<p>Your link shows estimated magnitude, and it gets quite dim when it gets close to the horizon.</p>
<p><a href="https://i.sstatic.net/Ej43B.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Ej43B.png" alt="enter image description here" /></a></p>
<p><strong>above:</strong> from <a href="http://heavens-above.com/passdetails.aspx?lat=52.2681&amp;lng=-113.8112&amp;loc=Red%20Deer&amp;alt=859&amp;tz=MST&amp;satid=7735&amp;mjd=57796.1104311148" rel="nofollow noreferrer">heavens-above</a>, (from url: lat=52.2681&amp;lng=-113.8112)</p>
<p>As a spacecraft in low earth orbit appears to approach the horizon, the line-of-sight distance from it to you can change from a few hundred to a few thousands kilometers, which is why the brightness in your table changes so much.</p>
<p>The path in the sky shown in the link is going to be almost vertical (reaches 70 degrees). Wikipedia says <a href="https://celestrak.org/satcat/search.asp" rel="nofollow noreferrer">GEOS-3</a> is a satellite put into orbit in 1975. These days there is a big effort to de-orbit the &quot;leftovers&quot; so they burn up in the atmosphere (space junk mitigation) but back then it was common for each launch to leave other stuff up there for decades or longer.</p>
<p>Wikipedia says the COSPAR-ID for the actual GOES-3 satellite is 1975-027A. That means it was the 27th internationally recognized launch in 1975. &quot;A&quot; is assigned to the GEOS-3 satellite itself, but if you look up <code>1975-027</code> in the satellite catalog (SatCat) at <a href="https://celestrak.org/satcat/search.asp" rel="nofollow noreferrer">Celestrak.org</a> you can see there are were four other objects associated with the launch being tracked. One of them has burned up, but the others are still there.</p>
<p>You can double check if 1975-027B is the one that your link is talking about. Anyway, since they are so old, none of them is capable of a spectacularly sudden engine burn and change in orbit. So I'd have to say that whatever you did see, it isn't associated with the GEOS-3 launch.</p>
<p>Another point to consider; if you just coming out of a restaurant, the chances are low that you could see a 5th magnitude object. Near the horizon the apparent speed would be much slower than that of a satellite overhead.</p>
<p><a href="https://i.sstatic.net/Bbq05.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Bbq05.png" alt="enter image description here" /></a></p>

CC BY-SA 3.0
2017-02-13T05:29:57.777Z
Yes an engine burn like that would have been impossible even for an actual functional rocket. The brightness doesn't match up perfectly with what we saw but my understanding is it's not uncommon for the predicted brightness on heaven-above to be off the mark particularly for odd objects like left over rockets. While your answer is very informative it doesn't make an argument for what could have caused the appearance of movement that we observed.
Ceribia
CC BY-SA 3.0
2017-02-13T06:33:05.630Z
Actually a satellite with flat surfaces - especially solar panels - can deviate quite a bit brighter than expected if the angle is just right. But it's an interesting question how a relatively smooth cylinder, covered in diffuse white paint could do that. It could get dimmer, but I'm not sure if a rocket body can get substantially brighter. Even end-on, the end of a tank would likely be rounded rather than flat, but I'll try to find out if a rocket body has the same "flare" vocabulary as a satellite, it's an interesting question.
uhoh
CC BY-SA 3.0
2017-02-13T06:41:11.960Z
Are you asking for a spaced based (astronomical or spacecraft) answer for something that can appear ... *to dart side to side (over 15 degree sweeps) ludicrously quickly*..."? You are asking for a known, identifiable source of ludicrous darting motion? How rapid was the azimuthal motion? 15 degrees in one second, 10 seconds? If you can add an estimate to the text of the question that might be helpful, as "[ludicrous mode](http://www.wired.co.uk/article/tesla-ludicrous-mode-faraday-future-race)" is still limited to land-based craft.
uhoh
CC BY-SA 3.0
2017-02-13T16:20:16.727Z
I don't see that this addresses the question.
Carl Witthoft
CC BY-SA 3.0
2017-02-13T16:32:13.683Z
@CarlWitthoft offering [ludicrous explanations](http://astronomy.stackexchange.com/questions/20033/#comment33128_20033) for ludicrously fast darting spacecraft is not an option in a proper Astronomy stackexchange answer. I'm trying to walk the OP back into science, where an explanation might be found.
uhoh
CC BY-SA 3.0
2017-02-13T17:01:23.027Z
@uhoh I've updated my question with some timing information. There's no need to, "walk the OP back into science", as I've always been quite firmly there.
Ceribia
CC BY-SA 3.0
2017-02-13T20:09:03.900Z
@Ceribia I should have said "walk the explanation back". So a fist at arm's length is about 10 degrees. When the sun is all the way down, touching the horizon, the full refractive power of the atmosphere has bent the rays only about 0.5 degrees, or 1/20th of a fist. It's hard to see how an atmospheric event can do this. Did it look blurred at all? Any chance there was an incinerator, tractor-trailer exhaust. gas turbine, or gas burn-off vent making the air very close to you and in the line of sight extremely hot?
uhoh
CC BY-SA 3.0
2017-02-13T21:53:27.817Z
@uhoh Fist at arms length is what I was using to estimate, and 25-30 seems pretty much right. It is possible buildings were throwing me off true horizon or something like that, amateur observer and all. No heavy blurring that I recall but can't rule it out. City is mostly light business and residential where I was looking so a large vent seems unlikely but can't rule it out. Winter weather is something I've considered but haven't been able to find much good info on. As a one off event it seems like the answer is going to be more, "It could have been this or this", rather than, "this for sure"
Ceribia
CC BY-SA 3.0
2017-02-14T04:15:22.043Z
Just a thought on the motion... I realize actual motion has pretty much been ruled out at this point, but to prove that concept:
nflemming2004
CC BY-SA 3.0
2017-02-14T04:30:56.697Z
(cont'd)
GOES3 orbits with a perigee of about 22,200 km.  Even if it were directly above (when it's closest to you), if it were moving in a 15-degree arc in <1s, that would mean it was traveling at about 0.02c.  
Thinking about turbulence, were you seeing it above the restaurant by chance?  They might have had an exhaust from their kitchen causing significant turbulence with the cold air.

