<p>You are right!</p>
<ol>
<li>Apogee is higher than Perigee, except when the orbit is perfectly circular when they're equal.</li>
<li>Semi-major axis will be half-way between the two.</li>
<li>572 km doesn't make sense.</li>
</ol>
<p>As pointed out in comments, expressed like this they are the distances from Earth's center minus a fixed equatorial radius of the earth, in this case about 6378.137 kilometers. From the numbers in Wikipedia for peri and apo you'd call this a 567 x 515 km orbit. It's a simple way to express roughly the size and shape.</p>
<p>The linked <a href="https://de.wikipedia.org/wiki/Technology_Experiment_Satellite" rel="nofollow noreferrer">de.Wikipedia page</a> says</p>
<pre><code>Umlaufzeit:       95,3 min[1]
Bahnhöhe:         572 km
Bahnneigung:      97.7°
Apogäumshöhe:     567 km
Perigäumshöhe:    515 km

[1]  Bahndaten nach [TES](https://www.n2yo.com/satellite/?s=26957). N2YO, 18. November 2017, abgerufen am 18. November 2017
</code></pre>
<p>I don't know what Bahnhöhe means, google translates it as &quot;track height&quot;, so I've asked <a href="https://german.stackexchange.com/q/61157/38291">What exactly would a distance labeled Bahnhöhe mean in the context of a satellite's orbit around the Earth?</a> in German SE.</p>
<p>While the data might be static, the mentioned <a href="https://www.n2yo.com/satellite/?s=26957" rel="nofollow noreferrer">n2yo link</a> says:</p>
<pre><code>NORAD ID:           26957 
Int'l Code:         2001-049A 
Perigee:            513.2 km 
Apogee:             564.0 km 
Inclination:        97.7 ° 
Period:             95.3 minutes 
Semi major axis:    6909 km 
</code></pre>
<p>and looking it up <a href="https://celestrak.org/satcat/search.php" rel="nofollow noreferrer">in Celestrak</a> gives the <a href="https://en.wikipedia.org/wiki/Two-line_element_set" rel="nofollow noreferrer">two line element set</a> or TLE as</p>
<pre><code>TES                     
1 26957U 01049A   20269.88561907  .00000195  00000-0  15464-4 0  9995
2 26957  97.7413  31.7408 0036778 246.8588 112.8763 15.11565287 39121
</code></pre>
<p>The TLE is also shown in n2y0.</p>
<p>Here's a link direct to Celestrak for this object. They are always changing, the orbits of Earth satellites are never really fixed.</p>
<p>Atmospheric drag tends to lower them and Earth's lumpy gravity causes them to precess, just for starters.</p>
<p>Many satellites have small thrusters to raise their orbit after atmospheric drag lowers it, so we can't expect numbers in static Wikipedia data fields to be accurate.</p>

CC BY-SA 4.0
2020-09-26T11:40:59.160Z
2020-09-26T12:34:49.363Z
2022-09-27T22:27:30.220Z
uhoh
<p>I read in the <a href="https://de.wikipedia.org/wiki/Technology_Experiment_Satellite" rel="nofollow noreferrer">German Wikipedia</a> for the Indian Technology Experiment Satellite, that the apogee (Apogäumshöhe) is 567 km, while the height of the orbit (Bahnhöhe) is 572 km. I had always thought that the apogee is the furthest point of the orbit from the Earth and I wonder how can there be a height greater than that.</p>

