The Galileo Jupiter probe was launched in 1989“Atlantis”Nospace shuttleLaunched from theNASAThe first direct dedicated exploration of Jupiterspacecraft。It is also one of the most successful probes launched by NASA.It was launched on October 18, 1989[6], entered the orbit around Jupiter in December 1995.
It traveled 2.8 billion miles and its end date was six years later than originally expected.Galileo orbited Jupiter 34 times, and the observation results greatly improved people's understanding of Jupiter and four Galileo satellites.In December 1995, the Galileo orbiter released a Jupiter atmosphere detector, and obtained first-hand detection data about Jupiter's atmosphere.
On October 18, 1989, the Galileo Jupiter probe sent into orbit by the space shuttle Atlantis[6], YesNASAThe first spacecraft directly dedicated to detecting Jupiter.GalileoThe Jupiter exploration program began in 1978. It was initially planned to launch in January 1982. Later, due to insufficient funds, flight design modifications, and the failure of the space shuttle launch, nine plans were changed successively.As a result, the launch was repeatedly postponed, and the research and development expenditure was up to 1.36 billion dollars.The Galileo Jupiter exploration program was launched by the United States andFederal GermanyJointly conducted.
Galileo Jupiter probe
The spacecraft is equipped with camerasNear infraredsurveySpectrometer、Magnetic intensity meter17 kinds of scientific instruments, such as cloud gauge, atmospheric structure meterJupiter's atmosphereSurvey and research on composition, cloud structure, temperature, magnetic field, etc.“Galileo”After its launch, it kept flying towards the sun for two years, passed Venus in February 1990, and passed for the first time at a speed of 142900 kilometers per hour in December 1990Earth orbitAt the speed of 127100 kilometers per hour, it passed the Earth orbit and the Earth Moon rendezvous orbit for the second time in December 1992, and made infrared observations of them in passing.Finally, it reached Jupiter on December 7, 1995 at a speed of 140300 kilometers per hour.After releasing the detector, its orbiter became Jupiter's artificial satellite, and the detector descended to the surface of Jupiter and sent back all kinds of valuable detection data to the earth continuously in time.It is the first time for human beings to understand this planet, which is very far away from the earth.[1]
Structural characteristics
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Structure diagram and instrument of Galileo detector
The Galileo probe has an irregular long body, which is the most sophisticatedInterstellar vehicleFirst, the entire launch plan costs about $1.5 billion.The total weight of the spaceship is 2550kg, and there is onenuclear powerDevice, 22.7kg insideradioactivityUranium-238.It is composed of Jupiter's orbiter and re-entry vehicle. About 150 days before arriving at Jupiter, the two parts will separate, and the orbiter will orbit Jupiter for detection;The reentry vehicle goes deep into Jupiter's atmosphere.
Tracker
The orbiter is made in the United StatesJet Propulsion LaboratoryDesigned, manufactured and operated, with a total weight of 2378kg, and 3.15rpm under normal conditionsSpin stability。The main equipment on it is:;Propulsive cabin, including a motorized thruster and a single in orbit thruster, which together with the propellant weighs about 1185 kg;2 setsradio isotopeThermocouple generator, which can provide 0~480 watts of power;
A high gain earth communication antenna with a diameter of about 5 meters is used to communicate with the earth in S and X bands, and the orientation accuracy is 0.1 degree.There are also many precisionDetecting instrument, mainly including:CCD cameraThe resolution of the photos sent back is 20-1000 times higher than that of the Voyager probe, and the details within 30-50 meters of Jupiter's satellite surface can be distinguished;Near infrared mapping spectrometer can detect nitrogen, phosphine, water, methane, germanium and other components;The ultraviolet spectrometer can detect nitrogen, hydrogen and oxygen;Photon polarizationradiometer, can be measuredpolarized lightAnd light intensity;magnetometer、High-energy particleDetector, plasma detectorPlasma waveSubsystem (measuring electric and magnetic field changes), dustparticleTester andHeavy ionCounters, etc., can be used for JupiterMagnetosphereAnd so on.
Reentry device
The re-entry vehicle was designed by the Ames Research Center of NASA,Hughes Aircraft Created.Its shape is a flat cone, and its total weight is about 339 kg, of which only the heat shield weighs 220 kg.There are two 1-band transmitters on it, which can send measurement data at the rate of 128 bits/second, and relay it to the earth through the orbiter.The detection instruments on the reentry device include:Atmospheric structureThe detector can measure the temperature and pressure of Jupiter's atmosphere;neutralMass spectrometer, can measure the atmospheric composition of Jupiter;Helium component detector, used to measure theheliumContent;Cloud gauge, pure flowradiometerAnd optical and radio detectors.
