Cassini–Huygens
67941
225485338
2008-07-13T23:03:11Z
201.76.248.144
{{Mergefrom|Saturn Orbiter/Titan Probe|date=January 2008}}
{{Current spaceflight}}
{{Infobox_Spacecraft
| Name = ''Cassini–Huygens''
| Image = [[Image:Cassini Saturn Orbit Insertion.jpg|300px]]
| Caption = An artist's concept of ''Cassini''
| Organization = [[NASA]]/[[European Space Agency|ESA]]/[[Italian Space Agency|ASI]]
| Major_Contractors =
| Mission_Type = Fly-by, orbiter, and lander
| Flyby_Of = [[Jupiter (planet)|Jupiter]], [[Venus]], [[Earth]], [[Saturn's moons]]
| Satellite_Of = '''[[Saturn]]'''
| Launch = [[October 15]] [[1997]] <small>({{age in days|1997|10|15}} days ago)</small>
| Launch_Vehicle = [[Titan IV]]-B/Centaur launch vehicle
| Decay =
| Mission_Duration =
| Mass =
| NSSDC_ID = 1997-061A
| Webpage = [http://saturn.jpl.nasa.gov/home/index.cfm Cassini–Huygens Home]
| Semimajor_Axis =
| Eccentricity =
| Inclination =
| Orbital_Period =
| Apoapsis =
| Periapsis =
| Orbits =
}}
'''''Cassini–Huygens''''' is a joint [[NASA]]/[[European Space Agency|ESA]]/[[Italian Space Agency|ASI]] [[robotic spacecraft]] mission currently studying the planet [[Saturn (planet)|Saturn]] and [[Saturn's natural satellites|its moons]]. The [[spacecraft]] consists of two main elements: the NASA '''''Cassini'' orbiter''', named after the Italian-French astronomer [[Giovanni Domenico Cassini]], and the ESA [[Huygens probe|'''''Huygens'' probe''']], named after the Dutch astronomer, mathematician and physicist [[Christiaan Huygens]]. It was launched on [[October 15]] [[1997]] and entered into [[orbit]] around Saturn on [[July 1]] [[2004]]. On [[December 25]] [[2004]] the ''Huygens'' probe separated from the orbiter at approximately 02:00 [[Coordinated Universal Time|UTC]]; it reached Saturn's moon [[Titan (moon)|Titan]] on [[January 14]] [[2005]] where it made an atmospheric descent to the surface and relayed scientific information. On [[April 18]] [[2008]], NASA announced a two year extension of the mission.<ref>http://www.cnn.com/2008/TECH/science/04/16/NASA.Saturn.ap/index.html</ref> ''Cassini'' is the first spacecraft to orbit Saturn and the fourth to visit it.
==Overview==
''Cassini'' has seven primary objectives:
# Determine the three-dimensional structure and dynamic behavior of the [[planetary ring|rings]] of Saturn
# Determine the composition of the [[satellite]] surfaces and the [[geological]] history of each object
# Determine the nature and origin of the dark material on [[Iapetus (moon)|Iapetus's]] leading hemisphere
# Measure the three-dimensional structure and dynamic behavior of the [[magnetosphere]]
# Study the dynamic behavior of Saturn's [[Celestial body atmosphere|atmosphere]] at [[cloud]] level
# Study the time variability of [[Titan (moon)|Titan's]] clouds and [[haze]]s
# Characterize Titan's surface on a regional scale
The ''Cassini–Huygens'' spacecraft was launched on [[October 15]] [[1997]] from [[Cape Canaveral Air Force Station]]'s [[Cape Canaveral Air Force Station Launch Complex 40|Launch Complex 40]] using a [[US Air Force]] [[Titan IV]]B/[[Centaur rocket|Centaur]] launch vehicle. The launch vehicle was made up of a two-stage [[Titan IV]] [[booster rocket]], two strap-on solid [[rocket motor]]s, the Centaur upper stage, and a payload enclosure, or fairing. The complete ''Cassini'' flight system was composed of the launch vehicle and the spacecraft.
The spacecraft was composed of the ''Cassini'' [[orbiter]] and the ''Huygens'' probe. The orbiter was designed to orbit Saturn and its moons for four years. The probe was to dive into the atmosphere of Titan and land on its surface, which it did early in the mission. Seventeen nations contributed to building the spacecraft. The ''Cassini'' orbiter was built and managed by NASA/[[California Institute of Technology|Caltech's]] [[Jet Propulsion Laboratory]]. The ''Huygens'' probe was built by the [[European Space Agency]] (ESA). The [[Italian Space Agency]] (ASI) provided ''Cassini'''s high-gain [[communication]] [[antenna (radio)|antenna]], and a revolutionary compact and light-weight multimode radar (synthetic aperture radar, radar altimeter, radiometer).
The total cost of the mission is about [[United States dollar|US$]]3.26 [[1000000000 (number)|billion]], including $1.4 billion for pre-launch development, $704 [[million]] for mission operations, $54 million for tracking and $422 million for the launch vehicle. The US contributed $2.6 billion, ESA $500 million and ASI $160 million.
The nominal end of the mission is in 2008 but an extension to the mission until 2010 was approved. It is possible that funding will be granted for additional extensions.
A list of [[Cassini–Huygens#Glossary_of_Terms|Cassini–Huygens abbreviations]] is available.
==History==
[[Image:Cassini-Huygens launch.jpg|thumb|200px|Launch occurred at 4:43 a.m. EDT (8:43 UTC) on [[October 15]] [[1997]] from Launch Complex 40 at Cape Canaveral Air Force Station, Florida]]
''Cassini–Huygens'''s origins date to 1982, when the [[European Science Foundation]] and the American [[United States National Academy of Sciences|National Academy of Sciences]] formed a [[working group]] to investigate future cooperative missions. Two European scientists suggested a paired Saturn Orbiter and Titan Probe as a possible joint mission. In 1983, NASA's [[Solar System Exploration Committee]] recommended the same Orbiter and Probe pair as a core NASA project. NASA and the [[European Space Agency]] (ESA) performed a joint study of the potential mission from 1984 to 1985. ESA continued with its own study in 1986, while American astronaut [[Sally Ride]], in her influential 1987 report "[[The Ride Report|NASA Leadership and America's Future in Space]]," also examined and approved of the ''Cassini'' mission.
