Re: Phase Angle
Jim Varney (sat_watcher@rocketmail.com)
Tue, 23 Sep 1997 23:05:21 -0700 (PDT)
---"Sue J. Worden" <worden@uts.cc.utexas.edu> wrote:
> Is not the QuickSat "sun-object-observer angle", i.e.,
> angle sun->satellite->observer, the same as the Jim's
> "angle subtended from sun to satellite to observer"?
>
> I am very confused at this point. I would appreciate
> someone shedding some light on this, and at full phase
> illumination, please. :-)
No, you're not confused, I was. I confused "phase angle" for "phase,"
as in lunar phase = % illuminated. I got into the habit of ignoring
both the phase and phase angle as useful quantities because most
satellites don't show that much brightness variation due to phase. I
guess I got so good at ignoring phase and phase angle I forgot their
respective definitions.
I do apologize to anyone I may have confused!
And Richard Clark is correct: phase angle is a 2-D angle subtended
between two 3-D vectors, while the az-el quantities are 3-D because
they are in essence unit vectors. Whew.
__________________________________________________
Jim Varney 121.398W 38.458N 8m Sacramento, CA
jamesv@softcom.net, sat_watcher@rocketmail.com
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