spase://CNES/Observatory/CDPP-Archive/ROSETTA

The ROSETTA mission is an interplanetary mission whose main objectives are the rendezvous and in-situ measurements of the comet 67P/Churyumov-Gerasimenko, scheduled for 2014/2015. The spacecraft carries a Rosetta Lander, named Philae, to the nucleus and deploys it onto its surface.
A brief description of the mission and its objectives can be found in :
Glassmeier, K.H. et al. (2007), The Rosetta Mission: Flying Towards the Origin of the Solar System, Space Science Reviews, Volume 128, Issue 1-4, pp.1-21, doi:10.1007/s11214-006-9140-8 .

On its long way to the comet nucleus after a Launch by Ariane 5 P1+ in March 2004, the ROSETTA spacecraft orbited the Sun for one year until it returned to Earth for the first swing-by. The planet Mars was reached in February 2007, about 3 years after launch. In November 2007 a second Earth swing-by took place and a third one in November 2009. Two asteroid flybys (2867 Steins and 21 Lutetia) were performed on the way to the comet. These two asteroids had been selected at the Science Working Team meeting on 11th March 2004 among all the available candidate asteroids, depending on the scientific interest and the propellant required for the correction manoeuvre. Around the aphelion of its orbit, which is 5.3 AU from the Sun, the spacecraft has been in a spinning hibernation mode for about 2.5 years.

Rosetta rendezvoused with comet 67P/Churyumov-Gerasimenko in August 2014. The Philae lander was deployed to the surface of the comet on 12 November 2014.
The end of the nominal mission is planned in December 2015.
The mission has been extended to 30th September 2016.

Please note:
The ROSETTA spacecraft was originally designed for a mission to the comet 46 P/Wirtanen to be launched in January 2003. Due to a delay of the launch a new comet (67P/Churyumow-Gerasimenko) had been selected by the Science Working Team on 3rd-4th April 2003. The compliance of the design was checked and where necessary adapted for this new mission. Therefore in the following all the details and characteristics for this new mission are used.

ROSETTA Mission Objectives

The scientific objectives of the ROSETTA mission can be considered from three main viewpoints:

First of all, comets and asteroids are fully-fledged members of our solar system, which means, that they are objects of intrinsic interest to planetary scientists. The level of investigations conducted on these bodies is therefore far below that achieved for the other objects of the solar system. The study of the small solar-system bodies arguably represents the last major gap in the tremendous worldwide effort that has been made to reveal our planetary neighbours to us.
The most important scientific rationale for studying small solar- system bodies is the key role-play in helping us to understand the formation of the solar system. Comets and asteroids have a close genetic relationship with the planetesimals, which formed from the solar nebula 4.57 billion years ago. Most of our present understanding of these processes has been obtained by studying meteorites, which constitute a biased sample of asteroidal material, and micrometeoroids, which may represent cometary grains processed by solar radiation and atmospheric entry. There is therefore a strong scientific case of studying cometary material in situ, as it is surely more primitive than extraterrestrial samples.
A third scientific aspect is the study of the physio-chemical processes, which are specific to comets and asteroids. In this respect, asteroids can provide information on impact phenomena, particularly on very large scale. However, the increase in cometary activity as these bodies approach the Sun undoubtedly represents one of the most complex and fascinating processes to be observed in the solar system.

Science Objectives

The prime scientific objectives as defined in the Announcement of Opportunity [RO-EST-AO-0001] by the Rosetta Science Team can be summarized as:

• Global characterisation of the nucleus, determination of dynamic properties, surface morphology and composition
• Chemical, mineralogical and isotropic compositions of volatiles and refractories in a cometary nucleus
• Physical properties and interrelation of volatiles and refractories in a cometary nucleus
• Study of the development of cometary activity and the processes in the surface layer of the nucleus and in the inner coma (dust-gas interaction)
• Origin of comets, relationship between cometary and interstellar material
• Implications for the origin of the solar system
• Global characterisation of the asteroid, determination of dynamic properties, surface morphology and composition

Orbiter Experiments

ALICE

ALICE, an Ultraviolet Imaging Spectrometer, characterise the composition of the nucleus and coma, and the nucleus/coma coupling of comet 67 P/Churyumov-Gerasimenko. This is accomplished through the observation of spectral features in the extreme and far ultraviolet (EUV/FUV) spectral regions from 70 to 205 nm.