While Ride's report described the Saturn orbiter and probe as a NASA solo mission, in 1988 the Associate Administrator for Space Science and Applications of NASA Len Fisk returned to the idea of a joint NASA and ESA mission. He wrote to his counterpart at the ESA, Roger Bonnet, strongly suggesting that the ESA choose the ''Cassini'' mission from the three candidates at hand and promising that NASA would commit to the mission as soon as ESA did.
At the time, NASA was becoming more sensitive to the strain that had developed between the American and European space programs as a result of European perceptions that NASA had not treated it like an equal during previous collaborations. NASA officials and advisers involved in promoting and planning ''Cassini–Huygens'' attempted to correct this trend by stressing their desire to evenly share any scientific and technology benefits resulting from the mission. In part, this newfound spirit of cooperation with Europe was driven by a sense of competition with the [[Soviet Union]], which had begun to cooperate more closely with Europe as the ESA drew further away from NASA.
The collaboration not only improved relations between the two space programs but also helped ''Cassini–Huygens'' survive congressional budget cuts in the United States. ''Cassini–Huygens'' came under fire politically in both 1992 and 1994, but NASA successfully persuaded the [[Congress of the United States|U.S. Congress]] that it would be unwise to halt the project after the ESA had already poured funds into development because frustration on broken space exploration promises might spill over into other areas of foreign relations. The project proceeded politically smoothly after 1994, although, as noted below, citizens' groups concerned about its potential environmental impact attempted to derail it through protests and lawsuits until and past its 1997 launch.
==Spacecraft design==
[[Image:Cassini assembly.jpg|right|thumb|200px|''Cassini'' assembly]]
The spacecraft was originally planned to be the second three-axis stabilized, [[Radioisotope thermoelectric generator|RTG]]-powered [[Mariner Mark II]], a class of spacecraft developed for missions beyond the orbit of [[Mars (planet)|Mars]]. ''Cassini'' was being developed together with the ''[[Comet Rendezvous Asteroid Flyby]]'' (''CRAF'') spacecraft, but various budget cuts and rescopings of the project forced NASA to terminate ''CRAF'' development in order to save ''Cassini''. As a result, the ''Cassini'' spacecraft became a more specialized design, canceling the implementation of the Mariner Mark II series.
The spacecraft, including the orbiter and the probe, is the largest and most complex [[interplanetary]] spacecraft built to date. The orbiter has a mass of 2,150 kg (4,739 lbs), the probe 350 kg (770 lbs). With the launch vehicle adapter and 3,132 kg (6,900 lbs) of propellants at launch, the spacecraft had a mass of about 5,600 kg (12,345 lbs). Only the two [[Phobos program|Phobos]] spacecraft sent to [[Mars]] by the [[Soviet Union]] were heavier. The ''Cassini'' spacecraft is more than {{convert|6.8|m|ft|sp=us}} high and more than {{convert|4|m|ft|sp=us}} wide. The complexity of the spacecraft is necessitated both by its [[trajectory]] (flight path) to Saturn, and by the ambitious program of scientific observations once the spacecraft reaches its destination. It functions with 1,630 interconnected [[electronic components]], 22,000 wire connections, and over {{convert|14|km|mi|sp=us}} of cabling.
Now that ''Cassini'' is orbiting Saturn, it is between 8.2 and 10.2 [[astronomical unit]]s from [[Earth]]. Because of this, it takes between 68 to 84 minutes for signals to travel from Earth to the spacecraft, and vice versa. Thus, ground controllers cannot give "real-time" instructions to the spacecraft, either for day-to-day operations or in cases of unexpected events. Even if they respond immediately after becoming aware of a problem, nearly three hours will have passed before the satellite receives a response.
===Instruments===
''Cassini'''s instrumentation consists of: a synthetic aperture [[radar|RADAR]] mapper, a [[charge-coupled device]] imaging system, a visible/[[infrared]] mapping [[spectrometer]], a composite infrared spectrometer, a [[cosmic dust]] analyzer, a [[radio]] and [[Plasma (physics)|plasma]] wave experiment, a plasma spectrometer, an [[ultraviolet]] imaging spectrograph, a [[magnetosphere|magnetospheric]] imaging instrument, a [[magnetometer]] and an [[ion]]/neutral [[mass spectrometer]]. Telemetry from the communications [[antenna (electronics)|antenna]] and other special transmitters (an [[S band|S-band]] transmitter and a dual-frequency [[Ka band|K<sub>a</sub>-band]] system) will also be used to make observations of the atmospheres of Titan and Saturn and to measure the [[gravity]] fields of the planet and its satellites.
; '''''Cassini'' Plasma Spectrometer (CAPS)''' : The CAPS is a direct sensing instrument that measures the energy and electrical charge of particles that the instrument encounters, (the amount of electrons and protons in the particle). CAPS will measure the molecules originating from Saturn's ionosphere and also determine the configuration of Saturn's magnetic field. CAPS will also investigate [[Plasma (physics)|plasma]] in these areas as well as the solar wind within Saturn's magnetosphere.<ref name="instruments-cassini-caps.cfm">[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-caps.cfm Cassini-Huygens: Spacecraft-Instruments-Cassini Plasma Spectrometer (CAPS)<!-- Bot generated title -->]</ref>
; '''Cosmic Dust Analyzer (CDA)''' : The CDA is a direct sensing instrument that measures the size, speed, and direction of tiny dust grains near Saturn. Some of these particles are orbiting Saturn, while others may come from other solar systems. The CDA on the orbiter is designed to learn more about these mysterious particles, the materials in other celestial bodies and potentially about the origins of the universe.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-cda.cfm Cassini-Huygens: Spacecraft-Instruments-Cosmic Dust Analyzer (CDA)<!-- Bot generated title -->]</ref>
