Inertial Navigation

I suppose we could talk Kalman filters, but no, something more practical.

When we sent to the moon and came back, we must have aligned the gyros on the moon. What reference did we use and how accurate is that?


Hardy

On Wed, 29 Oct 2014 11:12:37 -0700, gyansorova wrote:

> I suppose we could talk Kalman filters, but no, something more
> practical.
> 
> When we sent to the moon and came back, we must have aligned the gyros
> on the moon. What reference did we use and how accurate is that?

If you know the rate that you're rotating in the inertial frame to well 
within the accuracy of your gyros, you can adjust the bias until the gyros 
read what they should.  We know how fast the moon rotates in the inertial 
frame, so there's your answer.

Alternately, if your gyros are gimbaled, you can align their axis of 
rotation along your axis of rotation and null them.

Given that Kalman filters were pretty much developed FOR the space 
program, I wouldn't be much surprised if some variation of it wasn't used 
in flight -- if the gyros and accelerometers are accurate enough, you 
could align the craft with the occasional astronomical sighting, or 
possibly radar ranging of various handy objects like the moon, the earth, 
or a report of the position of your craft as seen by earth-based radar.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com