<p>Because satellites are only visible when they are in sunlight, they are not visible when they go into the Earth's shadow. The app most likely predicts where this occurs and ends the arc.</p>

<p>In other words, it does not make sense for an observer to look for a satellite when it is not visible, so there is no need to draw the path when it is in the shadow.</p>

CC BY-SA 4.0
2018-12-26T18:55:33.187Z
So is it basically like a lunar eclipse, except because the satellite is much smaller, it happens much more frequently?
Mav
CC BY-SA 4.0
2018-12-26T20:56:03.147Z
More like because it orbits so much closer to the Earth than Moon, there is an "eclipse" (I'm not sure how to call this event) during every orbit.
NikoNyrh
CC BY-SA 4.0
2018-12-26T22:02:43.407Z
@NikoNyrh I like to call it "night" - it's fair because the ISS, for instance, has more in common with a airliner than the moon when it comes to this
wedstrom
CC BY-SA 4.0
2018-12-26T18:47:21.170Z
2018-12-26T18:47:21.170Z
JohnHoltz
<p>I recently got an app that let me track the ISS. I noticed that during the time it's visible, it disappears <strong>before</strong> reaching the horizon, and sometimes reappears soon after for a bit.</p>

<p>Can somebody explain to me how the ISS and other satellites orbit? Specifically, what makes their visible period such a narrow one, that doesn't span all the way down to the horizon? (which is what my layman brain expected)</p>

CC BY-SA 4.0
2018-12-27T17:48:00.740Z
Because they've reached the edge wall.
Valorum
CC BY-SA 4.0
2018-12-28T08:26:04.357Z
@Valorum this should be the accepted answer
Mav
CC BY-SA 4.0
2018-12-28T08:39:35.730Z
@Valorum [good timing?](https://awo.oooooooooooooo.ooo/i/hy3k8287.png)
ave
<orbit><artificial-satellite>
Why do satellites arcs end abruptly when observed from Earth
Mav
# Why do satellites arcs end abruptly when observed from Earth

(Asked by: username_0 on 2018-12-26)

I recently got an app that let me track the ISS. I noticed that during the time it's visible, it disappears **before** reaching the horizon, and sometimes reappears soon after for a bit.

Can somebody explain to me how the ISS and other satellites orbit? Specifically, what makes their visible period such a narrow one, that doesn't span all the way down to the horizon? (which is what my layman brain expected)

**Tags:** orbit, artificial-satellite

> **Comments:**
> **username_1**: Because they've reached the edge wall.  
> **username_0**: @username_1 this should be the accepted answer  
> **username_2**: @username_1 [good timing?](https://awo.oooooooooooooo.ooo/i/hy3k8287.png)  

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## 1 answers

### Answer by username_3 on 2018-12-26. Score: 41 | Accepted answer

Because satellites are only visible when they are in sunlight, they are not visible when they go into the Earth's shadow. The app most likely predicts where this occurs and ends the arc.

In other words, it does not make sense for an observer to look for a satellite when it is not visible, so there is no need to draw the path when it is in the shadow.

> **Comments:**
> **username_0**: So is it basically like a lunar eclipse, except because the satellite is much smaller, it happens much more frequently?  
> **username_4**: More like because it orbits so much closer to the Earth than Moon, there is an "eclipse" (I'm not sure how to call this event) during every orbit.  
> **username_5**: @username_4 I like to call it "night" - it's fair because the ISS, for instance, has more in common with a airliner than the moon when it comes to this  

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