24 research outputs found
Apparent close approaches between near-Earth asteroids and quasars. Precise astrometry and frame linking
No full textReproduced with permission. Copyright ESO. Article published by EDP Sciences and available at www.aanda.org.International audienceAims. We investigate the link between the International Celestial Reference Frame (ICRF) and the dynamical reference frame realized by the ephemerides of the Solar System bodies. Methods. We propose a procedure that implies a selection of events for asteroids with accurately determined orbits crossing the CCD field containing selected quasars. Using a Bulirsch-Stoer numerical integrator, we constructed 8-years (2010-2018) ephemerides for a set of 836 numbered near-Earth asteroids (NEAs). We searched for close encounters (within a typical field of view of groundbased telescopes) between our selected set of asteroids and quasars with high-accuracy astrometric positions extracted from the Large Quasars Astrometric Catalog (LQAC). Results. In the designated period (2010-2018), we found a number of 2924, 14 257, and 6972 close approaches (within 10') between asteroids with a minimum solar elongation value of 60◦and quasars from the ICRF-Ext2, the Very Large Baseline Array Calibrator Survey (VLBA-CS), and the Very Large Array (VLA), respectively. This large number of close encounters provides the observational basis needed to investigate the link between the dynamical reference frame and the ICRF
Near infra-red spectroscopy of the asteroid 21 Lutetia. II. Rotationally resolved spectroscopy of the surface
Get PDFReproduced with permission. Copyright ESO. Article published by EDP Sciences and available at http://www.aanda.orgInternational audienceAims. In the framework of the ground-based science campaign dedicated to the encounter with the Rosetta spacecraft, the mineralogy of the asteroid (21) Lutetia was investigated. Methods. Near-infrared (NIR) spectra of the asteroid in the 0.8−2.5 μm spectral range were obtained with SpeX/IRTF in remote observing mode from Meudon, France in March and April 2006. We analysed these data together with previously acquired spectra - March 2003, August 2004. I-band relative photometric data obtained on 20 January 2006 using the 105 cm telescope from Pic du Midi, France has been used to build the ephemeris for physical observations. A χ2 test using meteorite spectra from the RELAB database was performed in order to find the best fit of complete visible + infrared (VNIR) spectra of Lutetia. Results. The new spectra reveal no absorption features. We find a clear spectral variation (slope), and a good correspondence between spectral variations and rotational phase. Two of the most different spectra correspond to two opposite sides of the asteroid (sub-Earth longitude difference around 180◦). For the neutral spectra a carbonaceous chondrite spectrum yields the best fit, while for those with a slightly positive slope the enstatitic chondrite spectra are the best analog. Based on the chosen subset of the meteorite samples, our analysis suggests a primitive, chondritic nature for (21) Lutetia. Differences in spectra are interpreted in terms of the coexistence of several lithologies on the surface where the aqueous alteration played an important role
EURONEAR: First results
No full textInternational audienceThe European Near Earth Asteroid Research (EURONEAR) is a project which envisions to build a coordinated network which will follow-up and recover potentially hazardous asteroids (PHAs) and near earth asteroids (NEAs). We aim to include in EURONEAR two automated 1 m telescopes located in Chile and Europe, in addition to other non-permanent facilities. Astrometry will be the main aim of the project in order to secure and follow-up newly discovered NEAs, also to recover PHAs at their second or following oppositions, while photometry of bright PHAs will bring information on their physical properties. In this paper, first we review briefly the existent and past NEAs programs. Next, we include the results obtained in 2006 from three observing runs at Pic du Midi using the 1 m telescope, Haute-Provence employing the 1.2 m telescope, and Bucharest using a small 23 cm telescope. These add a total of 153 positions for 16 PHAs and NEAs, which were accepted by Minor Planet Center. Recently, a 1 m telescope was allocated by ESO in La Silla to be automated and used as the Southern dedicated facility by EURONEAR
EURONEAR - First Results at Pic du Midi
No full textInternational audienceEURONEAR - The European Near Earth Asteroid Research is a project initiated recently by a small team presently based in France, Romania, and South Africa. It envisions to build a coordinated network which will follow-up and recover Potentially Hazardous Asteroids (PHAs) and Near Earth Asteroids (NEAs), using time available at 1m class telescopes in Europe and elsewhere. Astrometry is the main aim of the project, in order to follow-up and secure newly discovered NEAs, also to recover bright PHAs at their second or following oppositions. Photometry of bright PHAs will allow contributions to determinations of their physical properties. The first observing run took place between 15-24 May 2006, using the 1m telescope at Pic du Midi Observatory in France. 13 PHAs and NEAs were observed there, mostly new objects, flagged as desirable by Minor Planet Center (MPC). 124 astrometric positions were accepted by the MPC and included in the NEODyS database. This is the first run in a series planned to be carried out in the next two years at Pic du Midi and elsewhere. Other potential collaborators are welcomed
EURONEAR - First Results at Pic du Midi
No full textInternational audienceEURONEAR - The European Near Earth Asteroid Research is a project initiated recently by a small team presently based in France, Romania, and South Africa. It envisions to build a coordinated network which will follow-up and recover Potentially Hazardous Asteroids (PHAs) and Near Earth Asteroids (NEAs), using time available at 1m class telescopes in Europe and elsewhere. Astrometry is the main aim of the project, in order to follow-up and secure newly discovered NEAs, also to recover bright PHAs at their second or following oppositions. Photometry of bright PHAs will allow contributions to determinations of their physical properties. The first observing run took place between 15-24 May 2006, using the 1m telescope at Pic du Midi Observatory in France. 13 PHAs and NEAs were observed there, mostly new objects, flagged as desirable by Minor Planet Center (MPC). 124 astrometric positions were accepted by the MPC and included in the NEODyS database. This is the first run in a series planned to be carried out in the next two years at Pic du Midi and elsewhere. Other potential collaborators are welcomed