; '''Composite Infrared Spectrometer (CIRS)''' : The CIRS is a remote sensing instrument that measures the [[infrared light]] coming from an object to learn about its temperature, thermal properties and composition. Throughout the Cassini–Huygens mission, CIRS will measure infrared emissions from atmospheres, rings and surfaces in the vast Saturn system. It will map the atmosphere of Saturn in three dimensions to determine temperature and pressure profiles with altitude, gas composition, and the distribution of [[aerosols]] and clouds. It will also measure thermal characteristics and the composition of satellite surfaces and rings.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-cirs.cfm Cassini-Huygens: Spacecraft-Instruments-Composite Infrared Spectrometer (CIRS)<!-- Bot generated title -->]</ref>
; '''Ion and Neutral Mass Spectrometer (INMS)''' : The INMS is a direct sensing instrument that analyzes charged particles (like protons and heavier ions) and neutral particles (like atoms) near Titan and Saturn to learn more about their atmospheres. INMS is intended also to measure the positive ion and neutral environments of Saturn's icy satellites and rings.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-inms.cfm Cassini-Huygens: Spacecraft-Instruments-Ion and Neutral Mass Spectrometer (INMS)<!-- Bot generated title -->]</ref><ref>{{cite journal| title= The Cassini ion and neutral mass spectrometer (INMS) investigation| author= Waite J. H., Lewis S., Kasprzak W. T., Anicich V. G., Block B. P., Cravens T. E., Fletcher G. G., Ip W. H., Luhmann J. G., McNutt R. L., Niemann H. B., Parejko J. K., Richards J. E., Thorpe R. L., Walter E. M., Yelle R. V.|journal=Space Science Review|volume= 114|pages=113–231|year= 2004 |doi= 10.1007/s11214-004-1408-2}}</ref>
; '''Imaging Science Subsystem (ISS)''' : The ISS is a remote sensing instrument that captures images in [[visible light]], and some in infrared and [[ultraviolet light]]. Scientists expect that ISS will return hundreds of thousands of images of Saturn and its rings and moons. ISS has a wide angle [[camera]] (WAC), that can take broad pictures, and a narrow angle camera (NAC), that can record small areas in fine detail. Each camera uses a sensitive charge-coupled device (CCD) as its detector. Each CCD consists of a 1,024 square array of pixels, 12 [[micrometre|μm]] on a side. The camera's system allows for many data collection modes, including on-chip data compression. The cameras are fitted with spectral filters that rotate on a wheel—to view different bands within the electromagnetic spectrum ranging from 0.2 to 1.1 μm.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-iss.cfm Cassini-Huygens: Spacecraft-Instruments-Imaging Science Subsystem (ISS)<!-- Bot generated title -->]</ref><ref>{{cite journal| title= Cassini Imaging Science: Instrument characteristics and anticipated scientific investigations at Saturn |author= Porco C. C., West R. A., Squyres S., McEwen A., Thomas P., Murray C. D., Delgenio A., Ingersoll A. P., Johnson T. V., Neukum G., Veverka J., Dones L., Brahic A., Burns J. A., Haemmerle V., Knowles B., Dawson D., Roatsch T., Beurle K., Owen W.|journal=Space Science Review|volume=115|year= 2004|pages= 363–497| doi= 10.1007/s11214-004-1456-7 }}</ref>
; '''[[Magnetometer#In_space_exploration|Dual Technique Magnetometer]] (MAG)''' : The MAG is a direct sensing instrument that measures the strength and direction of the magnetic field around Saturn. The magnetic fields are generated partly by the intensely hot molten core at Saturn's center. Measuring the magnetic field is one of the ways to probe the core, even though it is far too hot and deep to visit. MAG aims to develop a three-dimensional model of Saturn's magnetosphere, and determine the magnetic state of Titan and its atmosphere, and the icy satellites and their role in the magnetosphere of Saturn.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-mag.cfm Cassini-Huygens: Spacecraft-Instruments-Dual Technique Magnetometer (MAG)<!-- Bot generated title -->]</ref><ref>{{cite journal|title= The Cassini magnetic field investigation|author= Dougherty M. K., Kellock S., Southwood D. J., Balogh A., Smith E. J., Tsurutani B. T., Gerlach B., Glassmeier K. H., Gleim F., Russell C. T., Erdos G., Neubauer E. M., Cowley S. W. H.|journal=Space Science Review|volume= 114 |pages= 331–383|year= 2004|doi= 10.1007/s11214-004-1432-2 }}</ref>
; '''Magnetospheric Imaging Instrument (MIMI)''' : The MIMI is both a direct and remote sensing instrument that produces images and other data about the particles trapped in Saturn's huge magnetic field, or magnetosphere. This information will be used to study the overall configuration and dynamics of the magnetosphere and its interactions with the solar wind, Saturn's atmosphere, Titan, rings, and icy satellites.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-mimi.cfm Cassini-Huygens: Spacecraft-Instruments-Magnetospheric Imaging Instrument (MIMI)<!-- Bot generated title -->]</ref><ref>{{cite journal|title= Magnetosphere imaging instrument (MIMI) on the Cassini mission to Saturn/Titan |author= Krimigis S. M., Mitchell D. G., Hamilton D. C., Livi S., Dandouras J., Jaskulek S., Armstrong T. P., Boldt J. D., Cheng A. F., Gloeckler G., Hayes J. R., Hsieh K. C., Ip W. H., Keath E. P., Kirsch E., Krupp N., Lanzerotti L. J., Lundgren R., Mauk B. H., McEntire R. W., Roelof E. C., Schlemm C. E., Tossman B. E., Wilken B., Williams D. J. |journal=Space Science Review|volume= 114 |pages= 233–329|year= 2004|doi= 10.1007/s11214-004-1410-8}}</ref>
; '''Radio Detection and Ranging Instrument (RADAR)''' : The [[RADAR]] is a remote active and remote passive sensing instrument that will produce maps of Titan's surface. It measures the height of surface objects (like mountains and canyons) by sending radio signals that bounce off Titan's surface and timing their return. Radio waves can penetrate the thick veil of haze surrounding Titan. The RADAR will listen for radio waves that Saturn or its moons may be producing.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-radar.cfm Cassini-Huygens: Spacecraft-Instruments-Cassini Radio Detection and Ranging Instrument (Radar)<!-- Bot generated title -->]</ref>
; '''Radio and Plasma Wave Science instrument (RPWS)''' : The RPWS is a direct and remote sensing instrument that receives and measures radio signals coming from Saturn, including the radio waves given off by the interaction of the solar wind with Saturn and Titan. RPWS is to measure the electric and magnetic wave fields in the interplanetary medium and planetary magnetospheres. It will also determine the electron density and temperature near Titan and in some regions of Saturn's magnetosphere. RPWS studies the configuration of Saturn's magnetic field and its relationship to Saturn Kilometric Radiation (SKR), as well as monitoring and mapping Saturn's ionosphere, plasma, and lightning from Saturn's (and possibly Titan's) atmosphere.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-rpws.cfm Cassini-Huygens: Spacecraft-Instruments-Radio and Plasma Wave Science (RPWS)<!-- Bot generated title -->]</ref>
