It is written here that before the final descent Rosetta was programmed for "auto shutoff" after reaching the surface of the comet, to prevent the possibility of the further communications in the case of unlikely survival.

What is the reason for wasting time in programming such a behavior? If the probe is no longer required, why cannot it just be abandoned? And maybe it could take a couple of extra pictures from the surface of the comet before that, or at least finish the transmission of data collected during the descent? And if not, then not, since the chances are low.

While the team of tele-operators costs money, the probe has been flying for many years. It would be strange to hear that it is not possible to afford this team for the extra month or two.

This seems so strange that I even suspect that the "auto shutoff" may be a kind of urban legend. Could this be true?

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    $\begingroup$ I am 99.9% sure that the answer is to prevent signal pollution, but I cannot find a source saying whether that is the only reason. $\endgroup$
    – called2voyage
    Commented Oct 4, 2016 at 21:15

2 Answers 2


At first it might seem a bit crazy to crash a still working satellite into the comet. You could say that if you wait long enough the comet will come around again providing enough energy for more research.

This does bring some risks however, to name 2 obvious ones, the satellite could slowly drift out of orbit or it could never wake up again due to the harsh conditions it is in. In both cases, you lost your valuable satellite and now have debris that can endanger other missions.

Because space debris already is a growing problem an international treaty was signed to reduce the amount of debris in space. This states that all missions should have a end of life plan. In this case a crash landing on the comet.

But what if the satellite crashes into the comet, yet still survives the crash? In that case, each time the satellite receives enough energy, it will start to transmit desperately trying to contact earth. Now instead of the useless satellite debris, there is a comet that sends a useless signal, which can in fact disrupt the signals from other missions.

So to make sure it is completely harmless, it is not only crashed, but also turned off, just in case it survives.

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    $\begingroup$ And it is turned off because the beam is very sensitive to direction; it's virtually guaranteed that after the landing it will never be able to locate Earth again. The phrase further communications is badly chosen - there can't be any. $\endgroup$
    – user10509
    Commented Oct 5, 2016 at 10:19
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    $\begingroup$ The risk of the drifting probe causing any issue is 0, or at least statistically insignificant. It might be "obvious" but it can be completely ignored. $\endgroup$
    – Antzi
    Commented Oct 5, 2016 at 10:26
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    $\begingroup$ @Martini The chance that any random course will ever cause a problem (occlude, hit, or even be seen again) is basically zero. Space is big, the probe is small. $\endgroup$
    – Yakk
    Commented Oct 5, 2016 at 13:39
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    $\begingroup$ @ Yakk, that's true, after reading the response of Antzi again I see his objection was to the chance of causing issues, not on the actual drifting. Thanks, and @Antzi, you're right, the actual chance of hitting Rosetta is next to nothing. $\endgroup$
    – Martini
    Commented Oct 5, 2016 at 13:54
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    $\begingroup$ The question was not why did they land it, but rather why did they shut it off. (And whether they really did that.) The spacecraft could have left the comet, assuring that they would never see each other again, and then shut it off. That would have met their disposal needs. Collision is non-issue in deep space. Also they could have landed and not shut it off, so why they landed has nothing to do with the original question. In any case, they landed because they could get more science with really close-up pictures. And because it would be cool. Which it was. $\endgroup$
    – Mark Adler
    Commented Oct 5, 2016 at 17:52

It is true.

As soon as Rosetta hits the surface, its main systems will be turned off, including the attitude and control systems, as well as the main transmitter, the latter in order to meet regulations aimed at avoiding interference on deep space network communications channels. The software that will enable this ‘passivation’ will be uploaded to the spacecraft a week prior to the planned end of mission, and it will be activated around the time of the collision course manoeuvre, approximately ten hours prior to impact. No automated re-activation will be possible after the systems have shutdown on impact. In any case, as soon as Rosetta hits the surface, its high-gain antenna will very likely no longer be pointing towards Earth, making any potential communications impossible.

From this Rosetta FAQ page. (Emphasis added.)

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    $\begingroup$ This confirms but not yet explains very well why. Hence I upvote but not accept yet. $\endgroup$
    – Nightrider
    Commented Oct 5, 2016 at 6:46
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    $\begingroup$ The 'why' is in the last sentence: 'making any potential communications impossible'. There's no point in keeping the spacecraft working if you can't extract data from it. $\endgroup$
    – Hobbes
    Commented Oct 5, 2016 at 9:00
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    $\begingroup$ The 'why' is also in the first sentence: 'in order to meet regulations'. $\endgroup$
    – OrangeDog
    Commented Oct 5, 2016 at 10:37
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    $\begingroup$ I find it meaningful that the quote states "no automated re-activation will be possible." That feels more like the perspective the OP wants to see. It suggests that, if we feel like it, we can upload new code to wake it up (presuming lucky antenna pointing), but unless we do so, it stays quiet. $\endgroup$
    – Cort Ammon
    Commented Oct 5, 2016 at 18:03
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    $\begingroup$ @CortAmmon: I think it means that if someone (human or otherwise) were to visit the probe in person (and was able to find anything left of it) it might be possible to restart the systems by means of physical manipulation, but that otherwise the system will remain inert. $\endgroup$
    – supercat
    Commented Oct 5, 2016 at 18:33

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