Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions
Context. Near-Earth asteroid 162173 (1999 JU3) is a potential flyby and rendezvous target for interplanetary missions because of its easy-to-reach orbit. The physical and thermal properties of the asteroid are relevant for establishing the scientific mission goals and also important in the context of near-Earth object studies in general.
Aims: Our goal was to derive key physical parameters such as shape, spin-vector, size, geometric albedo, and surface properties of 162173 (1999 JU3).
Methods: With three sets of published thermal observations (ground-based N-band, Akari IRC, Spitzer IRS), we applied a thermophysical model to derive the radiometric properties of the asteroid. The calculations were performed for the full range of possible shape and spin-vector solutions derived from the available sample of visual lightcurve observations.
Results: The near-Earth asteroid 162173 (1999 JU3) has an effective diameter of 0.87 ± 0.03 km and a geometric albedo of 0.070 ± 0.006. The χ2-test reveals a strong preference for a retrograde sense of rotation with a spin-axis orientation of λecl = 73°, βecl = -62° and Psid = 7.63 ± 0.01 h. The most likely thermal inertia ranges between 200 and 600 J m-2 s-0.5 K-1, about a factor of 2 lower than the value for 25143 Itokawa. This indicates that the surface lies somewhere between a thick-dust regolith and a rock/boulder/cm-sized, gravel-dominated surface like that of 25143 Itokawa. Our analysis represents the first time that shape and spin-vector information has been derived from a combined data set of visual lightcurves (reflected light) and mid-infrared photometry and spectroscopy (thermal emission).
Astronomy and Astrophysics
- Pub Date:
- January 2011
- minor planets;
- asteroids: individual: 162173 (1999 JU3);
- radiation mechanisms: thermal;
- techniques: photometric;
- infrared: planetary systems;
- Astrophysics - Earth and Planetary Astrophysics
- 6 pages, 5 figures, 2 tables, accepted for publication in A&