; '''[[Radio Science Subsystem]] (RSS)''' : The RSS is a remote sensing instrument that uses radio antennas on Earth to observe the way radio signals from the spacecraft change as they are sent through objects, such as Titan's atmosphere or Saturn's rings, or even behind the [[Sun]]. The RSS also studies the compositions, pressures and temperatures of atmospheres and ionospheres, radial structure and particle size distribution within rings, body and system masses and gravitational waves. The instrument uses the spacecraft X-band communication link as well as S-band downlink and K<sub>a</sub>-band uplink and downlink.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-rss.cfm Cassini-Huygens: Spacecraft-Instruments-Radio Science Subsystem (RSS)<!-- Bot generated title -->]</ref>
; '''Ultraviolet Imaging Spectrograph (UVIS)''' : The UVIS is a remote sensing instrument that captures images of the ultraviolet light reflected off an object, such as the clouds of Saturn and/or its rings, to learn more about their structure and composition. Designed to measure ultraviolet light over wavelengths from 55.8 to 190 nm, this instrument is also a valuable tool to help determine the composition, distribution, aerosol particle content and temperatures of their atmospheres. Unlike other types of spectrometer, this sensitive instrument can take both spectral and spatial readings. It is particularly adept at determining the composition of gases. Spatial observations take a wide-by-narrow view, only one [[pixel]] tall and 60 pixels across. The spectral dimension is 1,024 pixels per spatial pixel. Also, it can take many images that create movies of the ways in which this material is moved around by other forces.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-uvis.cfm Cassini-Huygens: Spacecraft-Instruments-Ultraviolet Imaging Spectrograph (UVIS)<!-- Bot generated title -->]</ref>
; '''Visible and Infrared Mapping Spectrometer (VIMS)''' : The VIMS is a remote sensing instrument that captures images using visible and infrared light to learn more about the composition of moon surfaces, the rings, and the atmospheres of Saturn and Titan. It is made up of two cameras in one: one used to measure visible light, the other infrared. VIMS measures reflected and emitted radiation from atmospheres, rings and surfaces over wavelengths from 350 to 5100 nm, to help determine their compositions, temperatures and structures. It also observes the sunlight and starlight that passes through the rings to learn more about their structure. Scientists plan to use VIMS for long-term studies of cloud movement and morphology in the Saturn system, to determine Saturn's weather patterns.<ref>[http://saturn.jpl.nasa.gov/spacecraft/instruments-cassini-vims.cfm Cassini-Huygens: Spacecraft-Instruments-Visual and Infrared Mapping Spectrometer (VIMS)<!-- Bot generated title -->]</ref>
=== Plutonium power source and controversy ===
[[Image:RTG radiation measurement.jpg|thumb|Inspection of ''Cassini'' spacecraft RTGs before launch]]
Because of Saturn's distance from the [[Sun]], [[Solar cell|solar arrays]] were not feasible power sources for the spacecraft. To generate enough power, such arrays would have been too large and heavy. Instead, the ''Cassini'' orbiter is powered by three [[radioisotope thermoelectric generator]]s (RTGs), which use heat from the natural decay of [[plutonium]] (in the form of plutonium dioxide) to generate direct current electricity. The RTGs have the same design as those on the ''[[Galileo probe|Galileo]]'' and ''[[Ulysses probe|Ulysses]]'' spacecrafts and are designed to have a long operational lifetime. At the end of the 11-year Cassini mission, they will still be able to produce at least 628 [[watt]]s of power. One of Cassini's spare RTGs was used to power the [[New Horizons]] mission to [[Pluto]] and the [[Kuiper Belt]].
The use of 32.8 kg (72 lbs) of plutonium—the most launched into space until then—attracted significant protest from environmental groups, physicists, and some former NASA staff. NASA made several statements intended to mean that the mission was acceptably safe: the chances of radioactive release during the first 3½ minutes after launch were 1 in 1,400; the chances of a release later in the rocket's climb into orbit were 1 in 476; the chances of the craft falling to Earth later were less than 1 in a million; a worst-case scenario would mean 120 humans could die from ''Cassini''-caused [[cancer]] over 50 years. These figures were derided as wild guesses by commentators that included the theoretical physicist Professor [[Michio Kaku]], who suggested that 200,000 humans would die if the plutonium canisters survived reentry and crashed in a heavily populated area, though his estimates were based on atmospheric dispersal of the plutonium over a [[metropolis]]. ''Cassini'''s launch trajectory did not bring it within suitable vicinity of any large metropolis and the design of the RTGs would mean that they would be very unlikely to fracture even in the case of a catastrophic mission abort.
To gain momentum, ''Cassini'''s trajectory included several [[gravitational slingshot]] maneuvers: two passes of [[Venus (planet)|Venus]], one of [[Earth]], then one of [[Jupiter (planet)|Jupiter]]. The Earth fly-by was the final point when ''Cassini'' posed any danger to humans, and occurred successfully on [[August 18]], [[1999]]. Had it suffered a malfunction that caused it to impact, NASA's final environmental impact study estimated<ref>[http://saturn.jpl.nasa.gov/spacecraft/safety-eis.cfm Cassini-Huygens: Spacecraft-Safety<!-- Bot generated title -->]</ref> that in the worst case a significant fraction of the plutonium inside the RTGs would have dispersed into Earth's atmosphere, but the chances of that were nearly ten million to one. This worst case involved an acute angle of entry in which ''Cassini'' would gradually burn up and be vaporized in the upper atmosphere, a highly unlikely scenario. A small number of activists continued to protest after the maneuver.
