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In order to prepare for the arrival of the Dawn spacecraft at Ceres, a search for satellites was undertaken by the Hubble Space Telescope (HST) to enhance the mission science return and to ensure spacecraft safety. Previous satellite searches from ground-based telescopes have detected no satellites within Ceres’ Hill sphere down to a size of 3km (Gehrels et al. 1987) and early HST investigations searched...
The surface composition of the northern regions of Vesta, observed by the Dawn spacecraft, offers the possibility to test several hypotheses related to impact-related processes. We used mostly imaging spectrometry in the visible and near infrared to assess the distribution of mafic lithologies, hydrated components and albedo properties, and use the link with howardite, eucrite and diogenite meteorites...
Mapping Vesta’ surface composition in the Sextilia region offers the unique possibility to investigate stratigraphic relationship of the surface compounds throughout the transition from Rheasilvia, Vesta’s prominent impact basin, to Vesta’s northern equatorial region. The VIR data point to an upper eucrite-dominated layer overlaying extended deposits of diogenite in the subsurface, which reaches the...
Earth-bound searches for natural satellites of 4 Vesta have been reported since 1987. With use of technological advances and observing capability has come a reduction in the detectable size of a possible satellite. The Dawn mission brought a small camera close to Vesta itself. In our search, which was carried out with a comprehensive data acquisition strategy and by experienced searchers, we find...
Observations of Asteroid (4) Vesta by NASA’s Dawn spacecraft are interesting because its surface has the largest range of albedo, color and composition of any other asteroid visited by spacecraft to date. These hemispherical and rotational variations in surface brightness and composition have been attributed to impact processes since Vesta’s formation. Prior to Dawn’s arrival at Vesta, its surface...
Data from the Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) mission show Comet 103P/Hartley 2 is a bi-lobed, elongated, nearly axially symmetric comet 2.33km in length. Surface features are primarily small mounds <40m across, irregularly-shaped smooth areas on the two lobes, and a smooth but variegated region forming a “waist” between the two lobes. Assuming parts...
We imaged the region around Asteroid (4) Vesta in nine long exposures using the Wide Field Planetary Camera 2 on the Hubble Space Telescope on May 14 and 16, 2007 to conduct a deep search for satellites in support of NASA’s Dawn mission that orbited (4) Vesta in 2011–2012. Several previous search efforts have been undertaken, but no satellites were detected. Our search covered distances from 14 to...
We report a comprehensive review of the UV–visible spectrum and rotational lightcurve of Vesta combining new observations by Hubble Space Telescope and Swift Gamma-ray Burst Observatory with archival International Ultraviolet Explorer observations. The geometric albedos of Vesta from 220nm to 953nm are derived by carefully comparing these observations from various instruments at different times and...
We report an improved measurement of the rotational axis orientation of Asteroid (4) Vesta. By analyzing and combining all previous measurements using a limb-fitting technique from ground/HST data collected from 1983 to 2006, we derive a pole solution of (RA=304.5°, Dec=41.5°). Images of Vesta acquired with the Wide Field Camera 3 onboard the Hubble Space Telescope (HST) in February 2010 are combined...
We present the surface mapping of the southern hemisphere of Asteroid (4) Vesta obtained from Hubble Space Telescope (HST). From 105 images of Vesta through four filters in the wavelengths best to characterize the 1-μm pyroxene band, we constructed albedo and color-ratio maps of Vesta. These new maps cover latitudes −50° to +20°. The southern hemisphere of Vesta displays more diverse albedo and color...
The disk-resolved flyby images of the nucleus of Comet 81P/Wild 2 collected by Stardust are used to perform a detailed study of the photometric properties of this cometary nucleus. A disk-integrated phase function from phase angle 11° to about 100° is measured and modeled. A phase slope of 0.0513±0.0002 mag/deg is found, with a V-band absolute magnitude of 16.29±0.02. Hapke’s photometric model yields...
Images returned from the Deep Space 1 (DS-1) spacecraft during its encounter with Comet 19P/Borrelly are used to study its disk-integrated and disk-resolved photometry and its thermal properties. A disk-integrated phase function was constructed from a combination of DS-1 images and ground-based observations, giving a geometric albedo of 0.072±0.020 and a phase slope of 0.043 mag deg −1 . The...
Deep Impact images of the nucleus of Comet Tempel 1 reveal pervasive layering, possible impact craters, flows with smooth upper surfaces, and erosional stripping of material. There are at least 3 layers 50–200 m thick that appear to extend deep into the nucleus, and several layers 1–20 m thick that parallel the surface and are being eroded laterally. Circular depressions show geographical variation...
The photometric properties of the nucleus of Comet 9P/Tempel 1 are studied from the disk-resolved color images obtained by Deep Impact (DI). Comet Tempel 1 has typical photometric properties for comets and dark asteroids. The disk-integrated spectrum of the nucleus of Tempel 1 between 309 and 950 nm is linear without any features at the spectral resolution of the filtered images. At V-band, the red...
Deep Impact images of the nucleus of Comet Tempel 1 reveal pervasive layering, possible impact craters, flows with smooth upper surfaces, and erosional stripping of material. There are at least 3 layers 50–200 m thick that appear to extend deep into the nucleus, and several layers 1–20 m thick that parallel the surface and are being eroded laterally. Circular depressions show geographical variation...
The photometric properties of the nucleus of Comet 9P/Tempel 1 are studied from the disk-resolved color images obtained by Deep Impact (DI). Comet Tempel 1 has typical photometric properties for comets and dark asteroids. The disk-integrated spectrum of the nucleus of Tempel 1 between 309 and 950 nm is linear without any features at the spectral resolution of the filtered images. At V-band, the red...
The highest resolution (pixel scale 30 km) images of Ceres to date have been acquired by the Advanced Camera for Surveys onboard Hubble Space Telescope, through three wide band filters, centered at 535, 335, and 223 nm, covering more than one rotation of Ceres. The lightcurve at 535 nm agrees with earlier observations at V-band [Tedesco, E.F., Taylor, R.C., Drummond, J., Harwood, D., Nickoloff, I...
A photometric model of (433) Eros at wavelengths from 450 to 1050 nm is constructed using the combination of the images from the multispectral imager (MSI) obtained during the one-year long orbital phase of the NEAR mission, ground-based lightcurves from earlier observations, and our theoretical forward modeling simulations coupled with the NEAR shape model. The single scattering albedo is found to...
The Near Earth Asteroid Rendezvous (NEAR) spacecraft will conduct the first photometric imagery of a C-class asteroid when it flies by 253 Mathilde. An absorption feature seen in ground-based disk-integrated spectra of many C-class asteroids has been attributed to oxidized iron in phyllosilicate minerals of the serpento-chlorite groups. We have designed a method of identifying this absorption feature...
We have analyzed the only two known images taken of Comet 107P = Asteroid (4015) Wilson–Harrington while it was a distinctly cometary object. The images reside on two Palomar Observatory Sky Survey (POSS) photographic plates taken on 19 November 1949 UT and provide a unique way of studying the fading gasps of a dying comet. The comet appears as a streak, a tail is evident, but the coma is indistinguishable...
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