On September 15, 2017, the 20-year-old "veteran" Cassini probe ended his great and magnificent life after completing his last mission. As it rushes to saturn's surface, it turns into a wisp of dust and eventually becomes part of Saturn, as if the ashes of a hero were scattered on the land he loved and struggled for all his life.
To that end, NASA JPL (National Aeronautics and Space Administration Jet Propulsion Laboratory) produced a tear-jerking video for Cassini called < Cassini's Grand Finale> to commemorate Cassini's last mission and glorious life. Let me first watch the greatest curtain of the solar system.
The greatest curtain of the solar system, Cassini CASSINI_ Bilibili _bilibili
NASA's "Cassini's Grand Finale> <) Please click to watch ▲
In the 1960s and 1970s, due to the hegemony of the United States and the Soviet Union, the two countries invested huge funds in the space race, which also promoted the rapid development of human spaceflight in disguise. During this period, NASA led a number of space exploration programs in the United States, such as the "Apollo Program", "Sailor Program", "Voyager Program" and so on. Nasa designed and built a number of probes in these programs, the three most famous of which are Voyager 1, Voyager 2, and Cassini. These probes have been given souls and lives since they were created, and they are like children of mankind, running away from home to the distant space with their respective missions, some of them traveling alone to the depths of the universe, and some of them heroically sacrificing themselves to sleep forever in a "foreign land". This article is dedicated to these pioneers on the cassini.
From 1962 to 1973, NASA launched a series of unmanned probes designed to explore the three planets of Mars, Venus and Mercury in the "Mariner Program", of which 7 of the 10 probes of Mariner 1-1 Mariner 0 succeeded and 3 failed. Later, due to the tightening of the budget, the Mariner 11 and Mariners 12 programs were forced to fly by Jupiter and Saturn, which was the predecessor of the later "Voyager Program". In the summer of 1964, a graduate student at the California Institute of Technology named Gary Flandro interned at NASA JPL. His mission is to calculate what possible routes are available from Earth to other planets. It's a lowly technical job, so most people are reluctant to do it. But after counting hundreds of mundane routes, Flanders discovered a route of great significance.
Flandro found that between 1976 and 1977, Jupiter, Saturn, Uranus and Neptune would all move to particularly suitable positions. During this time, if a probe is fired at Jupiter, it will first be thrown toward Saturn by Jupiter's gravitational slingshot effect, then by Saturn's gravitational slingshot toward Uranus, then by Uranus's gravitational slingshot toward Neptune, and finally by Neptune's gravitational slingshot into outer space. That is to say, with the help of the gravitational slingshot effect, a single probe can travel to all four planets at the same time. This not only saves a lot of fuel, but also increases the speed of the probe to a degree that is difficult for conventional rocket thrusters to achieve, thus saving the probe a lot of roaming time (under normal circumstances, it takes at least 40 years to fly to Neptune; but if you choose this route, you can shorten the sailing time to 12 years). In fact, this is a once-in-a-century opportunity: if the space probe cannot be launched by 1977, the next time you have to travel to all four planets at the same time, you will have to wait a full 176 years. The discovery of this route began the great voyage of Voyager.
Voyager 2 route map ▲
On November 12, 1980, Voyager 1 flew 12,600 kilometers from Saturn, and it flew out of the solar system with just a cursory glimpse of Saturn's appearance. The glimpse sent back more than 10,000 color photographs of Saturn, in which scientists found that Saturn's rings could be subdivided into thousands of small rings with strong magnetic fields and large red spots; that Titan was shrouded in a 280-kilometer-thick fog, and that the atmospheric composition was mainly nitrogen instead of methane as previously thought; and that Titan was 4,828 kilometers in diameter instead of the original estimate of 5,800 kilometers.
In order to figure out saturn's ring belt and Titan's specific atmosphere, NASA intends to launch a special probe to conduct a full range of space exploration of Saturn, and the Cassini plan was proposed. The program is a collaborative project between nasa, the European Agency and the Italian space agency. Cassini-Huygens (Cassini) was named after the famous astronomer Cassini in honor of his contribution to the discovery of Saturn; Huygens was named after the famous astronomer Huygens in honor of his contribution to the discovery of Titan). The probe consisted of two parts, Cassini and Huygens, which were linked together, with Cassini's mission to orbit Saturn and its atmosphere, rings, moons and magnetic field, and Huygens's mission to land on Titan (hereinafter referred to as Cassini). Cassini was 3 meters in diameter, 7 meters high and weighed 5.7 tons, and was launched with 27 of the most advanced detection equipment of the time. It was the last interplanetary probe of the twentieth century.