The primary mission for ''Cassini'' will end on [[2008-07-06]], with a two-year mission extension already approved, and a second one possible. NASA is targeting decommissioning ''Cassini'' in 2012. Unlike the [[Galileo spacecraft|''Galileo'' spacecraft]], which was plunged into [[Jupiter]] to disintegrate in a fiery atmospheric entry, a similar approach for ''Cassini'' may impact a large object within the rings and make it uncontrollable. Instead, NASA is considering a high-altitude parking orbit and an impact on a smaller moon where RTG contamination will not be a problem.<ref>{{cite news |url=http://www.space.com/businesstechnology/061108_cassini_fate.html |title=Death of a Spacecraft: The Unknown Fate of Cassini |publisher=SPACE.com |date=[[November 8]], [[2006]]|quote="The issue is the heat that would be generated by the RTGs and the environment that would be created (melted ice) that could be conducive to the viability of any Earth organisms that might have survived on the spacecraft to that point," says Mitchell. |accessdate=2007-08-06}}</ref> <!-- preceding space.com cite makes following claim dubious: -->
Specifically, scientists do not want to contaminate Enceladus or Titan with the radioactive waste since those satellites may have organic materials.{{Fact|date=January 2008}}<!-- link is dead, please repair: --><ref>http://adsabs.harvard.edu/abs/2005cosp.meet..545B</ref>
==''Huygens'' probe==
{{main|Huygens probe}}
<!-- Commented out because image was deleted: [[Image:huygensprobe.jpg|thumb|An artist's impression of the ''Huygens'' probe as it descends through Titan's atmosphere (painted before the mission).]] -->
The ''Huygens'' probe, supplied by the [[European Space Agency]] (ESA) and named after the Dutch 17th century astronomer [[Christiaan Huygens]], scrutinized the clouds, atmosphere, and surface of Saturn's moon [[Titan (moon)|Titan]] in its descent on [[January 15]] [[2005]]. It was designed to enter and brake in Titan's atmosphere and parachute a fully instrumented robotic laboratory down to the surface.
The probe system consisted of the probe itself which descended to Titan, and the probe support equipment (PSE) which remained attached to the orbiting spacecraft. The PSE includes electronics that tracks the probe, recovers the data gathered during its descent, and processes and delivers the data to the orbiter that transmits it to Earth. The data was transmitted by a radio link between ''Huygens'' and ''Cassini'' provided by Probe Data Relay Subsystem (PDRS). As the probe's mission cannot be telecommanded from Earth because of the great distance, it is automatically managed by the Command Data Management Subsystem (CDMS). The PDRS and CDMS were provided by the [[Italian Space Agency]] (ASI).
==Important events and discoveries==
{{main|Cassini–Huygens timeline}}
===Venus and cruise to Jupiter===
''Cassini'' performed two [[Gravity assist|gravity-assist flybys]] of [[Venus (planet)|Venus]] on [[April 26]], [[1998]] and [[June 24]], [[1999]].
[[Image:Fullbl.jpg|thumb|right|Picture of Moon during flyby]] On [[August 18]], [[1999]] at 03:28 UTC ''Cassini'' did a gravity-assist flyby of Earth. An hour and 20 minutes before closest approach, ''Cassini'' made the closest approach to the Moon at 377,000 km, and took a series of calibration images.
On Jan. 23, 2000, ''Cassini'' performed a flyby of [[Asteroid]] [[2685 Masursky]] around 10:00 UTC. ''Cassini'' took images<ref>{{cite press release| url=http://saturn.jpl.nasa.gov/news/press-releases-00/20000211-ia-a.cfm| title=New Cassini Images of Asteroid Available| date=[[February 11]], [[2000]]| publisher=JPL| accessdate=2006-10-14}}</ref> 5 to 7 hours before at 1.6 million km distance and estimated a diameter of 15 to 20 km.
===Jupiter flyby===
''Cassini'' made its closest approach to [[Jupiter (planet)|Jupiter]] on [[December 30]] [[2000]], and made many scientific measurements. About 26,000 images of Jupiter were taken during the months-long flyby. It produced the most detailed global color portrait of Jupiter yet (see image at right), in which the smallest visible features are approximately 60 km (40 miles) across.<ref>{{cite journal|title= The Cassini–Huygens flyby of Jupiter|author= Hansen C. J., Bolton S. J., Matson D. L., Spilker L. J., Lebreton J. P.|journal=ICARUS |volume=172|pages= 1–8|year=2004 | doi = 10.1016/j.icarus.2004.06.018}}</ref>
The [[New Horizons|''New Horizons'' mission to Pluto]] captured more recent images of Jupiter, with a closest approach on February 28th, 2007.
[[Image:PIA04866 modest.jpg|thumb|right|Jupiter flyby picture]]
A major finding of the flyby, announced on [[March 6]] [[2003]], was of Jupiter's atmospheric circulation.<ref>[http://saturn.jpl.nasa.gov/news/press-releases-03/20030306-pr-a.cfm Cassini-Huygens: News-Press Releases-2003<!-- Bot generated title -->]</ref> Dark "belts" alternate with light "zones" in the atmosphere, and scientists had long considered the zones, with their pale clouds, to be areas of upwelling air, partly because many clouds on Earth form where air is rising. But analysis of ''Cassini'' imagery showed that individual storm cells of upwelling bright-white clouds, too small to see from Earth, pop up almost without exception in the dark belts. According to [[Anthony Del Genio]] of [[NASA]]'s [[Goddard Institute for Space Studies]], "the belts must be the areas of net-rising atmospheric motion on Jupiter, [so] the net motion in the zones has to be sinking."
Other atmospheric observations included a swirling dark oval of high atmospheric-haze, about the size of the [[Great Red Spot]], near Jupiter's north pole. Infrared imagery revealed aspects of circulation near the poles, with bands of globe-encircling winds, with adjacent bands moving in opposite directions.
The same announcement also discussed the nature of Jupiter's [[planetary ring|rings]]. Light scattering by particles in the rings showed the particles were irregularly shaped (rather than spherical) and likely originate as ejecta from micrometeorite impacts on Jupiter's moons, probably [[Metis (moon)|Metis]] and [[Adrastea (moon)|Adrastea]].
===Test of Einstein's theory of general relativity===
On [[October 10]] [[2003]], the ''Cassini'' science team announced the results of a test of [[Albert Einstein|Einstein's]] theory of [[general relativity]], using radio signals from the ''Cassini'' probe. The researchers observed a [[frequency]] shift in the radio waves to and from the spacecraft, as those signals traveled close to the [[Sun]]. According to the theory of general relativity, a massive object like the Sun causes space-time to curve, and a beam of radio waves (or light) that passes by the Sun has to travel farther because of the curvature. The extra distance that the radio waves travel from ''Cassini'' past the Sun to Earth delays their arrival; the amount of the delay provides a sensitive test of the predictions of Einstein's theory. Although deviations from general relativity are expected in some cosmological models, none were found in this experiment. Past tests were in agreement with the theoretical predictions with an accuracy of one part in one thousand. The ''Cassini'' experiment improved this to about 20 parts in a million, with the data still supporting Einstein's theory.