ALICE make measurements of noble gas abundances in the coma, the atomic budget in the coma, and major ion abundances in the tail and in the region where solar wind particles interact with the ionosphere of the comet. ALICE determine the production rates, variability, and structure of H2O and CO, and CO2 gas surrounding the nucleus and the far-UV properties of solid grains in the coma.

ALICE studied Mars and the Rosetta asteroid flyby targets while en route to Churyumov- Gerasimenko. ALICE also map the cometary nucleus in the FUV

Instrument References: Stern, S.A. et al. (2007), Alice: The rosetta Ultraviolet Imaging Spectrograph, Space Science Reviews, Volume 128, Issue 1-4, pp.507-527, doi:10.1007/s11214-006-9035-8

CONSERT

CONSERT (Comet Nucleus Sounding Experiment by Radio wave Transmission) is an experiment that perform tomography of the comet nucleus revealing its internal structure.
CONSERT operates as a time domain transponder between the Lander on the comet surface and the Orbiter. A radio signal passes from the orbiting component of the instrument to the component on the comet surface and is then immediately transmitted back to its source, the idea being to establish a radio link that passes through the comet nucleus. The varying propagation delay as the radio waves pass through different parts of the cometary nucleus is used to determine the dielectric properties of the nuclear material. Many properties of the comet nucleus is examined as its overall structural homogeneity, the average size of the sub-structures (Cometesimals) and the number and thickness of the various layers beneath the surface.

Instrument References: Kofman, W. et al. (2007), The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT): A Short Description of the Instrument and of the Commissioning Stages, Space Science Reviews, Volume 128, Issue 1-4, pp.413-432, doi:10.1007/s11214-006-9034-9

COSIMA

The Cometary Secondary Ion Mass Analyser is a secondary ion mass spectrometer equipped with a dust collector, a primary ion gun, and an optical microscope for target characterization. Dust from the near comet environment is collected on a target. The target is then moved under a microscope where the positions of any dust particles are determined. The cometary dust particles are then bombarded with pulses of indium ions from the primary ion gun. The resulting secondary ions are extracted into the time-of-flight mass spectrometer.

Instrument References: Kissel, J. et al. (2007), COSIMA - High resolution time-of-flight secondary ion mass spectrometer for the analysis of cometary dust particles onboard Rosetta, Space Science Reviews, Volume 128, Issue 1-4, pp.823-867, doi:10.1007/s11214-006-9083-0

GIADA

The Grain Impact Analyser and Dust Accumulator measures the scalar velocity, size and momentum of dust particles in the coma of the comet using an optical grain detection system and a mechanical grain impact sensor. Five microbalances measure the amount of dust collected as the spacecraft orbits the comet.

Instrument References: Colangeli, L. et al. (2007), MIDAS - The Micro-Imaging Dust Analysis System for the Rosetta Mission, Space Science Reviews, Volume 128, Issue 1-4, pp.869-904, doi:10.1007/s11214-006-9038-5

MIDAS

The Micro-Imaging Dust Analysis System is intended for the microtextural and statistical analysis of cometary dust particles. The instrument is based on the technique of atomic force microscopy. This technique, under the conditions prevailing at the Rosetta Orbiter permits textural and other analysis of dust particles to be performed down to a spatial resolution of 4nm.

Instrument References: Riedler, W. et al. (2007), The Grain Impact Analyser and Dust Accumulator (GIADA) experiment for the Rosetta mission: design, performances and first results, Space Science Reviews, Volume 128, Issue 1-4, pp.803-821, doi:10.1007/s11214-006-9040-y

MIRO

MIRO (Microwave Instrument for the Rosetta Orbiter) is composed of a millimetre wave mixer receiver and a submillimetre heterodyne receiver. The submillimetre wave receiver provides both broad band continuum and high resolution spectroscopic data, whereas the millimetre wave receiver provides continuum data only.

