Roset­ta - Eu­rope's comet chas­er

Philae landing on comet
Phi­lae land­ing on comet
Image 1/4, Credit: ESA–C. Carreau/ATG medialab.

Philae landing on comet

Artist’s im­pres­sion of the Roset­ta or­biter de­ploy­ing the Phi­lae lan­der to comet 67P/Churyu­mov–Gerasi­menko (not to scale).
Gas and dust streams from the ‘neck’ of Comet 67P/ Churyu­mov-Gerasi­menko
Image 2/4, Credit: ESA/Rosetta/NAVCAM - CC BY-SA IGO 3.0.

Gas and dust streams from the ‘neck’ of Comet 67P/ Churyumov-Gerasimenko

Since its ar­rival at the comet, Roset­ta has ob­served jets of gas and dust. Nu­mer­ous gas erup­tions have been ob­served orig­i­nat­ing from the ‘neck’ of the comet. Us­ing the mea­sure­ments per­formed by the VIR­TIS spec­trom­e­ter, it has been pos­si­ble to recog­nise a day/night cy­cle of cometary ac­tiv­i­ty and iden­ti­fy the mech­a­nism re­spon­si­ble.
Roset­ta's jour­ney through the So­lar Sys­tem (Click on the pic­ture to see in larg­er scale); (c) DLR CC-BY 3.0
Image 3/4, Credit: DLR (CC-BY 3.0)

Rosetta's journey through the Solar System (Click on the picture to see in larger scale); (c) DLR CC-BY 3.0

To reach its des­ti­na­tion adapt­ing its route to match the comet's tra­jec­to­ry and sub­stan­tial changes in speed were nec­es­sary. In prac­ti­cal terms, the or­biter ac­cel­er­at­ed by build­ing mo­men­tum as it passed by Earth or Mars on what is known as a swing-by ma­noeu­vre.
From time to time, the Rosetta orbiter was manoeuvred to within two kilometres of the comet in preparation for the end of the mission
From time to time, the Roset­ta or­biter was ma­noeu­vred to with­in two kilo­me­tres of the comet in prepa­ra­tion for the end of the mis­sion.
Image 4/4, Credit: Main image and lander inset: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; context: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

From time to time, the Rosetta orbiter was manoeuvred to within two kilometres of the comet in preparation for the end of the mission.

On these oc­ca­sions the OSIRIS cam­era man­aged to ac­quire im­ages show­ing de­tails just a few cen­time­tres across. The sur­prise came on 2 Septem­ber 2016: Phi­lae was found in the shad­ows of a rock for­ma­tion, ly­ing side­ways.

The European Space Agency (ESA) Rosetta mission was designed to study the formation and evolution of the Solar System by exploring one of the oldest and most primordial heavenly bodies – comets. The mission consisted of the Rosetta orbiter and the Philae lander. The probes were launched on 2 March 2004, travelled 6.4 billion kilometres in 10 years and, with the help of a few planet swing-bys, arrived at Comet 67P/Churyumov-Gerasimenko on 6 August 2014.

DLR played a major role in the construction of the lander and operated the Lander Control Center (LCC), from where the difficult task of landing on the comet on 12 November 2014 – a feat never before accomplished – was designed and controlled. On 27 July 2016, after almost two years of cometary exploration, the communications unit on board the Rosetta orbiter (which it used to communicate with the Philae lander) was switched off. On 30 September 2016, the operational part of the mission came to an official end, with the orbiter's controlled descent.

Rosetta at a glance - technical data and timeline

Timeline
The European Space Agency (ESA) approves the Rosetta mission:November 1993
Original launch date:
(to comet 46P/Wirtanen;
postponed due to technical problems
with the launcher)
Beginning of 2003
Launch of Rosetta to comet 67P/Churyumov-Gerasimenko:02 March 2004, 08:17 CET
1st Earth gravity assist:04 March 2005
Mars gravity assist:25 February 2007
2nd Earth gravity assist:13 November 2007
Asteroid Steins flyby:05 September 2008
3rd Earth gravity assist:13. November 2009
Asteroid Lutetia flyby:10 July 2010
Enter deep space hibernation:08 June 2011
Exit deep space hibernation:20 January 2014, 10:00 GMT
Major comet rendezvous manoeuvre:May 2014
Arrive at comet:06 August 2014
Philae lander delivery:12 November 2014
Perihelion passage
(Closest approach to Sun):
13 August 2015
Mission end:30 September 2016

Mission
Launch date:2 March 2004, 08:17 CET
Launch site:Kourou, French Guiana
Launcher:Ariane 5 G
Mission duration:12 years in total, until December 2015
Mission Control Centre:European Space Operations Center (ESOC), Darmstadt
Philae Lander Control Centre:DLR Microgravity User Support Centre, Cologne
Ground stations:Perth, Australia and Kourou, French Guiana
Launch mass:3000 kilograms
Fuell:1670 kilograms
Science payload:165 kilograms

