Galileo To Commit Mechacide

taylor writes "The Sydney Morning Herald reports that the old explorer spacecraft Galileo will soon commit suicide after flying a final mission. The spacecraft has been orbiting Juptiter for seven years. Tomorrow, Galileo will pass Amalthea, a tiny moon of that planet, to gather information about the moon's gravitational pull on the spacecraft, and thus about its material makeup. Immediately thereafter, Galileo will move quickly through Jupiter's rings, exposing itself to 100 times the radiation a human could withstand. The spacecraft will likely not survive; it is already crippled from the large amounts of radiation it has encountered thus far. In any case, Galileo will then begin its final orbit of Jupiter, ending next September in a fatal crash into the planet's dense atmosphere. Read the full article on SMH.com.au."

Comments

Re:Radiation?

[Anonymous Coward]

As an example, take EMP. That's just electromagnetic radiation but machines are not too fond of it (they go kaput).

Radiation damages biological systems by smacking the DNA. It's the same sort of deal with a machine, little bits of it get whacked by some radiation. It's not quite as vulnerable since damage to one structure doesn't go on to replicate itself like cancer does in the biological world.

silicon or something like it

[EEgopher]

if the radiation were to alter or ruin the physical structure of the transistors' semiconductor lattice, the resulting electrical signals could be distorted beyond utility or recovery.
The semiconductors are doped by high-velocity, high-temperature particle bombardment. I imagine radiation could have a counterintuitively destructive effect.

Re:Radiation?

[Wyatt Earp]

The magnetic field of Jupiter are very strong.

http://www-ssc.igpp.ucla.edu/personnel/russell/p ap ers/jup_mag/

"It also has the largest magnetic moment (computed as the product of the equatorial surface field and the cube of the planetary radius). Consequently it also has the largest magnetosphere in the solar system, large enough to encompass easily the Sun and the visible corona. If the Jovian magnetosphere were visible from Earth, it would be bigger than the Moon in the night sky. Jupiter is also a powerful emitter of radio waves. Its giant magnetosphere acts both as a trap and an accelerator of energetic charged particles. The most energetic of the trapped electrons radiate at radio frequencies, and it was the radio frequency radiation that led in 1955 to the discovery that Jupiter had a magnetic field (Burke and Franklin,1955). Jupiter's magnetosphere differs importantly from the Earth's magnetosphere in that its energy is predominantly derived from sources internal to the magnetosphere rather than through its interaction with the solar wind."

Here is a real-world illustration of a radiation effect on machines, take an external power supply from a Deskwriter series HP printer, set it next to a CRT monitor and watch the fun happen.

http://spaceflightnow.com/news/n0012/30galileora d/

"Exposure to Jupiter's intense radiation caused two effects -- an alarm received from Galileo's camera system, and a computer reset of the non-spinning portion of the spacecraft. The reset was a transient event that has happened during radiation exposures on several previous orbits. The computer reset was handled properly by onboard software responses, and mission engineers are investigating the out-of-the-ordinary measurement that triggered the camera alarm.

Other systems on Galileo were operating normally more than 12 hours after the closest approach to Jupiter.

"Adverse effects from the radiation close to Jupiter are not unexpected," said Jim Erickson, Galileo project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Galileo had already endured more than three times the cumulative radiation exposure it was designed to withstand, and has operated more than three years above and beyond its original two-year mission in orbit around Jupiter.

Galileo had flown within 2,337 kilometers (1,452 miles) of Jupiter's largest moon, Ganymede, and taken images of it several hours before the camera began indicating a possible problem. The camera and other scientific instruments onboard the orbiter are continuing to record data about Jupiter and its moons."

Radiation can be very damaging to machines. It can degrade the strength of metals, plastics and ceramics used in the construction of the spacecraft. It will damage electronics and can effect the ability of the batteries to take a charge.

It's hostile out there in space, and not just because of the cold/hot and lack of atmosphere.

Re:Radiation?

[spaceyhackerlady]

I was under the impression that radiation was only dangerous to organic life forms. How could it damage machines?

There are several mechanisms.

Radiation neutralizes the stored charge in EPROMs. This is the same mechanism as erasing them with UV light. At one time people just didn't use them in space applications, but have now found that you can if you're careful, and don't leave them in space too long. Flash is still generally off-limits.

Radiation can alter the characteristics of semiconductor junctions.

Radiation can alter the characteristics of passive components.

And so on...

...laura

mars viking lander:Radiation and Core memory

[goombah99]

I worked on the mars viking lander project. The viking lander used a high tech variation of core memory for ram and for storage it used a steel tape used in a tape recorder. You are probably wondering why they did not use ordinary magnetic tape and silicon RAM. well in addition to radiation concerns there was a bigger issue.

NASA was very worried about contaminating mars so the entire lander had to be autoclaved on earth. the high temperatures of the autoclave would destroy ordinary magnetic tape. and the core memoery was low power since it is non-volatile.

For you kids who dont know what "core" memory is (or why for example you get files called "core" dumps on your computer when a program crashes) gramps will explain. Core origiginally was a donut shaped peice of ferrite. Next imagine set of 100 parallel wires spaced 1cm appart. on top of this is laying another set of 100 parallel wires running at right angles to the first set. At every crossing point in this grid a small ferrite disk is threaded by these two wires. and voila random access memory. each core is a single bit. to program it you run a current equal to half the hysterisis level down one of the wires in the first set and an equivalent current down one of the second set of wires. Only one core, at the insterescion, gets the double dose of current that exceeds the hysterisis value. this flips the magnetic polarization of the donut. To read it out one simply monitors the inductance: if you flip the bit the voltage is higher than if you are not flipping it. turn off the power and the magnetic memory stays. It is impervious to cosmic rays. the donuts are called "cores". why these are called cores is a different topic

Core memory on the viking lander was a bit more sophisticated. the magnetic material was coated/evaporated directly onto the wires so the whole thing could be very dense.

Silicon memory was available back then but it was not deemed relaible in the face of unknown radiation levels, and thermal stress. It was a great sacrifice to have such a small amount of ram (core has low bit density compared to silicon). But it was the only way to solve the problems.

Following its namesake.

[JohnFred]

Galileo himself died nearly blind, so there's a certain poignancy to the fate of this machine.

I must point out that the idea that his blindness was due to observations of the Sun is a myth: he made the observations by projection, the way anyone with half a brain would. His blindness was actually due to glaucoma and cataracts at the age of 72. My source is Galileo's Daughter by Dava Sobel.