Also, could you add time and location info?
nflemming2004
CC BY-SA 3.0
2017-02-14T04:56:23.020Z
@nflemming2004 Your thinking and math are good, but better take a moment to read this answer again, or even just look at the screen shots once more. Satellites don't fly up from the ground by themselves, they have "helpers". I made sure to restate the time and location here as well. The source is the prediction the OP linked in the question. Also look again at the complete name of the object in the body of the question, and link
uhoh
CC BY-SA 3.0
2017-02-13T05:09:09.460Z
2017-02-13T05:09:09.460Z
2022-09-27T22:27:30.220Z
uhoh
<p>Yesterday while coming out of a restaurant my wife and I noticed what appeared be a satellite passing quite high in the sky. Based on the location, time, and brightness this appears to have been <a href="http://heavens-above.com/passdetails.aspx?lat=52.2681&amp;lng=-113.8112&amp;loc=Red%20Deer&amp;alt=859&amp;tz=MST&amp;satid=7735&amp;mjd=57796.1104311148" rel="nofollow noreferrer">a passing of the GEOS 3 Rocket</a>. What made this unusual is that when it got low (perhaps 25-30 degrees off the horizon) it suddenly appeared to dart side to side (over 15 degree sweeps) multiple times over perhaps a second, while continuing its general western trend, before vanishing. </p>

<p>Since this all happened rather quickly I had to estimate the distances after the fact using my hands and what few reference points were available. It is certainly possible that it was lower in the sky than my estimate as that is always a tricky part to judge. I'm quite certain of the sweep distance but an answer that could explain a smaller sweep could still be very useful.</p>

<p>What could cause a satellite to appear to move side to side in this fashion?</p>

CC BY-SA 3.0
2017-02-13T03:09:32.117Z
This sounds like the guys over at space exploration SE could help you better with...
AtmosphericPrisonEscape
CC BY-SA 3.0
2017-02-13T16:19:48.717Z
Could well be atmospheric turbulence -- same source that causes those ripples when looking down a very hot beach or road at a distant object.
Carl Witthoft
CC BY-SA 3.0
2017-02-13T16:29:37.553Z
@CarlWitthoft the OP says 15 degree sweeps side to side while at an altitude of at least 25 degrees above the horizon. There is no atmospheric physics that can do that. None. Not even close.
uhoh
CC BY-SA 3.0
2017-02-13T16:33:41.997Z
@uhoh yes, I'm well aware that that's a huge swing.  Notwithstanding, at near-horizon viewpoints ugly stuff happens. We've all seen pix of a setting sun where the sun is fully "split."  Since the OP was observing without tools, I'm taking that "15-degree" estimate with a large grain of salt.  (And, yes,  IAAAOP  (adaptive-optics physicist) :-)
Carl Witthoft
CC BY-SA 3.0
2017-02-13T16:40:08.430Z
@CarlWitthoft OK, but that's a good 2 order of magnitude grain of salt. The total refraction of the Earth's atmosphere near the horizon is less than one degree at an altitude of 1 degree, and it's vertical. Physically possible variation in that mean angle are even smaller, and once again, vertical.
uhoh
CC BY-SA 3.0
2017-02-13T16:52:58.947Z
@CarlWitthoft It happened fast enough that I had to estimate all of the angles after the fact and using the hand method. I think they are reasonably accurate but wouldn't be shocked to find out I was wrong. If you have an answer that would address a lower, or less extreme, swing it could still be a very useful answer.
Ceribia
<artificial-satellite><optics>
What could have made a satellite appear to move side to side while near the horizon?
Ceribia
# What could have made a satellite appear to move side to side while near the horizon?

