What is deep space refers to?

We have not even explore our nearby planets (till Mars) then why space agencies are going for deep space missions (like voyager-1 and voyager-2)? What do they want to achieve, which cannot be achieved by telescopes?

If astronauts are going for deep space missions then can we say that they are going for a suicidal mission? If not how would they comeback?


closed as unclear what you're asking by Rory Alsop, Nathan Tuggy, Dr Sheldon, peterh, Bear Oct 1 '18 at 19:00

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    $\begingroup$ Which nearby planets, and which deep space missions are you thinking of? $\endgroup$ – Steve Linton Oct 1 '18 at 15:30
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    $\begingroup$ Important point: as deep-space says, don't confuse "deep space" with "interstellar". $\endgroup$ – Nathan Tuggy Oct 1 '18 at 16:51
  • $\begingroup$ @NathanTuggy is right and articulates what I failed to say clearly enough in my earlier comment. I meant to lead the OP to the realization that "deep space" usually just means beyond cis-lunar space. I don't think misunderstanding how shallow deep space's starting point is deserves four down votes though. I've up voted to try to counter some of that. $\endgroup$ – uhoh Oct 2 '18 at 3:40
  • $\begingroup$ Hi Amar in the future it's always good to try to refer to specific articles or texts or links when you ask questions about missions or projects. At this point, since you've accepted an answer, it's probably not good to try to modify the question too much. Instead, choose something that can be addresses specifically, give examples of what you've read so far, and then describe what it is that you're asking about that's not covered sufficiently in what you've read. For example, the Voyagers had telescopes, but they were much closer to their targets than those on Earth, so that's kind-of obvious $\endgroup$ – uhoh Oct 2 '18 at 7:23
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    $\begingroup$ Can you stick to one question at a time? There's 3 now. $\endgroup$ – Jan Doggen Oct 2 '18 at 7:53

We have not even explore our nearby planets then why space agencies are going for deep space mission?

We have explored our nearby planets. We already know vastly more about the Moon, Venus and Mars than we did in 1950. This exploration is not complete, but that's not a reason not to look further.

The human species has 7 billion members. We don't all focus on one task: we can't, and we don't have to. In planetary exploration as in every other human endeavor, different people specialize in different subjects. Some study Mars, other study gas giants etc.

What do they want to achieve, which cannot be achieved by telescopes?

A lot. To illustrate: A picture of Pluto taken by one of the best telescopes we have:

Pluto as seen by Hubble

A picture of Pluto as taken by New Horizons, a few thousand km from Pluto's surface: Pluto's heart

We can do a lot with telescopes on Earth. But our first mission to Pluto has, in one stroke, multiplied our knowledge of that planet by a factor of 1000, if not more.

  • image resolution is vastly better when you are a million times closer
  • New Horizons has ~10 instruments on board for in-situ measurements that are simple impossible to do from a distance
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    $\begingroup$ This is a great answer, however I think the OP was believing that "deep space" meant beyond the solar system. It looks like the question is "Why should we go to deep space if there is still a lot to be done in the Solar System" and so the answer is really just "The solar system is deep space". I can't post that because the hold now blocks me from doing so. $\endgroup$ – uhoh Oct 2 '18 at 2:19

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