Redetermination of the space weathering rate using spectra of Iannini asteroid family members
Rewriting a shorter abstract.
astro-ph↗
arXiv subjects
Robert Jedicke
Publications and source records attributed to Robert Jedicke.
The Thousand Asteroid Light Curve Survey
We present the results of our Thousand Asteroid Light Curve Survey (TALCS) conducted with the Canada-France-Hawaii Telescope in September 2006. Our untargeted survey detected 828 Main Belt asteroids to a limiting magnitude of g'~22.5 corresponding to a diameter range of 0.4 km <= D <= 10 km. Of these, 278 objects had photometry of sufficient quality to perform rotation period fits. We debiased the observations and light curve fitting process to determine the true distribution of rotation periods and light curve amplitudes of Main Belt asteroids. We confirm a previously reported excess in the fraction of fast rotators but find a much larger excess of slow rotating asteroids (~15% of our sample). A few percent of objects in the TALCS size range have large light curve amplitudes of ~1 mag. Fits to the debiased distribution of light curve amplitudes indicate that the distribution of triaxial ellipsoid asteroid shapes is proportional to the square of the axis-ratio, (b/a)^2, and may be bi-modal. Finally, we find six objects with rotation periods that may be less than 2 hours with diameters between 400 m and 1.5 km, well above the break-up limit for a gravitationally-bound aggregate. Our debiased data indicate that this population represents <4% of the Main Belt in the 1-10 km size range.
astro-ph.EP↗
Detection of Earth-impacting asteroids with the next generation all-sky surveys
We have performed a simulation of a next generation sky survey's (Pan-STARRS 1) efficiency for detecting Earth-impacting asteroids. The steady-state sky-plane distribution of the impactors long before impact is concentrated towards small solar elongations (Chesley and Spahr, 2004) but we find that there is interesting and potentially exploitable behavior in the sky-plane distribution in the months leading up to impact. The next generation surveys will find most of the dangerous impactors (>140m diameter) during their decade-long survey missions though there is the potential to miss difficult objects with long synodic periods appearing in the direction of the Sun, as well as objects with long orbital periods that spend much of their time far from the Sun and Earth. A space-based platform that can observe close to the Sun may be needed to identify many of the potential impactors that spend much of their time interior to the Earth's orbit. The next generation surveys have a good chance of imaging a bolide like 2008TC3 before it enters the atmosphere but the difficulty will lie in obtaining enough images in advance of impact to allow an accurate pre-impact orbit to be computed.
astro-ph.EP↗
The Distribution of Basaltic Asteroids in the Main Belt
We present the observational results of a survey designed to target and detect asteroids whose colors are similar to those of Vesta family members and thus may be considered as candidates for having a basaltic composition. Fifty basaltic candidates were selected with orbital elements that lie outside of the Vesta dynamical family. Optical and near-infrared spectra were used to assign a taxonomic type to 11 of the 50 candidates. Ten of these were spectroscopically confirmed as V-type asteroids, suggesting that most of the candidates are basaltic and can be used to constrain the distribution of basaltic material in the Main Belt. Using our catalog of V-type candidates and the success rate of the survey, we calculate unbiased size-frequency and semi-major axis distributions of V-type asteroids. These distributions, in addition to an estimate for the total mass of basaltic material, suggest that Vesta was the predominant contributor to the basaltic asteroid inventory of the Main Belt, however scattered planetesimals from the inner Solar System (a < 2.0 AU) and other partially/fully differentiated bodies likely contributed to this inventory. In particular, we infer the presence of basaltic fragments in the vicinity of asteroid 15 Eunomia, which may be derived from a differentiated parent body in the middle Main Belt (2.5 < a < 2.8). We find no asteroidal evidence for a large number of previously undiscovered basaltic asteroids, which agrees with previous theories suggesting that basaltic fragments from the ~100 differentiated parent bodies represented in meteorite collections have been "battered to bits" [Burbine, T.H., Meibom, A., Binzel, R.P., 1996. Mantle material in the Main Belt: Battered to bits? Met. & Planet. Sci. 31, 607].
astro-ph↗
A Spectroscopically Unique Main Belt Asteroid: 10537 (1991 RY16)
We present visible and near-infrared reflectance spectra and interpreted surface mineralogy for asteroid 10537 (1991 RY16). The spectrum of this object is without precedent amongst the Main Belt asteroids. A unique absorption band centered at 0.63 microns could be attributed to one of several mineralogies. Pronounced 1- and 2-micron absorption bands suggest that the composition of 10537 is a mixture of pyroxenes and olivine and that it originated from a parent body that was partially or fully differentiated. The closest available analog is the large Main Belt asteroid 349 Dembowska but 10537 may be an isolated fragment from a completely eroded parent body.
