detections of small solar system bodies, mostly asteroids. Typically, the reported astrometry is not enough to compute an orbit and/or perform an identification with an already discovered object. The classical methods for preliminary orbit determination fail in such cases: a new approach is necessary. When the observations are not enough to compute an orbit we represent the data with an attributable (two angles and their time derivatives). The undetermined variables range and range rate span an admissible region of solar system orbits, which can be sampled by a set of Virtual Asteroids (VAs) selected by an optimal triangulation. The attributable results from a fit and has an uncertainty represented by a covariance matrix, thus the predictions of future observations can be described by a quasi-product structure (admissible region times confidence ellipsoid), which can be approximated by a triangulation with each node surrounded by a confidence ellipsoid. The problem of identifying two independent short arcs of observations has been solved. For each VA in the admissible region of the first arc we consider prediction at the time of the second arc and the corresponding covariance matrix, and we compare them with the attributable of the second arc with its own covariance. By using the penalty (increase in the sum of squares, as in the algorithms for identification) we select the VAs which can fit together both arcs and compute a preliminary orbit. Even two attributables may not be enough to compute an orbit with a convergent differential corrections algorithm. The preliminary orbits are used as first guess for constrained differential corrections, providing solutions along the Line Of Variations (LOV) which can be used as second generation VAs to further predict the observations at the time of a third arc. In general the identification with a third arc will ensure a least squares orbit, with uncertainty described by the covariance matrix.

show abstract

Orbit determination with very short arcsII. Identifications

Cited by 63 publications

References 19 publications

Unbiased orbit determination for the next generation asteroid/comet surveys

Unbiased orbit determination for the next generation asteroid/comet surveys

Topocentric orbit determination: Algorithms for the next generation surveys

From Astrometry to Celestial Mechanics: Orbit Determination with Very Short Arcs

Contact Info

Product

Resources

About