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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.08.011 Byline: Stephen D. Wolters (a), Simon F. Green (a), Neil McBride (a), John K. Davies (b) Keywords: Asteroids; Thermal infrared spectrometry and spectrophotometry; Near-Earth asteroids Abstract: We present thermal infrared photometry and spectrophotometry of four near-Earth asteroids (NEAs), namely (433) Eros, (66063) 1998 RO.sub.1, (137032) 1998 UO.sub.1, and (138258) 2000 GD.sub.2, using the United Kingdom Infrared Telescope (UKIRT) in 2002. For two objects, i.e. (433) Eros and (137032) 1998 UO.sub.1, quasi-simultaneous optical observations were also obtained, using the Jacobus Kapteyn Telescope (JKT). For (127032) 1998 UO.sub.1, we obtain a rotation period P=3.0[+ or -]0.1 h and an absolute visual magnitude H.sub.V=16.7[+ or -]0.4. The Standard Thermal Model (STM), Fast Rotating Model (FRM) and near-Earth asteroid Thermal Model (NEATM) have been fitted to the IR fluxes to determine effective diameters D.sub.eff, geometric albedos p.sub.v, and beaming parameters I*. The derived values are (433) Eros: D.sub.eff=23.3[+ or -]3.5 km (at lightcurve maximum), p.sub.v=0.24[+ or -]0.07, I*=0.95[+ or -]0.19; (66063) 1998 RO.sub.1: D.sub.eff= 0.62.sub.-0.09.sup.+0.25 km, p.sub.v= 0.30.sub.-0.17.sup.+0.09; (137032) 1998 UO.sub.1: D.sub.eff Author Affiliation: (a) Planetary and Space Sciences Research Institute, The Open University, Milton Keynes, MK7 6AA, UK (b) Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK Article History: Received 2 February 2007; Revised 7 August 2007

We present a number of spectra of Near-Earth Objects taken in the period 1998-2003 with two different instruments (CGS4 and UIST) on the UKIRT telescope. Since observations with CGS4 require multiple spectral fragments to be observed sequentially and then spliced together we assess the re|lability of this technique using comparisons between multiple observations of the same object, between observations of the same object with both instruments and with independent spectra of common objects. We conclude that while problems in the spectral splicing can occur, they are usually intuitively obvious and that overall our dataset is sound. The objects for which we present new spectral data are: 1627 Ivar, 4179 Toutatis, 5381 Sekhmet, (5587) 1990 SB, 6489 Golevka, (11405) 1999 C[V.sub.3], (14402) 1991 DB, 25143 Itokawa, (25330) 1999 K[V.sub.4], (52760) 1998 M[L.sub.14], (66391) 1999 K[W.sub.4], and (101955) 1999 R[Q.sub.36]. Our results, together with albedo data from the literature, suggest carbonaceous compositions for 25330 and 101955. The available data for 14402 suggest it may belong to the relatively rare M class. Our analysis suggests an S or Sq classification for 52760 and a V classification for 5381 Sekhmet. For all remaining objects the UKIRT data are consistent with published spectral classifications. We find that only 3 of the 12 objects are not S/Q/V-class, which is roughly consistent with the results of Binzel et al. [Binzel, R.P., Rivkin, A.S., Stuart, J.S., Harris, A.W., Bus, S.J., Burbine, T.H., 2004. Icarus 170, 259-294]. Four spectra of Toutatis taken over a range of solar phase angles between 0.7[degrees]-81 [degrees] and at intervals of several weeks are indistinguishable within the uncertainties and therefore do not reveal any evidence for phase reddening or surface variegation. Keywords: Asteroids; Infrared observations; Spectroscopy