[[Image:H cassini spokes 02.jpg|thumb|right|Spokes imaged by ''Cassini'' in 2005]]
=== New moons of Saturn ===
[[Image:S2005 S1.jpg|thumb|right|Discovery photograph of moon [[Daphnis (moon)|Daphnis]]]]
Using images taken by ''Cassini'', three new moons of [[Saturn]] were discovered in 2004. They are very small and were given the provisional names S/2004 S 1, S/2004 S 2 and S/2004 S 5 before being named [[Methone (moon)|Methone]], [[Pallene (moon)|Pallene]] and [[Polydeuces (moon)|Polydeuces]] at the beginning of 2005.
On [[May 1]] [[2005]], a new moon was discovered by ''Cassini'' in the [[Keeler gap]]. It was given the designation S/2005 S 1 before being named [[Daphnis (moon)|Daphnis]]. The only other known moon inside Saturn's ring system is [[Pan (moon)|Pan]].
[[Image:Phoebe.png|thumb|Image of Phoebe]]
===Phoebe flyby===
On [[June 11]] [[2004]], ''Cassini'' flew by the moon [[Phoebe (moon)|Phoebe]]. This was the first opportunity for close-up studies of this moon since the ''[[Voyager 2]]'' flyby. It also was ''Cassini'''s only possible flyby for Phoebe due to the mechanics of the available orbits around Saturn.<ref>{{cite journal|title= Cassini Imaging Science: Initial results on Phoebe and Iapetus|author= Porco C. C., Baker E., Barbara J., Beurle K., Brahic A., Burns J. A., Charnoz S., Cooper N., Dawson D. D., Del Genio A. D., Denk T., Dones L., Dyudina U., Evans M. W., Giese B., Grazier K., Heifenstein P., Ingersoll A. P., Jacobson R. A., Johnson T. V., McEwen A., Murray C. D., Neukum G., Owen W. M., Perry J., Roatsch T., Spitale J., Squyres S., Thomas P. C., Tiscareno M., Turtle E., Vasavada A. R., Veverka J., Wagner R., West R.|
journal= Science|volume= 307|pages= 1237–1242|year= 2005 |doi=10.1126/science.1107981|pmid= 15731440}}</ref>
First close up images were received on [[June 12]], [[2004]], and mission scientists immediately realized that the surface of Phoebe looks different from asteroids visited by spacecraft. Parts of the heavily cratered surfaces look very bright in those pictures, and it is currently believed that a large amount of water ice exists under its immediate surface.
===Saturn rotation===
In an announcement on [[June 28]] [[2004]] ''Cassini'' scientists described the measurement of the rotational period of [[Saturn]].<ref>[http://www.jpl.nasa.gov/news/news.cfm?release=2004-164 JPL.NASA.GOV: News Releases<!-- Bot generated title -->]</ref> Since there are no fixed features on the surface that can be used to obtain this period, the repetition of radio emissions was used. These new data agree with the latest values measured from Earth, and constitute a puzzle to the scientists. It turns out that the radio rotational period has changed since it was first measured in 1980 by [[Voyager program|''Voyager'']], and that it is now 6 minutes longer. This doesn't indicate a change in the overall spin of the planet, but is thought to be due to movement of the source of the radio emissions to a different latitude, at which the rotation rate is different.
===Orbiting Saturn===
On [[July 1]] [[2004]], the spacecraft flew through the gap between the [[Rings of Saturn|F and G rings]] and achieved [[orbit]], after a seven year voyage. <ref name="carolyn"> {{Citation | title=Cassini, the first one thousand days | first1=Carolyn C. | last1=Porco | journal=American Scientist | volume=95 | issue=4 | pages=pp. 334–341 | year=2007 }} </ref> It is the first spacecraft to ever orbit Saturn.
The Saturn Orbital Insertion (SOI) maneuver performed by ''Cassini'' was complex, requiring the craft to orient its High-Gain Antenna away from Earth and along its flight path, to shield its instruments from particles in Saturn's rings. Once the craft crossed the ring plane, it had to rotate again to point its engine along its flight path, and then the engine fired to decelerate the craft and allow Saturn to capture it. ''Cassini'' was captured by Saturn's gravity at around 8:54 p.m. [[Pacific Daylight Time]] on [[June 30]] [[2004]]. During the maneuver ''Cassini'' passed within 20,000 km (13,000 miles) of Saturn's cloud tops.
===Titan flybys===
[[Image:Titan globe.jpg|thumb|[[Titan (moon)|Titan's]] surface]]
''Cassini'' had its first distant flyby of [[Saturn (planet)|Saturn's]] largest moon, [[Titan (moon)|Titan]], on [[July 2]] [[2004]], only a day after orbit insertion, when it approached to within 339,000 kilometers (211,000 miles) of Titan and provided the best look at the moon's surface to date. Images taken through special filters (able to see through the moon's global haze) showed south polar clouds thought to be composed of [[methane]] and surface features with widely differing brightness. On [[October 27]] [[2004]] the spacecraft executed the first of the 45 planned close flybys of Titan when it flew a mere 1,200 kilometers above the moon. Almost four [[gigabit]]s of data were collected and transmitted to Earth, including the first [[radar]] images of the moon's haze-enshrouded surface. It revealed the surface of Titan (at least the area covered by radar) to be relatively level, with topography reaching no more than about 50 meters in altitude. The flyby provided a remarkable increase in imaging resolution over previous coverage. Images with up to 100 times higher resolution were taken and are typical of resolutions planned for subsequent Titan flybys.
===''Huygens'' encounter with Titan===
{{main|Huygens probe}}
''Cassini'' released the ''Huygens'' probe on [[December 25]] [[2004]], by means of a spring. It entered the atmosphere of Titan on [[January 14]] [[2005]]. It landed on solid ground with no liquids in view. Although Cassini successfully relayed 350 of the pictures that it received from Huygens of its descent and landing site, a software error failed to turn on one of the Cassini receivers and caused the loss of the other 350 pictures.