MIRO measures the near surface temperature of the comet, allowing estimation of the thermal and electrical properties of the surface. In addition, the spectrometer portion of MIRO allows measurements of water, carbon monoxide, ammonia, and methanol in the comet coma.

Instrument References: Gulkis, S. et al. (2007), MIRO: Microwave Instrument for Rosetta Orbiter, Space Science Reviews, Volume 128, Issue 1-4, pp.561-597, doi:10.1007/s11214-006-9032-y

OSIRIS

OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is a dual camera imaging system operating in the visible, near infrared and near ultraviolet wavelength ranges. OSIRIS consists of two independent camera systems sharing common electronics. The narrow angle camera is designed to produce high spatial resolution images of the nucleus of the target comet. The wide angle camera has a wide field of view and high straylight rejection to image the dust and gas directly above the surface of the nucleus of the target comet. Each camera is equipped with filter wheels to allow selection of imaging wavelengths for various purposes. The spectroscopic and wider band infrared imaging capabilities originally proposed and incorporated in the instrument name were descoped during development.

Instrument References: Keller, H.U. et al. (2007), OSIRIS - The Scientific Camera System Onboard Rosetta, Space Science Reviews, Volume 128, Issue 1-4, pp.403-506, doi:10.1007/s11214-006-9128-4

ROSINA

ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) consists of two mass spectrometers, since no one technique is able to achieve the resolution and accuracy required to fulfil the ROSETTA mission goals over the range of molecular masses under analysis. In addition, two pressure gauges provide density and velocity data for the cometary gas.

The two mass analysers are:

A double focusing magnetic mass spectrometer with a mass range of 1 - 100 amu and a mass resolution of 3000 at 1 % peak height, optimised for very high mass resolution and large dynamic range
A reflectron type time-of-flight mass spectrometer with a mass range of 1 -300 amu and a mass resolution better than 500 at 1 % peak height, optimised for high sensitivity over a very broad mass range

Instrument References: Balsiger, H. et al. (2007), ROSINA - Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Volume 128, Issue 1-4, pp.745-801, doi:10.1007/s11214-006-8335-3

The Rosetta Plasma Consortium

RPC (Rosetta Plasma Consortium) is a set of five sensors sharing a common electrical and data interface with the Rosetta orbiter. The RPC sensors are designed to make complementary measurements of the plasma environment around the comet 67P/Churyumov-Gerasimenko.

The RPC sensors are:

ICA: an Ion Composition Analyser, which measures the three-dimensional velocity distribution and mass distribution of positive ions
IES: an Ion and Electron Sensor, which simultaneously measures the flux of electrons and ions in the plasma surrounding the comet
LAP: a Langmuir Probe, which measures the density, temperature and flow velocity of the cometary plasma
MAG: a Fluxgate Magnetometer, which measures the magnetic field in the region where the solar wind plasma interacts with the comet
Instrument References: Glassmeier, K.H. et al. (2007), RPC-MAG The Fluxgate Magnetometer in the ROSETTA Plasma Consortium, Space Science Reviews, Volume 128, Issue 1-4, pp.649-670, doi:10.1007/s11214-006-9114-x
MIP: a Mutual Impedance Probe, which derives the electron gas density, temperature, and drift velocity in the inner coma of the comet.

Instrument References: Carr, C. et al. (2007), RPC - The ROSETTA Plasma Consortium, Space Science Reviews, Volume 128, Issue 1-4, pp.629-647, doi:10.1007/s11214-006-9136-4

RSI

RSI (Radio Science Investigation) makes use of the communication system that the Rosetta spacecraft uses to communicate with the ground stations on Earth. Either one-way or two-way radio links can be used for the investigations. In the one-way case, a signal generated by an ultra-stable oscillator on the spacecraft is received on earth for analysis. In the two way case, a signal transmitted from the ground station is transmitted back to Earth by the spacecraft. In either case, the downlink may be performed in either X-band or both X -band and S-band.

RSI investigates the nondispersive frequency shifts (classical Doppler) and dispersive frequency shifts (due to the ionised propagation medium), the signal power and the polarization of the radio carrier waves. Variations in these parameters yields information on the motion of the spacecraft, the perturbing forces acting on the spacecraft and the propagation medium.

