1 / 16

The relevance of asteroid occultation measurements

The relevance of asteroid occultation measurements. Detlef Koschny, Gerhard Drolshagen, Nicolas Bobrinsky European Space Agency, Solar System Missions Division Keplerlaan 1 NL-2201 AZ Noordwijk ZH Detlef.Koschny@esa.int. Asteroid occultation primer Predictions How are they observed?

daxia
Download Presentation

The relevance of asteroid occultation measurements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The relevance of asteroid occultation measurements Detlef Koschny, GerhardDrolshagen, Nicolas Bobrinsky European Space Agency,Solar System Missions DivisionKeplerlaan 1NL-2201 AZ Noordwijk ZH Detlef.Koschny@esa.int Asteroid occultation primerPredictionsHow are they observed? Results: Size and shapeResults: PositionsConclusions Image courtesy: David A. Hardy

  2. Asteroid occultation primer Prediction error because of position uncertainties

  3. These observations are relevant because: • This is the only direct method of determining shape and size of an object other than going there (optical interferometry was used and published in Feb 2009 – almost direct but not quite, see Delbo 2009, using the VLT/MIDI) • The main contributing error in the determined astrometric position is the error of the star position in the catalog => milliarcsec accuracy is achievable

  4. These observations are relevant because: • This is the only direct method of determining shape and size of an object other than going there (optical interferometry was used and published in Feb 2009 – almost direct but not quite, see Delbo 2009, using the VLT/MIDI) • The main contributing error in the determined astrometric position is the error of the star position in the catalog => milliarcsec accuracy is achievable Is it useful to include occultation work in our SSA systems?

  5. Occultation primer - predictions Steve Preston’s predictions Hristo Pavlov’s ‘OccultWatcher’ David Herald’s ‘Occult’ Oliver Klos’ maps

  6. How are they observed? • Use telescope with video camera to record a video of the star • Ensure high-accurate timing measurements by inserting GPS-synchronized time into video

  7. Resulting video

  8. Star intensity versus time

  9. Star intensity versus time Occultation

  10. Results: Size/shape • Combining several observations, size and possibly even shape of theasteroid (in the planeof observation) can bedetermined directly

  11. Occultation observations Shape model derived from photometric observations

  12. Results: Positions • D. Herald (Australia) has set up an interface with the Minor Planet Center to allow submission of positions determined by occultations, using the IAU observatory code 244. • Accuracies can be obtained to 0.01” down to 0.0002” relative to the star. Star accuracies are about 0.07” (=> Optical astrometry results in ~0.1”) • When better positions available data can be improved (e.g. using the USNO Robotic Astrometric Telescope, Zacharias et al. 2009; J-MAPS – Gaume + Dorland 2008; Gaia)

  13. Conclusions - I • Asteroid occultations (= asteroid occults star) can provide shape and size of asteroids in the plane of observation • They can provide high-accuracy position measurements • Accuracy limited by accuracy of star in catalogue • Observation limit is the magnitude of the star (not the asteroid) • Observations mainly done by amateurs • Pipeline for shape/size: see work by Euraster, E. Frappa • Pipeline for position measurements set up by D. Herald • BUT: For objects <a few km accuracy issues • Timing accuracy => go to higher frame rate • Star positions => get better star catalogue • Path uncertainty => use more observing stations

  14. Conclusions - II • Possible improvements • One central system for predictions • One central database for results • Use larger aperture for more events (fainter stars) or just better signal-to-noise • Organise campaigns forshape/centroid determinations • Use better cameras,e.g. EM-CCDs; more dynamics,higher frame rate • Go space-based – Kepler?

  15. Conclusions - III • Yes… but: • 0.02 s timing accuracy needs to be ensured – higher accuracy preferred (use high-speed cameras) • Good signal-to-noise needed • Enough stations to cover predicted path and still give reasonable spatial accuracy are needed Is it useful to include occultation work in our SSA systems?

  16. Resources • Steve Preston’s predictions • http://www.asteroidoccultation.com/ • Occult • http://www.lunar-occultations.com/iota/occult4.htm • OccultWatcher (prediction software) • http://hristopavlov.net/OccultWatcher/OccultWatcher.html • European Asteroidal Occultation Network • http://www.astrosurf.com/eaon/ • Euraster – results from European occultation observations • http://www.euraster.net/ • Asteroid occultation page by the Czech Astronomical Society (on behalf of the International Occultation Timing Association IOTA • http://mpocc.astro.cz/ • Database of observations by Mike Kretlow • http://sky-lab.net/?Solar_System_-_Occultations • LiMovie – Light Measurement tool for occulations • http://www005.upp.so-net.ne.jp/k_miyash/occ02/limovie_en.html • Bruno Sicardy’s home page • http://www.lesia.obspm.fr/perso/bruno-sicardy/ • Leslie Young’s home page • http://www.boulder.swri.edu/~layoung/occl/ • Archive of occultations in the Planetary Data System (PDS) • http://www.psi.edu/pds/resource/occ.html • Japanese page on occultations • http://uchukan.satsumasendai.jp/data/occult-e/occult-e.html • Australasian page on occultations • http://occsec.wellington.net.nz/ • North America’s page on occultations • http://www.asteroidoccultation.com/observations/Results

More Related