This article provides a Timeline of the Cassini-Huygens () (commonly called Cassini) mission. Cassini was a collaboration between the United States' NASA, the European Space Agency ("ESA"), and the Italian Space Agency ("ASI") to send a probe to study the planet Saturn and its system, including its rings and natural satellites. The Flagship-class unmanned robotic spacecraft comprised both NASA's Cassini probe, and ESA's Huygens lander module which would be landed on Saturn's largest moon, Titan. Cassini was the fourth space probe to visit Saturn and the first to enter its orbit. The craft were named after astronomers Giovanni Cassini and Christiaan Huygens.
Launched aboard a Titan IVB/Centaur on 15 October 1997, Cassini had been active in space for nearly 20 years, with 13 years spent orbiting Saturn, studying the planet and its system since entering orbit on 1 July 2004. The voyage to Saturn included flybys of Venus (April 1998 and June 1999), Earth (August 1999), the asteroid 2685 Masursky, and Jupiter (December 2000). Its mission ended on 15 September 2017, when Cassini flew into Saturn's upper atmosphere and burned up at a very high temperature, in order to prevent any risk of contaminating Saturn's moons, some of which have active environments that could potentially bear life. (At that point Cassini lacked sufficient power to leave the Saturn system so it could only be left in orbit where it might collide with a moon or be destroyed). The mission is widely perceived to have been successful beyond expectation. Cassini-Huygens has been described by NASA's Planetary Science Division Director as a "mission of firsts", that has revolutionized human understanding of the Saturn system, including its moons and rings, and our understanding of where life might be found in the Solar System.
Cassini's original mission was planned to last for four years, from June 2004 to May 2008. The mission was extended for another two years until September 2010, branded the Cassini Equinox Mission. The mission was extended a second and final time with the Cassini Solstice Mission, lasting another seven years until 15 September 2017, on which date Cassini was de-orbited by being allowed to burn up in Saturn's upper atmosphere.
The Huygens module traveled with Cassini until its separation from the probe on 25 December 2004; it was successfully landed by parachute on Titan on 14 January 2005. It successfully returned data to Earth for around 90 minutes, using the orbiter as a relay. This was the first landing ever accomplished in the outer Solar System and the first landing on a moon other than our own. Cassini continued to study the Saturn system in the following years.
At the end of its mission, the Cassini spacecraft executed the "Grand Finale" of its mission: several risky passes through the gaps between Saturn and Saturn's inner rings. The purpose of this phase was to maximize Cassini's scientific outcome before the spacecraft was destroyed. The atmospheric entry of Cassini effectively ended the mission, although data analysis and production will continue afterwards.
Video Timeline of Cassini-Huygens
1997
15 October 01:43 Pacific Daylight Time (PDT) - Cassini launched at 08:43 UTC inside Titan IVB/Centaur rocket.
Maps Timeline of Cassini-Huygens
Trajectory
The initial gravitational-assist trajectory of Cassini-Huygens is the process whereby an insignificant mass approaches a significant mass "from behind" and "steals" some of its orbital momentum. The significant mass, usually a planet, loses a very small proportion of its orbital momentum to the insignificant mass, the space probe in this case. However, due to the space probe's small mass, this momentum transfer gives it a relatively large velocity increase in proportion to its initial velocity, speeding up its travel through outer space.
The Cassini-Huygens space probe performed two gravitational assist fly-bys at Venus, one more fly-by at the Earth, and a final fly-by at Jupiter.
1998
26 April 06:52 PDT - Gravity-assisted flyby of Venus at 284 km, receiving a boost in speed of about 7 kilometers per second.
3 December 22:06 PST - Cassini fired its main rocket engine for 90 minutes, setting the spacecraft on course for its second Venus flyby in 1999. The engine burn slowed the spacecraft by close to 450 meters per second (about 1,006 miles per hour) relative to the Sun. Cassini's speed went from 67,860 kilometers per hour (42,168 miles per hour) at the start of the maneuver to 66,240 kilometers per hour (41,161 miles per hour) at the end of the engine firing.
1999
24 June 13:30 PDT - Gravity-assisted flyby of Venus at 623 km.
18 August 03:28 UTC - Gravity-assisted flyby of Earth. An hour 20 minutes before closest approach, Cassini made the closest approach to the Moon at 377,000 km, and took a series of calibration images. The spacecraft flew past Earth at a distance of 1,171 kilometers (728 mi), passing most closely above the eastern South Pacific at 23.5°S 128.5°W / -23.5; -128.5. Cassini received a 5.5-kilometer-per-second (about 12,000-mile-per-hour) boost in velocity.
