Jim Weir wrote:

As I recall, Dick said something about Edwards and China Lake both tracking it
on radar. At best, that might give you a hundred meter accuracy.

Do you recall him holding his hands apart? I have to admit,
my attention was distracted right about then, so I can't
recall exactly what he said.

A radar altimeter at 63 miles is a hell of a feat AND subject to severe angle
errors.

I took a class in the early '70's on radar mapping of Venus
and the moon from ground based radar dishes. The basic
technique says you send out a spherical wave, and the
leading edge of your return wave is the closest point to
you. I don't have any info on radar altimeters, but
shouldn't they be reasonably self aligning if you get the
point below into your beam? I recognize that might be hard
for a craft in free-fall, but if it's not tumbling and the
beam width isn't too narrow ... of course, now you've got
power and detection problems at wide beam and 63 miles. :-)

I'd probably rely on GPS. As Dick indicated, two feet is about the
resolution you can get with a regular old GPS (unenhanced). That is my bet.

Makes sense. Cheaper too.

Todd Pattist
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