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Cassini–Huygens Probe

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Author Topic: Cassini–Huygens Probe  (Read 203 times)
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« on: June 21, 2007, 02:03:29 am »

Cassini–Huygens timeline

October 15 — Cassini launched at 08:43 UTC.

April 26 — Gravity-assisted flyby of Venus.


June 24 — Gravity-assisted flyby of Venus.
August 18 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.

January 23 — flyby of Asteroid 2685 Masursky around 10:00 UTC. Cassini took images[1] 5 to 7 hours before at 1.6 million km distance and estimated a diameter of 15 to 20 km.

December 30 — Gravity-assisted flyby of Jupiter. Cassini was at its closest point 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 miles) across.

May 30 — 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.

July 23 — 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 the hoped 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 July 9, a picture showed that the removal procedure was completed successfully, which was announced on July 23.[2]

October 10 — 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.

February 27 — A new, high-resolution picture of Saturn taken by Cassini on February 9 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.[3] Another picture, in infrared light, taken on February 16 shows cloud height differences and the same disturbance visible throughout the 1990s in Hubble Space Telescope images.[4]

March 12 — Pictures taken on February 23 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 show a set of "clumps" moving along the "F" ring.[5]

March 26 — 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.[6] The pictures were taken during the days from February 15 to February 19.

April 8 — 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 March 19 to March 20. Both storms had a diameter of about 1,000 km (620 mi) before they merged

April 15 — NASA announced that two moons discovered by Voyager 1 were sighted again by Cassini in pictures taken on March 10: Prometheus and Pandora. These are no ordinary moons, but their gravitational effects on the "F" ring led scienties to call them "shepherd moons". They fascinate all researchers interested in the dynamic 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.

May 18 — Cassini entered the Saturn system. The gravitational pull of Saturn began to overtake the influence of the Sun.
May 20 — The first picture of Titan with better resolution than any Earth based observation was released. It was taken May 5 from a distance of 29.3 million kilometers (18.2 million miles).

May 27 — 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 June 11.

June 11 — 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.

June 16 — 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 June 21 was cancelled.

July 1 — The Saturn Orbit Insertion burn was successfully executed. It began at 01:12 UT in Spacecraft Event Time and ended at 02:48 UT. Right after that burn, pictures of the rings were taken and sent back to mission scientist.

Scientist 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."

July 2 — 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 June 3, 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.

August 16 — 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.

August 23 — The last major firing of the main engine took place to adjust the next closest approach to Saturn and avoid the particles in the ring system. After a 51 minute burn, that distance was moved 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.

September 14 — Final checkout of the Huygens lander was completed successfully. The separation of the probe stays scheduled for December 25, with the landing anticipated on January 14, 2005.

October 26 — The second flyby of Titan (called "Titan-A") was successfully executed. Data started to arrive at the JPL mission center at 01:30 UTC, October 27, 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.

November 23 — 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.

December 13 — The "Titan-B" flyby was executed successfully and the collected data are analyzed by mission scientists.

December 25 — Huygens probe separated from Cassini orbiter at 02:00 UTC.

December 27 — 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.

December 28 — 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.

December 31 — 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.

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