Alice: The rosetta Ultraviolet Imaging Spectrograph

Stern, S. A.; Slater, D. C.; Scherrer, J.; Stone, John Marshall; Versteeg, M. H.; A’Hearn, Michael F.; Bertaux, Jean-Loup; Feldman, P. D.; Festou, M. C.; Parker, J. W.; Siegmund, O.

doi:10.1007/s11214-006-9035-8

Cited by 89 publications

(82 citation statements)

References 10 publications

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“…to measure the far ultraviolet (λ ≈ 1500 Å) albedo of Lutetia to enable better planning of the flyby observations by the Alice ultraviolet (UV) spectral imager (Stern et al 2007); 2. to measure the near UV (λ ≈ 2000−3000 Å) and visible (λ ≈ 4000−7000 Å) albedo, thereby providing the spectral energy distribution across a wide wavelength range and possibly yielding improved insights into the nature of the surface composition and taxonomic class of Lutetia; 3. to search for dust debris and companions near Lutetia that might pose a hazard to the Rosetta spacecraft, using deep, visible-band observations; 4. to use spatially resolved HST images of Lutetia to constrain its size and shape.…”

Section: Introductionmentioning

confidence: 99%

Ultraviolet and visible photometry of asteroid (21) Lutetia using the Hubble Space Telescope

Weaver¹,

Feldman²,

Merline³

et al. 2010

A&A

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Context. The asteroid (21) Lutetia is the target of a planned close encounter by the Rosetta spacecraft in July 2010. To prepare for that flyby, Lutetia has been extensively observed by a variety of astronomical facilities. Aims. We used the Hubble Space Telescope (HST) to determine the albedo of Lutetia over a wide wavelength range, extending from ∼1500 Å to ∼7000 Å. Methods. Using data from a variety of HST filters and a ground-based visible light spectrum, we employed synthetic photometry techniques to derive absolute fluxes for Lutetia. New results from ground-based measurements of Lutetia's size and shape were used to convert the absolute fluxes into albedos. Results. We present our best model for the spectral energy distribution of Lutetia over the wavelength range 1200−8000 Å. There appears to be a steep drop in the albedo (by a factor of ∼2) for wavelengths shorter than ∼3000 Å. Nevertheless, the far ultraviolet albedo of Lutetia (∼10%) is considerably larger than that of typical C-chondrite material (∼4%). The geometric albedo at 5500 Å is 16.5 ± 1%. Conclusions. Lutetia's reflectivity is not consistent with a metal-dominated surface at infrared or radar wavelengths, and its albedo at all wavelengths (UV-visibile-IR-radar) is larger than observed for typical primitive, chondritic material. We derive a relatively high FUV albedo of ∼10%, a result that will be tested by observations with the Alice spectrograph during the Rosetta flyby of Lutetia in July 2010.

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Section: Introductionmentioning

confidence: 99%

Ultraviolet and visible photometry of asteroid (21) Lutetia using the Hubble Space Telescope

Weaver¹,

Feldman²,

Merline³

et al. 2010

A&A

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“…The ALICE ultraviolet spectrometer and the ROSINA instrument should put upper limits on the noble gas abundances in the coma of comet 67P/Churyumov-Gerasimenko (Balsiger et al 2007;Stern et al 2007) that will probably help understand the formation conditions of comets in the primordial nebula. However, the measurement of solar or subsolar noble gas abundances in comets will require a new generation of instruments such as the cryotrap,…”

Section: Discussionmentioning

confidence: 99%

The Dual Origin of the Nitrogen Deficiency in Comets: Selective Volatile Trapping in the Nebula and Postaccretion Radiogenic Heating

Mousis

Guilbert-Lepoutre

Lunine

et al. 2012

ApJ

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We propose a scenario that explains the apparent nitrogen deficiency in comets in a way that is consistent with the fact that the surfaces of Pluto and Triton are dominated by nitrogen-rich ice. We use a statistical thermodynamic model to investigate the composition of the successive multiple guest clathrates that may have formed during the cooling of the primordial nebula from the most abundant volatiles present in the gas phase. These clathrates agglomerated with the other ices (pure condensates or stoichiometric hydrates) and formed the building blocks of comets. We report that molecular nitrogen is a poor clathrate former, when we consider a plausible gas-phase composition of the primordial nebula. This implies that its trapping into cometesimals requires a low disk temperature (∼20 K) in order to allow the formation of its pure condensate. We find that it is possible to explain the lack of molecular nitrogen in comets as a consequence of their postformation internal heating engendered by the decay of short-lived radiogenic nuclides. This scenario is found to be consistent with the presence of nitrogen-rich ice covers on Pluto and Triton. Our model predicts that comets should present xenon-to-water and krypton-to-water ratios close to solar xenon-to-oxygen and krypton-to-oxygen ratios, respectively. In contrast, the argon-to-water ratio is predicted to be depleted by a factor of ∼300 in comets compared to solar argon-to-oxygen, as a consequence of poor trapping efficiency and radiogenic heating.