Cassini probe ▲
In 1997, 20 years after Voyager was launched, Cassini also began its journey with the help of the gravitational slingshot effect. First, it flew in the opposite direction to Venus and borrowed power from Venus twice in April 1998 and June 1999; then, in August 1999, it flew back near Earth and borrowed force from Earth once; then, in December 2000, it flew near Jupiter and borrowed another force from Jupiter; and finally, it flew to Saturn in July 2004, becoming Saturn's first artificial moon. Although the entire journey is 2.5 times the normal distance, the final flight time is greatly reduced due to the gravitational slingshot that greatly increases the speed of the probe's flight. [1]
Route map of cassini
After a long interstellar journey of 6 years, 8 months and 17 days, on May 18, 2004, Saturn's gravitational pull began to exceed the Sun's gravitational pull on Cassini for the first time, which meant that Cassini officially entered the Saturn system. However, this does not mean that Cassini has successfully entered the Saturn system. Since Cassini flew toward Saturn at a high speed, it is likely that Saturn's powerful gravitational field would have captured Cassini directly, causing Cassini to crash into Saturn's atmosphere. On July 1, 2004, Cassini began to enter saturn's orbit, the gripping "final jump". In order to prevent direct access to Saturn, Cassini turned on a deceleration rocket, completed a critical deceleration of up to 96.4 minutes, and finally successfully entered the orbit around Saturn, and the first Saturn artificial satellite in human history was born. [2]
Saturn recently photographed▲
After entering orbit, Cassini quickly began its work, first taking advantage of the opportunity to enter the predetermined orbit, risking being hit by saturn's ring particles twice through the widest ring of Saturn's rings, observing Saturn's rings, and then turning off the fire in the predetermined orbit, and began to make close observations, photographs, measurements, etc. of Saturn, Saturn's moons and Saturn's rings.
Saturn's rings are close-up▲
In January 2005, cassini sent the Huygens surface probe it was carrying to Titan in order to take surface photographs of Titan . On 15 January 2005, Huygens landed directly on Titan's surface and made a soft landing on Titan's surface. However, due to the very cold surface of Titan, below minus 170 degrees Celsius, Huygens quickly exhausted its energy, and after ninety minutes it lost contact with Earth and remained permanently in Titan. The data transmitted back by Huygens led humans to discover that Titan had a similar surface to Earth.' Its first field measurement of Titan's atmosphere determined the atmospheric pressure, density and temperature from an altitude of 1400 km to the ground. Its Doppler Wind Experiment (DWE) found strong east-west winds in the atmosphere, some of which rotated faster than the satellites themselves. It reveals why Titan's atmosphere contains methane, nitrogen and tiny aerosols, in quantities, and detects signs of geological processes and features, such as ice volcanoes, and the potential for large subsurface oceans.
Huygens landing imagery▲
Since Cassini arrived in Saturn's rings in 2004, he has shown us an astonishing picture of Saturn and its moons, and his mission has been extended more than once but twice. He spotted Saturn's polar hexagonal hurricanes on Saturn, superstorms that appeared in Saturn's northern hemisphere, ripples and "relief" structures inherent in Saturn's rings, among others.
Saturn's polar hexagonal hurricane ▲
Superstorms in Saturn's northern hemisphere ▲
The ripples inherent in Saturn's rings and the "relief" structure ▲
Cassini's exploration is also not limited to Saturn, which has found methane and ethane lakes on Saturn's largest moon, Titan, the only liquid lake known to exist outside of Earth. Cassini not only unveiled the strange landforms of these planets, but also discovered geysers at the icy South Pole of Enceladus, unveiling the liquid ocean hidden beneath the icy crust. These observations help us determine that the solar system is littered with worlds with oceans, where life may have evolved and even flourished on planets far from the sun.
On July 18, 2013, NASA published Cassini looking back in The direction of Earth after entering orbit and taking the first photo of Earth and Saturn from the outer solar system. The image was taken in the shadow of Saturn, and although Saturn's rings and atmosphere are illuminated, a pale blue dot-like planet can be clearly seen from it, and this small blue dot is the Earth on which we live. Looking at the vast universe, the earth is like a drop in the ocean, it is too small.
