Avi Blizovsky
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The aging Galileo spacecraft, whose computing and communication systems were silenced after it got too close to Jupiter's radiation belt, has come back to life. Galileo entered a safe state precisely when it was on its last scientific mission - the study of the small moon Amalthea on November 5.
The data recordings from the instruments on the spacecraft survived the passage that brought Galileo to a distance of 71 thousand kilometers from Jupiter's clouds. The recording devices seem to have suffered a heatstroke, and efforts to restore them too will take several more weeks, says Eileen Theling, the scientist in charge of Galileo at NASA's Jet Propulsion Laboratory in Pasadena, California.
This approach, which is the most dangerous since Galileo came close to the giant planet seven years ago, was right inside the dangerous radiation belt that surrounds Jupiter.
Galileo, which had already survived radiation levels far greater than those it was designed to go through, automatically shut down when the radiation levels reached dangerous levels. This is a reflexive response called "safe mode" and is designed to protect the sensitive electronic equipment. The radiation in the current pass was twice as strong as the radiation experienced by the spacecraft in previous passes through the radiation belt. The "radiation baths" claimed several victims from the spaceship. Galileo's camera is paralyzed and the tape drive has jammed several times already.
NASA engineers have so far succeeded in extracting the tape, but diagnostic tests show that the problem is different this time. They hope to be able to repair the device and download the information from the November 5 dive. Jupiter's radiation belt accompanying Jupiter's dust ring.
The observations include data on the amount of dust on the moon, the amount of charged particles and possibly also the composition and density of Amalthea - an irregularly shaped moon about 250 km wide.
Whether or not they manage to recover the data, Galileo, almost out of fuel, will continue on a crash course on Jupiter in September 2003. The planned crash was intended to prevent the bus-sized spacecraft from crashing into the moon Europa so as not to contaminate it with terrestrial bacteria that may have managed to survive on the spacecraft all these years.
The beginning of the end of Galileo
In less than a year, the Galileo research spacecraft will complete its mission
Dr. Noah Brosh
On November 5, at 8:19 a.m. Israel time, the "Galileo" spacecraft passed only 160 km above the surface of the tiny moon "Amalthea" - one of the moons of the planet Jupiter. This encounter between the spacecraft and the proximity of the moon The Tiny is the last event planned in this impressive research operation.
An hour after Galileo passed by "Amalthea", the spacecraft passed only 71,400 km above Jupiter's upper cloud layer and in a year, on September 23, 2003, it will penetrate the atmosphere
of justice - and then you will crash on his face. Operation Galileo actually began on October 18, 1989, when the spacecraft, which was "packaged" in the cabin
The cargo of a space shuttle - emerged from it, and began to fly under its own power towards Jupiter. The journey lasted six years. She began her scientific mission only in December 1995.
Its main task was to carry out an in-depth study of the planet Jupiter and its moon system, while carrying out a series of encounters with most of the known moons. At each encounter, the spacecraft passed relatively close to the target, photographed and measured physical quantities, and transmitted the results back to Earth.
Some of Jupiter's moons have turned out to be of great interest to science, so they are studied in a more targeted manner. For example: the moon "Europa", for which there is a hypothesis defined as probable according to which there are seas under its ice surface, oceans of water, in a liquid accumulation state. For this reason, Galileo was referred to him for 11 research sessions.
During the meetings, the faces of the moons were photographed and the color photographs, some with a fairly high detail separation, have already become an iron sheep asset in the study of the moons in the solar system.
But the last operation with a moon of the planet Jupiter was not for collecting photographs. The Galileo camera stopped working a long time ago. She operated well beyond her intended life time.
One of the important goals of the last operation, with Amalthea, was to measure the degree of influence of the moon's gravity on the spacecraft's trajectory. This measurement makes it possible to calculate the mass of this very small moon, whose gravitational influence on the other moons is negligible. The only way to measure the mass, from Earth, is therefore by monitoring disturbances in the orbit of the spacecraft
Galileo.
Based on these data regarding the mass and others measured from previous photographs, it is possible to calculate the average density of the moon - and from this to conclude about the manner of its formation. When Galileo passed by Jupiter in order to study Amalthea, the spacecraft penetrated so deeply into the giant planet's magnetic field - that it was exposed to an unprecedented amount of radiation.
The high radiation caused the cessation of the activity of many instruments in the spacecraft. For nine hours, the "star tracker" - the system that stabilizes Galileo - did not work either. But this period of time was used to collect data about the regime of the particles that met the spacecraft, in addition to the acceleration data, due to the force of gravity.
In addition to these measurements, the dust detectors also worked, which measure collisions between microscopic particles that are near the planet Jupiter and collide with the sides of the spacecraft.
As mentioned, Galileo is going to crash into Jupiter next year. The assumption is that even in her last hours - maybe even in her last moments - she will still try to transmit scientific data to Earth.
The fireball that will envelop her, during the crash to her death - will no longer allow the radio signals to go out into space. Galileo will cease to exist in a tremendous flash of light - but we will only know about it almost an hour after the fact - because that is the time it will take for the radio waves to reach us from Jupiter's environment.
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