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.02.001 Byline: Frank Postberg (a), Sascha Kempf (a), Ralf Srama (a), Simon F. Green (b), Jon K. Hillier (b), Neil McBride (b), Eberhard Grun (a)(c) Keywords: Jupiter; Interplanetary dust; Io; Volcanism; Satellites; atmospheres Abstract: The Cassini spacecraft encountered Jupiter in late 2000. Within more than 1 AU of the gas giant the Cosmic Dust Analyser onboard the spacecraft recorded the first ever mass spectra of jovian stream particles. To determine the chemical composition of particles, a comprehensive statistical analysis of the dataset was performed. Our results imply that the vast majority (>95%) of the observed stream particles originate from the volcanic active jovian satellite Io from where they are sprinkled out far into the Solar System. Sodium chloride (NaCl) was identified as the major particle constituent, accompanied by sulphurous as well as potassium bearing components. This is in contrast to observations of gas in the ionian atmosphere, its co-rotating plasma torus, and the neutral cloud, where sulphur species are dominant while alkali and chlorine species are only minor components. Io has the largest active volcanoes of the Solar System with plumes reaching heights of more than 400 km above the moons surface. Our in situ measurements indicate that alkaline salt condensation of volcanic gases inside those plumes could be the dominant formation process for particles reaching the ionian exosphere. Author Affiliation: (a) MPI fur Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany (b) Planetary and Space Sciences Research Institute, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK (c) Hawaii Institute of Geophysics and Planetology, University of Hawaii, 1680 East West Road, Honolulu, HI 96822, USA Article History: Received 21 October 2005; Revised 26 January 2006

We present thermal infrared photometry and spectrophotometry of six Near-Earth Asteroids (NEAs) using the 3.8 m United Kingdom Infrared Telescope (UKIRT) together with quasi-simultaneous optical observations of five NEAs taken at the 1.0 m Jacobus Kapteyn Telescope (JKT). For Asteroid (6455) 1992 HE we derive a rotational period P = 2.736 [+ or -] 0.002 h, and an absolute visual magnitude H = 14.32 [+ or -] 0.24. For Asteroid 2002 H[K.sub.12] we derive H = 18.22 (+0.37, -0.30). The Standard Thermal Model (STM), the Fast Rotating Model (FRM) and the Near-Earth Asteroid Thermal Model (NEATM) have been fitted to the measured fluxes to derive albedos and effective diameters. The derived geometric albedos and effective diameters are (6455) 1992 HE: [p.sub.[upsilon]] = 0.26 [+ or -] 0.08, [D.sub.eff] = 3.55 [+ or -] 0.5 km; 1999 H[F.sub.1]: [p.sub.[upsilon]] = 0.18 [+ or -] 0.07, [D.sub.eff] = 3.73 (+1.0, -0.5) km; 2000 E[D.sub.104]: [p.sub.[upsilon]] = 0.18 [+ or -] 0.05, [D.sub.eff] = 1.21 [+ or -] 0.2 km; 2002 H[K.sub.12]: [p.sub.[upsilon]] = 0.24 (+0.25, -0.11), [D.sub.eff] = 0.62 [+ or -] 0.2 km; 2002 N[X.sub.18]: [p.sub.[upsilon]] = 0.031 [+ or -] 0.009, [D.sub.eff] = 2.24 [+ or -] 0.3 km; 2002 Q[E.sub.15]: [p.sub.[upsilon]] = 0.15 (+0.08, -0.06), [D.sub.eff] = 1.94 [+ or -] 0.4 km. The limitations of using the NEATM to observe NEAs at high phase angles are discussed. Keywords: Asteroids; Infrared observations; Photometry: Spectrophotometry

We present new visible-infrared (V-J) observations of 17 Kuiper Belt objects, of which 14 were observed in the visible and infrared wavebands simultaneously to limit the effects of lightcurve variations. Combining these data with our previously published visible-infrared data provides a dataset of 29 objects, 25 of which offer simultaneous V-J colors. We examine the resulting dataset for evidence of relationships between physical properties and orbital characteristics. We find no evidence of a color-size relationship (as previously suspected), at least over the size range sampled. The dataset supports the trend, reported elsewhere, that there is a predominance of red material on the surfaces of objects having perihelia beyond 40 AU. Our data are also supportive, albeit weakly, of a reported correlation between inclination and color in the classical Kuiper Belt--although it is perhaps more correct to say that our data show that there appears to be a lack of low inclination blue objects. Our V-J colors appear broadly correlated with published optical colors, thus suggesting that the surfaces of Kuiper Belt objects are subject to a single reddening agent. Keywords: Kuiper Belt objects; Photometry; Infrared; Visible