2000
23 January - flyby of Asteroid 2685 Masursky around 10:00 UTC. Cassini took images 5 to 7 hours before at 1.6 million km distance and estimated a diameter of 15 to 20 km.
30 December 10:05 UTC - Gravity-assisted flyby of Jupiter. Cassini was at its closest point (9.7 million kilometres, 137 Jovian radii) to Jupiter at this date, and performed many scientific measurements. It also produced the most detailed global color portrait of Jupiter ever produced (seen on the right); the smallest visible features are approximately 60 km (37 mi) across.
2001
30 May - During the coast phase between Jupiter and Saturn, it was noticed that "haze" became visible in the pictures taken by the narrow-angle camera of Cassini. This was first seen when a picture of the star Maia in the Pleiades was taken after a routine heating period.
2002
23 July - In late January, a test was performed to remove the "haze" from the narrow-angle camera lens by heating it. Warming the camera to 4 degrees Celsius (39 degrees Fahrenheit) for eight days produced positive results. Later, the heating was extended to 60 days, and a picture of the star Spica showed an improvement of more than 90 percent compared to before the heating period. On 9 July, a picture showed that the removal procedure was completed successfully, which was announced on 23 July.
2003
10 October - The Cassini science team announced the results of a test of Einstein's theory of gravity, using radio signals from the Cassini probe. The researchers observed a frequency shift in the radio waves to and from the space craft, as those signals traveled close to the Sun. 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.
2004
27 February - A new, high-resolution picture of Saturn taken by Cassini on 9 February was released, and it was noted that mission scientists were puzzled by the fact that no "spokes" in Saturn's ring are visible. These dark structures in the "B" section of the ring had been discovered in pictures taken by the Voyager probe in 1981. Another picture, in infrared light, taken on February 16s shows cloud height differences and the same disturbance visible throughout the 1990s in Hubble Space Telescope images.
12 March - Pictures taken on 23 February do show a feature discovered by Voyager: Clumps in the outer "F"-ring. What could not be ascertained at the time was the exact lifetime of these clumps, and it is hoped that Cassini will provide conclusive data about this question. The first set of pictures shows a set of "clumps" moving along the "F" ring.
26 March - The Cassini science team published a first sequence of pictures of Saturn showing clouds moving at high speed around the planet. Using a filter to better see water haze on top of the dense cloud cover, motions in the equatorial and southern regions are clearly visible. The pictures were taken during the days from 15 to 19 February.
8 April - The first "long-term" observation of cloud dynamics in Saturn's atmosphere were published by mission scientists. A set of pictures shows two storms in the southern latitudes merge during a period from 19 to 20 March. Both storms had a diameter of about 1,000 km (620 mi) before they merged.
15 April - NASA announced that two moons discovered by Voyager 1 were sighted again by Cassini in pictures taken on 10 March: Prometheus and Pandora. These are no ordinary moons, but their gravitational effects on the "F" ring led scientists to call them "shepherd moons". They fascinate all researchers interested in the dynamics of the ring system, because their orbits are close enough that they interact with each other in a chaotic manner. They have a history of defying predictions of their orbits. One of Cassini's missions will be to monitor the movements of these bodies closely.
18 May - Cassini entered the Saturn system. The gravitational pull of Saturn began to overtake the influence of the Sun.
20 May - The first picture of Titan with better resolution than any Earth based observation was released. It was taken 5 May from a distance of 29.3 million kilometers (18.2 million miles).
27 May - TCM-20, the Phoebe approach TCM (Trajectory Correction Maneuver) was executed at 22:26:00 UTC. This was a 5-minute and 56 second burn of the main engine, which was not used since December 1998. It therefore doubled as a "dress rehearsal" for the 96 minute burn during "Saturn Orbit Insertion" (SOI). However, TCM-20 was mainly designed to change Cassini's velocity by 34.7 m/s (78 mph), setting up a flyby of the moon Phoebe 11 June.
