reply to post by decisively
No, you have it backwards (well, "backwards" depending on circumstances):
The platform's orientation is what the computer uses to find the stars...
Yes......to REFINE and continue to correct errors in the (inevitable) drift due to precession
errors that accumulate (especially, as back then,
gyroscopes...now (even without GPS enhancements), the use of "laser-ring" gyros minimizes the old mechanical friction-induced
errors, that required more frequent corrections.
----(Might wish to "Google" precession
as it applies to gyroscopes, and friction....I'd link it, but I feel that sometimes a search for
information is more 'rewarding' if conducted on one's own initiative, and quest for further knowledge....and personal edification.....)----
Losing "alignment" the (inertial reference platform) because of a power (electrical) interruption, on a spacecraft, is FAR more serious that a similar
event on an airplane, down here in Earth's atmosphere. (***)
(***) Since, although airplanes, of course, operate in a three-dimensional environment, ONE component of those three is altitude.....above the
surface. UNLIKE a spacecraft, in a vacuum, and many thousands of miles away from a planet (or a Moon)....
AND, just as on airliners, even losing "Main" electrical power is not
immediately going to equal losing 'alignment' of the inertial
references.....there are battery back-up contingencies. Of course, ANY system can suffer severe losses, and be "knocked off-line".....so,
specifically for spacecraft, a method to provide an emergency re-alignment, using HUMAN observations (as in, via the on-board sextant) gives a
preliminary stabilization, relative to the "baseline' reference...
...."shooting" a few stars....("shooting" is slang for using the sextant to sight known reference stars) could then be inputted, to aid in platform
re-alignment.....AFTER that, the computers could further refine, to make the "tolerances" within the standard, as originally aligned, prior to
I tend to the impression that you really do not know what you're talking about.....and, this is a layman's error, usually......
edit on Mon 14 May 2012 by ProudBird because: (no reason given)