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“…The details of the Alice instrument are described in Stern et al (2007), with key specifications noted here. The FUV wavelength range of the detector, 700−2050 Å, is spanned by 1024 pixels, and 20 spatial channels (of 32 on the detector) span the 5.5 • long entrance slit at every wavelength.…”

Section: Observationsmentioning

confidence: 99%

“…During this time period, Alice collected data regularly, but only subsets of the data meet the criteria laid out below for each of our analyses: determining the phase dependence and completing a comparative mineralogical study. All of the Alice calibrated data were produced using a typical data reduction algorithm and run through the automated Alice pipeline (Stern et al 2007). The geometries of the observations were calculated and recorded in the data files for each Alice pixel along the slit based on SPICE kernels and the shape model derived by the OSIRIS team (SHAP5; Jorda et al 2015).…”

Section: Observationsmentioning

confidence: 99%

“…For the first time, the morphology and composition of the nucleus and coma, their volatile content and development of activity, and evolution of the surface-coma interface will be studied in great detail. Alice, part of the Rosetta orbiter instrument suite (Stern et al 2007), is a low-power, lightweight imaging spectrograph designed primarily to determine the onset of activity, production rates, and distribution of the primary volatiles (H 2 O, CO 2 , and CO), search for and inventory noble gases in the near nucleus coma, and document the atomic budget of the coma as a function of time. Secondarily, Alice will study the properties of small grains in the FUV, search for variability in ionic emissions in the coma and ion tail, and characterize the nuclear surface in the FUV, including mapping the distribution of FUV absorbers on the surface (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Far-UV phase dependence and surface characteristics of comet 67P/Churyumov-Gerasimenko as observed with Rosetta Alice

Feaga

Protopapa

Schindhelm

et al. 2015

A&A

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Aims. The Alice far-ultraviolet (FUV) spectrograph onboard Rosetta has, for the first time, imaged the surface of a comet, 67P/Churyumov-Gerasimenko (67P), in the FUV. With spatially resolved data, the nucleus properties are characterized in the FUV, including phase dependence, albedo, and spectral slope. Regional measurements across the nucleus are compared to discern any compositional variations. Methods. Hapke theory was utilized to model the phase dependence of the material on the surface of 67P. The phase dependence of 67P was derived from a subset of data acquired at various phase angles in November 2014, within 50 km of the comet such that the nucleus was spatially resolved. The derived photometric correction was then applied to a different subset of spatially resolved data sampling several distinct geographical regions on the nucleus acquired in August−November 2014 under similar viewing geometries. Results. In the FUV, the surface of 67P is dark, blue sloped, has an average geometric albedo of 0.054 ± 0.008 at 1475 Å near the center of the Alice bandpass, and is mostly uniform from region to region, with the exception of the Hatmehit region, which is slightly more reflective. These results are consistent with the suggestion made by the Rosetta OSIRIS and VIRTIS teams that the surface of 67P is covered with a homogeneous layer of material and that surface ice is not ubiquitous in large abundances. The modeled Hapke parameters, specifically the single scattering albedo (w) and the asymmetry factor (ζ), are determined to be 0.031 ± 0.003 and −0.530 ± 0.025 near the center of the Alice bandpass at 1475 Å. These parameters are consistent with measurements of other comet nuclei that have been observed by flyby missions in the visible and the near-infrared regimes.

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Alice: The rosetta Ultraviolet Imaging Spectrograph

Cited by 89 publications

References 10 publications

Ultraviolet and visible photometry of asteroid (21) Lutetia using the Hubble Space Telescope

Ultraviolet and visible photometry of asteroid (21) Lutetia using the Hubble Space Telescope

The Dual Origin of the Nitrogen Deficiency in Comets: Selective Volatile Trapping in the Nebula and Postaccretion Radiogenic Heating

Far-UV phase dependence and surface characteristics of comet 67P/Churyumov-Gerasimenko as observed with Rosetta Alice

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