Cassini photographed the Earth
By 2017, Cassini had been in orbit for 12 years. With Cassini running out of fuel, his navigation team explored several possible trajectories for the Cassini spacecraft when it ran out of fuel: it could orbit Saturn permanently and continue to send us messages back to Saturn for years to come. It is also possible to rush into Saturn's rings and give us an idea of what they are like. It could also crash into a moon of Saturn, or leave Saturn for another giant planet or a quirky asteroid in the outer solar system.
In order to prevent him from falling into Saturn's moons and protect Saturn's moons with signs of life from collision pollution, NASA decided to end Cassini's life by taking a controlled impact on Saturn. This also provides Cassini with a unique opportunity to use the waste heat and go deep into the height that the average detector does not dare to approach, and for the first time obtain scientific data such as the temperature, magnetic field and plasma density of Saturn's ionosphere and thermosphere.
On November 30, 2016, Cassini embarked on his penultimate mission, entering a new orbit, the Ring-Grazing Orbit, and passing through saturn's rings for the first time on December 4, 2016. The so-called "grazing orbit" refers to Cassini's passage from the plane where Saturn's rings are located at the edge of Saturn's F ring. This mission phase will last until 22 April 2017, and Cassini will complete a total of 20 "orbital grazing orbits". During this time, Cassini was not only able to perform sampling analysis, but also to photograph Saturn from an unprecedented perspective.
After completing the OrbitAlge mission on April 22, 2017, Cassini will make one last flight over Titan and use its gravitational pull to correct its orbit, entering the final mission phase on April 26. By then, Cassini will travel 22 times between Saturn and its innermost ring (D-ring). The gray curve below is Cassini's grazing orbit, the blue curve is Cassini's finale orbit, and the orange curve is Cassini's orbit toward Saturn.
Map of the trajectory of cassini's mission ending
At 3:53 a.m. on September 13, 2017, Cassini mission engineer Michael Staab gave the spacecraft final instructions. Although the cassini spacecraft's route had been set, a final series of instructions determined its fate. Hours before the cassini spacecraft was destroyed, Staab laughed and said, "I'm a ruthless engineer." ”
From its launch in 1997 to 2017, Cassini flew 220 million miles, carried out 2.4 million commands, taken 379,300 photos, discovered 10 satellites, and transmitted back 599GB of data from which scientists researched and published 3,616 papers. To this day, almost all we know about Saturn comes from Cassini's observations.
Eventually, at 4:55 a.m. Pacific Time on September 15, 2017 (19:55 Beijing time on September 15), cassini's signal disappeared, meaning that the probe had evaporated at high pressure and heat 83 minutes earlier, fully into Saturn's arms. It also marked the end of the Cassini Saturn exploration mission. NASA personnel calmly monitored the signal until the last minute, and after the person in charge of the scene announced that the signal was gone, all stood up and applauded the hero.
Cassini's lifelong exploration of Saturn not only revealed saturn's unknown secrets to mankind, but also showed mankind the wonders of the universe. As a lone warrior, if Cassini had thoughts and did not know how he should feel when he finally looked back at the earth, perhaps he knew the concern, hope, and praise of mankind for him, perhaps he would feel sad for his short life, and I think it should be more the tragedy of seeing death as a homecoming. Perhaps one day, more detectors will visit "Cassini's new home", follow the footsteps of the forerunners, walk through the places he has traveled, and pass through the stories he has experienced, and start a new journey for mankind to explore the universe.
-THE END-
exegesis:
Gravitational Slingshot Effect: Research by American mathematician Minovich shows that when a spacecraft approaches a planet, it is attracted by its gravitational pull. Since the planet itself is also rotating around the sun at a very high speed, it will drag the spacecraft with it and run with it, thus transmitting its own speed to the spacecraft. In this way, as long as the spacecraft is not captured by the planet, it can obtain the extra speed provided by the planet and be thrown out at a much larger speed than the original.
Photo editor: Wu Yanqiang
disclaimer:
This article cites some of the article's content and the author's point of view:
Citations from:
[1] The Cassini Road Opened by the Three-Body Problem
https://www.sohu.com/a/192715591_465226
[2] "What Cassini Discovered on Saturn on a 13-Year Journey to Space"
https://baijiahao.baidu.com/s?id=1671935234895948736&wfr=spider&for=pc
[3] Cassini sends back the first images of Saturn taken after entering a new orbit https://www.sohu.com/a/121007645_341698
The image comes from the Internet
Video from: https://solarsystem.nasa.gov/resources/17628/cassinis-grand-finale/
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