HOME

TheInfoList



OR:

The '' Cassini''
space probe A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; o ...
was deliberately disposed of via a controlled fall into
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
's atmosphere on September 15, 2017, ending its nearly two-decade-long mission. This method was chosen to prevent biological contamination of any of the moons of Saturn now thought to offer potentially habitable environments. Factors that influenced the mission end method included the amount of rocket fuel left, the health of the spacecraft, and funding for operations on Earth. Some possibilities for ''Cassini'' later stages were aerobraking into orbit around Titan, leaving the Saturn system, or making close approaches and/or changing its orbit. For example, it could have collected
solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
data in a
heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun ...
.


End of mission options

During planning for its extended missions, various future plans for ''Cassini'' were evaluated on the basis of scientific value, cost, and time. Some of the options examined included collision with Saturn atmosphere, an icy satellite, or rings; another was departure from
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
orbit to
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...
,
Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...
,
Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 time ...
, or a
centaur A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as bein ...
. Other options included leaving it in certain stable orbits around Saturn, or departure to a heliocentric orbit. Each plan required certain amounts of time and changes in velocity. Another possibility was aerobraking into orbit around Titan. This table is based on page 19 of ''Cassini Extended Missions'' (NASA), from 2008.


Atmospheric entry and destruction

On July 4, 2014, the ''Cassini'' science team announced that the proximal orbits of the probe would be named the "Grand Finale". This would be immediately preceded by a gradual shift in inclination to better view Saturn's polar hexagon, and a flyby of
Enceladus Enceladus is the sixth-largest moon of Saturn (19th largest in the Solar System). It is about in diameter, about a tenth of that of Saturn's largest moon, Titan. Enceladus is mostly covered by fresh, clean ice, making it one of the most refle ...
to more closely study its
cryovolcanism A cryovolcano (sometimes informally called an ice volcano) is a type of volcano that erupts volatiles such as water, ammonia or methane into an extremely cold environment that is at or below their freezing point. The process of formation is known ...
. This was followed by a dive into Saturn's atmosphere. There was budgetary drama in 2013–14 about NASA receiving U.S. government funding for the Grand Finale. The two phases of the Grand Finale ended up being the equivalent of having two separate Discovery Program-class missions in that the Grand Finale was completely different from the main ''Cassini'' regular mission. The U.S. government in late 2014 approved the Grand Finale at the cost of $200 million. This was far cheaper than building two new probes in separate Discovery-class missions. Scientific data was collected using eight of its twelve science instruments. All of the probe's magnetosphere and plasma science instruments, plus the spacecraft's radio science system, and its infrared and ultraviolet spectrometers collected data during the final plunge. The data rates flowing back from Saturn could not support imaging during the final plunge, so all pictures were downlinked (transmitted back to Earth) and cameras were switched off, before the final plunge began. The predicted altitude for loss of signal was approximately above Saturn's cloud tops, when the spacecraft began to tumble and burn up like a meteor. ''Cassini''s final transmissions were received by the
Canberra Deep Space Communication Complex The Canberra Deep Space Communication Complex (CDSCC) is a satellite communication station, part of the Deep Space Network of NASA's Jet Propulsion Laboratory (JPL), located at Tidbinbilla in the Australian Capital Territory. Opened in 1 ...
, located in
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
at 18:55:46
AEST Australia uses three main time zones: Australian Western Standard Time (AWST; UTC+08:00), Australian Central Standard Time (ACST; UTC+09:30), and Australian Eastern Standard Time (AEST; UTC+10:00). Time is regulated by the individual state ...
. In a bittersweet ending for the scientists involved, some of whom had been involved in the mission for decades, data was received for 30 seconds longer than anticipated, and the spacecraft's ultimate demise was predicted to have occurred within 45 seconds after that. Homages were paid on social media. NASA's video won an
Emmy The Emmy Awards, or Emmys, are an extensive range of awards for artistic and technical merit for the American and international television industry. A number of annual Emmy Award ceremonies are held throughout the calendar year, each with the ...
for "Outstanding Original Interactive Program".


See also

* Deliberate crash landings on extraterrestrial bodies * Timeline of ''Cassini–Huygens''


References


Further reading

*


External links


''Cassini-Huygens''
at ESA
''Cassini-Huygens'' main page
at
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

''Cassini'' Mission Homepage
by the
Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, La Cañada Flintridge, California ...

''Cassini-Huygens'' Mission Profile
by NASA's Solar System Exploration
''Grand Finale'' Overview
at
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
{{DEFAULTSORT:Cassini-Huygens retirement Cassini–Huygens Spacecraft endings Extraterrestrial atmosphere entry 2017 in spaceflight