=== Enceladus flybys ===
{{Wikinewspar|Cassini discovers organic material on Saturn moon}}
During the first two close flybys of the moon [[Enceladus (moon)|Enceladus]] in 2005, ''Cassini'' discovered a "deflection" in the local magnetic field that is characteristic for the existence of a thin but significant atmosphere. Other measurements obtained at that time point to ionized water vapor as being its main constituent. ''Cassini'' also observed water ice geysers erupting from the south pole of Enceladus, which gives more credibility to the idea that Enceladus is supplying the particles of Saturn's E ring. Mission scientists hypothesize that there may be pockets of liquid water near the surface of the moon that fuel the eruptions, making Enceladus one of the few bodies in our solar system to contain liquid water.<ref>[http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=639 Cassini-Huygens: News<!-- Bot generated title -->]</ref>
On [[March 12]] [[2008]], ''Cassini'' made a close fly-by of Enceladus, getting within 50 km of the moon's surface.<ref>[http://www.nasa.gov/mission_pages/cassini/media/cassini-20080310.html Cassini Spacecraft to Dive Into Water Plume of Saturn Moon] NASA.gov, March 10, 2008</ref>. The spacecraft passed through the plumes extending from its southern geysers, detecting water, carbon dioxide and various hydrocarbons with its mass spectrometer, while also mapping surface features that are at much higher temperature than their surroundings with the infrared spectrometer.<ref>[http://www.nasa.gov/mission_pages/cassini/media/cassini-20080326.html Cassini Tastes Organic Material at Saturn's Geyser Moon] NASA.gov, March 26, 2008</ref> ''Cassini'' was unable to collect data with its cosmic dust analyzer due to an unknown software malfunction. The probe will pass near Enceladus again later in 2008, and could make another attempt to collect the data. <ref>[http://space.newscientist.com/article/dn13467-cassini-probe-failed-to-taste-moons-geysers-in-flyby.html Cassini Probe Failed To 'Taste' Moon's Geysers in Flyby] newscientist.com, March 14, 2008</ref>
=== Radio occultations of Saturn's rings ===
In May 2005, ''Cassini'' began a series of [[occultation]] experiments, to measure the size-distribution of particles in [[rings of Saturn|Saturn's rings]], and measure the atmosphere of Saturn itself. For over 4 months, ''Cassini'' completed orbits designed for this purpose. During these experiments, ''Cassini'' flew behind the ring plane of Saturn, as seen from Earth, and transmitted radio waves through the particles. The radio signals were received on Earth, where the frequency, phase, and power of the signal was analyzed to help determine the structure of the rings.
===Spoke phenomenon verified===
In images captured [[September 5]] [[2005]], ''Cassini'' finally detected spokes in Saturn's rings, hitherto seen only by famed visual observer [[Stephen James O'Meara]] in 1977 and later confirmed by the [[Voyager program|''Voyager'']] spacecraft in the early 1980s.<ref>[http://photojournal.jpl.nasa.gov/catalog/PIA05380 Catalog Page for PIA05380<!-- Bot generated title -->]</ref> The exact cause of the spokes is not yet understood; some models predicted spokes would not be visible again until 2007.
===Lakes of Titan===
[[Image:Titan North Pole Lakes PIA08630.jpg|left|thumb|Lakes of Titan]]
{{main|Lakes of Titan}}
Radar images obtained on [[July 21]] [[2006]] appear to show lakes of [[liquid hydrocarbon]] (such as [[methane]] and [[ethane]]) in Titan's northern latitudes. This is the first discovery of currently-existing lakes anywhere besides Earth. The lakes range in size from about a kilometer to one which is one hundred kilometers across.<ref>[http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=679 Cassini-Huygens: News<!-- Bot generated title -->]</ref>
[[Image:TitanSeaComparison.jpg|right|thumb|Titan 'sea' (left) compared at scale to [[Lake Superior]] (right)]]
On [[March 13]] [[2007]], [[JPL]] announced that it found strong evidence of [[sea]]s of methane and ethane in the northern hemisphere. At least one of these is larger than any of the [[Great Lakes]] in [[North America]].<ref>[http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=731 Cassini-Huygens: News<!-- Bot generated title -->]</ref>
===Saturn hurricane===
In November 2006, scientists discovered a storm at the south pole of Saturn with a distinct eyewall. This is characteristic of a [[hurricane]] on Earth and had never been seen on another planet before. Unlike a hurricane, the storm appears to be stationary at the pole. The storm is {{convert|8000|km|mi|sp=us}} across, {{convert|70|km|mi}} high with winds blowing {{convert|560|km/h|mph|sp=us}}.<ref>{{cite news|url=http://news.bbc.co.uk/2/hi/science/nature/6135450.stm| title=Huge 'hurricane' rages on Saturn |publisher=BBC News |date=[[November 10]], [[2006]] |accessdate=2006-11-10}}</ref>
<ref>{{cite web|url=http://www.floridatoday.com/apps/pbcs.dll/article?AID=/20061111/NEWS02/611110322/1007| title=Saturn hurricane's winds hit 350 mph |accessdate=November 11|accessyear=2006}}</ref>
===Iapetus flyby===
On [[September 10]] [[2007]], ''Cassini'' completed its flyby of the strange, two-toned, walnut-shaped moon, [[Iapetus (moon)|Iapetus]]. Images were taken from {{convert|1000|mi|km|-2|sp=us}} above the surface. As it was sending the images back to Earth, it was hit by a [[cosmic ray]] which forced it to temporarily enter [[safe mode]]. All of the data from the flyby was recovered.<ref name="FOX News">[http://www.foxnews.com/story/0,2933,296726,00.html FOXNews.com - Cassini Probe Flies by Iapetus, Goes Into Safe Mode - Science News | Science & Technology | Technology News<!-- Bot generated title -->]</ref>
===Extended mission===
On [[April 15]] [[2008]], Cassini received funding for a two-year extended mission. It will consist of 60 more orbits of [[Saturn]], and will include 23 more [[Titan]] flybys, seven of [[Enceladus]], and one each of [[Dione]], [[Rhea (moon)|Rhea]], and [[Helene]].
==Trajectory==
[[Image:Cassini interplanet trajectory.svg|center]]
The image above displays the initial gravity-assist trajectory of ''Cassini–Huygens''. This is the process whereby an insignificant mass approaches a significant mass 'from behind' and 'steals' some of its orbital energy. The significant mass, usually a planet, loses a very small proportion of its orbital energy to the insignificant mass, in this case, the probe. However, due to the spacecraft's small mass, this energy transfer gives it a relatively large energy increase in proportion to its orbital energy, speeding its travel through space.
''Cassini–Huygens'' performed two gravity assists at Venus, one at Earth and one at Jupiter.
[[Image:Cassini Tour (hypothetical).jpg|center]]
The above simplified diagram shows, in two dimensions, the orbital motion of ''Cassini–Huygens'' on and after arrival at Saturn.
