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1.
Philippe L. Lamy Imre Toth Björn J. R. Davidsson Olivier Groussin Pedro Gutiérrez Laurent Jorda Mikko Kaasalainen Stephen C. Lowry 《Space Science Reviews》2007,128(1-4):23-66
In 2003, comet 67P/Churyumov–Gerasimenko was selected as the new target of the Rosetta mission as the most suitable alternative
to the original target, comet 46P/Wirtanen, on the basis of orbital considerations even though very little was known about
the physical properties of its nucleus. In a matter of a few years and based on highly focused observational campaigns as
well as thorough theoretical investigations, a detailed portrait of this nucleus has been established that will serve as a
baseline for planning the Rosetta operations and observations. In this review article, we present a novel method to determine
the size and shape of a cometary nucleus: several visible light curves were inverted to produce a size–scale free three–dimensional
shape, the size scaling being imposed by a thermal light curve. The procedure converges to two solutions which are only marginally
different. The nucleus of comet 67P/Churyumov–Gerasimenko emerges as an irregular body with an effective radius (that of the
sphere having the same volume) = 1.72 km and moderate axial ratios a/b = 1.26 and a/c = 1.5 to 1.6. The overall dimensions
measured along the principal axis for the two solutions are 4.49–4.75 km, 3.54–3.77 km and 2.94–2.92 km. The nucleus is found
to be in principal axis rotation with a period = 12.4–12.7 h. Merging all observational constraints allow us to specify two
regions for the direction of the rotational axis of the nucleus: RA = 220°+50°
−30° and Dec = −70° ± 10° (retrograde rotation) or RA = 40°+50°
-30° and Dec = +70°± 10° (prograde), the better convergence of the various determinations presently favoring the first solution. The phase function,
although constrained by only two data points, exhibits a strong opposition effect rather similar to that of comet 9P/Tempel
1. The definition of the disk–integrated albedo of an irregular body having a strong opposition effect raises problems, and
the various alternatives led to a R-band geometric albedo in the range 0.045–0.060, consistent with our present knowledge of cometary nuclei. The active fraction
is low, not exceeding ~ 7% at perihelion, and is probably limited to one or two active regions subjected to a strong seasonal
effect, a picture coherent with the asymmetric behaviour of the coma. Our slightly downward revision of the size of the nucleus
of comet 67P/Churyumov-Gerasimenko resulting from the present analysis (with the correlative increase of the albedo compared
to the originally assumed value of 0.04), and our best estimate of the bulk density of 370 kg m−3, lead to a mass of ~ 8 × 1012 kg which should ease the landing of Philae and insure the overall success of the Rosetta mission. 相似文献
2.
Tilman Spohn Karsten Seiferlin Axel Hagermann Jörg Knollenberg Andrew J. Ball Marek Banaszkiewicz Johannes Benkhoff Stanislaw Gadomski Wojciech Gregorczyk Jerzy Grygorczuk Marek Hlond Günter Kargl Ekkehard Kührt Norbert Kömle Jacek Krasowski Wojciech Marczewski John C. Zarnecki 《Space Science Reviews》2007,128(1-4):339-362
MUPUS, the multi purpose sensor package onboard the Rosetta lander Philae, will measure the energy balance and the physical parameters in the near-surface layers – up to about 30 cm depth- of the
nucleus of Rosetta’s target comet Churyumov-Gerasimenko. Moreover it will monitor changes in these parameters over time as
the comet approaches the sun. Among the parameters studied are the density, the porosity, cohesion, the thermal diffusivity
and conductivity, and temperature. The data should increase our knowledge of how comets work, and how the coma gases form.
The data may also be used to constrain the microstructure of the nucleus material. Changes with time of physical properties
will reveal timescales and possibly the nature of processes that modify the material close to the surface. Thereby, the data
will indicate how pristine cometary matter sampled and analysed by other experiments on Philae really is. 相似文献
3.
