15 September 2017

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In Depth 11 Facts about Cassini Mission Grand Finale Mission Goodbye Cassini

In Depth 11 Facts about NASA Cassini Mission Grand Finale Mission Goodbye Cassini

Cassini–Huygens or more commonly, Cassini, was a Flagship-class unmanned robotic spacecraft which was planned, built, launched, and operated in collaboration between NASA, the European Space Agency, and the Italian Space Agency, and was sent to the planet Saturn.
Cassini-Huygens is a joint NASA/ESA/ASI mission.
NASA’s Cassini spacecraft continues to orbit Saturn, making an extensive survey of the ringed planet and its moons.
The ESA Huygens probe is the first to land on a world in the outer Solar System - on the surface of Titan, Saturn’s largest moon.

Cassini-Huygens is the largest interplanetary spacecraft ever built. The other planetary flagships include Galileo, Voyager, and Viking

When Galileo Galilei was observing Saturn in the 1600s, he noticed strange objects on each side of the planet. He drew in his notes a triple-bodied planet system with ears. These “ears” were later discovered to be the rings of Saturn.

Saturn orbits our sun and is the sixth planet from the sun at an average distance of about 886 million miles or 9.5 AU.

Only a handful of missions have made their way to Saturn: Pioneer 11, Voyager 1 and 2, and Cassini-Huygens, which is there now. Since 2004, Cassini has been exploring Saturn and its moons and rings—but will complete its journey on Sept. 15, 2017.

Development of Cassini began in the 1980s. Its design included a Saturn orbiter (Cassini) and a lander (Huygens) for the moon Titan. The two spacecraft were named after astronomers Giovanni Cassini and Christiaan Huygens

Christiaan Huygens (1629-1695) was a Dutch scientist who discovered Saturn's rings and, in 1655, its largest moon, Titan.

Italian Jean-Dominique Cassini (1625-1712) discovered the Saturnian satellites Iapetus, Rhea, Tethys and Dione. In 1675, he discovered what is known today as the 'Cassini Division', the narrow gap separating Saturn's rings.

Launch 15 October 1997 (Titan-IVB/Centaur at Cape Canaveral, United States).
The Cassini-Huygens spacecraft was launched from Launch Complex 40 at Cape Canaveral in Florida on a Titan IV-B/Centaur launch vehicle on 15 October 1997.

As tall as a 22-story building, the Titan/Centaur rocket lifted off perfectly on schedule, at 4:43 a.m. EDT, with the 5650-kilogram Cassini-Huygens spacecraft on board.

Two minutes and 23 seconds later, the launch sequence continued with the separation from the Titan IV/B launch vehicle. By then, the spacecraft was already at an altitude of 91 440 metres and traveling at 7046 kilometres per hour.

The Centaur upper stage separated successfully at 42 minutes and 40 seconds into the flight. Flying on its own for the first time, 10 minutes later the Cassini-Huygens spacecraft successfully opened its communications link with NASA's Deep Space Network tracking complex near Canberra, Australia.

The Titan IV-B/Centaur launch vehicle consists of a two-stage, liquid-propellant booster rocket with two strap-on solid rocket motors, a Centaur upper stage and 30-metre high payload enclosure or fairing.

The whole vehicle stands at 55.8 metres high and has a total launch weight of (vehicle and payload) of 1 038 000 kilograms. (The Centaur upper stage measures 4.3 metres wide, 8.8 metres tall, and with propellant weight 24 000 kilograms.)

Cost of mission: $3.9 billion. This figure includes $2.5 billion in pre-launch costs (including launch vehicle and contributions from ESA and the Italian Space Agency), and $1.4 billion in post-launch costs (including operations and tracking for 20 years in flight).

Number of people who worked on some portion of Cassini-Huygens: More than 5,000

The Cassini-Huygens mission is an international collaboration involving three space agencies, with 19 countries contributing hardware to the flight system. The Cassini spacecraft carries 12 instruments, Huygens carried six more, and scientists from 26 nations are participating in the investigations. Among the many pioneering technologies of the mission are new solid-state data recorders with no moving parts that have since replaced tape recorders, solid-state power switches (space-based versions of circuit breakers), and advanced solid-state electronics. The spacecraft has over 9 miles (14 kilometers) of cabling and 22,000 connections.

Status The spacecraft arrived at Saturn in July 2004. Cassini is in operation, orbiting around Saturn. The Huygens probe landed on Titan on 14 January 2005.
The primary mission for Cassini was completed on July 30, 2008.
The mission was extended to June 2010 (Cassini Equinox Mission). This studied the Saturn system in detail during the planet's equinox, which happened in August 2009.

Journey -
The 5.6-tonne Cassini-Huygens spacecraft made four gravity-assist swing-by manoeuvres. These manoeuvres were: Venus (April 1998), Venus (June 1999), Earth (August 1999), and Jupiter (December 2000). In December 2004, towards the end of Cassini's third orbit around Saturn, the Huygens probe was ejected on a 22-day cruise to Titan. Huygens reached Titan on 14 January 2005.

