scholarly journals The 67P/Churyumov–Gerasimenko observation campaign in support of the Rosetta mission

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160249 ◽  
Author(s):  
C. Snodgrass ◽  
M. F. A'Hearn ◽  
F. Aceituno ◽  
V. Afanasiev ◽  
S. Bagnulo ◽  
...  
Keyword(s):  
Large Scale ◽  
Activity Patterns ◽  
Mission Planning ◽  
Context Information ◽  
Large Collection ◽  
Future Studies ◽  
Early Results ◽  
Rosetta Mission ◽  
Comet 67P

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov–Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively ‘well-behaved’ comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends—in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies. This article is part of the themed issue ‘Cometary science after Rosetta’.

scholarly journals The Rosetta mission orbiter science overview: the comet phase

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160262 ◽  
Author(s):  
M. G. G. T. Taylor ◽  
N. Altobelli ◽  
B. J. Buratti ◽  
M. Choukroun
Keyword(s):  
Remote Sensing ◽  
Solar System ◽  
Cometary Nucleus ◽  
Rosetta Mission ◽  
Interstellar Material ◽  
The Relationship ◽  
Mission Operations ◽  
Comet 67P ◽  
Cometary Activity

The international Rosetta mission was launched in 2004 and consists of the orbiter spacecraft Rosetta and the lander Philae. The aim of the mission is to map the comet 67P/Churyumov–Gerasimenko by remote sensing, and to examine its environment in situ and its evolution in the inner Solar System. Rosetta was the first spacecraft to rendezvous with and orbit a comet, accompanying it as it passes through the inner Solar System, and to deploy a lander, Philae, and perform in situ science on the comet's surface. The primary goals of the mission were to: characterize the comet's nucleus; examine the chemical, mineralogical and isotopic composition of volatiles and refractories; examine the physical properties and interrelation of volatiles and refractories in a cometary nucleus; study the development of cometary activity and the processes in the surface layer of the nucleus and in the coma; detail the origin of comets, the relationship between cometary and interstellar material and the implications for the origin of the Solar System; and characterize asteroids 2867 Steins and 21 Lutetia. This paper presents a summary of mission operations and science, focusing on the Rosetta orbiter component of the mission during its comet phase, from early 2014 up to September 2016. This article is part of the themed issue ‘Cometary science after Rosetta’.

scholarly journals Outgassing-induced acceleration of comet 67P/Churyumov-Gerasimenko

2019 ◽  
Vol 630 ◽  
pp. A4 ◽  
Author(s):  
T. Kramer ◽  
M. Läuter
Keyword(s):  
Rotation Axis ◽  
Gravitational Acceleration ◽  
Axis Orientation ◽  
Fourier Decomposition ◽  
Sublimation Process ◽  
Rosetta Mission ◽  
Position Data ◽  
Comet 67P ◽  
Local Noon

Context. Cometary activity affects the orbital motion and rotation state through sublimation-induced forces. The availability of precise rotation-axis orientation and position data from the Rosetta mission allows us to accurately determine the outgassing of comet Churyumov-Gerasimenko/67P (67P). Aims. We derived the observed non-gravitational acceleration of 67P directly from the trajectory of the Rosetta spacecraft. From the non-gravitational acceleration, we recovered the diurnal outgassing variations and study a possible delay of the sublimation response with respect to the peak of the solar illumination. This allowed us to compare the non-gravitational acceleration of 67P with expectations based on empirical models and common assumptions about the sublimation process. Methods. We used an iterative orbit refinement and Fourier decomposition of the diurnal activity to derive the outgassing-induced non-gravitational acceleration. The uncertainties of the data reduction were established by a sensitivity analysis of an ensemble of best-fit orbits for comet 67P. Results. We find that the Marsden non-gravitational acceleration parameters reproduce part of the non-gravitational acceleration, but need to be augmented by an analysis of the nucleus geometry and surface illumination to draw conclusions about the sublimation process on the surface. The non-gravitational acceleration closely follows the subsolar latitude (seasonal illumination), with a small lag angle with respect to local noon around perihelion. The observed minor changes of the rotation axis do not favor forced precession models for the non-gravitational acceleration. Conclusions. In contrast to the sublimation-induced torques, the non-gravitational acceleration does not place strong constraints on localized active areas on the nucleus. We find a close agreement of the orbit-deduced non-gravitational acceleration and the water production that is independently derived from Rosetta in situ measurements.

scholarly journals Elemental and molecular abundances in comet 67P/Churyumov-Gerasimenko