11 June - Cassini flew by the moon Phoebe at 19:33 UT in Spacecraft Event Time at 2068 kilometers distance. All of the eleven onboard instruments operated as expected and all data was acquired. Scientists plan to use the data to create global maps of the cratered moon, and to determine Phoebe's composition, mass and density. It will take scientists several days to pore over the data to make more concrete conclusions.
16 June - TCM-21 took place with a 38-second main engine burn. It was planned as the last correction of the trajectory of Cassini before SOI. A few days later the final TCM-22 tentatively scheduled for 21 June was cancelled.
1 July - The Saturn Orbit Insertion burn was successfully executed. At 7:11 p.m. PDT (10:11 p.m. EDT), Cassini crossed the ring plane between Saturn's F and G rings. Its antenna was oriented forward acting as a shield against small ring particles. At 7:36 p.m. PDT (10:36 p.m. EDT), the spacecraft began a critical 96-minute main engine burn to cut its velocity by 626 meters per second and permit a 0.02 x 9 million kilometer Saturn orbit. Right after that burn, pictures of the rings were taken and sent back to mission scientist as the spacecraft approached within 19,980 kilometers (12,400 miles) from the cloud tops.
Scientists were surprised by the clarity and detail of the pictures and will be poring over them for quite some time. "We won't see the whole puzzle, only pieces, but what we are seeing is dramatic," said Dr. Carolyn Porco, Cassini imaging team leader, Space Science Institute, Boulder, Colo. "The images are mind-boggling, just mind-boggling. I've been working on this mission for 14 years and I shouldn't be surprised, but it is remarkable how startling it is to see these images for the first time."
2 July - Cassini's first flyby of Titan was executed and first close up pictures were sent back to Earth. Due to the planning of the initial orbit, Cassini was passing over the south pole of the moon and from a larger distance than in later flybys. However, during a press conference on 3 June, mission scientist presented pictures that are already forcing them to rethink previous theories. It now seems that the darker and brighter albedo features on the surface do represent different materials. But in contrast to expectation, the icy regions seem to be darker than the areas where other (possibly organic) matter is mixed in with the ice.
16 August - Mission scientists announce the discovery of two new moons of Saturn, and with it the successful start of one of the programs of Cassini: Locating small and yet unknown moons. Later named "Methone" (S/2004 S 1) and "Pallene" (S/2004 S 2), these objects are small compared to other moons and they orbit between Mimas and Enceladus.
23 August - At a distance of 9 million kilometers from Saturn, the last major firing of the main engine took place to adjust the next closest approach and avoid the particles in the ring system. The 51 minute burn increased the velocity of the probe by 325 meters per second, moving the orbital periapsis point about 300,000 km farther away from Saturn than its smallest distance during SOI. At the same time, the new course will bring Cassini very close to Titan on its next flyby.
14 September - Final checkout of the Huygens lander was completed successfully. The separation of the probe stays scheduled for 25 December, with the landing anticipated on 14 January 2005.
26 October - The second flyby of Titan (called "Titan-A") was successfully executed. Data started to arrive at the JPL mission center at 01:30 UTC, 27 October, and included the highest resolution pictures ever taken of the surface of that moon. Also, first high-resolution infra-red spectra and pictures were taken from the atmosphere and surface. The spacecraft successfully skimmed the hazy, smoggy atmosphere of Titan, coming within 1,176 kilometers of Titan's surface. The flyby was the closest that any spacecraft has ever come to Titan. The pictures, spectra and radar data revealed a complex, puzzling surface. Analysis of all data is on-going. The only glitch during the "Titan-A" event involved the CIRS instrument. During playback the instrument team observed corrupted data. A decision was made to power the instrument off to reboot it. CIRS was powered back on within 24 hours and is currently in its nominal state.
23 November - The last in-flight checkout of the Huygens probe before separation was completed successfully. All systems are ready for an on-time deployment of the probe.
13 December - The "Titan-B" flyby was executed successfully and the collected data are analyzed by mission scientists.
24 December - Huygens probe separated from Cassini orbiter at 02:00 UTC.
27 December - NASA published a picture of Huygens taken from Cassini two days after release. It reported that the analysis of that picture shows that the probe is on the correct course within the expected error range. These checks were necessary in order to place the orbiter in the correct orientation to receive the data from the probe when it enters Titan's atmosphere.
28 December - OTM-10 was executed at 03:00 UTC in Spacecraft Event Time. This maneuver, also called the Orbit Deflection Maneuver (ODM), took Cassini off of a Titan-impacting trajectory and on to a flyby trajectory with the required altitude to receive data from the Huygens probe as it plunges into Titan.