Atmospheric detector
Galileo
The atmospheric detector consists of a brake heat shield and a spherical instrument compartment.The brake heat shield is a 120 degreeCone angleWith a thick layer of carbonablationThermal barrier.This layer of heat shield accounts for 50% of the total weight of the detector.The spherical instrument cabin is equipped with atmospheric component detectorMass spectrometer、heliumConcentration meter, cloud meter,radiometer，High energy particle detectionIt is also equipped with parachute system, radio transmitter and power supply system.The total weight of the atmospheric detector is 345kg.The orbiter arrived 150 days before the orbit of Jupiter in July 1995. After releasing the atmospheric probe, it carried out the exploration mission along the elliptical orbit of Jupiter and flew around Jupiter for 22 months, taking a large number of clear pictures of Jupiter and its satellites;The atmospheric detector goes deep into Jupiter's atmosphere to detect the composition and physical characteristics of the atmosphere.The detector entered the narrow channel at a speed of 48 kilometers per second and finally entered the atmosphere. It withstood an acceleration of 400g, with a surface pressure of up to 14 atmospheres and a surface temperature of up to 780 degrees Celsius. In the process of opening the parachute and slowly descending, it carried out various measurements.As the altitude drops, the atmospheric pressure and temperature become higher and higher, and finally up to 20 atmospheres. At this time, the annular detector is collapsed by atmospheric pressure, and the detection work is forced to terminate.The whole work lasted 1 hour.[2]
Space Tour
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Galileo
Galileo was launched in 1989 and reached the orbit around Jupiter in December 1995.It traveled 2.8 billion miles and its end date was six years later than originally expected.GalileoFlying around Jupiter 34 times, we got the information aboutJupiter's atmosphereIn 1995, a probe was placed on Jupiter.Galileo's observations have further deepened theVoyagerLater understanding of Jupiter and its satellite system, such asGanymedeThere is a spontaneous dipole magnetic field and underground saline ocean,EuropaViolent plate tectonics.
The Galileo probe crashed into Jupiter on September 21, 2003, ending its nearly 14 years of space exploration.This will be NASA'sLunar explorer probeFor the first time since the Lunar Prospector, the probe was controlled to crash on a celestial body outside the Earth.
Takeoff plan
“Galileo”The process of the probe's going into space can be described as ups and downs.At first, NASA planned to launch it in January 1982. Later, due to the change of flight plan, it was postponed to May 1986.On January 28, 1986“challenger”The space shuttle "Galileo" blasted off, delaying the plan of "Galileo" again.Since then, due to funding reasons, NASA has switched to rockets with smaller thrust.Just because of this change, Galileo abandoned the original plan of flying directly to Jupiter and took a unique flight route, accelerating with the help of the gravity of Venus and the Earth.In this way, the time of its arrival at Jupiter has been extended from 2 years to 6 years.On October 18, 1989, after leaving the space shuttle Atlantis, the Galileo Jupiter probe first flew to the sun.Since then, according to the predetermined route, it first passed Venus in February 1990, then passed the Earth twice in December of the same year and December of 1992 to make full use of their gravity to accelerate, and then officially embarked on the journey to Jupiter.After three years of space travel, Galileo finally entered the orbit around Jupiter on December 7, 1995.
Go to Jupiter
Galileo's journey was unlucky.It was originally planned that the space shuttle would send it and its propulsion rocket--CentaurRocket launchEarth orbit。Then the Centaur rocket will take two and a half years to send Galileo to Jupiter.In the early 1980s, when Galileo was completedCarrier rocketNot ready.So the launch was delayed.When everything was ready, the launch date was set in May 1986.However, after the tragedy of the space shuttle Challenger in January 1986, the United States government stopped all launch activities and reviewed the safety standards.Galileo's liftoff was postponed to three years later.New safety rules have also been added, including the use of low-power propulsion rockets, and the prohibition of placing fuel in the shuttle's transport bunker.This means that the Centaur rocket will be canceled.In order to enter the expected orbit, the spacecraft will first enter the orbit of Venus, then accelerate with the help of gravity, and then return to the Earth twice to accelerate, and then go to Jupiter.This makes the trip that was originally scheduled to last two and a half years become six years.During the three years of waiting for launch, Galileo was transformed, transported and stored many times.Some people think that the "journey" of these three years may be the cause of many problems after takeoff.
Galileo made use of the increased journey to compare the surface chemicals on the light side and dark side of the moon, and also compared theozone layerAtmospheric observations were made.But before leaving the earth for the last time, the problem arises again.Galileo's main antenna--High gain antennaIt is found that it cannot be opened accurately.As the main tool for Galileo to communicate with the earth, the error of the high gain antenna has caused serious consequences.Originally, Galileo could send back a picture to the earth every few minutes, but after the failure, it became a picture every few weeks.Fortunately, the development of computer technology has made up for this.Data can be compressed and then transmitted, which reduces the transmission time of photos to several hours.