We present infrared (JHK) and visible (VRI) observations of the Centaurs 2060 Chiron, 5145 Pholus, 7066 Nessus, 1995 [DW.sub.2], 1995 GO, and 1997 [CU.sub.26]. These are combined whenever possible to derive relative reflectance spectra between 0.55 and 2.2 [[micro]meter]. The extreme visible to infrared color of Pholus found in 1992 is confirmed, as is the redness of 7066 Nessus. We refine the rotation period and lightcurve of 1995 GO and resolve ambiguous determinations of its V-R color. We find that 1997 [CU.sub.26] has V-JHK colors very similar to 1995 GO. Our data imply changes in the visible-IR color of 2060 Chiron with level of cometary activity and, aware of the difficulties of combining nonsimultaneous data, we comment on the likely reality of these. We find a wide range of reflectances within the Centaur population with no obvious correlations with heliocentric distance. Key Words: Centaurs; Kuiper Belt; photometry; infrared; visible.

Minor Planet 1996 PW is unusual in having the orbital characteristics of a long period comet but showing no sign of cometary activity around the time of its discovery. We present optical data which reveals a double peaked lightcurve (period 35.44 [+ or -] 0.02 hrs and amplitude 0.44 [+ or -] 0.03 magnitudes) and VRIJHK photometry which shows colors (V - R = 0.56 [+ or -] 0.04, V - I = 1.03 [+ or -] 0.06, V - J = 1.80 [+ or -] 0.05, V - H = 2.19 [+ or -] 0.05, and V - K = 2.32 [+ or -] 0.05) typical of D type asteroids and suspected bare comet nuclei. A low signal to noise reflectance spectrum in the K band shows a fiat continuum with no evidence for spectral features. Image profiles from co-added frames in the R band indicate no apparent cometary activity with an implied upper limit to the dust production rate of 0.03 kg [s.sup.-1]. Key Words: asteroids; rotation; photometry; infrared; comets.

Minor planet 1993SC, with a semi-major axis of 39.67 AU, is one of the brightest of numerous recently discovered objects with orbits close to or beyond Neptune. It is a member of the Kuiper Belt, a planetesimal population remaining from the formation of the Solar System. We present optical photometry which indicates a lightcurve amplitude of less than 0.2 magnitude for 1993SC and which does not support the 0.5 magnitude lightcurve of I. P. Williams et al. (Icarus 116, 180-185, 1995). We derive (Kron-Cousins photometric system) V - R = 0.54 [+ or -] 0.14, V - I = 0.97 [+ or -] 0.14, and V - J = 2.08 [+ or -] 0.15, which confirm that 1993SC has optical/infrared colors closer to Centaur 1993H[A.sub.2] than to the extremely red 5145 Pholus. We also find that VRI colors published by J. X. Luu and D.C. Jewitt (Astron. J. 111, 499-503, 1996) are inconsistent with their reflectance spectrum of 1993SC and we derive new values from their reflectance spectrum of V - R = 0.56 [+ or -] 0.08 and V - I = 1.19 [+ or -] 0.18, which give reasonable agreement with our results.

A study shows that the rotational lightcurve of Apollo asteroid 4179 Toutatis is not periodic and has a large amplitude of about 1.2 magnitudes. This could be due to complex and tumbling rotation of the asteroid, with a characteristic period of three to seven days. The study is done using data collected from asteroid observation in Dec 1992, when it passed within 0.0242 AU of Earth.

We present a reflectance spectrum of 2060 Chiron over the wavelength range 1.6-2.2 (mu)m. The 2-(mu)m water ice absorption feature seen in several other Centaurs at (lambda) = 2.03 (mu)m is identified at the 5% level below the continuum. Key Words: Chiron; Centaurs; spectroscopy.