(Asked by: username_0 on 2017-02-13)

Yesterday while coming out of a restaurant my wife and I noticed what appeared be a satellite passing quite high in the sky. Based on the location, time, and brightness this appears to have been [a passing of the GEOS 3 Rocket](http://heavens-above.com/passdetails.aspx?lat=52.2681&lng=-113.8112&loc=Red%20Deer&alt=859&tz=MST&satid=7735&mjd=57796.1104311148). What made this unusual is that when it got low (perhaps 25-30 degrees off the horizon) it suddenly appeared to dart side to side (over 15 degree sweeps) multiple times over perhaps a second, while continuing its general western trend, before vanishing.

Since this all happened rather quickly I had to estimate the distances after the fact using my hands and what few reference points were available. It is certainly possible that it was lower in the sky than my estimate as that is always a tricky part to judge. I'm quite certain of the sweep distance but an answer that could explain a smaller sweep could still be very useful.

What could cause a satellite to appear to move side to side in this fashion?

**Tags:** artificial-satellite, optics
> **Comments:**
> **username_1**: This sounds like the guys over at space exploration SE could help you better with...  
> **username_2**: Could well be atmospheric turbulence -- same source that causes those ripples when looking down a very hot beach or road at a distant object.  
> **username_3**: @CarlWitthoft the OP says 15 degree sweeps side to side while at an altitude of at least 25 degrees above the horizon. There is no atmospheric physics that can do that. None. Not even close.  
> **username_2**: @uhoh yes, I'm well aware that that's a huge swing.  Notwithstanding, at near-horizon viewpoints ugly stuff happens. We've all seen pix of a setting sun where the sun is fully "split."  Since the OP was observing without tools, I'm taking that "15-degree" estimate with a large grain of salt.  (And, yes,  IAAAOP  (adaptive-optics physicist) :-)  
> **username_3**: @CarlWitthoft OK, but that's a good 2 order of magnitude grain of salt. The total refraction of the Earth's atmosphere near the horizon is less than one degree at an altitude of 1 degree, and it's vertical. Physically possible variation in that mean angle are even smaller, and once again, vertical.  
> **username_0**: @CarlWitthoft It happened fast enough that I had to estimate all of the angles after the fact and using the hand method. I think they are reasonably accurate but wouldn't be shocked to find out I was wrong. If you have an answer that would address a lower, or less extreme, swing it could still be a very useful answer.  

---

## 1 answers

### Answer by username_3 on 2017-02-13. Score: 1

Your link shows estimated magnitude, and it gets quite dim when it gets close to the horizon.

[![enter image description here](https://i.sstatic.net/Ej43B.png)](https://i.sstatic.net/Ej43B.png)

**above:** from [heavens-above](http://heavens-above.com/passdetails.aspx?lat=52.2681&lng=-113.8112&loc=Red%20Deer&alt=859&tz=MST&satid=7735&mjd=57796.1104311148), (from url: lat=52.2681&lng=-113.8112)

As a spacecraft in low earth orbit appears to approach the horizon, the line-of-sight distance from it to you can change from a few hundred to a few thousands kilometers, which is why the brightness in your table changes so much.

The path in the sky shown in the link is going to be almost vertical (reaches 70 degrees). Wikipedia says [GEOS-3](https://celestrak.org/satcat/search.asp) is a satellite put into orbit in 1975. These days there is a big effort to de-orbit the "leftovers" so they burn up in the atmosphere (space junk mitigation) but back then it was common for each launch to leave other stuff up there for decades or longer.