Rosetta orbiter
Orbiter dimensions:2.8 x 2.1 x 2.0 metres
Solar panel dimensions:Two panels, each 14 metres long; total surface area of 64 square metres
Power via solar panels:850 W at 3.4 AU*, 395 W at 5.25 AU*
(* AU = Astronomical Unit = roughly the distance from Earth to the Sun)
Communications antenna:Two-axis steerable high-gain antenna, 2.2 metres in diameter
nstruments on the orbiter (11)
ALICE:imaging ultraviolet spectrometer to analyse the composition of the comet's nucleus, coma and ion tail.
CONSERT (COmet Nucleus Sounding Experiment by Radio wave Transmission):transmits long-wave radio signals through the comet's nucleus to explore its structure.
COSIMA (COmetary Secondary Ion Mass Spectrometer):mass spectrometer that collects cometary dust grains and analyses their chemical composition.
GIADA (Grain Impact Analyser and Dust Accumulator):determines the number, size and speed of the dust grains in the coma.
MIDAS (Micro-Imaging Dust Analysis System):high-resolution scanning probe microscope that studies the fine structure of the dust particles around the asteroids and comet.
MIRO (Microwave Spectrometer for the Rosetta Orbiter):microwave instrument for determining the composition of the core and coma, as well as for measuring cometary activity and determining physical properties of the surface of the nucleus (temperature) and coma molecules (density, temperature, and velocity).
OSIRIS (Optical, Spectroscopic, and InfraRed Remote Imaging System):a telephoto and wide-angle camera that will acquire high-resolution images in different spectral bands for the characterisation of the nucleus and its surroundings.
ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis):the instrument consists of two mass spectrometers and a pressure sensor and determines the chemical composition of the coma, the isotope ratios and the temperature and speed of the gas molecules.
RPC (Rosetta Plasma Consortium):comprises ion and electron detectors and a magnetometer to measure physical properties of the nucleus and coma as well as the interaction of the coma and tail with the solar wind.
RSI (Radio Science Investigation):uses the spacecraft communication system to determine the gravitational field, the comet size, mass and shape, as well as the structure of the nucleus.
VIRTIS (Visible and Infrared Thermal Imaging Spectrometer):Abbildendendes Spektrometer, das die Zusammensetzung und Temperatur der Oberfläche misst sowie die Gasmoleküle in der Koma charakterisiert.

Philae lander
Weight:100 kilograms
Data transmission:16 kilobytes per second via the orbiter
Energy supply:Solar generator, 4 Watts, primary (for the first 60 hours after the landing on the comet) and secondary (rechargeable) batteries
Instruments on the lander (10)
APX (Alpha-Particle-X-Ray-Spectrometer):spectrometer for analysing the chemical composition of matter directly on the comet's surface.
CIVA (Comet Infrared and Visible Analyzer):photographs the landing site and examines the samples of the comet’s surface acquired with the SD2 drill through microscopes.
CONSERT (Comet Nucleus Sounding Experiment by Radio wave Transmission):radio wavelength probe for the screening of the nucleus in conjunction with the orbiter.
COSAC (Cometary Sampling and Composition):determines the elementary, isotopic and chemical composition of the frozen components of the comet’s surface to a depth of 30 centimetres.
MUPUS (Multi-Purpose Sensors for Surface and Subsurface Science):several sensors measure the surface temperature and thermal conductivity of the ground.
PTOLEMY:an evolved gas analyser, which obtains accurate measurements of isotopic ratios of light elements.
ROLIS (Rosetta Lander Imaging System):panoramic camera to photograph the landing site during and after Philae's landing phase.
ROMAP (Rosetta Lander Magnetometer and Plasmamonitor):studies the magnetic field of the comet and the comet/solar-wind interaction.
SD2 (Sample, Drill and Distribution):drilling mechanism for obtaining samples at a depth of up to 30 centimetres.
SESAME (Surface Electric Sounding and Acoustic Monitoring Experiment):comprises sensors for measuring the acoustic and dielectric characteristics of the nucleus as well as a particle impact monitor.

Comet 67P/Churyumov-Gerasimenko
Origin:

Kuiper Belt object moving in an elliptical orbit around the Sun between Jupiter and
Earth; belongs to the Jupiter family of comets.

Year of discovery:1969
Discoverers:K. Churyumov, University of Kiev, Ukraine
S. Gerasimenko, Institute of Astrophysics, Dushanbe, Tajikistan.
First images of comet nucleus:Acquired on 12 March 2003 by the Hubble Space Telescope; they show an oval body roughly 3 by 5 kilometres.
Mean diameter of nucleus:4 kilometres
Orbital period around the Sun:6.45 years
Minimum distance to the Sun (perihelion):186 million kilometres (1.24 AU* )
Maximum distance from the Sun (aphelion):857 million kilometres (5.68 AU* )
Orbital eccentricity:0.64 (elliptical orbit)
Rotation period:12.4 to 12.9 hours
Development of orbit:In 1840, the perihelion distance was 4 AU; a Jupiter flyby followed, decreasing the perihelion distance. By 1959, the perihelion distance was 2.7 AU; another Jupiter flyby in February 1959 reduced it further to today's value.
Albedo (reflectivity):0.04 (very low, darker than coal).
Density of the surface material:100 to 500 kilograms per cubic metre (comparable with a dry sponge).
Mass loss:During the perihelion pass on 13 August 2015, up to 300 kilograms of comet dust per second were swept to space by sublimating ice.

* AU = Astronomical Unit = roughly the distance from Earth to the Sun

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