astro-ph↗
Orbit Determination with Topocentric Correction: Algorithms for the Next Generation Surveys
Given a set of astrometric observations of the same object, the problem of orbit determination is to compute the orbit and to assess its uncertainty and reliability. For the next generation surveys, with much larger number density of observed objects, new algorithms or substantial revisions of the classical ones are needed. The problem has three main steps, preliminary orbit, least squares orbit, and quality control. The classical theory of preliminary orbits was incomplete: the consequences of the topocentric correction had not been fully studied. We show that it is possible to account for this correction, possibly with an increase in the number of preliminary solutions, without impairing the overall orbit determination performance. We have developed modified least squares orbit determination algorithms that can be used to improve the reliability of the procedure. We have tested the complete procedure on two simulations with number densities comparable to that expected from the next generation surveys such as Pan-STARRS and LSST. To control the problem of false identifications we have introduced a quality control on the fit residuals based on an array of metrics and a procedure to remove duplications and contradictions in the output. The results confirm that large sets of discoveries can be obtained with good quality orbits and very high success rate losing only 0.6 to 1.3% of objects and a false identification rate in the range 0.02 to 0.06%.
astro-ph↗
Efficient intra- and inter-night linking of asteroid detections using kd-trees
The Panoramic Survey Telescope And Rapid Response System (Pan-STARRS) under development at the University of Hawaii's Institute for Astronomy is creating the first fully automated end-to-end Moving Object Processing System (MOPS) in the world. It will be capable of identifying detections of moving objects in our solar system and linking those detections within and between nights, attributing those detections to known objects, calculating initial and differentially-corrected orbits for linked detections, precovering detections when they exist, and orbit identification. Here we describe new kd-tree and variable-tree algorithms that allow fast, efficient, scalable linking of intra and inter-night detections. Using a pseudo-realistic simulation of the Pan-STARRS survey strategy incorporating weather, astrometric accuracy and false detections we have achieved nearly 100% efficiency and accuracy for intra-night linking and nearly 100% efficiency for inter-night linking within a lunation. At realistic sky-plane densities for both real and false detections the intra-night linking of detections into `tracks' currently has an accuracy of 0.3%. Successful tests of the MOPS on real source detections from the Spacewatch asteroid survey indicate that the MOPS is capable of identifying asteroids in real data.
astro-ph↗
The Size-Frequency Distribution of Dormant Jupiter Family Comets
We estimate the total number and the slope of the size frequency distribution (SFD) of dormant Jupiter Family Comets (JFCs) by fitting a one-parameter model to the known population. We first select 61 Near Earth Objects (NEOs) that are likely to be dormant JFCs because their orbits are dynamically coupled to Jupiter (Bottke et al, 2002). Then, from the numerical simulations of Levison & Duncan (1997), we construct an orbit distribution model for JFCs in the NEO orbital element space. We assume an orbit independent SFD for all JFCs, the slope of which is our unique free parameter. Finally, we compute observational biases for dormant JFCs using a calibrated NEO survey simulator (Jedicke et al. 2003). By fitting the biased model to the data, we estimate that there are ~75 dormant JFCs with H<18 in the NEO region and that the slope of their cumulative SFD is -1.5 +/- 0.3. Our slope for the SFD of dormant JFCs is very close to that of active JFCs as determined by Weissman and Lowry (2003). Thus, we argue that when JFCs fade they are likely to become dormant rather than to disrupt and that the fate of faded comets is size independent. Our results imply that the size distribution of the JFC progenitors - the scattered disk trans-Neptunian population - either (i) has a similar and shallow SFD or (i') is slightly steeper and physical processes acting on the comets in a size-dependent manner creates the shallower active comet SFD. Our measured slope, typical of collisionally evolved populations with a size dependent impact strength (Benz and Asphaug 1999), suggests that scattered disk bodies reached collisional equilibrium inside the proto-planetary disk prior to their removal from the planetary region.
astro-ph↗
Identifying Near Earth Object Families
The study of asteroid families has provided tremendous insight into the forces that sculpted the main belt and continue to drive the collisional and dynamical evolution of asteroids. The identification of asteroid families within the NEO population could provide a similar boon to studies of their formation and interiors. In this study we examine the purported identification of NEO families by Drummond (2000) and conclude that it is unlikely that they are anything more than random fluctuations in the distribution of NEO osculating orbital elements. We arrive at this conclusion after examining the expected formation rate of NEO families, the identification of NEO groups in synthetic populations that contain no genetically related NEOs, the orbital evolution of the largest association identified by Drummond (2000), and the decoherence of synthetic NEO families intended to reproduce the observed members of the same association. These studies allowed us to identify a new criterion that can be used to select real NEO families for further study in future analyses, based on the ratio of the number of pairs and the size of strings to the number of objects in an identified association.
astro-ph↗
A Strategy for Finding Near Earth Objects with the SDSS Telescope
We present a detailed observational strategy for finding Near Earth Objects (NEOs) with the Sloan Digital Sky Survey (SDSS) telescope. We investigate strategies in normal, unbinned mode as well as binning the CCDs 2x2 or 3x3, which affects the sky coverage rate and the limiting apparent magnitude. We present results from 1 month, 3 year and 10 year simulations of such surveys. For each cadence and binning mode, we evaluate the possibility of achieving the Spaceguard goal of detecting 90% of 1 km NEOs (absolute magnitude H <= 18 for an albedo of 0.1). We find that an unbinned survey is most effective at detecting H <= 20 NEOs in our sample. However, a 3x3 binned survey reaches the Spaceguard Goal after only seven years of operation. As the proposed large survey telescopes (PanStarss; LSST) are at least 5-10 years from operation, an SDSS NEO survey could make a significant contribution to the detection and photometric characterization of the NEO population.
astro-ph↗