The Rosetta spacecraft is a robotic spacecraft built by the European Space Agency (ESA). The craft was launched on March 2, 2004 and is designed to perform a rendezvous with Comet 67P/Churyumov-Gerasimenko in 2014. It will become the first spacecraft to land on a comet nucleus and study it in-situ.
The name of the Rosetta mission comes from its key science objectives: as comets are considered primitive building blocks of the Solar System, understanding their composition and origins will provide clues about how the Solar System formed. The main goals of Rosetta are therefore to study the comet’s composition, structure, dynamics and environment during its closest approach to the Sun (perihelion). Additionally, although not part of its primary science objectives,Rosetta will also search for evidence of water ice on or near the surface of 67P/C-G. If present, this could help support theories that cometary activity was responsible for delivering water to Earth early in its history.
The total budget for ESA’s Rosetta mission is about 1 billion euros. The bulk of this cost has been covered by ESA member states; additional funds have been provided by NASA and other space agencies around the world through bilateral agreements with ESA. As part of these agreements, NASA has provided several key instruments for inclusion on board Rosetta including: 1) A mid-infrared spectrometer called MIRO; 2) An ultraviolet imaging spectrograph called ALICE; 3) One of two ion traps called ROSINA (the other is being supplied by Switzerland); 4) Radio receivers that will be used as part of an ongoing effort to track asteroids; 5) And finally, one camera – OCAMS – which will take high resolution images during close flybys past 67P/C-G.
Instrument Description:
MIRO: The Microwave Instrument for Rosetta Orbiter is a sensitive radiometer that uses five submillimeter waveguides operating at different frequencies between 118 and 183 GHz with carbon dioxide gas as tuning elements . MIRO maps gasses emitted from Cometary Nucleus Surfaces (CNS), providing information about outgassing rates as function temperature profile below ~30 cm depth where most active CNS regions are expected reside . In addition mapping gasses distribution across surfaces provides insight into processes governing coma formation . MIRO observations also searched unsuccessfullyfor periodic variations in emission related sublimation jets seen Halley’s Comet 1986 . Nevertheless because MIRO operates over wide range wavelengths it can detect many other molecules emitted comets , some which may serve tracers specific physical processes such gas release sites or chemical interactions surface ices exposed solar radiation vacuum conditions . operationally , commands sent ground directly manipulate calibration devices internal cryogenic dewar prevent sample loading optical path ; data downlinked realtime 8 kbps rate stored onboard solidstate recorder mass memory system later transmitted ground station pass via relay satellites when lineofsight available ALICE : UV Imaging Spectrograph capable detecting photons wavelengths 115180 nm using Rowland Circle configuration echelle grating crossdispersed photomultiplier tubes photon counting mode operation low backgrounds dark current noise levels instrument very wellsuited observing faint extended sources like coma clouds surrounding comet nucleiALICE slitless spectroscopic design means scattered light photons detected along line sight instrument often large problem when trying obtain spatiallyresolved measurements but advantage far outweighed disadvantages case where targets completely fill field view due small angular size emissions expected coma inner coma diameters < 5000 km~0 05radian simple geometric considerations show even highly dispersed spectrum would fit within single pixel detector area 20 micron square array 10241024 pixels size 10 times smaller than typically found CCD cameras used astronomical applications since telemetry constraints limit amount data could returned ground team decision made only use full 1024x1024 pixel mode operations close enough target image entire nucleus comfortably contained field view resulting amazing spatial resolutions eventually achievable images taken closer encounter phase mission example 100 mpixel−1 scale 0 005km100 m measured 6 periode days allowed full map rotation period made possible reconstruct 3D shape model nucleus shape knowledge gained critical importance landing site selection Philae Lander another important aspect scientific return ALICE instrument provides direct measure elemental abundance ratio isotopes common materials present coma giving clues origin composition parent body material initially accreted form solar nebula matter later ejected following heating events either impact cratering volcanism exothermic reactions surface ices reformation refractory minerals embedded volatile organics exposed increased temperatures perihelion passage 68P ChuryumovGerasimenko typical velocity dispersion values order 15 ms−1 obtained resolving power Rλ 1500 corresponding resolving power E 400000 implies ability distinguish emission lines separated less 200 pm wavelength range 115180 nm ROSINA : Double Focusing Mass Spectrometer acronym stands “Rosetta Orbiter Sensor dust INA” consists two separate mass spectrometers sharing same ion optics but different pressure regimes reflectors mounted inside meterlong cylinder focus ions perpendicular plane incident beam entrance aperture hole diameter 50 microns located end rear section instrument front section hosts pair electrostatic deflectors extract ions passing central aperture then send them towards set second pair electrostatic lenses focus parallel first lens system output slits allow filtered ions reach detectors placed above below focal point each lens system achieve mass resolving powers 300000 300 Da measurement precision better 1% functions detecting identify molecules present atmosphere specifically looking noble gases H O CO CH NH DMSO HCN HCHO H S CS SO NH OCS CH CN HF OH families these species thought play role production tholins haze particles believed major contributors reddish tinge color observed some cometary nuclei OCAMS : Optical Camera System abbreviation “OSIRIS Camera Suite” refers collection three cameras taking visiblewavelength photographs 16 megapixels pixel arrays 2048x2048 18 micron pixels format size 45mm 45mm detector back illuminated CCD chip thinned deepdepletion technology minimize scattering stray light four filters BGGR centered wavelengths 440 490 550 650nm applied raw images correct optical distortion flat fielding effects produce linearized calibrated images effective exposure time individual frames limited 8 seconds order avoid saturation star tracker stars background subtracted aid centering target comet frame acquisition rates 5 Hz fast slewing maneuvers 30 degrees second possible before tracking lost guide stars long term tracking rates much lower depend telescope pointing stability thermal expansion characteristics aluminum honeycomb structure payload bay walls References :