RE: An (old) curious observation

Richard Baldridge (
Thu, 15 Oct 1998 08:15:00 -0700

There are quite a few satellites in retrograde orbits.  Most are quite
faint and are not easy naked-eye targets typically.  A whole series of
OV1 satellites launched in 1965/66 are in orbit with inclinations of 144
degrees, meaning they reach 36 degrees north and south of the equator,
about the mid-latitude of the US (and almost straight overhead passes
for my site in San Jose, California) where they appear to travel exactly
East to West when near the "top" of their sine-curve.

My understanding of the purpose of these types of inclinations is to
DECREASE the time between successive passes as viewed from a particular
ground station in order to provide increased time resolution of
observations, whatever type they may be.  (But I'm no expert, someone
correct me if I'm wrong.)  A low-earth, prograde orbit crosses the same
LONGITUDE about every 97 minutes -- a similar but retrograde orbit
crosses every 87 minutes.  This gives about 2 additional passes per day
over a particular ground station.

Ofeq 3 (Norad 23549) is an often interesting target and can be seen
naked eye (faintly) even from a mildly light-polluted skies, but
binoculars definitely help in tracking it down.

Rick Baldridge,  W121.9770  N37.2718

From: John Stone
Subject: An (old) curious observation
Date: Thursday, October 15, 1998 5:34AM

Does anyone know if a sat has ever been launched into a retrograde orbit
.. ( and for that matter why you would want to do it).

Years ago I was flying in an F-4 at FL 30 and I saw what looked exactly
like a sat going from E to W. Over the years I about decided that what I
saw was an SR-71, way above me, lighting off the afterburners...