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.
Okay, 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, 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 (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 "rose" that we were able to send the "turn off the tape recorder" command, approximately 15 hours after the anomaly was detected.
Why is it now not possible to photograph Io and Europa on December 7, as planned?
Having Galileo take pictures of Io and Europa isn't the problem--the difficulty is in storing the images so that they can be sent down to Earth at some later time.
Although the tape recorder is working, the Project wants to limit use of the tape recorder until we 1) better understand the anomaly and 2) identify what are safe modes of operation for the recorder, because there is a chance that we could, unknowingly, further damage the recorder. Engineers are still analyzing exactly why there was an anomaly, as well as identifying exactly what activities the tape recorder can perform. How fast can the tape safely move? Can the tape move in both directions? Until these questions, and others like them, are answered, the project wants to use the tape recorder as little as possible.
The tape recorder will be used on December 7th-- to store probe data, the number one scientific priority of the entire mission. The spacecraft will also record over 3 hours of Io plasma torus observations, as well as recording engineering data during the Jupiter Orbit Insertion burn.
When will Galileo surpass Hubble's imaging capabilities?
The Hubble Wide Field/Planetary Camera has two imaging modes: either Wide Field or Planetary. The imaging systems on board Galileo have a resolution capability twenty times less than the Hubble Wide Field setting, and 45 times less than the Planetary.
On average, Jupiter is located 5 astronomical units (one astronomical unit = the average distance from the Sun to the Earth) away from the Earth. At that distance, Galileo passed up Hubble's Wide Field resolution of Jupiter on October 6, 1995, and passed up the Planetary on November 13, 1995. If you want to consider the best possible resolution that Hubble is capable of (namely, when Jupiter is closest to Earth--a mere four astronomical units away), Galileo passed the Wide Field performance on October 21, 1995, and the Planetary on November 18, 1995.
What data can we expect to see on December 7, when the spacecraft arrives at Jupiter?
Unlike the Voyager flybys of Jupiter, Saturn, Uranus and Neptune, Galileo won't be sending back pictures "live" on arrival day. The atmospheric probe's data, and fields and particles observations of Io's plasma torus, will be stored on board the spacecraft for later transmission to Earth.
So, what will we see in the "real time" data? For starters, we'll get confirmation that the orbiter is "in lock" with the probe, and that the probe relay is proceding as planned. Although we won't be seeing the actual data, this will still be a tremendous reassurance to the project and to the probe's scientists--keep in mind that there has been no communication with the probe since its release last July! We'll also be seeing engineering and tracking data that will show us that Galileo's 400-Newton main engine is performing as scheduled, sending the craft into orbit around Jupiter. You can be sure that this will also bring forth major sighs of relief from the flight team, since the orbiter's mission is completely dependent on orbiting Jupiter, and not flying by it!
Will there be any images released prior to Dec. 7?
No. On October 11, 1995, Galileo's Solid State Imaging camera took a Jupiter Approach Global Image, designed to give scientists a closer look at the Probe Entry Site just prior to arrival. Because of the tape recorder anomaly, this image will not be sent down to Earth.
When can I see images from the Probe's plunge into Jupiter's atmosphere?
Most people are surprised to learn that the Probe doesn't have a camera at all (so there aren't going to be any images from the Probe at all). Keep in mind that the Probe sends data to the Orbiter at 128 bits per second per channel, and that the Probe mission only lasts 75 minutes at most. A single picture from the Solid State Imaging camera on the Orbiter can easily run around 160 kilobytes, so there wouldn't have been time to send up very many pictures from the Probe before the end of its mission.
A partial "quick look" set of the Probe data will be sent back to Earth December 10-13 (investigators will be announcing their preliminary results at a December 19 press conference). A full playback of the entire Probe data set will start in January 1996, following the end of the solar conjunction period (where the Sun lies almost directly between the Earth and Jupiter), and end in March.
When can we expect to see the first images from the spacecraft?
Since we won't be returning images from the Io flyby on December 7, initial plans for release of the first images have changed. Now, Galileo's first close flyby images will be from the first flyby of Ganymede in early July of 1996. We currently expect that those first images will be released to the public in early July.
Galileo's insulating blankets are 1/5 of an inch thick, but are in fact 60 times more effective than typical household fiberglass insulation at that same thickness. However, that comparison is based on the application for which each insulator was designed.
Fiberglass insulation is designed to work in Earth's atmosphere. Over 90% of the insulation is provided by the air that is trapped between the fiberglass fibers.
Galileo's thermal blankets were designed for use in the vacuum of space and therefore do not have the luxury of using air as an insulator. Alternate layers of Mylar/Dacron netting and aluminized Kapton provide most of the insulation while carbon-polyester coated Kapton (black blankets) and "second-surface aluminized" Kapton (gold blankets) outer layers provide further insulation by absorbing or reflecting the sun's heat.
As such, you can imagine that there is a significant difference between the cost of fiberglass and the cost of the specialized materials that make up Galileo's insulation!
The speed that is posted daily is the speed of the orbiter with respect to the Sun. The Galileo orbiter is currently in an orbit around the Sun and is just past aphelion (the furthest point from the Sun) where the orbiter's speed is the slowest in its orbit. However, if we look at a Sun-centered coordinate system, the orbiter is actually ahead of Jupiter (i.e. Jupiter is coming up from behind the orbiter). As Jupiter "catches up" to the orbiter, its gravitational attraction is actually slowing the orbiter down with respect to the Sun. Between one and two days prior to arrival the orbiter's "forward" motion around the Sun will actually stop. Then, moving in the opposite direction (backwards), the orbiter speeds up again as it moves around the back side of Jupiter. While all of this is happening, the orbiter speed with respect to Jupiter is continuously increasing due to Jupiter's gravitational attraction. The JOI maneuver slows the orbiter down and allows it to be captured in the desired orbit.
Will Earthbound observers be able to see the "flash" from the Probe's entry?
As seen from Earth, Probe entry will occur such that the Probe crosses the dusk terminator (the line dividing day from night) during its mission. The 15,500 degree C (28,000 degree F) incandescent plasma envelope generated ahead of the Probe, which is produced by hypersonic compression and friction with the atmosphere, will briefly be brighter than the Sun's surface.
However, will the high-temperature streak generated by the Probe be detectable?
Unfortunately the answer to this question is NO. Although the length of the streak may be several degrees long in the night sky, the width of the streak is WELL below the resolution of any Earth-based telescope imaging system. Keep in mind, too, that Jupiter is quite near the Sun in the sky, adding another observing difficulty.