RE: Pre-solstice spysat launches: why?
Ted Molczan (molczan@fox.nstn.ca)
Mon, 30 Dec 1996 03:12:33 -0500
Allen Thomson asked:
> Why, for the past decade, has the US launched its
>sunsynchronous spysats in the month before the winter solstice?
Well, not all were launched one month before
the solstice: 87090A was launched on 26 Oct
and 88099A was launched on 6 Nov. I recommend
that we also include the failed Kh-9 launch of
Apr'96. (It was believed to have been a
replacement for the failed Kh-11 launch of
28 Aug 1985.)
In discussions concerning this, some general explanations have
been offered, to wit,
>1) There is some technical reason, probably related to solar
> illumination of the targets on the ground or the solar panels on
> the spacecraft that makes pre-solstice launch desirable.
Always a good hunch, but difficult to prove.
>2) Pre-solstice launch prevents northern-hemisphere optical
> observation(**) of the payload during deployment and for two or
> three months thereafter. There is a paucity of known optical
> observers in the southern hemisphere, and anyway the
> distribution of land and population down there mitigates
> against spotting satellites launched in November and
> December.
I have never believed that military space
operations planning includes considerations
of amateur observers abilities. There are
too many other more important variables
constraining missions without adding us
into the mix.
> But what's the point? One would presume the USSR (now Russia) and
> possibly other countries have been following the payloads with radar,
> and maybe with daylight visual/IR methods from launch onward. In any
> event, the launch timing, azimuth and booster configuration, along
> with observation of the payloads of previous similar launches let
> the orbits be inferred quite nicely, as evinced by amateur observers'
> success in finding and identifying the satellites when they become
> visible in March and April.
I agree, there is no point based on denial of
observability.
> One slightly paranoid suggestion that's been made to resolve
> this puzzle is that there are actually two payloads on the
> boosters (Titan-IVs with oversize payload shrouds),
As far as I know since the Kh-9 program which
began in 1971, the payload has been about 15 m long,
requiring a 17 m shroud. I have never heard of an
over-size shroud used for a Kh-9 or Kh-11, but
I do not have proof of that.
>of course, there's always
>
>3) There's nothing to explain. The pattern didn't exist before about ten
> years ago, not that many satellites have flown subsequently,
> and the pre-solstice "pattern" is most likely a fluke of small-
> sample statistics.
I like that explanation the best.
Ted Molczan