Gravity-assists from two swing-bys of Venus and one of Earth provide the equivalent of 68 040 kilograms of rocket fuel.
During the long journey to Saturn, ESA scientists 'woke up' the Huygens probe every six months to check that all was well.
The Huygens probe can withstand temperatures of up to 18 000°C in front of the heat shield. The heat generated as Huygens travelled through Titan's thick gas atmosphere was immense.
Titan is one of the most mysterious objects in our Solar System. It is the second largest moon and the only one with a thick, methane-rich, nitrogen atmosphere. Experts think that its atmosphere resembles that of a very young Earth.

Mission objectives -
Cassini-Huygens is designed to shed light on many of the unsolved mysteries arising from previous observations, such as:
what is the source of heat inside Saturn that produces 87 per cent more energy than the planet absorbs from sunlight?
what is the origin of Saturn’s rings?
where do the subtle colours in the rings come from?
are there any more moons?
why has the moon Enceladus such an abnormally smooth surface? (Has recent melting erased craters?)
what is the origin of the dark organic material covering one side of the moon Iapetus?
which chemical reactions are occurring in Titan’s atmosphere?
what is the source of methane, a compound associated to biological activity on Earth, which is so abundant in Titan’s atmosphere?
are there any oceans on Titan?
do more complex organic compounds and ‘pre-biotic’ molecules exist on Titan?

Cassini-Huygens was launched on a Titan IV-B/Centaur launch vehicle on 15 October 1997. It is a massive spacecraft - no existing launch vehicle could have sent the 5600-kilogram craft directly to Saturn, so a technique called 'gravity assist' (or 'fly-bys') was used.

Gravity assist manoeuvres work because of the mutual gravitational pull between a moving planet and a spacecraft. The planet pulls on the spacecraft as it is flying past, but the spacecraft's own mass also pulls on the planet. This permits an exchange of energy.

Cassini-Huygens looped around the Sun twice. On the first loop, it flew close behind Venus in its solar orbit, where it 'stole' some of the planet's orbital momentum on 26 April 1998.

The next orbit provided a second fly-by of Venus on 24 June 1999, and one of Earth on 18 August 1999. Given these three gravity assist boosts, Cassini-Huygens finally had enough orbital momentum to reach the outer Solar System.

One last gravity assist manoeuvre from Jupiter on 30 December 2000 gave Cassini-Huygens the final thrust of energy it needed to project itself all the way to Saturn. The mission arrived at Saturn in July 2004.

Huygens was released from Cassini on 25 December 2004. On 14 January 2005, it entered the murky atmosphere of Titan, Saturn's biggest moon, and descended via parachute onto its mysterious surface.

The Huygens probe sent its measurements and images to Cassini, which then beamed them back to Earth.

Key dates of the Cassini-Huygens mission –

11 June 2004 (19:32 UT) - Fly-by of the furthest moon orbiting Saturn, Phoebe, at an altitude of 2000 km

1 July 2004 - Crossing of Saturn's ring plane during the spacecraft's critical Saturn Orbit Insertion (SOI) sequence

25 December 2004 (02:00 UT) - Huygens probe separates from the Cassini orbiter and begins its 22-day journey to Titan

14 January 2005 (09:00 UT) - Huygens encountered the upper fringes of Titan's atmosphere, beginning its descent and landing on the surface about two and half hours later.

15 september 2017 - Final Grand Mission

Cassini Spacecraft –

The Cassini-Huygens spacecraft is one of the largest, heaviest and most complex interplanetary spacecraft ever built. Of all interplanetary spacecraft, only the two Phobos spacecraft sent to Mars by the former Soviet Union were heavier.

Loaded with an array of powerful instruments and cameras, the spacecraft is capable of taking accurate measurements and detailed images in a variety of atmospheric conditions and light spectra.

Two elements comprise the spacecraft: the Cassini orbiter and the Huygens probe. After arrival at Saturn, the spacecraft will then orbit around the Saturnian system for four years; sending data back to Earth that will help us understand this region.

Cassini-Huygens is equipped for 27 diverse science investigations. The Cassini orbiter has 12 instruments and the Huygens probe has six. The instruments often have multiple functions, equipped to thoroughly investigate all the important elements of the Saturnian system.

Cassini was the first planetary spacecraft to use solid-state recorders without moving parts instead of the older tape recorder.

Communications -
The Cassini-Huygens spacecraft communicates with Earth through its antenna subsystem, consisting of one high-gain antenna and two low-gain antennas.
The primary function of the high-gain antenna is to support communication with Earth, but it is also used for scientific experiments. During the early portion of the long journey to Saturn, the high-gain antenna was positioned toward the Sun, functioning like an umbrella to shield the spacecraft’s instruments from the harmful rays of the Sun.
The spacecraft would communicate through one of its low-gain antennas only in the event of a power failure or other such emergency situation.

Dimensions -
The Cassini spacecraft stands more than 6.7 metres high and is more than 4 metres wide. The magnetometer instrument is mounted on an 11-metre boom that extends outward from the spacecraft.
The orbiter alone weighs 2125 kilograms. Total mass of the Huygens probe is 349 kilograms, including payload (49 kilograms) and probe support equipment on the orbiter (30 kilograms).
The launch mass of Cassini-Huygens was 5.82 tonnes, of which 3.1 tonnes were propellant.