Difficulties abound
Galileo
Skip on GalileoAsteroid beltGalileoAsteroid 951And asteroid 243 (Ida), found Ida's satellite and named it Dactyl.In the astronomical spectacle of the comet hitting Jupiter in 1994, Galileo observedComet Shoemaker Levy 9The Earth's telescopes have to wait for Jupiter's rotation to observe its shadow.
However, two months before reaching Jupiter, another problem occurred.GalileoThe tape recorder for has failed.The main task of the tape recorder is to record the results detected by various instruments on Galileo and send them back to the Earth at an appropriate time.After the failure of the main antenna, the role of the tape recorder becomes very important.In order to make adjustments to the tape recorder, Galileo abandoned the original detectionIoPlan for.
Galileo is equipped with a detector whose mission is to rush into Jupiter's atmosphere and send back as many data as possible before burning out.This is a difficult task. Friction with Jupiter's atmosphere will produce a high temperature of 21000 degrees Fahrenheit.After opening the parachute to decelerate, the detector will be separated from the heat shield to resist the high temperature.Alone with Jupiter's storms, heat and tremendous pressure.On December 7, 1995, the probe entered Jupiter's atmosphere.The probe successfully sent back a signal, and 57 minutes after landing, the probe was burned by the heat from Jupiter.But these 57 minutes have greatly increased our understanding of Jupiter's atmosphere and climate.
GalileoIt has also made great contributions to the study of Jupiter's satellites.Before Galileo arrived at Jupiter, people found a total of 16 Jupiter's moons.Galileo discovered many more satellites after its arrival.This number has risen to 63.
Due to radiation damage, Galileo's photographic device ceased operation on 17 January 2002.Engineers can repair the tape data, so it can continue to send data back to Earth before crashing.
The latest data from the Galileo probe in the United States shows thatEuropaThere may be oceans beneath the surface of.This new evidence once again adds a heavy weight to the hypothesis made by scientists earlier based on the data that there is water on Europa, and causes biologists to debate whether there is life on Europa.
The discovery of Europa
“Galileo”Detector No. 1 is at the distanceEuropaIt flew over 351 kilometers above.Surprisingly, EuropaMagnetic northThe geographical position of the pole is changing, and it moves frequently, moving a certain distance almost every five and a half hours.
This result has puzzled many scientists: what force drives Europa's magnetic north pole to move continuously?"I think these findings tell us that there is a liquid water layer beneath Europa's surface," said space scientist Margaret Kivilson.According to scientists, if there is a liquid conductive layer - such as a salt water layer - under Europa's surface, it will most fully explain the continuous change of magnetic poles."These new discoveries are very convincing for the idea of oceans on Europa," Kivilson said
After Galileo's mission,NASAThe next probe of is namedJupiter Icy Moons Orbiter (Jupiter Icy Moons Orbiter, JIMO), in the drafting stage.[3]
Longer life
The original mission of the detector for about two years has been extended three times.In more than seven years after flying into the orbit around Jupiter in December 1995, it created records as follows: it orbited Jupiter 34 times, met 35 major satellites of Jupiter, sent back 30000 megabit data including 14000 photos, found evidence of the existence of underground liquid brine on three satellites of Jupiter, and conducted a complete investigation of Jupiter's system from orbit for the first time,The first direct measurement of Jupiter's atmosphere was made.
Galileo
NASA had planned to keep Galileo in orbit around Jupiter, but the probeEuropaThe discovery that there might be an ocean on the sea changed the minds of experts.Galileo's main mission is not to search for life outside the planet. The detector was not disinfected when it was designed.When it is about to run out of fuel, its orbit may change under the action of Jupiter's gravity, and it may collide with Europa.In theory, the collision between the probe and Europa may cause the microbes on Earth to have a foothold on Europa, which will affect the future work of searching for native life on this satellite.
NASA therefore decided to let Galileo be buried on other celestial bodies except Europa when its fuel was not completely exhausted and its orbit could be controlled. This "burial place" was finally designated as Jupiter.
Crash Jupiter
NASAGalileo spacecraftUS TimeIn the afternoon of September 21, 2003 (Beijing timeSeptember 22ndIt ended its eight year mission in Jupiter. It hit the largest planet as expected, and scientists celebrated on Earth.
On the day of the crash, Galileo will run to the back of Jupiter, and then crash into Jupiter at a speed of about 170000 kilometers per houratmosphere。“Galileo”The high temperature formed during the friction between the spacecraft and Jupiter's atmosphere will cause the probe to burn violently and eventually crash into Jupiter.About 1500 representatives from all walks of life related to the Galileo exploration program will gather at NASAJet Propulsion Laboratory, which is the end of this detector.Galileo PlanMs. Terige, the host, said: "The Galileo spacecraft is aging, its fuel is running out, and it is constantly exposed to radiation. It is right to let the spacecraft end in a controlled way before it leaves our control." For those who participate in the construction, launch and care of Galileo, September 21 will mark the end of an era.