2019 ◽  
Vol 489 (1) ◽  
pp. 594-607 ◽  
Author(s):  
Martin Rubin ◽  
Kathrin Altwegg ◽  
Hans Balsiger ◽  
Jean-Jacques Berthelier ◽  
Michael R Combi ◽  
...  
Keyword(s):  
Solar System ◽  
Early Period ◽  
Major Elements ◽  
Rosetta Mission ◽  
Solar System Objects ◽  
Dust Composition ◽  
Solar Abundances ◽  
Molecular Abundances ◽  
Comet 67P

ABSTRACT Comets are considered to be some of the most pristine and unprocessed Solar system objects accessible to in situ exploration. Investigating their molecular and elemental composition takes us on a journey back to the early period of our Solar system and possibly even further. In this work, we deduce the bulk abundances of the major volatile species in comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency’s (ESA) Rosetta mission. The basis are measurements obtained with the ROSINA instrument suite on board the Rosetta orbiter during a suitable period of high outgassing near perihelion. The results are combined with both gas and dust composition measurements published in the literature. This provides an integrated inventory of the major elements present in the nucleus of 67P/Churyumov-Gerasimenko. Similar to comet 1P/Halley, which was visited by ESA’s Giotto spacecraft in 1986, comet 67P/Churyumov-Gerasimenko also shows near-solar abundances of oxygen and carbon, whereas hydrogen and nitrogen are depleted compared to solar. Still, the degree of devolatilization is lower than that of inner Solar system objects, including meteorites and the Earth. This supports the idea that comets are amongst the most pristine objects in our Solar system.

The Latest (Dusty) Pieces in the Rosetta Story

2020 ◽  
Author(s):  
Stavro Lambrov Ivanovski
Keyword(s):  
Large Scale ◽  
Collaborative Approach ◽  
Cometary Dust ◽  
Additional Information ◽  
Data Analyses ◽  
Entire Duration ◽  
Comet 67P ◽  
Critical Results

<p>The ESA’s Rosetta spacecraft had the unique opportunity to follow comet 67P/Churyumov-Gerasimenko (hereafter 67P) for about 2.5 years – from January 2014 to September 2016 – observing how the comet evolved while approaching the Sun, passing through perihelion and then moving back into the outer solar system. Remote sensing and in-situ instruments onboard Rosetta acquired data to study the comet’s dust environment during the entire duration of the mission, while telescopes followed the large-scale coma and tails from Earth. Here we report the latest advances of the ongoing multi-instrument approach that the Rosetta dust working group has been following in the recent years. Individual instrument data analyses have been carried on providing a first characterization of 67P dust environment. Timely, multi-instruments data analyses are now progressing a step forward in understanding how comet works and are providing critical results for a more comprehensive and unified knowledge of cometary dust environments. We will illustrate the progress we have made and the results we have reached following this constructive and collaborative approach.</p><p>We also discuss the latest achievements on the cometary dust modelling using the multi-instrument Rosetta data. In particular, what additional information these calibrated dust models provide and what we are still missing in cometary dust characterization.</p>

Synchronizing Brain Rhythms to Improve Cognition

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Shrey Grover ◽  
John A. Nguyen ◽  
Robert M.G. Reinhart
Keyword(s):  
Large Scale ◽  
Activity Patterns ◽  
Neuropsychiatric Disorders ◽  
Network Activity ◽  
Human Cognition ◽  
Annual Review ◽  
Publication Date ◽  
Early Results ◽  
Transcranial Alternating Current Stimulation ◽  
Communication Dynamics

Impaired cognition is common in many neuropsychiatric disorders and severely compromises quality of life. Synchronous electrophysiological rhythms represent a core mechanism for sculpting communication dynamics among large-scale brain networks that underpin cognition and its breakdown in neuropsychiatric disorders. Here, we review an emerging neuromodulation technology called transcranial alternating current stimulation that has shown remarkable early results in rapidly improving various domains of human cognition by modulating properties of rhythmic network synchronization. Future noninvasive neuromodulation research holds promise for potentially rescuing network activity patterns and improving cognition, setting groundwork for the development of drug-free, circuit-based therapeutics for people with cognitive brain disorders. Expected final online publication date for the Annual Review of Medicine, Volume 72 is January 27, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals Generation of photoclinometric DTMs for application to transient changes on the surface of comet 67P/Churyumov-Gerasimenko

2019 ◽  
Vol 630 ◽  
pp. A10 ◽  
Author(s):  
Y. Tang ◽  
S. P. D. Birch ◽  
A. G. Hayes ◽  
R. Kirk ◽  
N. Kutsop ◽  
...  
Keyword(s):  
Large Scale ◽  
Shape From Shading ◽  
Small Scale ◽  
Digital Terrain ◽  
Terrain Models ◽  
Rosetta Mission ◽  
The Many ◽  
Pixel Scale ◽  
Comet 67P ◽  
Temporal Coverage

