Yes, the tape recorder does have an automatic shutoff at the end or beginning of tape. The problem wasn't with the automatic shutoff not working; as it turns out, the tape recorder mechanism was moving along, but the tape itself stayed put.
So why didn't engineers turn off the tape recorder as soon as they knew that there was a problem? We need to have the capability to send a command to Galileo saying "shut off the tape recorder" and, at the time of the tape recorder problem, that commanding capability wasn't present.
The problem was discovered over Goldstone, California, but it was too late in the tracking period to send a command to Galileo. The next station to "rise" and start tracking Galileo was Canberra, Australia (which has a 12 hour view of the spacecraft). Unfortuantely, Canberra's transmitter wasn't available--it was down for maintenance. So it wasn't until the station at Madrid, Spain, "rose" that we were able to send the "turn off the tape recorder" command, approximately 15 hours after the problem was detected. (60 sec)
Charge-coupled devices like those in Galileo's television systems are used in some of our home video cameras, yielding sharper images than ever conceived of in the days before the project began. Radiation-resistant components developed for Galileo are now used in research, businesses, and military applications where radiation environment is a concern. Another advance, integrated circuits resistant to cosmic rays, has helped to handle disturbances to computer memory that are caused by high-energy particles; these disturbances plague extremely high-speed computers on Earth and all spacecraft. (34 sec)
The Jovian system contains clues to much of the early history of the solar system. When the solar system formed and then cooled, most of the planets and other orbiting bodies "spun off" the local solar nebular material, especially hydrogen and helium, while proto-Jupiter's great gravitational attraction held on to this material. Because it retains this primordial composition, Jupiter makes a better cosmological "laboratory" than any of the other planets. The Jovian system is also a solar system in miniature, and a tour of this system not only enables observation of a giant gas planet but also a wide range of smaller planetary bodies on different evolutionary paths.
Also, advances in such fields as meteorology, geochemistry, geology and geophysics, atmospheric sciences, and space physics are expected. These are all disciplines which benefit all the Earth sciences and understanding both our own planet and our place in the universe. (50 sec)
There are many mysteries about the Jupiter system. What scientists still want to know is how similar to the original solar nebula is Jupiter's atmosphere, what drives the weather on Jupiter, how volcanic is the moon Io, does Europa have a liquid water ocean under its ice crust, how does the magnetosphere work, how does it interact with the satellites, and do the satellites have their own magnetic fields. (27 sec)
We don't know the precise composition of the atmosphere. We don't know the basic nature of the driving forces for its meteorology. We don't understand the processes forming the Io torus and the mechanisms which energize the magnetosphere. We don't understand the geologic histories and physical state of the Galilean satellites. (22 sec)
Combined with the discovery of the moon's magnetic field, scientists believe that Ganymede has a metallic core about 250 to 800 miles in, surrounded by a rocky silicate mantle, which is in turn enclosed by an ice shell about 500 miles thick. Depending on whether the core is pure iron or an alloy of iron and iron sulfide, it could account for as little as 1.4 percent or as much as one-third of the total mass of Ganymede. This structure is the most likely cause of Ganymede's newly discovered magnetic field, which in turn gives rise to the magnetosphere.
Scientists suspect Ganymede's magnetic field is generated the same way as Earth's, through the dynamo action of the fluid mantle rotating above a metallic core. The only other solid bodies in the Solar System known to have magnetic fields are Mercury, Earth, and possibly Jupiter's volcanic moon Io. Ganymede's magnetic field is strong enough to carve out a magnetosphere with clearly defined boundaries within Jupiter's magnetosphere, making it the only 'magnetosphere within a magnetosphere' known in the solar system. Study of this phenomena will help scientists understand better the complex interplay of magnetic forces and matter throughout the universe. (67 sec)
The Galileo Probe apparently entered Jupiter at a rather unique location, as no thick dense clouds were found. Upper atmospheric densities and temperatures were significantly higher than expected, with an atmospheric pressure of about 24 bars, meaning 24 times the atmospheric pressure at sea level on Earth, which equals the pressure at a depth of 230 meters -- 750 feet -- in the ocean, and a temperature of 305 degrees F (152 C). An additional source of heating beyond sunlight appears to be necessary to account for this result. At deeper levels the temperatures and pressures were close to expectations. The vertical variation of temperature in the 6-15 bar pressure range (about 100-150 km below visible clouds) indicated the deep atmosphere is dryer than expected and is convective. This means our ideas about the abundance and distribution of water on Jupiter will need to be reconsidered.
