When the Galileo probe was crashed into Jupiter it could have made an image from what is considered the "surface" (level of Earth-like atmospheric pressure) of Jupiter or the atmosphere more below or above. Something like that: https://sangitpoudel.com.np/wp-content/uploads/2019/01/dmitry-bogolyubov-jupiter-1024x576.jpg Galileo could even have filmed its fall into Jupiter if it had a good camera for that. Why wasn't that planned for Galileo? The same question applies for Cassini's fall into Saturn.
3 Answers
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I think the overarching consideration is that it wasn't thought that a worthwhile picture would be obtained, and transmitting the picture would compete for bandwidth with more "interesting" instruments in the last seconds before the spacecraft were destroyed.
There are a variety of reasons to suppose you couldn't get a good image. The spacecrafts' camera optics were telephoto optimized for taking pictures of objects thousands of miles away with a small angular velocity. The spacecraft during entry would be moving at tremendous velocity with respect to the planets' cloud tops, so any images captured close to the cloud tops would be smeared out (Juno pans rapidly to avoid this when imaging close to the cloud tops of Jupiter, but Juno is much farther away than the entering spacecraft would be). If the spacecraft survived into the cloud layer, even if you had wide-angle optics you very well might not be able to see anything at all. And well above the clouds, I believe the planets' atmosphere is thick enough that the heat from the entering spacecraft would create a plasma layer which would be opaque.
So there was just no way to get an image with any interesting information in it during the final stages of entry.
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Galileo could even have filmed its fall into Jupiter if it had a good camera for that. Why wasn't that planned for Galileo?
Because it wasn't possible for the Galileo Probe, which did not have a camera (good or bad), and it wouldn't have made sense (it wouldn't even have worked) for the Galileo spacecraft.
The Galileo Probe and the Galileo spacecraft are two different things. The probe was a small atmospheric sounder; it had no cameras. It broadcast data at a rate of 128 bits per second during its descent into the Jovian atmosphere to the Galileo spacecraft. The spacecraft recorded the data transmitted by the probe and later re-transmitted the data back to Earth.
Unlike the Galileo Probe, the Galileo spacecraft had no heat shield, no parachutes. It would have disintegrated near the top of Jupiter's atmosphere. The vehicle could not have taken the picture you want to see.
The Galileo spacecraft was intended to use its high gain antenna to transmit data at 134000 bits per second to Earth. The high gain antenna however did not completely deploy itself. The vehicle instead had to use its two low gain antennae in tandem to transmit at 160 bits per second. The vehicle took a long, long time to transmit recorded imagery to Earth. A transmission during the spacecraft's final descent would not have been possible.
This gets to how NASA designs its deep space probes in general. They record data for a short period of time and then take their sweet time to transmit it to Earth. As an example, it took the New Horizons spacecraft fifteen months to transmit the data gathered during the roughly weeklong encounter with Pluto.
answered Mar 19, 2020 at 16:06
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$\begingroup$ What do you mean with "a camera (good or bad)"? That's a weird formulation in the answer. $\endgroup$– user35272Mar 19, 2020 at 18:57
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$\begingroup$ @user30007 - "Be it good or bad" is an idiomatic phrase in English. The question posited a "good camera", which I quoted. The Galileo Probe did not have a bad camera or a good camera. It had no camera, period. I could have used that phraseology, but since you asked for a "good camera" I used the idiomatic form. $\endgroup$ Mar 19, 2020 at 19:14
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To complement other answers:
- here is the book about full history of Galileo spacecraft.
On page 76 in pdf file (page 121 in the book)
Quote: "the probe was only capable of transmitting data at the rate of 128 bits per second"
Because of this an imaging camera was not selected for the entry probe.