Context. The wide spatial and temporal coverage of 67P/Churyumov-Gerasimenko (67P) by the Rosetta mission has revealed a surface created by scattered large-scale changes and numerous small-scale changes. The many small-scale changes are of particular interest because they are unexpected and ubiquitous. As their topographic relief is often smaller than one meter, which is below the resolution of any shape models, we need higher resolution topography to analyze them properly. Aims. We describe a photoclinometry method that is able to retrieve surface elevations for a single OSIRIS image of the surface of 67P. With this method, we can provide accurate measures, along with error estimates, of the centimeter-scale topography of observed transient changes. Methods. Photoclinometry, or shape-from-shading, estimates heights by examining the light reflection of the surface as dictated by a photometric model under a specified set of viewing geometries. Assuming a standard photometric model for 67P, we can recreate the shading of a surface under specified viewing geometries. The output is a high-resolution height map that matches the original image pixel by pixel. We then provide estimates of the error in the retrieved heights and ensure that our method is valid with a series of checks. Results. We generate digital terrain models (DTMs) with a vertical resolution comparable to or smaller than the pixel scale. This allows us to accurately measure changes in the surface topography on centimeter scales. We find that most changes within the smooth terrains involve the transport or removal of material thinner than one meter.

scholarly journals Plasma source and loss at comet 67P during the Rosetta mission

2018 ◽  
Vol 618 ◽  
pp. A77 ◽  
Author(s):  
K. L. Heritier ◽  
M. Galand ◽  
P. Henri ◽  
F. L. Johansson ◽  
A. Beth ◽  
...  
Keyword(s):  
Impact Ionization ◽  
Energetic Electron ◽  
Plasma Source ◽  
Number Density ◽  
Time Period ◽  
Rosetta Mission ◽  
Impedance Probe ◽  
Photo Ionization ◽  
Comet 67P

Context.The Rosetta spacecraft provided us with a unique opportunity to study comet 67P/Churyumov–Gerasimenko (67P) from a close perspective and over a 2-yr time period. Comet 67P is a weakly active comet. It was therefore unexpected to find an active and dynamic ionosphere where the cometary ions were largely dominant over the solar wind ions, even at large heliocentric distances.Aims.Our goal is to understand the different drivers of the cometary ionosphere and assess their variability over time and over the different conditions encountered by the comet during the Rosetta mission.Methods.We used a multi-instrument data-based ionospheric model to compute the total ion number density at the position of Rosetta. In-situ measurements from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the Rosetta Plasma Consortium (RPC)–Ion and Electron Sensor (IES), together with the RPC–LAngmuir Probe instrument (LAP) were used to compute the local ion total number density. The results are compared to the electron densities measured by RPC–Mutual Impedance Probe (MIP) and RPC–LAP.Results.We were able to disentangle the physical processes responsible for the formation of the cometary ions throughout the 2-yr escort phase and we evaluated their respective magnitudes. The main processes are photo-ionization and electron-impact ionization. The latter is a significant source of ionization at large heliocentric distance (>2 au) and was predominant during the last 4 months of the mission. The ionosphere was occasionally subject to singular solar events, temporarily increasing the ambient energetic electron population. Solar photons were the main ionizer near perihelion at 1.3 au from the Sun, during summer 2015.

In-situ detection of cometary cyanogen (NCCN)

2020 ◽  
Author(s):  
Nora Hänni ◽  
Kathrin Altwegg ◽  
Boris Pestoni ◽  
Martin Rubin ◽  
Isaac Schroeder ◽  
...  
Keyword(s):  
Production Rate ◽  
Hydrogen Cyanide ◽  
Space Science ◽  
Upper Limit ◽  
Rosetta Mission ◽  
Long Time ◽  
Double Focusing ◽  
In Situ Detection ◽  
Comet 67P

