I'm still confused over what exactly falls under the scope of Navigation, Guidance, and Estimation systems.

Say I have a bunch of IMUs and use them to determine my position and orientation and my velocity and acceleration relative to earth. That's navigation, right?

Now say I specify a launch pitch program relative to some earth centered frame and apply some transforms to that program to resolve it on my rocket's main frame in order to compute the pitch errors to correct for with my gimballed engines. Is all of this guidance? Is some or all of this navigation?

And if I calculate my delta-V and time-to-go using thrust, mass flow rate, and instantaneous mass. Am I now doing estimation? What else would fall under the scope of estimation?

Sorry for the rookie question. Thanks if you know and can clarify!

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    $\begingroup$ Where do you see the term "Estimation System" used? $\endgroup$ – user20636 Jan 21 at 0:32
  • $\begingroup$ General nomenclature: A ship's captain charts a course on a map and then gives the helmsman instructions. This is navigation. The helmsman then turns the wheel and adjusts the throttle accordingly to ensure the ship stays on the planned course. This is guidance. $\endgroup$ – Dragongeek Jan 21 at 13:55
  • $\begingroup$ @Dragongeek that's not the way NASA uses it. See my answer. They'd say your first thing is guidance and your second thing is flight control. $\endgroup$ – Organic Marble Jan 21 at 14:33
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    $\begingroup$ Ah! I should think more about the icons I see. $\endgroup$ – user36480 Jan 21 at 22:26
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    $\begingroup$ I can't believe the shuttle navigation system cycled at 0.25-0.5 Hz. That is the slowest rate I've seen mentioned for a rocket/spacecraft so far. Wow. $\endgroup$ – user36480 Jan 21 at 22:27

Simply stated, navigation equipment and software keep track of where the [vehicle] is located, guidance computes where it needs to be to satisfy mission requirements, and flight control gets it there.

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  • $\begingroup$ ... and estimation is part of navigation? and possibly guidance? $\endgroup$ – user20636 Jan 21 at 0:14
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    $\begingroup$ @JCRM Not familiar with estimation in the sense used by the OP. I don't think they are talking about Kalman filtering etc. $\endgroup$ – Organic Marble Jan 21 at 0:28
  • $\begingroup$ Do you have a more modern source? The ASC GNC 2102 is over half a century old... $\endgroup$ – Dragongeek Jan 21 at 15:11
  • $\begingroup$ @Dragongeek the quote is from the 2nd document (sadly not online) dated 2004. I don't think anything has changed in the definition. $\endgroup$ – Organic Marble Jan 21 at 15:14

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