31 December - Cassini's flyby of Iapetus occurred at 18:45:37 UTC at an altitude of 122645 kilometers. First raw pictures were available the next day.
2005
14 January - Huygens entered Titan's atmosphere at 09:06 UTC and had landed softly on its surface about two hours later. This was confirmed by the reception of the carrier wave emitted by the probe during its descent and touchdown. At 16:19 UTC the Cassini orbiter started to relay to Earth the scientific data received from the probe. The first picture was released at 19:45 UTC, showing a view from about 16 km above the surface. A second picture taken from the probe at rest on the surface was released a short time later. Analysis of the data is ongoing.
15 February - Successful Titan flyby, with new regions of its surface scanned by radar. Cassini 's mapping radar acquired a picture that shows a large crater on Titan, with an estimated diameter of 440 km (270 mi).
17 February - The first close flyby of Enceladus was executed and first closeup images were sent back to Earth. The flyby distance was about 1,180 km (730 mi).
9 March - The second flyby of Enceladus was performed and Cassini passed the moon with minimum distance of 500 km (310 mi).
17 March - The Cassini probe reveals that Saturn's moon Enceladus has an atmosphere. It has been described as "substantial" by its discoverers.
31 March - The fourth planned flyby of Titan with a minimum distance of about 2,400 kilometers was executed. Images and other data are currently being evaluated.
16 April - The fifth planned flyby of Titan with a minimum distance of about 1,025 kilometers was executed at 19:12 UTC. This was the closest flyby up to this date, and provided the opportunity to obtain more detailed data on the constituents in the upper atmosphere of Titan. A first analysis of that data showed a large range of complex carbon molecules. On 25 April a mass plot was published that demonstrates the existence of these molecules.
3 May - Cassini begins Radio occultation experiments on Saturn's Rings, to determine ring particle size distribution, on the scale of centimetres.
10 May - At the beginning of a period of focussed observation of the ring system of Saturn, slated to take until September, mission scientists announced the discovery of a new moon in the "Keeler gap" inside the "A" ring. Provisionally named S/2005 S 1 and later named Daphnis, it was first seen in a time-lapse sequence of images taken on 1 May. Imaging scientists had predicted the new moon's presence and its orbital distance from Saturn after last July's sighting of a set of peculiar spiky and wispy features in the Keeler gap's outer edge.
14 July - The closest flyby of Enceladus with a distance of 175 km (109 mi) was executed successfully. First raw pictures were published.
22 August - Flyby of Titan with a minimum distance of 3,669 km (2,280 mi).
7 September - Flyby of Titan at a distance of 1,075 km (668 mi), data gathered partially lost due to software problem.
24 September - Flyby of Tethys at a distance of 1,500 km (930 mi).
26 September - Flyby of Hyperion at a distance of 1,010 km (630 mi), the closest flyby and only visit to the moon during the primary mission.
11 October - Flyby of Dione at a distance of 500 km (310 mi).
28 October - Flyby of Titan at a distance of 1,400 km (870 mi).
26 November - Flyby of Rhea at a distance of 500 km (310 mi).
26 December - Flyby of Titan at a distance of 10,410 km (6,470 mi).
2006
15 January - Flyby of Titan at a distance of 2,040 km (1,270 mi).
27 February - Flyby of Titan at a distance of 4,390 km (2,730 mi).
18 March - Flyby of Titan at a distance of 1,950 km (1,210 mi).
30 Apr - Flyby of Titan at a distance of 1,855 km (1,153 mi).
20 May - Flyby of Titan at a distance of 1,880 km (1,170 mi).
2 July - Flyby of Titan at a distance of 1,910 km (1,190 mi).
27 July - NASA confirms the presence of hydrocarbon lakes in Titan's northern polar region.
23 September - Flyby of Titan at a distance of 960 km (600 mi).
2007
1 March - NASA releases several remarkable images of Saturn from Cassini, many in angles not possible from Earth.
10 September - Flyby of Iapetus at a distance of 1,600 km (990 mi).
2008
12 Mar -- Cassini is scheduled to do an unprecedented "in your face" flyby of Saturn's moon Enceladus.
28 May - Cassini completed its 43rd flyby of Titan, ending its primary mission. Renamed Cassini Equinox mission, Cassini will observe Saturn during its equinox crossing, or summertime. and the probe is capable of at least a second mission extension beyond that, tentatively named "Cassini Solstice mission".