Power -
Three Radioisotope Thermoelectric Generators (RTGs) provide power for the spacecraft, including the instruments, computers, radio transmitters, attitude thrusters and reaction wheels.
Cassini is powered by 32.7 kg of plutonium-238—the heat from the material's radioactive decay is turned into electricity. Huygens was supported by Cassini during cruise, but used chemical batteries when independent.

In short about Missions
a-Prime Mission, July 2004 through June 2008
b-Cassini Equinox Mission was a two-year mission extension which ran from July 2008 through September 2010.
c-Cassini Solstice Mission ran from October 2010 through April 2017 (also known as the XXM mission)
d-Grand Finale (spacecraft eventually sent into Saturn), April 2017 to September 15, 2017

Grand Finale where no man or spacecraft  has ever gone – Cassini will go for the mankind

For the first time ever, our Cassini spacecraft dove through the narrow gap between Saturn and its rings on April 26. At 5 a.m. EDT, Cassini crossed the ring plane with its science instruments turned on and collecting data.
This area between Saturn and its rings has never been explored by a spacecraft before. What we learn from these daring final orbits will further our understanding of how giant planets, and planetary systems everywhere, form and evolve.
how did this spacecraft maneuver its orbit between Saturn and its rings? Well…let us explain!

On April 22, Cassini made its 127th and final close approach to Saturn’s moon Titan. The flyby put the spacecraft on course for its dramatic last act, known as the Grand Finale.

As the spacecraft passed over Titan, the moon’s gravity bent its path, reshaping the robotic probe’s orbit slightly so that instead of passing just outside Saturn’s main rings, Cassini would begin a series of 22 dives between the rings and the planet.

This final chapter of exploration and discovery is in many ways like a brand-new mission. Twenty-two times, the Cassini spacecraft will dive through the unexplored space between Saturn and its rings. What we learn from these ultra-close passes over the planet could be some of the most exciting revelations ever returned by the long-lived spacecraft.

After 20 years in space, the Cassini spacecraft is running out of fuel.

In 2010, Cassini began a seven-year mission extension in which the plan was to expend all of the spacecraft’s propellant exploring Saturn and its moons. This led to the Grand Finale and ends with a plunge into the planet’s atmosphere at 6:32 a.m. EDT on Friday, September 15, 2017.

The spacecraft will ram through Saturn’s atmosphere at four times the speed of a re-entry vehicle entering Earth’s atmosphere, and Cassini has no heat shield. So, temperatures around the spacecraft will increase by 30-to-100 times per minute, and every component of the spacecraft will disintegrate over the next couple of minutes…

Cassini’s gold-colored multi-layer insulation blankets will char and break apart, and then the spacecraft’s carbon fiber epoxy structures, such as the 11-foot (3-meter) wide high-gain antenna and the 30-foot (11-meter) long magnetometer boom, will weaken and break apart. Components mounted on the outside of the central body of the spacecraft will then break apart, followed by the leading face of the spacecraft itself.

September 15, 2017 - Orbit 293
Distant flyby (altitude = 111,000 km; 69,000 mi) of moon Janus
Distant flyby (altitude = 91,000 km; 57,000 mi) of moon Pan
Distant flyby (altitude = 86,000 km; 53,000 mi) of moon Pandora
Distant flyby (altitude = 92,000 km; 57,000 mi) of moon Epimetheus
End of mission, atmospheric entry into Saturn

When Cassini plunges into Saturn’s atmosphere, it will have spent nearly every last drop of fuel it’s carrying, a fitting end to a spacecraft that pushed itself to the limit...and in many ways, beyond.

On the final orbit, Cassini will plunge into Saturn fighting to keep its antenna pointed at Earth as it transmits its farewell. In the skies of Saturn, the journey ends, as Cassini becomes part of the planet itself.

After losing contact with Earth, the spacecraft will burn up like a meteor, becoming part of the planet itself.

On Sept. 15, 2017, the Cassini spacecraft will make a fateful plunge into Saturn's atmosphere, ending the mission just one month shy of its 20th launch anniversary.

Because Saturn is so far from Earth, Cassini will have been gone for about 83 minutes by the time its final signal reaches the Deep Space Network's Canberra station in Australia on Sept. 15, 2017.

The current predicted time for loss of signal on Earth is 4:55 a.m. PDT (7:55 a.m. EDT) on Sept. 15, 2017. This time may change as Saturn's atmosphere slows Cassini during each of the final orbits.

Why NASA decided to End Mission?
In order to avoid the unlikely possibility of Cassini someday colliding with one of Two moons of Saturn, Enceladus and Titan, NASA has chosen to safely dispose of the spacecraft in the atmosphere of Saturn. This will ensure that Cassini cannot contaminate any future studies of habitability and potential life on those moons.

Watch A short, animated video describing Cassini's Grand Finale

Reality views by sm –

Friday, September 15, 2017

Tags – NASA History Cassini Facts Grand Finale