Instrument References: Pätzold, M. et al. (2007), Rosetta Radio Science Investigations (RSI), Space Science Reviews, Volume 128, Issue 1-4, pp.599-627, doi:10.1007/s11214-006-9117-7

VIRTIS

VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) is an imaging spectrometer that combines three data channels in one instrument. Two of the data channels are committed to spectral mapping and are housed in the Mapper optical subsystem. The third channel is devoted solely to spectroscopy and is housed in the High resolution optical subsystem.

The mapping channel optical system is a Shafer telescope consisting of five aluminium mirrors mounted on an aluminium optical bench. The mapping channel uses a silicon charge coupled device (CCD) to detect wavelengths from 0.25 micron to 1 micron and a mercury cadmium telluride (HgCdTe) infrared focal plane array (IRFPA) to detect from 0.95 micron to 5 microns.

The high resolution channel is an echelle spectrometer. The incident light is collected by an off-axis parabolic mirror and then collimated by another off-axis parabola before entering a cross- dispersion prism. After exiting the prism, the light is diffracted by a flat reflection grating, which disperses the light in a direction perpendicular to the prism dispersion. The high-resolution channel employs a HgCdTe IRFPA to perform detection from 2 to 5 microns.

Instrument References: Coradini, A. et al. (2007), Virtis : an imaging spectrometer for the Rosetta mission, Space Science Reviews, Volume 128, Issue 1-4, pp.529-559, doi:10.1007/s11214-006-9127-5

SREM

The Standard Radiation Environment Monitor (SREM) is a monitor-class instrument intended for space radiation environment characterisation and radiation housekeeping purposes. SREM provides continuous directional, temporal, and spectral data of high-energy electron, proton, and cosmic ray fluxes encountered along the orbit of the spacecraft, as well as measurements of the total accumulated radiation dose absorbed by SREM itself.

This instrument is a facility monitor flown on several ESA spacecrafts. It is not considered as a PI (Principal Investigator) instrument.

Instrument References: Mohammadzadeh A. et al. (2003), The ESA Standard Radiation Environment Monitor Program First Results From PROBA-I and INTEGRAL, IEEE Transactions on Nuclear Science, Volume 50, Issue 6, pp.2272-2277, doi:10.1109/TNS.2003.821796

Lander Experiments

The 100 kg Rosetta Lander, named Philae, is the first spacecraft ever to make a soft landing on the surface of a comet nucleus. The Lander is provided by a European consortium under the leadership of the German Aerospace Research Institute (DLR) and the French Space Research Center (CNES). Other members of the consortium are ESA and institutes from Austria, Finland, France, Hungary, Ireland, Italy and the UK. A description of the Lander can be found in [RO-EST-RS-3020].
The box-shaped Lander was carried in piggyback fashion on the side of the Orbiter until it arrived at Comet 67P/Churyumov-Gerasimenko. Once the Orbiter was aligned correctly, the ground station commanded the Lander to self-eject from the main spacecraft and unfold its three legs, ready for a gentle touch down at the end of the ballistic descent. The Landing is described above.
Immediately after touchdown, a harpoon was supposed to fire to anchor the Lander to the ground and prevent it escaping from the comet's extremely weak gravity. The system did not work and the Lander bounced several times.

Here a description of all the instruments of the Lander:

APXS: Alpha-p-X-ray spectrometer

The goal of the Rosetta APXS experiment is the determination of the chemical composition of the landing site and its potential alteration during the comet's approach to the Sun. The data obtained is used to characterize the surface of the comet, to determine the chemical composition of the dust component, and to compare the dust with known meteorite types.