NASAstayCaliforniaEger, spokesman of Pasadena's Jet Propulsion Laboratory, said that the laboratoryUS Eastern TimeAt 3:40 p.m. (3:40 a.m. Beijing time this morning), more than 2 hours and 36 minutes earlier than expected, more than 1000 people worked around Galileo, and they all came to the laboratory to celebrate the end of the mission.[4]
Many people will ask, why does a Jupiter probe cause thousands of scientists at NASA to sigh so deeply?Why does it attract the attention of many people all over the world?
It starts with the birth of the Galileo probe and the great discoveries it has brought to mankind.It took more than 30 years before and after, and the "Galileo" detector, which cost 1.4 billion dollars, was ugly, the size of a sports car, only 10 instruments were carried, and the computer controlling its nerve center was only equivalent to the performance of the "Apple II", and its main antenna and another important instrument failed soon after launch.
However, it has become the greatestSpace probe: It was the first to photograph the moon andcometPhotos of running together;It was the first to capture the spectacular scene of the Big Bang.In 1994, a comet hit Jupiter violently, and the explosion produced more power than the worldnuclear weaponThe explosion energy adds up to hundreds of thousands of times.The most touching thing about this scene is that if Jupiter did not "selflessly" attract the comet to his side, then life on earth would not be able to withstand the cometBig collision between heaven and earthTop priority;Most importantly, it was the first one to be photographedJupiter satelliteEuropaThere are photos of the ocean!This makes life on earth seeextraterrestrial life Hope.[5]
Question 2
Why did you let the Galileo burn?
Since“Galileo”No. 2 has achieved great success and has stable performance so far. Why must it be hitJupiter's atmosphereBurn yourself and perish?NASA's answer is very clear: it is its great discovery that determines its ultimate tragic fate!
Karen, head of NASA's Solar System Exploration DepartmentHartmannSay.One of the most important mysteries that mankind wants to uncover in space exploration is: "Is life on the earth really lonely in the vast space?" The Galileo probe lets mankind see the hope of life on other planets, because it comes from Jupiter's satellite“Europa”The picture sent back on shows that this Jupiter's moon has an ocean!On the earth, water means life, so if there is any sign of water in the atmosphere of other stars outside the earth, it means an oasis of life!The fuel on Galileo is about to run out. If there is no fuel, then thisCosmic probeWill lose control and may crash into the ocean of Europa“Galileo”It is possible that the earth bacteria on board could live or even develop in the strange alien sea, thus polluting the distant Europa sea and threatening the possible existence thereextraterrestrial life ！
Claudia, the person in charge of the "Galileo" project, said that it is right to let the "Galileo" probe burn itself, because Europa's environment is too precious and worthy of our protection, and Europa's oceans will certainly become the most focused planet for future human space exploration, because there may be partners of Earth's life - extraterrestrial life!
Galileo Jupiter probe
Question 3
How will the final journey of Galileo be carried out?
Of course, the most interesting and eye-catching part is the final journey of Galileo.So“Galileo”What will the last moment look like?
Galileo first entered the turbulent high radiation“particleOceans ".The Galileo detector also entered this extremely dangerous "particle ocean" several times before, and suffered more than four times the radiation of the original design of the detector. The detector paid a huge price for this - some instruments were damaged,cameraShattered, detector loadedMemory systemlose.In November 2002, the detector entered the danger zone again and was exposed to intense radiation equivalent to killing 1000 people a day.This time, after the Galileo probe enters the danger zone, the system it carries will entersafe modeHowever, it will still tenaciously send back a large amount of data to the earth. After a few hours, the detector will be completely silent,US Eastern TimeAt 16:00 p.m. on September 21, 2003, Galileo will turn to the back of Jupiter, and then it will hit the clouds above Jupiter at a speed of 100000 miles per hour. The resulting temperature and huge pressure equivalent to twice the sun's surface will destroy the detector in a few minutes!
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Galileo
Hundreds of scientists, engineers and their families gathered in PasadenaNASA Jet Propulsion Laboratory, Teletransmission“Galileo”No. 1 has finished the last part of the journey.Many people have worked in this project for decades, and they are very sad about the falling of the detector.A scientist named Lopez said: "It's a bit sad to say goodbye to an old friend." After the fall process began, the eyes of Ms. Alexander, the last project director, also became moist.
Although Galileo is an inanimate machine, it has experienced various glories and setbacks from gestation to crash, which are difficult for scientists to give up.
The Galileo exploration plan was first proposed in the early 1970s, and was approved by NASA in 1977, but it was not until 1989 that it was sent into space by the space shuttle Atlantis.After that, the main antenna on the detector failed, but the ground controller finally found another way to let it send back the detection data.