<p>For a long time it was thought that the cyano (CN) radical, observed remotely many times in various stellar and interstellar environments, is exclusively a photodissociation product of hydrogen cyanide (HCN). Bockelée-Morvan et al. (1984) first questioned this notion based on remote observations of comet IRAS-Araki-Alcock. They reported an upper limit for the HCN production rate which was smaller than the CN production rate previously derived by A’Hearn et al. (1983). Even today, this discrepancy observed for some comets is not resolved although many alternative parents have been suggested. Among the volatile candidates, cyanogen (NCCN), cyanoacetylene (HC<sub>3</sub>N) and acetonitrile (CH<sub>3</sub>CN), according to Fray et al. (2005), are the most promising ones. While cyanoacetylene and acetonitrile are known to be present in trace amounts in comets, as reported for comet Hale-Bopp by Bockelée-Morvan et al. (2000) and for comet 67P/Churyumov-Gerasimenko by Le Roy et al. (2015) and Rubin et al. (2019), the abundance of cyanogen in comets is unknown. Altwegg et al. (2019) were the first to mention its detection in the inner coma of comet 67P/Churyumov-Gerasimenko, target of ESA’s Rosetta mission.</p> <p>In this work, we track the signatures of cyanogen in the ROSINA/DFMS (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/ Double Focusing Mass Spectrometer; Balsiger et al. (2007)) data, collected during the Rosetta mission phase. We derive abundances relative to water for three distinct periods, indicating that cyanogen is not abundant enough to explain the CN production in comet 67P together with HCN. Our findings are consistent with the non-detection of cyanogen in the interstellar medium.</p> <p> </p> <p>A’Hearn M.F., Millis R.L., 1983, IAU Circ., 3802</p> <p>Altwegg K., Balsiger H., Fuselier S.A., 2019, Annu. Rev. Astron. Astrophys., 57, 113–55</p> <p>Balsiger H. et al., 2007, Space Science Reviews, 128, 745-801</p> <p>Bockelée-Morvan D., Crovisier J., Baudry A., Despois D., Perault M., Irvine W.M., Schloerb F.P., Swade D., 1984, Astron. Astrophys., 141, 411-418</p> <p>Bockelée-Morvan et al., 2000, Astron. Astrophys., 353, 1101–1114.</p> <p>Fray N., Bénilan Y., Cottin H., Gazeau M.-C., Crovisier J., 2005, Planetary and Space Science, 53, 1243-1262</p> <p>Le Roy L. et al., 2015, Astron. Astrophys., 583, A1</p> <p>Rubin M. et al., 2019, MNRAS, 489, 594-607</p>

scholarly journals Solar wind charge exchange in cometary atmospheres

2019 ◽  
Vol 630 ◽  
pp. A36 ◽  
Author(s):  
Cyril Simon Wedlund ◽  
Etienne Behar ◽  
Esa Kallio ◽  
Hans Nilsson ◽  
Markku Alho ◽  
...  
Keyword(s):  
Solar Wind ◽  
Charge Exchange ◽  
Solar Wind Speed ◽  
Analytical Models ◽  
Ion Temperature ◽  
Mass Load ◽  
Rosetta Mission ◽  
Solar Wind Charge Exchange ◽  
Comet 67P

Context. Solar wind charge-changing reactions are of paramount importance to the physico-chemistry of the atmosphere of a comet because they mass-load the solar wind through an effective conversion of fast, light solar wind ions into slow, heavy cometary ions. The ESA/Rosetta mission to comet 67P/Churyumov-Gerasimenko (67P) provided a unique opportunity to study charge-changing processes in situ. Aims. To understand the role of charge-changing reactions in the evolution of the solar wind plasma and to interpret the complex in situ measurements made by Rosetta, numerical or analytical models are necessary. Methods. An extended analytical formalism describing solar wind charge-changing processes at comets along solar wind streamlines is presented. It is based on a thorough book-keeping of available charge-changing cross sections of hydrogen and helium particles in a water gas. Results. After presenting a general 1D solution of charge exchange at comets, we study the theoretical dependence of charge-state distributions of (He2+, He+, He0) and (H+, H0, H−) on solar wind parameters at comet 67P. We show that double charge exchange for the He2+−H2O system plays an important role below a solar wind bulk speed of 200 km s−1, resulting in the production of He energetic neutral atoms, whereas stripping reactions can in general be neglected. Retrievals of outgassing rates and solar wind upstream fluxes from local Rosetta measurements deep in the coma are discussed. Solar wind ion temperature effects at 400 km s−1 solar wind speed are well contained during the Rosetta mission. Conclusions. As the comet approaches perihelion, the model predicts a sharp decrease of solar wind ion fluxes by almost one order of magnitude at the location of Rosetta, forming in effect a solar wind ion cavity. This study is the second part of a series of three on solar wind charge-exchange and ionization processes at comets, with a specific application to comet 67P and the Rosetta mission.

scholarly journals Laboratory measurements to interpret dust polarimetric observations and in-situ radar studies. Implications for the Rosetta mission.

2015 ◽  
Vol 11 (A29A) ◽  
Author(s):  
A.-Ch. Levasseur-Regourd ◽  
Yann Brouet ◽  
Edith Hadamcik
Keyword(s):  
Laboratory Studies ◽  
Laboratory Measurements ◽  
Scattering Media ◽  
Astronomical Observations ◽  
Dust Clouds ◽  
Rosetta Mission ◽  
Recent Developments ◽  
Solar System Bodies ◽  
Comet 67P

Polarimetric astronomical observations on dust clouds and regolithic surfaces require laboratory simulations on samples to provide clues to properties of the scattering media. Similarly, in-situ radar investigations of Solar System bodies require laboratory studies to infer the physical properties of their interiors. Recent developments are illustrated by analyses of comet 67P/Churyumov-Gerasimeko (C-G) remote observations and in-situ studies from Rosetta mission.

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