Instrument References: Klingelhöfer, G. et al. (2007), The Rosetta Alpha Particle X-Ray Spectrometer (APXS), Space Science Reviews, Volume 128, Issue 1-4, pp.383-396, doi:10.1007/s11214-006-9137-3

CIVA: Panoramic and microscopic imaging system

The Cometary Infrared and Visible Analiser (CIVA) is an integrated set of imaging instruments, designed to characterize the landing and sampling site, the 360 deg panorama as seen from the Rosetta Lander, all samples collected and delivered by the Drill Sample and Distribution System, and the stratigraphy within the boreholes. It is constituted by a panoramic stereo camera (CIVA-P), and a microscope coupled to an IR spectrometer (CIVA-M). CIVA is sharing a common Imaging Main Electronics (CIVA/ROLIS/IME) with ROLIS. CIVA-P will characterize the landing site, from the landing legs to the local horizon. The camera is composed of 6 identical micro-cameras, mounted of the Lander sides, with their optical axes separated by 60 deg. In addition, stereoscopic capability is provided by one additional micro- camera, identical to and co-aligned with one of the panoramic micro- camera, with its optical axis 10 cm apart.

CIVA-M combines in separated boxes, two ultra-compact and miniaturized channels, one visible microscope CIVA-M/V and one IR spectrometer CIVA-M/I, to characterize, by non-destructive analyses, the texture, albedo, mineralogical and molecular composition of each of the samples collected and distributed by the Drill Sample and Distribution System.

Instrument References: Bibring, J.P. et al. (2007), CIVA, Space Science Reviews, Volume 128, Issue 1-4, pp.397-412, doi:10.1007/s11214-006-9135-5

CONSERT: Radio sounding, nucleus tomography

The Comet Nucleus Sounding Experiment by Radio wave Transmission (CONSERT) is a complex experiment that performs tomography of the comet nucleus revealing its internal structure. CONSERT operates as a time domain transponder between the Lander, on the comet surface and the Orbiter orbiting the comet. A radio signal passes from the orbiting component of the instrument to the component on the comet surface and is then immediately transmitted back to its source, the idea being to establish a radio link that passes through the comet nucleus. The varying propagation delay as the radio waves pass through different parts of the cometary nucleus is used to determine the dielectric properties of the nuclear material. Many properties of the comet nucleus is examined as its overall structural homogeneity, the average size of the sub-structures (Cometesimals) and the number and thickness of the various layers beneath the surface.

Instrument References: Kofman, W. et al. (2007), The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT): A Short Description of the Instrument and of the Commissioning Stages, Space Science Reviews, Volume 128, Issue 1-4, pp.413-432, doi:10.1007/s11214-006-9034-9

COSAC: Evolved gas analyser - elemental and molecular composition

The COmetary SAmpling and Composition experiment COSAC is one of the two 'evolved gas analysers' (EGAs) on board the Rosetta-Lander. Whereas the other EGA, Ptolemy, aims mainly at accurately measuring isotopic ratios of light elements, the COSAC is specialised on detection and identification of complex organic molecules. The instrument can be described as an effort to analyse in situ, mainly with respect to the composition of the volatile fraction, cometary matter nearly as well and accurately as could be done in a laboratory on Earth. Due to the Rosetta Lander rotatability, the instrument can conduct analyses and investigations at different spots of the landing site and, aided by the drill, take samples for analysis from a depth up to at least 0.2 m.

Instrument References: Goesmann F. et al. (2007), COSAC, The Cometary Sampling and Composition Experiment on Philae, Space Science Reviews, Volume 128, Issue 1-4, pp.257-280, doi:10.1007/s11214-006-9000-6

PTOLEMY: Evolved gas analyser - isotopic composition

The size of a small shoe box and weighing less than 5 kg, Ptolemy uses gas chromatography / mass spectrometry (GCMS) techniques to investigate the comet surface & subsurface. The instrument concept is termed 'MODULUS' which is taken to mean Methods Of Determining and Understanding Light elements from Unequivocal Stable isotope compositions. The scientific goal of the PTOLEMY is to understand the geochemistry of light elements, such as hydrogen, carbon, nitrogen and oxygen, by determining their nature, distribution and stable isotopic compositions.

Instrument References: Wright, I. et al. (2007), Ptolemy - an Instrument to Measure Stable Isotopic Ratios of Key Volatiles on a Cometary Nucleus, Space Science Reviews, Volume 128, Issue 1-4, pp.363-381, doi:10.1007/s11214-006-9001-5

MUPUS: Measurements of surface and subsurface properties

The Multi-Purpose Sensor Experiment actually consists of different parts:

A penetrator, approximately 40 cm long, is hammered into the ground about 1m apart from the Lander for measuring during the penetration process the mechanical strength of the material by means of a depth sensor and a densitometer. The penetrator is equipped with a series of temperature sensors and heaters for determining the temperature as a function of depth and insolation.
An accelerometer and a temperature sensor accommodated in the harpoon(s)
A four-channel infrared radiometer measures surface temperatures in the vicinity of the Lander. Density of the nearsurface (down to 20cm) material is determined by measuring the absorption of gamma-rays emitted from a radioactive isotope mounted at the tip of the penetrator.