Wikipedia says the COSPAR-ID for the actual GOES-3 satellite is 1975-027A. That means it was the 27th internationally recognized launch in 1975. "A" is assigned to the GEOS-3 satellite itself, but if you look up `1975-027` in the satellite catalog (SatCat) at [Celestrak.org](https://celestrak.org/satcat/search.asp) you can see there are were four other objects associated with the launch being tracked. One of them has burned up, but the others are still there.

You can double check if 1975-027B is the one that your link is talking about. Anyway, since they are so old, none of them is capable of a spectacularly sudden engine burn and change in orbit. So I'd have to say that whatever you did see, it isn't associated with the GEOS-3 launch.

Another point to consider; if you just coming out of a restaurant, the chances are low that you could see a 5th magnitude object. Near the horizon the apparent speed would be much slower than that of a satellite overhead.

[![enter image description here](https://i.sstatic.net/Bbq05.png)](https://i.sstatic.net/Bbq05.png)

> **Comments:**
> **username_0**: Yes an engine burn like that would have been impossible even for an actual functional rocket. The brightness doesn't match up perfectly with what we saw but my understanding is it's not uncommon for the predicted brightness on heaven-above to be off the mark particularly for odd objects like left over rockets. While your answer is very informative it doesn't make an argument for what could have caused the appearance of movement that we observed.  
> **username_3**: Actually a satellite with flat surfaces - especially solar panels - can deviate quite a bit brighter than expected if the angle is just right. But it's an interesting question how a relatively smooth cylinder, covered in diffuse white paint could do that. It could get dimmer, but I'm not sure if a rocket body can get substantially brighter. Even end-on, the end of a tank would likely be rounded rather than flat, but I'll try to find out if a rocket body has the same "flare" vocabulary as a satellite, it's an interesting question.  
> **username_3**: Are you asking for a spaced based (astronomical or spacecraft) answer for something that can appear ... *to dart side to side (over 15 degree sweeps) ludicrously quickly*..."? You are asking for a known, identifiable source of ludicrous darting motion? How rapid was the azimuthal motion? 15 degrees in one second, 10 seconds? If you can add an estimate to the text of the question that might be helpful, as "[ludicrous mode](http://www.wired.co.uk/article/tesla-ludicrous-mode-faraday-future-race)" is still limited to land-based craft.  
> **username_2**: I don't see that this addresses the question.  
> **username_3**: @CarlWitthoft offering [ludicrous explanations](http://astronomy.stackexchange.com/questions/20033/#comment33128_20033) for ludicrously fast darting spacecraft is not an option in a proper Astronomy stackexchange answer. I'm trying to walk the OP back into science, where an explanation might be found.  
> **username_0**: @uhoh I've updated my question with some timing information. There's no need to, "walk the OP back into science", as I've always been quite firmly there.  
> **username_3**: @Ceribia I should have said "walk the explanation back". So a fist at arm's length is about 10 degrees. When the sun is all the way down, touching the horizon, the full refractive power of the atmosphere has bent the rays only about 0.5 degrees, or 1/20th of a fist. It's hard to see how an atmospheric event can do this. Did it look blurred at all? Any chance there was an incinerator, tractor-trailer exhaust. gas turbine, or gas burn-off vent making the air very close to you and in the line of sight extremely hot?  
> **username_0**: @uhoh Fist at arms length is what I was using to estimate, and 25-30 seems pretty much right. It is possible buildings were throwing me off true horizon or something like that, amateur observer and all. No heavy blurring that I recall but can't rule it out. City is mostly light business and residential where I was looking so a large vent seems unlikely but can't rule it out. Winter weather is something I've considered but haven't been able to find much good info on. As a one off event it seems like the answer is going to be more, "It could have been this or this", rather than, "this for sure"  
> **username_4**: Just a thought on the motion... I realize actual motion has pretty much been ruled out at this point, but to prove that concept:  
> **username_4**: (cont'd) GOES3 orbits with a perigee of about 22,200 km.  Even if it were directly above (when it's closest to you), if it were moving in a 15-degree arc in <1s, that would mean it was traveling at about 0.02c.   Thinking about turbulence, were you seeing it above the restaurant by chance?  They might have had an exhaust from their kitchen causing significant turbulence with the cold air.  Also, could you add time and location info?  
> **username_3**: @nflemming2004 Your thinking and math are good, but better take a moment to read this answer again, or even just look at the screen shots once more. Satellites don't fly up from the ground by themselves, they have "helpers". I made sure to restate the time and location here as well. The source is the prediction the OP linked in the question. Also look again at the complete name of the object in the body of the question, and link  

---

