Spitzer observations of spacecraft target 162173 (1999 JU3)

Campins, H.; Emery, Joshua P.; Kelley, Michael S. P.; Fernández, Yanga; Licandro, J.; Delbò, M.; Barucci, A.; Dotto, E.

doi:10.1051/0004-6361/200912374

Cited by 43 publications

(41 citation statements)

References 16 publications

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“…We expect that the surface of 162173 (1999 JU3) is therefore different in the sense that there might be fewer rocks and boulders and that the surface includes millimetre sized particles (as opposed to the cm-sized gravel on Itokawa). We also find a rigorous lower limit to the thermal inertia of about 100 J m −2 s −0.5 K −1 , similar to Campins et al (2009). This limit is not compatible with a thick dusty regolith covering the entire surface which would result in a very low thermal conductivity and thermal inertia values well below 100 J m −2 s −0.5 K −1 , which would in principle be possible for an object of that size and the relativly slow rotation rate.…”

Section: Thermal Inertia and Surface Roughnesssupporting

confidence: 80%

“…5 bottom) might be related to an additional error introduced by the flux scaling done by Campins et al (2009) to match the short-wavelength part of the spectrum (<14 μm) to the long-wavelength part of the spectrum (>14 μm).…”

Section: Radiometric Diameter and Albedo Solutionmentioning

confidence: 99%

“…The results (radiometric diameter of 0.92 ± 0.12 km, visual geometric albedo of 0.063 +0.020 −0.015 ) which indicate a thermal inertia larger than 500 J m −2 s −0.5 K −1 ), were based on a set of photometric A&A 525, A145 (2011) Subaru and Akari observations and connected to simplified shape and spin-axis assumptions. Campins et al (2009) have obtained a single-epoch Spitzer infrared spectrograph (IRS) spectrum. They used a spherical shape model, and for the spin-pole orientation they used the extreme case of an equatorial retrograde geometry and a prograde solution published by Abe et al (2008).…”

Section: Introductionmentioning

confidence: 99%

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Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions

Müller

Ďurech

Hasegawa

et al. 2010

A&A

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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 χ 2 -test reveals a strong preference for a retrograde sense of rotation with a spin-axis orientation of λ ecl = 73 • , β ecl = −62 • and P sid = 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).

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Section: Thermal Inertia and Surface Roughnesssupporting

confidence: 80%

Section: Radiometric Diameter and Albedo Solutionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions

Müller

Ďurech

Hasegawa

et al. 2010

A&A

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“…This result was also confirmed by Sugita et al (2012) and Moskovitz et al (2012) who observed the asteroid in June and July 2012 and found no indication of an absorption band in their spectra. Despite the lack of hydration bands in the spectra of 162173 (1999 JU3), the link with primitive carbonaceous chondrites is supported by the flat spectrum and the low albedo of about 0.07 obtained by three different authors Campins et al 2009;Muller et al 2011). Since the asteroid is now becoming too faint for reliable ground-based observations, we will need to wait for the Hayabusa2 space mission to arrive at the asteroid in 2020 to obtain better insight into the possible presence of compositional variations on its surface.…”

Section: Resultsmentioning

confidence: 88%

Rotational spectra of (162173) 1999 JU3, the target of the Hayabusa2 mission

Lazzaro

Barucci

Perna

et al. 2012

A&A

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Context. The Hayabusa2 mission, which will be launched by JAXA in 2014, will return samples from the C-type near-Earth asteroid (162173) 1999 JU3. To better plan the mission, it is important to obtain as many physical characteristics of the asteroid as possible from ground-based observations. Moreover, these can then be calibrated with the in-situ and laboratory studies and be used to better understand other similar objects. Regarding the surface composition of the target asteroid, previous spectroscopic studies in the visible provided conflicting results for the possible presence of a deep absorption band, which is usually related to aqueous alteration processes. Aims. Our goal is to better understand the surface composition of asteroid (162173) 1999 JU3, and how it relates to the spectral differences observed by diverse authors at different epochs and telescopes. Moreover, to support the JAXA mission planning, we aim to constrain the level of aqueous alteration and thermal activity undergone by the object. Methods. The adopted methodology was to observe different regions of the surface of the asteroid that rotates around its axis. Spectroscopic observations that cover about 70% of its surface were therefore obtained at the SOAR telescope in Chile on 2012 July 9−10. Results. Our results indicate that the surface of asteroid (162173) 1999 JU3 presents featureless spectra with very little variation. Conclusions. No sign of an absorption feature that could be related to aqueous alteration processes is detectable in the observed spectra.

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“…According to Campins et al (2009), "The measured spectral energy distribution (SED) depends on the object's size, composition, and temperature distribution. This last term is dependent on several factors, including distance from the Sun, albedo, thermal inertia, surface roughness, rotation rate, shape, and spin-pole orientation".…”

Section: Thermal Modelmentioning

confidence: 99%

5–14 μmSpitzerspectra of Themis family asteroids

Licandro

Hargrove

Kelley

et al. 2012

A&A

Self Cite

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Context. The Themis collisional family is one of the largest and best established families in the main belt. Composed of primitive asteroids, there is evidence that water is likely present in a large fraction of its members, either in aqueously altered silicates or in water ice reservoirs. The study of the abundance of water in the outer asteroid belt is important as it may be linked to the origin of Earth's water. Studying the Themis family can also help to constrain the compositional and thermal environment in the region of the solar nebula where these asteroids formed. Aims. Our aim is to constrain the composition and thermal properties of the surfaces of several Themis family asteroids. Methods. We present 5-14 μm spectra of 8 Themis family asteroids observed with Spitzer: (222) Lucia, (223) Rosa, (316) Goberta, (383) Janina, (468) Lina, (492) Gismonda, (515) Athalia, and (526) Jena. We determine their diameters, geometric albedos and beaming parameters using the near-Earth asteroid thermal model. Their emissivity spectra are studied in order to determine if they exhibit an emission plateau from 9 to 12 μm which has been observed in other primitive asteroids and attributed to fine-grained silicates (the Si-O stretch fundamental). Results. The derived mean albedo of our sample of Themis family asteroids isp V = 0.07 ± 0.02, and the mean beaming parameter is η = 1.05 ± 0.10. The derivedη value is close to unity, which implies that the infrared beaming is not significant, there is likely little night-side emission from the asteroids, and the thermal inertia is probably low. The emissivity spectra of at least 5 of our 8 asteroids show a 9-12 μm emission plateau with spectral contrast of ∼2-4%, similar but smaller than that observed in the spectra of Trojan asteroids and cometary dust. The plateau may be due to the surfaces having either small silicate grains embedded in a relatively transparent matrix, or from a very under-dense (fairy-castle) surface structure. Conclusions. The surfaces of a large fraction of Themis family asteroids with D ∼ 50 km are covered by a fine grained silicate mantle as observed on Trojan asteroids of similar or larger size. The lower amplitude of the silicate emission in Themis family asteroids spectra (2-4%) with respect to that of Trojan asteroids (10-15%) could be attributed to larger dust particles, a slightly denser structure, or a lower silicate dust fraction.

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Spitzer observations of spacecraft target 162173 (1999 JU3)

Cited by 43 publications

References 16 publications

Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions

Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions

Rotational spectra of (162173) 1999 JU3, the target of the Hayabusa2 mission

5–14 μmSpitzerspectra of Themis family asteroids

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