J. Kissel K. Altwegg B. C. Clark L. Colangeli H. Cottin S. Czempiel J. Eibl C. Engrand H. M. Fehringer B. Feuerbacher M. Fomenkova A. Glasmachers J. M. Greenberg E. Grün G. Haerendel H. Henkel M. Hilchenbach H. von Hoerner H. Höfner K. Hornung E. K. Jessberger A. Koch H. Krüger Y. Langevin P. Parigger F. Raulin F. Rüdenauer J. Rynö E. R. Schmid R. Schulz J. Silén W. Steiger T. Stephan L. Thirkell R. Thomas K. Torkar N. G. Utterback K. Varmuza K. P. Wanczek W. Werther H. Zscheeg 《Space Science Reviews》2007,128(1-4):823-867
The ESA mission Rosetta, launched on March 2nd, 2004, carries an instrument suite to the comet 67P/Churyumov-Gerasimenko. The COmetary Secondary Ion Mass Anaylzer – COSIMA – is one of three cometary dust analyzing instruments onboard Rosetta. COSIMA is based on the analytic measurement method of secondary ion mass spectrometry (SIMS). The experiment’s goal is in-situ analysis of the elemental composition (and isotopic composition of key elements) of cometary grains. The chemical characterization will include the main organic components, present homologous and functional groups, as well as the mineralogical and petrographical classification of the inorganic phases. All this analysis is closely related to the chemistry and history of the early solar system. COSIMA covers a mass range from 1 to 3500 amu with a mass resolution m/Δm @ 50% of 2000 at mass 100 amu. Cometary dust is collected on special, metal covered, targets, which are handled by a target manipulation unit. Once exposed to the cometary dust environment, the collected dust grains are located on the target by a microscopic camera. A pulsed primary indium ion beam (among other entities) releases secondary ions from the dust grains. These ions, either positive or negative, are selected and accelerated by electrical fields and travel a well-defined distance through a drift tube and an ion reflector. A microsphere plate with dedicated amplifier is used to detect the ions. The arrival times of the ions are digitized, and the mass spectra of the secondary ions are calculated from these time-of-flight spectra. Through the instrument commissioning, COSIMA took the very first SIMS spectra of the targets in space. COSIMA will be the first instrument applying the SIMS technique in-situ to cometary grain analysis as Rosetta approaches the comet 67P/Churyumov-Gerasimenko, after a long journey of 10 years, in 2014. 相似文献
4.
H. U. Auster I. Apathy G. Berghofer A. Remizov R. Roll K. H. Fornacon K. H. Glassmeier G. Haerendel I. Hejja E. Kührt W. Magnes D. Moehlmann U. Motschmann I. Richter H. Rosenbauer C. T. Russell J. Rustenbach K. Sauer K. Schwingenschuh I. Szemerey R. Waesch 《Space Science Reviews》2007,128(1-4):221-240
The scientific objectives, design and capabilities of the Rosetta Lander’s ROMAP instrument are presented. ROMAP’s main scientific
goals are longterm magnetic field and plasma measurements of the surface of Comet 67P/Churyumov-Gerasimenko in order to study
cometary activity as a function of heliocentric distance, and measurements during the Lander’s descent to investigate the
structure of the comet’s remanent magnetisation. The ROMAP fluxgate magnetometer, electrostatic analyser and Faraday cup measure
the magnetic field from 0 to 32 Hz, ions of up to 8000 keV and electrons of up to 4200 keV. Additional two types of pressure
sensors – Penning and Minipirani – cover a pressure range from 10−8 to 101 mbar. ROMAP’s sensors and electronics are highly integrated, as required by a combined field/plasma instrument with less
than 1 W power consumption and 1 kg mass. 相似文献
5.
W. Riedler K. Torkar H. Jeszenszky J. Romstedt H. St. C. Alleyne H. Arends W. Barth J. V. D. Biezen B. Butler P. Ehrenfreund M. Fehringer G. Fremuth J. Gavira O. Havnes E. K. Jessberger R. Kassing W. Klöck C. Koeberl A. C. Levasseur-Regourd M. Maurette F. Rüdenauer R. Schmidt G. Stangl M. Steller I. Weber 《Space Science Reviews》2007,128(1-4):869-904
The International Rosetta Mission is set for a rendezvous with Comet 67 P/Churyumov-Gerasimenko in 2014. On its 10 year journey
to the comet, the spacecraft will also perform a fly-by of the two asteroids Stein and Lutetia in 2008 and 2010, respectively.
The mission goal is to study the origin of comets, the relationship between cometary and interstellar material and its implications
with regard to the origin of the Solar System. Measurements will be performed that shed light into the development of cometary
activity and the processes in the surface layer of the nucleus and the inner coma.
The Micro-Imaging Dust Analysis System (MIDAS) instrument is an essential element of Rosetta’s scientific payload. It will
provide 3D images and statistical parameters of pristine cometary particles in the nm-μm range from Comet 67P/Churyumov-Gerasimenko.
