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To Ada Munroe's question: "If you did fall into Jupiter's atmosphere in a submarine, what would it actually look like? What would you see before you melted or burned up?"

Randall Munroe answers:

"We don't know! We've only flown spacecraft into a gas planet's atmosphere twice (both Jupiter). One had no cameras, and one went in at night (and was being disposed of, so wasn't taking pictures anyway)." -

Why wasn't the latter taking pictures? The reasons offered seem irrelevant.

Surely it's all down to design limitations, and/or budget. If so, I would like that confirmed (in which case this is a very boring question, and I would just like suggestions as to why Randall didn't even mention it if possible), and if not, I'd like to hear the whole story why we didn't do what, seemingly uncontroversially, and in keeping with NASA's reputation of the pure pursuit of knowledge, would clearly be a very worthwhile accomplishment: take pictures of the descent as much as possible.

We've certainly made it our business to get photographs from inside planets and moons before.

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    $\begingroup$ Scientists have several types and varieties of data available to them that will help give them answers to the questions they are asking. Photography isn't always one of the top priorities, even though as non-scientists that would seem to be the most useful thing, since to us all of the other data doesn't really mean anything, at least not as much as a photograph. But to a scientist other types of data can easily be much more valuable than photographs, again depending on what exactly they are researching, which is usually related to what particular theories they are trying to validate. $\endgroup$
    – Steve Pemberton
    Commented Nov 18 at 6:02
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    $\begingroup$ I don't know for sure, but that big chunk of chatterbot text is a likely attractor of down votes. I think most folks don't consider that as much "evidence of prior research" as they do a source of noise. I'd say just delete it and instead tell us what you think yourself. We're still (at least mostly) all humans here. Your actual question is very good and has already generated three presumably live human answers already! See also How deep could a gas giant communications network penetrate? $\endgroup$
    – uhoh
    Commented Nov 18 at 9:20
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    $\begingroup$ I don't agree with the downvotes @RabbiKaii, it's a perfectly good question if people actually read it. We've had a few really poor questions based on ChatGPT, I think some people automatically downvote based on simply seeing the word. I also think the word orthogonal is also a bit strange in context. $\endgroup$
    – GdD
    Commented Nov 18 at 11:39
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    $\begingroup$ I didn't downvote but some of your original wording sounded somewhat similar to posts that appear here sometimes by flat Earth, Moon hoax, or the NASA never went to space crowd. But as people realized that is not the case then you began to get legitimate answers. $\endgroup$
    – Steve Pemberton
    Commented Nov 18 at 19:12
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    $\begingroup$ @StevePemberton it's called trolling. To misquote the Borg "engagement is futile". I just flag those as either "no longer needed" or "something else" with an explanation, and they usually get cleaned up since they're an attempt to start a discussion unrelated to the post and its author. $\endgroup$
    – uhoh
    Commented Nov 19 at 16:16

4 Answers 4

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  1. A spacecraft entering without an suitable heat shield melts and breaks apart well above the cloud tops of Jupiter's (or any other planet's) atmosphere. So, its closest point of view isn't significantly different from a point of view outside the atmosphere.

  2. Galileo's data transmission rate was only 160 bits per second. It took hours to transmit an image. There wasn't time.

Edit:

The low data rate was due to the failure of Galileo's high gain antenna.

An entry vehicle has a completely different architecture than a surveillance vehicle. The heat shield is massive (especially so for Jupiter), and constrains everything else to be located inside the shock wave it produces. Those difficulties severely limit the scientific capabilities of the vehicle. Galileo would have been a much less capable mission if it had been designed for entry.

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    $\begingroup$ Perfectly fine answer + 1. Checkmark is available to someone who helps me understand better why NASA didn't give it a heat shield, better bitrate, or generally not even try to get the footage? Is it just budget? Also, I know it's only speculative, but I am still very confused why Randall didn't write what you wrote which would have been much more natural and relevant. Instead he just wrote "they were disposing of it", which just begs the question $\endgroup$
    – Rabbi Kaii
    Commented Nov 17 at 16:01
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    $\begingroup$ Budget is the end driver of all missions. They would have loved to have had an 8k live video feed. They probably would have crashed it on the daytime side if they had the opportunity of taking pictures. They shut everything down because sending pictures back wasn't an option, and instead focused on getting whatever data they could. $\endgroup$
    – Greg Miller
    Commented Nov 17 at 16:27
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    $\begingroup$ I'd just add to say that even if it had a working high-gain antenna, the atmospheric drag makes it very unlikely it would have been able to aim the antenna towards earth and stay on-target long enough to transmit anything, at least low enough to get photos of any interest. $\endgroup$
    – Darth Pseudonym
    Commented Nov 18 at 14:42
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    $\begingroup$ Not just budget, also size and mass. You're severely limited by the capabilities of your launch vehicle, which is restricted both in the size of the payload it can lift and the mass (even worse for a craft that needs to go far, it needs larger engines to drive it, thus less space and mass still for actual payload). $\endgroup$
    – jwenting
    Commented Nov 19 at 12:18
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    $\begingroup$ It also launched in 1989, the tech for both imaging and data transmission has come so far since then that it might be hard not to hold Galileo to modern standards. $\endgroup$
    – aherocalledFrog
    Commented Nov 19 at 15:44
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Supporting information for John Doty's answer here it is important to remember that Galileo was designed in the 80s, where most camera's still used electron tube imagers involving vacuum, high power heaters and glass. The main Galileo solid state imager weighed 29.7kg and was single colour, with colour images requiring taking multiple images through different filters and combining them after reception, which is a problem if the craft moves appreciable between shots.