The winds below the clouds were found to blow at 700 km/hour (435 mph) and are roughly independent of depth. Winds at the cloud tops monitored by the Hubble Space Telescope are of similar strength. These results have profound implications. The winds on Jupiter are probably not produced by heating due to sunlight, or by heating due to condensation of water vapor -- two heat sources which power winds on Earth. A likely mechanism for powering the winds now appears to be the heat escaping from Jupiter's deep interior.
The atmosphere was found to have much less oxygen -- mainly found as water vapor in Jupiter's atmosphere -- than the Sun's atmosphere, implying a surprisingly dry atmosphere. Other solar elements like carbon and sulfur were found in greater supply than in the sun, while neon was in less supply. Little evidence of organic molecules was found. (99 sec)
Pictures taken by Galileo's camera indicate "warm ice" or even liquid water may have existed, and perhaps still exists today beneath Europa's cracked icy crust. Such evidence brings scientists a step closer to determining whether some part of Europa may be warm and wet enough to meet the requirements to host life. (21 sec)
Galileo uses monomethylhydrazine for fuel. The fuel has to be oxidized in order to ignite, so nitrogen tetroxide is mixed into the fuel right before a burn. There are two separate tanks of helium pressurant. In all, Galileo carried 932 kg (2,050 lbs) of propellant at launch. (21 sec)
Galileo uses two Radioisotope Thermoelectric Generators (or RTGs for short) to generate electrical power. The RTGs power the spacecraft through the radioactive decay of plutonium-238. The decay emits heat, which is converted into electricity for the spacecraft to "see, sense, hear, and speak." Each RTG is mounted on a 5-meter long boom.
The spacecraft was able to generate 570 watts of electric power at launch and produced about 480 watts when the spacecraft arrived at Jupiter in December 1995. (32 sec)
Spacecraft that travel at or within Earth's orbit can use solar energy to power their instruments. However, at the great distance of Jupiter, the only feasible power source means using Galileo's Radioisotope Thermal Generators (or RTGs). Galileo would need a minimum of 700 to 1,600 square feet of solar panels--a solar panel about the size of a house!
Unlike other power sources, the RTGs are insensitive to the freezing cold of space, and are virtually invulnerable to high radiation fields, such as Earth's Van Allen belts and Jupiter's magnetosphere. (34 sec)
The World Wide Web has a home page on Galileo, maintained by the Jet Propulsion Laboratory; the web address is http://www.jpl.nasa.gov/galileo/. From there more websites as well as information about other resources is listed. Many videos are available for free through the JPL Teaching Resource Center in exchange for a new, quality-brand VHS cassette still in shrink-wrap; mail your request and tape to JPL Teacher Resource Center, 4800 Oak Grove Drive, MS CS-530, Pasadena, CA 91109. (33 sec)
The software written to run the main computers was written in a combination of assembly language and HALS, the same language used to program the U.S. Space Shuttle. Since Galileo's main computers and a number of instruments are reprogrammable, this software has been updated and improved a number of times since the systems were built, and the spacecraft can even get software uploaded to it during its flight and while orbiting Jupiter. (23 sec)
Gravity is what holds Jupiter -- and all the other planets -- together. Most people don't worry about the Earth falling apart, because we have a solid surface under our feet, but the Earth also contains a fair amount of gas as well --the atmosphere -- which isn't floating away into space (and a good thing, or we wouldn't have any air to breathe). Seeing that gravity binds the atmosphere to Earth makes it easier to understand that gravity can also hold together gas giants like Jupiter and Saturn. (29 sec)
The total cost of the Galileo mission, from the start of planning in 1977 through the end of mission in December 1997, is $1.354 billion. This value does not include launch costs, Deep Space Network tracking costs, and foreign contributions (the latter is estimated at about $110 million, a very substantial international contribution indeed!). The total breaks down into $892 million in development costs (through about 30 days after launch), and $462 million in operating costs. Galileo has cost each citizen of the U.S. only 27 cents a year during its 20 year life. (38 sec)