Re: An observation of the Atlas 5 launch (with the Cygnus cargo craft)

From: Steve Golson via Seesat-l <seesat-l_at_satobs.org>
Date: Sat, 12 Dec 2015 12:06:48 -0500
Edited, with my comments below.

On 12/9/15 1:19 AM, Skywayinc--- via Seesat-l wrote:
> It took about 2 minutes, then all of a  sudden, a bright light appeared in
> the SSE sky.  I would estimate its  magnitude to be about 0, and appeared
> approx 25 in altitude, moving smoothly  & quite rapidly towards the east.  I
> was sure that this was the 2nd  stage Centaur, illuminated by sunlight, just
> as Joe Rao had predicted. As it was  moving, two much dimmer (and tightly
> grouped lights) could be seen about 2 in  front (and slightly above) the
> Centaur. These two dim lights would fade in &  out, as the entire system of
> lights flew in tandem towards the east.  I was  confused to what I was actually
> viewing, as I could not account for the two,  tightly packed dim lights.  I
> had considered the two payload fairing  halves, however I would think that
> they would be "trailing" the 2nd stage  Centaur. The pass was observed for
> at least two minutes, eventually fading from  view along the eastern horizon.
>    At first, I did not post this  report
> 
> Then upon watching the post launch news conference, it was  mentioned that
> there were sightings of "multiple objects" viewed along the  coast. One
> thought was that it could have been the ISS, but no ISS pass was  viewable at
> that time.  I wrote to our expert Joe Rao, and he informed me  that a Father &
> Son team observed the exact same tandem of lights, while  viewing from up
> in Massachusetts. What they indicated was that the two dim  lights were
> actually the "two fairing halves", tumbling, thus fading in &  out of sunlight.
> The 0 magnitude light that was trailing them was indeed  the 2nd stage
> Centaur rocket.

Yes, my son and I saw this from Carlisle, Mass. We also observed the pair of somewhat dimmer lights fading in and out, brightness varying at a rate of perhaps once a second. This pair was ahead and above the brighter Centaur. We assumed they must be the fairing halves.

We also observed an ISS pass a few minutes earlier, on a low SSW to E trajectory. Centaur was following essentially the same path that ISS took.

> I must tell you that it was a "magnificent  sight", one of the best &
> clearest viewings of rocket launches that I have  ever observed.   However my one
> confusion is this - how could the two  fairing halves, that separated &
> fell away from the 2nd stage Centaur  minutes earlier, appear to me as "in
> front of" the 2nd stage centaur rocket,  from my prospective viewing location ???
> 
> The only rationale that I can  come up with is that these fairing halves
> were actually "much lower" than the  2nd stage Centaur as I viewed them. The
> Centaur engine continued to burn for  another 14 minutes after fairing sep,
> thereby speeding up & raising the  Centaur 2nd stage.  Also, perhaps the 2nd
> stage was steered more towards  the NE as it was firing, while the fairing
> halves continued their falling  trajectory along the coast. Anyway, somehow
> the fairing halves "appeared to be  in front of the 2nd stage Centaur", from
> my prospective observing  location.

This is an interesting geometrical conundrum. Yes the fairings appeared ahead of and higher than the Centaur.

Perhaps the fairings were closer to us (further west). Also it's possible the fairings were in fact at higher altitude. The fairings would continue on an upward ballistic trajectory after separation, whereas the Centaur might flatten out and accelerate more horizontally (i.e, parallel to the Earth's surface). And the Earth's surface is curving away from us.

We'd need an actual rocket scientist from ULA or Orbital to really confirm though :-)

Steve Golson
Carlisle, Mass.
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Received on Sat Dec 12 2015 - 11:07:27 UTC

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