According to cometary dust models and experience gained from the Giotto and Vega missions to 1P/Halley, there appears to be
an abundance of particles in this size range, which also covers the building blocks of pristine interplanetary dust particles.
The dust collector of MIDAS will point at the comet and collect particles drifting outwards from the nucleus surface. MIDAS
is based on an Atomic Force Microscope (AFM), a type of scanning microprobe able to image small structures in 3D. AFM images
provide morphological and statistical information on the dust population, including texture, shape, size and flux. Although
the AFM uses proven laboratory technology, MIDAS is its first such application in space. This paper describes the scientific
objectives and background, the technical implementation and the capabilities of MIDAS as they stand after the commissioning
of the flight instrument, and the implications for cometary measurements. 相似文献
6.
H. Balsiger K. Altwegg P. Bochsler P. Eberhardt J. Fischer S. Graf A. Jäckel E. Kopp U. Langer M. Mildner J. Müller T. Riesen M. Rubin S. Scherer P. Wurz S. Wüthrich E. Arijs S. Delanoye J. De Keyser E. Neefs D. Nevejans H. Rème C. Aoustin C. Mazelle J.-L. Médale J. A. Sauvaud J.-J. Berthelier J.-L. Bertaux L. Duvet J.-M. Illiano S. A. Fuselier A. G. Ghielmetti T. Magoncelli E. G. Shelley A. Korth K. Heerlein H. Lauche S. Livi A. Loose U. Mall B. Wilken F. Gliem B. Fiethe T. I. Gombosi B. Block G. R. Carignan L. A. Fisk J. H. Waite D. T. Young H. Wollnik 《Space Science Reviews》2007,128(1-4):745-801
The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer important questions posed by the mission’s
main objectives. After Giotto, this will be the first time the volatile part of a comet will be analyzed in situ. This is
a very important investigation, as comets, in contrast to meteorites, have maintained most of the volatiles of the solar nebula.
To accomplish the very demanding objectives through all the different phases of the comet’s activity, ROSINA has unprecedented
capabilities including very wide mass range (1 to >300 amu), very high mass resolution (m/Δ m > 3000, i.e. the ability to resolve CO from N2 and 13C from 12CH), very wide dynamic range and high sensitivity, as well as the ability to determine cometary gas velocities, and temperature.
ROSINA consists of two mass spectrometers for neutrals and primary ions with complementary capabilities and a pressure sensor.
To ensure that absolute gas densities can be determined, each mass spectrometer carries a reservoir of a calibrated gas mixture
allowing in-flight calibration. Furthermore, identical flight-spares of all three sensors will serve for detailed analysis
of all relevant parameters, in particular the sensitivities for complex organic molecules and their fragmentation patterns
in our electron bombardment ion sources. 相似文献
7.
K. J. Seidensticker D. Möhlmann I. Apathy W. Schmidt K. Thiel W. Arnold H.-H. Fischer M. Kretschmer D. Madlener A. Péter R. Trautner S. Schieke 《Space Science Reviews》2007,128(1-4):301-337
SESAME is an instrument complex built in international co-operation and carried by the Rosetta lander Philae intended to land
on comet 67P/Churyumov-Gerasimenko in 2014. The main goals of this instrument suite are to measure mechanical and electrical
properties of the cometary surface and the shallow subsurface as well as of the particles emitted from the cometary surface.
Most of the sensors are mounted within the six soles of the landing gear feet in order to provide good contact with or proximity
to the cometary surface. The measuring principles, instrument designs, technical layout, operational concepts and the results
from the first in-flight measurements are described. We conclude with comments on the consequences of the last minute change
of the target comet and how to improve and to preserve the knowledge during the long-duration Rosetta mission. 相似文献
8.