This means that fitting a camera into the planned descent probe was not going to be easy, and the best that was achieved was the Net Flux Radiometer, which was effectively a two pixel camera (and weighed 3kg at that).

Galileo itself was not designed for atmospheric entry, with the decision to enter Jupiter's atmosphere being to specifically destroy it rather than, because it had notable scientific merit. As such the already limited radio link capability was further constrained by the fact that it could not keep the low gain antenna facing towards earth was drag started to build up - the actual 'loss of signal' event during the entry was when it ran out of control authority to keep the antenna pointing rather than heat or drag related.

So it was a craft not designed for entry, with a failed radio link that could not usefully downlink images anywhere close to real time, with a camera that could not rapidly take images anyway and where loss of signal happened well before approaching anything particularly interesting to take images of.

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    $\begingroup$ Wish I could accept multiple answers as this certainly answers a big part of my question +1 and thanks $\endgroup$
    – Rabbi Kaii
    Commented Nov 18 at 11:44
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Scope Creep

Besides more technical and scientific reasons pointed out in the other answer(s), a critical part of successful project management is knowing when to draw the line.

Specifically the template:

If we are already [doing x] it would be minimal effort to [do y] while we're already at it!

...is very common in engineering projects, because it's very seductive to engineers (and basically everyone else too). Minimal effort for a cool new feature? Who would say no?

The problem is that "minimal effort" does not mean no effort, and if this isn't kept in check, there is a good chance for "snowballing" or scope Creep where the projects goals and ambitions steadily expand as ever more "minor things" are tacked on.

For a hypothetical example, let's say they did want to take pictures while descending, but after one of the engineers writes the code, they note that the data bandwidth won't be high enough to transmit much. Then, like any good engineer, they go searching for solutions and find an efficient one: they discover a simple change that can be made in the radio unit construction that will fix the data issue. Unfortunately, this small fix will require an update to the software, and throw the power budget out of whack, etc.

Here, a very "simple" thing rapidly ballooned into wide-reaching change, all for an original purpose that was only of questionable utility.

Combine this with the general traditional NASA philosophy of "Failure is not an option", and I think it's pretty clear to imagine why there is a lot of things that NASA didn't do despite them, on the surface, seeming like "gimmies"

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    $\begingroup$ People vastly underestimate the trouble that different accommodation requirements of subsystems cause. Everything has a shape, and the shapes don't fit together. Some systems need to be hot, some systems need to be cold. Different operational rhythms need to be respected. The difficulty of getting everything to fit and play together increases exponentially as you add objectives, and new subsystems to achieve them, to a mission. $\endgroup$
    – John Doty
    Commented Nov 17 at 17:51
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    $\begingroup$ NASA is, of course, renowned for their tight control over budgets and timescales $\endgroup$
    – Richard
    Commented Nov 17 at 22:21
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    $\begingroup$ @Richard NASA's troubles with budgets and schedules have more to do with private industry than with NASA itself. Starliner was a clear demonstration: NASA let Boeing manage it without interference and it has been very late and way over budget. $\endgroup$
    – John Doty
    Commented Nov 18 at 1:58
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    $\begingroup$ Wish I could accept multiple answers as this certainly answers a big part of my question +1 and thanks $\endgroup$
    – Rabbi Kaii
    Commented Nov 18 at 11:44
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Expanding on a point GremlinWranger made:

constrained by the fact that it could not keep the low gain antenna facing towards earth was drag started to build up

A spacecraft entering an atmosphere from orbital speed quickly encounters drag that makes maintaining attitude nearly impossible. But attitude control is required to point the antenna back at Earth to get any data from it, including pictures.

Back in 2017, National Geographic made a video about Cassini's retirement, in which it was deliberately crashed into Saturn:

The poingant narration says:

On the final orbit, Cassini will plunge into Saturn, fighting to keep its antenna pointed at Earth as it transmits its farewell.

P.S. The XKCD post linked in the question does not have a date, but it says "Juno, scheduled to reach Jupiter next year". Since Juno reached Jupiter in July 2016 (Jubilantly?), I deduce that post was written in 2015, two years before Cassini's retirement, which explains why it does not acknowledge a probe having entered Saturn's clouds.

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  • $\begingroup$ +1 very nice answer. Thought I already got all I was going to get but this question is the gift that keeps on giving $\endgroup$
    – Rabbi Kaii
    Commented Nov 18 at 22:54

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