# RE: Mir and the good old days

From: Randy John (rjohn@axarosenberg.com)
Date: Tue Jun 26 2001 - 16:03:12 PDT

• Next message: Jim Sebolt: "twin Iridium flare"

```Concerning using a globe to predict sat passes, Jonathon wrote:

> 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).

I believe that the process was to find the ascending node (by looking at where the string crossed the equator).  Then you calculate a new ascending node and start the string from there.  By placing the string at the proper inclination you can now see the
path on that pass.  However, I think that I see your point.  By using the longitude of your location instead of the ascending node you could still get pretty close.

As for calculating the altitude above the horizon, I probably just measured the distance along the globe from my location to the closest point in the path.  From that and the satellite height you can calculate the altitude above the horizon.  I think that
I usually just made a rough guess at the altitude.  However, the photo required some planning.  As I recall, there was an overhead pass but I was not be able to photograph it because it was deep in morning twilight.  So I looked back one orbit and found
that Mir would be 5 degrees above the horizon.  I took the photo but didn't actually see Mir until the next orbit as I was packing up the car.

Randy

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