# Re: Mir and the good old days

From: Jonathan T Wojack (tlj18@juno.com)
Date: Tue Jun 26 2001 - 14:36:12 PDT

• Next message: Randy John: "RE: Mir and the good old days"

> So, what do you do with elements when you don't have a computer?
> You use a
> 3 inch diameter globe (filled with pennies) and a piece of string of
> course.
> The first thing that you do is hope that the eccentricity is close
> enough to
> zero so that you can ignore it.  The only two numbers that are
> really
> important are the inclination and the period.  Using a known pass,
> you lay
> the string on the globe so that it passes through your site and has
> max/min
> latitude the same as the inclination.  Now you can make future
> predictions
> since you know where Mir will be in 15, 16, 30, 31, 46 or 47 orbits
> from
> now.  During these passes the Earth will have rotated approximately
> 1, 2 or
> 3 revolutions.  Of course, you had to make up for the difference
> between
> "approximately 1 rev" and the actual amount of time.

Using TLE data, I using a known H-A prediction for my site for SeaSat 1.
I used the data to project when the satellite would be visible 9 days
later.  My prediction was only 4 minutes off the H-A prediction (which
are almost always +/- 10 seconds that far into the future) !!!  So this
works!  Thanks a lot for sharing this with us.

> Using this method I successfully predicted a pass at my dark sky
> site more
> than 150 miles away from the prediction city.  If you don't believe
> me, I
> have a picture with Mir's trail about 5 degrees above the horizon to
> prove
> it (I didn't actually see it).

Randy, if you're listening, can you explain how to factor the inclination
of the satellite into the calculations.  I don't see why it matters (for
the sake of calculation) .  Also, is there a way to estimate the altitude
of the satellite when observed (I understand how to determine in what
area of the sky the satellite will "peak" in).

Thanks very much!

------------------------------
Jonathan T. Wojack                 tlj18@juno.com
39.706d N   75.683d W

4 hours behind UT (-4)

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