Thermal infrared observations of the near-Earth asteroids 2100 Ra-Shalom and 1991 EE are presented and interpreted with the aid of published asteroid thermal models. The broad wavelength range covered allows the best fitting of a family of model spectra to be selected, eliminating the ambiguity associated with deriving model parameters from observations at just one or two thermal wavelengths. Neither the 'standard' thermal model nor the 'fast rotating' model provide good fits to the thermal spectra. Much improved fits are obtained with a modified standard thermal model with values of the model 'beaming' parameter, [Eta], significantly higher than normally assumed in the standard thermal model. The results for the Aten asteroid 2100 Ra-Shalom provide convincing confirmation that this object has an unusually high surface thermal inertia. The resulting optical albedos (on the H, G magnitude system) and effective diameters are 0.13 [+ or -] 0.04 and 2.48 [+ or -] 0.35 km for 2100 Ra-Shalom (near lightcurve maximum) and 0.30 [+ or -] 0.10 and 1.01 [+ or -] 0.15 km for 1991 EE (referred to the lightcurve mean magnitude). The derived size for 2100 Ra-Shalom is consistent with previous estimates but the moderate albedo, coupled with infrared colors more typical of S-types, leads us to question its classification as C-type. These are the first size and albedo determinations for the Apollo asteroid 1991 EE. The near infrared colors and albedo of 1991 EE suggest an S-type classification. Key Words: asteroids; infrared observations.

Abstract: During its cruise phase, prior to encountering Jupiter, the Cosmic Dust Analyser (CDA) onboard the Cassini spacecraft returned time of flight mass spectra (TOF MS) of two interplanetary dust particles. Both particles were found to be iron-rich, with possible traces of hydrogen, carbon, nickel, chromium, manganese, titanium, vanadium and minor silicates. Carbon, hydrogen, oxygen and potassium are also present as possible contaminants of the impact target of CDA. Silicates and magnesium do not feature predominantly in the spectra; this is surprising considering the expected dominance of silicate-rich minerals in interplanetary dust particles. The particle masses are and . The corresponding radii ranges for the particles, assuming densities from 7874–2500 kg m−3 are 0.7–4 μm and 2.6–6.8 μm, respectively. With the same density assumptions the β values (ratio of radiation pressure to gravitational force) are estimated as 0.027–0.21 and 0.016–0.06 respectively, allowing possible orbits to be calculated. The resulting orbits are bound and prograde with semi-major axes, eccentricities and inclinations in the region of 0.3–1.26 AU, 0.4–1.0 and 0–60° for the first particle and 0.8–2.5 AU, 0.2–0.9 and 0–30° for the second. The more probable orbits within these ranges indicate that the first particle is in an Aten-like orbit, whilst the second particle is in an Apollo-like orbit, despite both grains having very similar, predominantly metallic compositions. Other possible orbital solutions for both particles encompass orbits which more closely resemble those of Jupiter-family comets. [Copyright &y& Elsevier]

Abstract: The Huygens probe landed on the then unknown surface of Titan in January 2005. A small, protruding penetrometer, part of the Surface Science Package (SSP), was pushed into the surface material measuring the mechanical resistance of the ground as the probe impacted the landing site. We present laboratory penetrometry into room temperature surface analogue materials using a replica penetrometer to investigate further the nature of Titan’s surface and examine the sensor’s capabilities. The results are then compared to the flight instrument’s signature and suggest the Titan surface substrate material consists of sand-sized particles with a mean grain size ∼2mm. A possible thin 7mm coating with mechanical properties similar to terrestrial snow may overlie this substrate, although due to the limited data we are unable to detect any further layering or grading within the near-surface material. The unusual weakening with depth of the signature returned from Titan has, to date, only been reproduced using a damp sand target that becomes progressively wetter with depth, and supports the suggestion that the surface may consist of a damp and cohesive material with interstitial liquid contained between its grains. Comparison with terrestrial analogues highlights the unusual nature of the landing site material. [ABSTRACT FROM AUTHOR]