[[Image:Cassini's speed related to the Sun.png|575px|center|thumb|''Cassini'''s speed relative to the Sun. The various [[gravitational slingshot]]s form visible peaks on the left, while the periodic variation on the right is caused by the spacecraft's orbit around Saturn. The data came from the [[JPL Horizons Ephemeris System]] in 2005. The speed above is [[instantaneous distance]] in kilometers per second. The date/time is [[Coordinated Universal Time|UTC]] in [[Spacecraft Event Time]], which is from 1997-Oct-16 00:00:01 to 2008-Jul-06 23:59:59 UTC, two [[leap second]]s during this period. Note also that the minimum velocity achieved during Saturnian orbit is more or less equal to Saturn's own orbital velocity, which is the ~5 km/s velocity which ''Cassini'' matched to enter orbit.]]
==See also==
{{commonscat|Cassini-Huygens}}
*[[Huygens probe]]
*[[Cassini–Huygens timeline]]
*[[Europlanet]]
==Glossary of Terms==
<div class="references-small" style="-moz-column-count:2; column-count:2;">
*'''AACS''': Attitude and Articulation Control Subsystem
*'''ACS''': Attitude Control Subsystem
*'''AFC''': AACS Flight Computer
*'''ARWM''': Articulated Reaction Wheel Mechanism
*'''ASI''': Agenzia Spaziale Italiana, the Italian space agency
*'''BIU''': bus interface unit
*'''CAM''': Command Approval Meeting
*'''CDS''': Command and Data Subsystem - Cassini computer that commands and collects data from the instruments
*'''CICLOPS''': [http://ciclops.org/index.php Cassini Imaging Central Laboratory for Operations]
*'''CIMS''': Cassini Information Management System
*'''DCSS''': Descent Control Subsystem
*'''DSCC''': Deep Space Communications Center
*'''DSN''': Deep Space Network (large antennas around the earth)
*'''DTSTART''': Dead Time Start
*'''ELS''': Electron Spectrometer (part of CAPS instrument)
*'''ERT''': Earth-received time, UTC of an event
*'''ESOC''': European Space Operations Centre
*'''FSW''': flight software
*'''HGA''': High Gain Antenna
*'''HMCS''': Huygens Monitoring and Control System
*'''HPOC''': Huygens Probe Operations Center
*'''IBS''': Ion Beam Spectrometer (part of CAPS instrument)
*'''IEB''': Instrument Expanded Blocks (instrument command sequences)
*'''IMS''': Ion Mass Spectrometer (part of CAPS instrument)
*'''ITL''': Integrated Test Laboratory - spacecraft simulator
*'''IVP''': Inertial Vector Propagator
*'''LGA''': Low Gain Antenna
*'''NAC''': Narrow Angle Camera
*'''OTM''': Orbit Trim Maneuver
*'''PDRS''': Probe Data Relay Subsystem
*'''PHSS''': Probe Harness SubSystem
*'''POSW''': Probe On-Board Software
*'''PPS''': Power and Pyrotechnic Subsystem
*'''PRA''': Probe Relay Antenna
*'''PSA''': Probe Support Avionics
*'''PSIV''': Preliminary Sequence Integration and Validation
*'''PSE''': probe support equipment
*'''RCS''': Reaction Control System
*'''RFS''': Radio Frequency Subsystem
*'''RPX''': ring plane crossing
*'''RWA''': Reaction Wheel Assembly
*'''SCET''': Spacecraft Event Time
*'''SCR''': sequence change requests
*'''SKR''': Saturn Kilometric Radiation
*'''SOI''': Saturn Orbit Insertion ([[1 July]] [[2004]])
*'''SOP''': Science Operations Plan
*'''SSPS''': Solid State Power Switch
*'''SSR''': Solid State Recorder
*'''SSUP''': Science and Sequence Update Process
*'''TLA''': Thermal Louver Assemblies
*'''USO''': UltraStable Oscillator)
*'''VRHU''': Variable Radioisotope Heater Units
*'''WAC''': Wide Angle Camera
</div>
==References==
{{reflist|2}}
==Further reading==
*{{cite book |author=David M. Harland |title=Mission to Saturn: Cassini and the Huygens Probe |publisher=Springer-Verlag |year=2002 |isbn=1-85233-656-0}}
*{{cite book |author=Ralph Lorenz and Jacqueline Mitton |title=Lifting Titan's Veil: Exploring the Giant Moon of Saturn |publisher=Cambridge University Press |year=2002 |isbn=0-521-79348-3}}
*{{cite book |author=[[Karl Grossman]] |title=The Wrong Stuff: The Space Program's Nuclear Threat to Our Planet |publisher=Common Courage Press |year=1997 |isbn=1-56751-125-2}}
==External links==
*[http://www.nasa.gov/mission_pages/cassini/main/ Cassini-Huygens Main Page] at '''[[NASA]]'''
*[http://saturn.jpl.nasa.gov/ Cassini Mission Homepage] by the [[Jet Propulsion Laboratory]]
*[http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Cassini Cassini-Huygens Mission Profile] by NASA's Solar System Exploration
*[http://ciclops.org/ Cassini Imaging Homepage]
*[http://nssdc.gsfc.nasa.gov/planetary/cassini.html Cassini information] by the [[National Space Science Data Center]] (NSSDC).
*[http://www.futura-sciences.com/communiquer/g/showgallery.php/cat/525/page/ Photo Gallery - full coverage]
*[http://www.spacedaily.com/news/cassini-01a.html Cassini's Tour de Saturn part A], [http://www.spacedaily.com/news/cassini-01b.html B], [http://www.spacedaily.com/news/cassini-01c.html C], [http://www.spacedaily.com/news/cassini-01d1.html D], [http://www.spacedaily.com/news/cassini-01e.html E], [http://www.spacedaily.com/news/cassini-01f1.html F] – descriptions of the 4-year tour of Saturn by Bruce Moomaw
*[http://www.spaceflightnow.com/cassini/ SpaceflightNow news coverage of the mission]
*[http://baltimorechronicle.com/cassini_probe_2.html Countdown to Cancel the Cassini Space Probe] by the Baltimore Peace Network in 1997 due to concerns over the use of plutonium
*[http://www.suekientz.com/cassini/ Spacecraft Cassini is Visiting Saturn!] — children's stories explaining the Cassini mission
*[http://tech.groups.yahoo.com/group/cassinihuygens/ Yahoo group for the Cassini Huygens mission]
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