Dust is an important constituent of cometary emission; its analysis is one of the major objectives of ESA’s Rosetta mission
to comet 67P/Churyumov-Gerasimenko (C–G). Several instruments aboard Rosetta are dedicated to studying various aspects of
dust in the cometary coma, all of which require a certain level of exposure to dust to achieve their goals. At the same time,
impacts of dust particles can constitute a hazard to the spacecraft. To conciliate the demands of dust collection instruments
and spacecraft safety, it is desirable to assess the dust environment in the coma even before the arrival of Rosetta. We describe
the present status of modelling the dust coma of 67P/C–G and predict the speed and flux of dust in the coma, the dust fluence
on a spacecraft along sample trajectories, and the radiation environment in the coma. The model will need to be refined when
more details of the coma are revealed by observations. An overview of astronomical observations of 67P/C–G is given, because
model parameters are derived from this data if possible. For quantities not yet measured for 67P/C–G, we use values obtained
for other comets, e.g. concerning the optical and compositional properties of the dust grains. One of the most important and
most controversial parameters is the dust mass distribution. We summarise the mass distribution functions derived from the
in-situ measurements at comet 1P/Halley in 1986. For 67P/C–G, constraining the mass distribution is currently only possible
by the analysis of astronomical images. We find that both the dust mass distribution and the time dependence of the dust production
rate of 67P/C–G are those of a fairly typical comet. 相似文献
9.
Adrienn Luspay-Kuti Olivier Mousis Jonathan I. Lunine Yves Ellinger Françoise Pauzat Ujjwal Raut Alexis Bouquet Kathleen E. Mandt Romain Maggiolo Thomas Ronnet Bastien Brugger Ozge Ozgurel Stephen A. Fuselier 《Space Science Reviews》2018,214(8):115
The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument onboard the Rosetta spacecraft has measured molecular oxygen (O2) in the coma of comet 67P/Churyumov-Gerasimenko (67P/C-G) in surprisingly high abundances. These measurements mark the first unequivocal detection of O2 in a cometary environment. The large relative abundance of O2 in 67P/C-G despite its high reactivity and low interstellar abundance poses a puzzle for its origin in comet 67P/C-G, and potentially other comets. Since its detection, there have been a number of hypotheses put forward to explain the production and origin of O2 in the comet. These hypotheses cover a wide range of possibilities from various in situ production mechanisms to protosolar nebula and primordial origins. Here, we review the O2 formation mechanisms from the literature, and provide a comprehensive summary of the current state of knowledge of the sources and origin of cometary O2. 相似文献
10.
MIRO: Microwave Instrument for Rosetta Orbiter 总被引:1,自引:0,他引:1
S. Gulkis M. Frerking J. Crovisier G. Beaudin P. Hartogh P. Encrenaz T. Koch C. Kahn Y. Salinas R. Nowicki R. Irigoyen M. Janssen P. Stek M. Hofstadter M. Allen C. Backus L. Kamp C. Jarchow E. Steinmetz A. Deschamps J. Krieg M. Gheudin D. Bockelée-Morvan N. Biver T. Encrenaz D. Despois W. Ip E. Lellouch I. Mann D. Muhleman H. Rauer P. Schloerb T. Spilker 《Space Science Reviews》2007,128(1-4):561-597
The European Space Agency Rosetta Spacecraft, launched on March 2, 2004 toward Comet 67P/Churyumov-Gerasimenko, carries a
relatively small and lightweight millimeter-submillimeter spectrometer instrument, the first of its kind launched into deep
space. The instrument will be used to study the evolution of outgassing water and other molecules from the target comet as
a function of heliocentric distance. During flybys of the asteroids (2867) Steins and (21) Lutetia in 2008 and 2010 respectively,
the instrument will measure thermal emission and search for water vapor in the vicinity of these asteroids.
The instrument, named MIRO (Microwave Instrument for the Rosetta Orbiter), consists of a 30-cm diameter, offset parabolic
reflector telescope followed by two heterodyne receivers. Center-band operating frequencies of the receivers are near 190
GHz (1.6 mm) and 562 GHz (0.5 mm). Broadband continuum channels are implemented in both frequency bands for the measurement
of near surface temperatures and temperature gradients in Comet 67P/Churyumov-Gerasimenko and the asteroids (2867) Steins
and (21) Lutetia. A 4096 channel CTS (Chirp Transform Spectrometer) spectrometer having 180 MHz total bandwidth and 44 kHz
resolution is, in addition to the continuum channel, connected to the submillimeter receiver. The submillimeter radiometer/spectrometer
is fixed tuned to measure four volatile species – CO, CH3OH, NH3 and three, oxygen-related isotopologues of water, H2
16O, H2
17O and H2
18O. The basic quantities measured with the MIRO instrument are surface temperature, gas production rates and relative abundances,
and velocity and excitation temperature of each species, along with their spatial and temporal variability. This paper provides
a short discussion of the scientific objectives of the investigation, and a detailed discussion of the MIRO instrument system. 相似文献