Cassini Equinox mission
9 and 11 August 9 and 31 October - With closest approach at 50, 25, and 200 km, respectively, Cassini's last three Enceladus flybys of 2008 utilized a new imaging technique named "skeet shooting" to successfully acquire very high resolution images. The flybys also allowed Cassini to directly sample Enceladus's cryovolcanic plumes.
3 and 14 November 5 and 21 December - Titan flybys 46 through 49 concentrated on radar, VIMS, and INMS sampling of Titan and its thick atmosphere. T47 involved high-resolution VIMS coverage of the Huygens landing site, while the other three flybys made use of radar and RSS. T49 allowed radar coverage of Ontario Lacus, one of the largest methane lakes on Titan.
2009
During 2009 Cassini made 15 flybys of Titan and 2 close flybys of Enceladus. From June to October Cassini observed Saturn during its equinox, or the time of Saturn's year where the sun is directly over its equator. Along with Titan and Enceladus, 2010 also saw very close flybys of Rhea (100 km), Dione (313 km), and Helene (1,133 km). Tethys, Telesto and Mimas were observed at relatively close range as well, with Cassini coming within 10,000 km of Mimas (the closest approach of the mission).
2010
On 2 November 2010, Cassini was triggered into a protective standby mode, or "safe mode", after a bit flip caused it to miss an important instruction. NASA announced the interruption in scientific processes on 8 November. However, by 8 November some of the craft's functionality had already been partly restored. Nominal scientific instrument sequencing events were successfully started on 10 November. Cassini was reactivated as scheduled on 24 November and has returned to perfect working order, in time for two scheduled close fly-bys with Enceladus. At this point there has been no public disclosure as to the data loss impact of the 11 November (T-73) flyby. However, no images were acquired on the 11 November polar flyby.
Cassini made two close flybys of Enceladus in December.
Cassini Solstice Mission (2010-2017)
On 3 February 2010, NASA announced that a second mission extension until May 2017, a few months past Saturn's summer solstice, had been funded. The schedule includes an additional 155 orbits, with 54 flybys of Titan, 11 of Enceladus, 2 of Rhea, and 3 of Dione. One of the flybys of Titan dipped below the ionosphere.
2017
On 15 September 2017, Cassini was deliberately disposed of via a controlled fall into Saturn's atmosphere, ending its nearly two-decade-long mission. The last signal was received at 04:55:46 PDT.
Cassini orbiter travel milestones
Detailed timeline of Huygens mission
All times given after 2005-Jan-14 09:11 UTC are expected event times and may differ from actual event times. This page will be updated after descent has occurred with corrections if they are necessary.
The data used in this section has been slightly out of date, an updated version of ephemeris from ESA was available 2005 January 6.
Huygens probe travel milestones
Celestial phenomena as seen from the landing site in the landing (Titan's) day
The landing day begins at 2005-Jan-08 04:05:08 UTC and ends at 2005-Jan-24 03:26:14 UTC.
According to Huygens predicted descent trajectory provided by ESA/JPL, valid as of 6 January 2005, the probe was projected to land at 10.2936 degrees south and 163.1775 degrees east. Prior to the landing, the location of the landing site could not be known exactly, since the probe was influenced by wind in Titan's atmosphere as it descended.
Timeline of Huygens landing process
Fly-bys
Following is a list of close fly-bys of Saturn's moons (at less than 5000 km). The closest approach for each moon is bolded.
Primary mission
Extended (Equinox) mission
Solstice mission
The second extended mission was scheduled from 2010 October 12 through the Saturnian summer solstice in May 2017, followed by two dozen proximal orbits of Saturn and the rings. Cassini's final optical navigation image of the mission was taken on 20 September 2016. The Cassini mission ended on 15 September 2017, when the craft disintegrated in Saturn's atmosphere.
- Proximal orbits
References
External links
- Cassini-Huygens press release archives
- "Cassini-Huygens Saturn Arrival" June 2004 (pdf)
- Draft White paper for Solar System Decadal Survey 2013-2023: Cassini-Huygens Solstice Mission 2009 (pdf)
- Tour dates
Source of the article : Wikipedia
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