Instrument References: Spohn, T. et al. (2007), Mupus - A Thermal and Mechanical Properties Probe for the Rosetta Lander Philae, Space Science Reviews, Volume 128, Issue 1-4, pp.339-362, doi:10.1007/s11214-006-9081-2

ROLIS: Descent & Down-Looking Imaging

The ROLIS Camera (Rosetta Lander Imaging System) delivered first close-ups of the environment of the landing place of comet 67P/Churyumov-Gerasimenko during the descent. After landing ROLIS made high-resolved investigations to study the structure (morphology) and mineralogy of the surface.

Instrument References: Mottola, S. et al. (2007), The Rolis Experiment on the Rosetta Lander, Space Science Reviews, Volume 128, Issue 1-4, pp.241-255, doi:10.1007/s11214-006-9004-2

ROMAP: Magnetometer and plasma monitor

The Rosetta Lander Magnetometer and Plasma Monitor ROMAP is a multi- sensor experiment. The magnetic field is measured with a fluxgate magnetometer. An electrostatic analyzer with integrated Faraday cup measures ions and electrons. The local pressure is measured with Pirani and Penning sensors. The sensors are situated on a short boom. The deployment on the surface of a cometary nucleus demanded the development of a special digital magnetometer of little weight and small power requirements. For the first time a magnetic sensor is operated from within a plasma sensor. A prototype of the magnetometer, named SPRUTMAG, was flown on space station MIR.

Instrument References: Auster U. et al. (2007), ROMAP: Rosetta Magnetometer and Plasma Monitor, Space Science Reviews, Volume 128, Issue 1-4, pp.221-240, doi:10.1007/s11214-006-9033-x

SD2: Sampling, Drilling and Distribution Subsystem

The Rosetta-Lander is equipped with a Sample Drill & Distribution (SD2) subsystem which is in charge to collect cometary surface samples at given depth and distribute them to the following instruments: CIVA-M (microscope (MS) & Infrared Spectrometer (IS)), the ovens, serving COSAC and PTOLEMY.

Comet sample from pre-determinated and/or known (measured) depth are collected and transported by SD2 to well defined locations:

MS & IS viewing place
ovens for high temperature (800 deg C) heating
ovens for medium temperature (130 deg C) heating.
ovens with a window, where samples can be investigated by CIVA-M

The sampling, drilling and distribution (SD2) subsystem provides microscopes and advanced gas analysers with samples collected at different depths below the surface of the comet. Specifically SD2 can bore up to 250 mm into the surface of the comet and collect samples of material at predetermined and/or known depths. It then transports each sample to a carousel which feeds samples to different instrument stations: a spectrometer, a volume check plug, ovens for high and medium temperatures and a cleaning station. SD2 is accommodated on the flat ground-plate of the Rosetta, where it is exposed to the cometary environment.

Instrument References: Ercoli-Finzi, A. et al. (2007), SD2 - How To Sample A Comet, Space Science Reviews, Volume 128, Issue 1-4, pp.281-299, doi:10.1007/s11214-006-9134-6

SESAME: Surface electrical, acoustic and dust impact monitoring

The SESAME (Surface Electrical, Seismic and Acoustic Monitoring Experiments) electronics board and the integration of the components are managed by the German Aerospace Center (DLR), Institute of Space Simulation, Cologne.

The results of SESAME help in understanding how comets, have formed and thus, how the solar system, including the Earth, was born.

Instrument References: Seidensticker, K.J. et al. (2007), Sesame - An Experiment of the Rosetta Lander Philae: Objectives and General Design, Space Science Reviews, Volume 128, Issue 1-4, pp.301-337, doi:10.1007/s11214-006-9118-6