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Location: UFOUpDatesList.Com > 2007 > Nov > Nov 21

Re: Skylab 3

From: Michael Tarbell <mtarbell.nul>
Date: Wed, 21 Nov 2007 09:09:09 -0700
Archived: Wed, 21 Nov 2007 15:54:33 -0500
Subject: Re: Skylab 3

>From: Bruce Maccabee <brumac.nul>
>To: <ufoupdates.nul>
>Date: Thu, 15 Nov 2007 11:26:26 -0500
>Subject: Re: Skylab 3

>>From: Michael Tarbell <mtarbell.nul>
>>To: ufoupdates.nul
>>Date: Mon, 12 Nov 2007 10:31:30 -0700
>>Subject: Re: Skylab 3

>>>From: Bruce Maccabee <brumac.nul>
>>>To: <ufoupdates.nul>
>>>Date: Sun, 11 Nov 2007 15:53:10 -0500
>>>Subject: Skylab 3


>>>If you want to find an astronaut sighting of an unidentified
>>>space object - USO; this one was not submerged - then here you

>>>Comments welcome



>>- Your calculation for the object size is based on an estimate
>>for object distance, which in turn is based on the time delay
>>between Skylab and the object entering earth's shadow. This
>>makes the implicit (and probably unwarranted) assumption that
>>the object is in the same orbit as Skylab, and pierces the same
>>point on the shadow zone surface. It would seem possible to
>>obtain a variety of object distances --and hence sizes-- by
>>relaxing this constraint, even for purely ballistic (i.e., non-
>>maneuvering) trajectories. I note that you consider perturbed
>>orbits later in the analysis, but as far as I can tell the
>>implications for the object size calculation are not mentioned.

>Of course, the farther away the object is assumed to have been
>at the time of the fourth photo the larger it must have been to
>have an angular size of .0029 radians (this assumes the 300 mm
>focal length lens was used). As pointed out in the analysis
>(especially the revised version now on my site), if the object
>was another man-made satellite or something ejected from the
>skylab (e.g trash), then it must have been no larger than 10 m
>(maximum separation of reflective points of the assumed
>satellite corresponding to the separation between the upper and
>lower red 'dots') and hence no further away than about 10
>m/.0029 rad = 3,400 = 3.4 km at the time of the fourth photo.
>There is a problem with the assumption that it was this close
>(or smaller and closer) when the Skylab went into the
>shadow:regardless of where you place the object relative to the
>Skylab, it would pass into the shadow no more than about 1
>second after the Skylab.


I have been away from the computer in recent days and my reply
is thus tardy... thanks for your detailed and informative
response, much of which I have snipped away here for brevity.

Your revised analysis (SL3.html) does cover the distance/size
issue in more depth than the original (and now deceased) link
you provided above. While the arguments presented against the
'Skylab debris' hypothesis are generally persuasive, the case
could actually be made ironclad in a straightforward --if
tedious-- manner:

While an analytic derivation would be difficult (perhaps
intractable), a brute-force march through trial perturbations of
the Skylab orbit would reveal whether it is possible even in
principle for a piece of Skylab debris to satisfy the given
constraints (shadow entry delay, angular displacement relative
to Skylab, etc). One need only launch an array of 'test
particles' at various points upstream along the Skylab orbit,
the elements of which are provided in the Oberg document. These
particles would be given an instantaneous velocity increment of
variable magnitude and direction, and then propagated forward
along their new orbits to the initial time of the sighting. If
none of them are consistent with the observed subsequent object
motion and sunlight/shadow timing, then it's case closed: Skylab
debris is explicitly ruled out.

This would not rule out the more general case of orbits that are
not obtained by impulsive perturbations of the Skylab orbit,
i.e., satellites or debris not associated with Skylab. The above
approach would not be practical for this broader problem without
some analytical filtering of the orbit sampling population based
on the observed constraints.

I have available the necessary orbital mechanics routines to
conduct such a study, although I would need to write a driver to
loop through the sampling variables, and also incorporate the
earth/sun shadow geometry. I will attend to this as time permits
and forward the results.


>>- Garriott makes the claim that Skylab and the object were not
>>in a region of the orbit in which sunlight was passing through
>>earth's atmosphere (and thus reddening it). But it is
>>unavoidable that sunlight illuminating Skylab and the object was
>>passing through earth's atmosphere when both objects were in the
>>vicinity of the edge of the shadow zone.

>That is true, but the passage through the region where the
>sunlight is reddened would have taken place in some number of
>seconds at the end of the 10 minute period of observation, most
>of which occurred when the Skylab and object were far from (but
>approaching) the reddened area.

"...some number of seconds" may understate the interval of
significant reddening. I should think it would begin with entry
into the penumbral shadow (when the figure of the sun first
intersects the limb of the earth) and proceed well beyond entry
into the the umbral shadow (where the figure of the sun is
completely blocked). Note that the totally eclipsed moon is
blood/copper red even though it has no line of sight to the sun.
Note also that Skylab and the object were approaching the shadow
cone surface obliquely, not perpendicularly. Here it would be
useful to have some first-hand testimony from astronauts
regarding the typical duration of this interval, although it may
not be obvious even to them unless they had some view of the
exterior of their vehicle.


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