Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Info wanted on Atlantis "secret" military satellite payload
Message-ID: <1988Dec12.180010.499@utzoo.uucp>
Organization: U of Toronto Zoology
References: <684@pyuxd.UUCP> <1988Dec4.225033.18207@utzoo.uucp> <6464@polyslo.CalPoly.EDU> <12418@bellcore.bellcore.com> <1988Dec8.001846.26121@utzoo.uucp> <12485@bellcore.bellcore.com>
Date: Mon, 12 Dec 88 18:00:10 GMT

In article <12485@bellcore.bellcore.com> karn@jupiter.UUCP (Phil R. Karn) writes:
>... I have run an eclipse predictor for the
>next six months on the last known orbital elements for STS-27.
>... by mid March 1989, the orbit plane will have precessed (and the
>terminator moved by the earth's motion around the sun) such that each day's
>passes over Moscow will all find it in darkness; the passes begin after
>sundown and end before sunrise....

I don't have much of a feel for eclipse geometries -- what's the equivalent
"shadow period" for, say, Sakhalin Island or Vladivostok?  That is, for
what period is the *whole* USSR "in shadow"?  That would seem a better
measure of the period in which the satellite is useless.  (My gut feeling
is that it's roughly the same period, since the underlying problem is
that the high-northern-latitude part of the orbit's ground track is in
shadow, but I'd be interested in confirmation.)

>...The evidence that the satellite
>does not require daylight over the USSR to function is therefore quite
>strong.

I'm afraid I have to disagree.  What Phil has done is to supply quantitative
backing for his earlier observation that this is far from an ideal orbit for
a "daylight" satellite.  That doesn't affect my observation, which is that
it's the best orbit the US can manage for a satellite that's too big for a
Titan 34D.  (The KH11 would fit on a Titan, but there are no more KH11s.)
I would amend Phil's conclusion to something like:

	There is therefore quite strong evidence that either (a) the
	satellite does not require daylight over the USSR to function,
	or (b) launching a new daylight-optical satellite was considered
	urgent enough to justify use of an orbit which seriously limits
	the satellite's usefulness.
-- 
SunOSish, adj:  requiring      |     Henry Spencer at U of Toronto Zoology
32-bit bug numbers.            | uunet!attcan!utzoo!henry henry@zoo.toronto.edu