CC BY-SA 4.0
2020-09-26T07:46:26.753Z
The numbers in that article don't seem to make sense and one should question at least some of the numbers there
planetmaker
CC BY-SA 4.0
2020-09-26T08:09:12.033Z
Just a guess, but probably the original orbit was circular at  572km, but it has now decayed. to the current elliptical orbit.  However this is not an astronomy question and you probalby won't get a good answer here. THere is "space exploration" which answers questions about artificial satellites.
James K
CC BY-SA 4.0
2020-09-26T09:51:52.523Z
the apogee is a fixed point, the height depends on the position of the point in the orbit, so what are we talking about?!? Additionally, height is distance from surface, apogee is distance from focus, hence, again, what are we talking about?
jumpjack
CC BY-SA 4.0
2020-09-26T11:12:37.413Z
It's wikipedia. It's wrong. The [English wikipedia page](https://en.wikipedia.org/wiki/Technology_Experiment_Satellite) on the same satellite has different values, perigee altitude = 551 km and apogee altitude = 579 km. And there's no telling if those different values in the English wikipedia page are correct. Wikipedia is oftentimes incorrect on specific technical details. One thing is certain: At least some of the numbers in the German wikipedia page are wrong.
David Hammen
CC BY-SA 4.0
2020-09-26T11:17:23.257Z
@jumpjack - For various esoteric reasons, the perigee and apogee altitude of a satellite are the minimum and maximum distances between the center of the Earth, minus the Earth's equatorial radius. Because the Earth is an oblate spheroid, this is not the same as minimum and maximum height above the surface of the Earth.
David Hammen
CC BY-SA 4.0
2020-09-26T12:53:33.507Z
@DavidHammen I thought about something like that. That would explain at least part of it. Not to say that the Wikipedia numbers are correct, of course.
Andyc
CC BY-SA 4.0
2020-09-26T13:21:30.087Z
@JamesK I didn't know about a "space exploration". Of course this question would be more suited there. If anyone wants to move it, please feel free to do so.
Andyc
CC BY-SA 4.0
2020-09-26T14:59:45.170Z
I’m voting to close this question because this should probably be migrated to space exploration SE
usernumber
CC BY-SA 4.0
2020-09-26T16:29:43.520Z
currently "apogee", "aphelion" and apo-whatelse are being replaced by "apoaxis". Should we recalculate, all numbers for Earth and Sun?
jumpjack
CC BY-SA 4.0
2020-09-27T00:12:30.810Z
I'd rather not see this migrated. The meta-question being asked here is "Is wikipedia reliable?" The answer to that question is unfortunately not.
David Hammen
CC BY-SA 4.0
2020-09-27T00:14:31.920Z
I’m voting to close this question because it ultimately is asking if wikipedia is reliable. Unfortunately, the answer is no. Wikipedia is good on basic, non-changing subjects. But addressing the quality of wikipedia pages is outside the bounds of any site on the Stack Exchange network.
David Hammen
<orbit><artificial-satellite>
Why is the height of a satellite greater than the apogee of its orbit?
Andyc
# Why is the height of a satellite greater than the apogee of its orbit?

(Asked by: username_0 on 2020-09-26)

I read in the [German Wikipedia](https://de.wikipedia.org/wiki/Technology_Experiment_Satellite) for the Indian Technology Experiment Satellite, that the apogee (Apogäumshöhe) is 567 km, while the height of the orbit (Bahnhöhe) is 572 km. I had always thought that the apogee is the furthest point of the orbit from the Earth and I wonder how can there be a height greater than that.

**Tags:** orbit, artificial-satellite
> **Comments:**
> **username_1**: The numbers in that article don't seem to make sense and one should question at least some of the numbers there  
> **username_2**: Just a guess, but probably the original orbit was circular at  572km, but it has now decayed. to the current elliptical orbit.  However this is not an astronomy question and you probalby won't get a good answer here. THere is "space exploration" which answers questions about artificial satellites.  
> **username_3**: the apogee is a fixed point, the height depends on the position of the point in the orbit, so what are we talking about?!? Additionally, height is distance from surface, apogee is distance from focus, hence, again, what are we talking about?  
> **username_4**: It's wikipedia. It's wrong. The [English wikipedia page](https://en.wikipedia.org/wiki/Technology_Experiment_Satellite) on the same satellite has different values, perigee altitude = 551 km and apogee altitude = 579 km. And there's no telling if those different values in the English wikipedia page are correct. Wikipedia is oftentimes incorrect on specific technical details. One thing is certain: At least some of the numbers in the German wikipedia page are wrong.  
> **username_4**: @jumpjack - For various esoteric reasons, the perigee and apogee altitude of a satellite are the minimum and maximum distances between the center of the Earth, minus the Earth's equatorial radius. Because the Earth is an oblate spheroid, this is not the same as minimum and maximum height above the surface of the Earth.  
> **username_0**: @DavidHammen I thought about something like that. That would explain at least part of it. Not to say that the Wikipedia numbers are correct, of course.  
> **username_0**: @JamesK I didn't know about a "space exploration". Of course this question would be more suited there. If anyone wants to move it, please feel free to do so.  
> **username_5**: I’m voting to close this question because this should probably be migrated to space exploration SE  
> **username_3**: currently "apogee", "aphelion" and apo-whatelse are being replaced by "apoaxis". Should we recalculate, all numbers for Earth and Sun?  
> **username_4**: I'd rather not see this migrated. The meta-question being asked here is "Is wikipedia reliable?" The answer to that question is unfortunately not.  
> **username_4**: I’m voting to close this question because it ultimately is asking if wikipedia is reliable. Unfortunately, the answer is no. Wikipedia is good on basic, non-changing subjects. But addressing the quality of wikipedia pages is outside the bounds of any site on the Stack Exchange network.  

---

## 1 answers

### Answer by username_6 on 2020-09-26. Score: 3

You are right!

Apogee is higher than Perigee, except when the orbit is perfectly circular when they're equal.
Semi-major axis will be half-way between the two.
572 km doesn't make sense.

As pointed out in comments, expressed like this they are the distances from Earth's center minus a fixed equatorial radius of the earth, in this case about 6378.137 kilometers. From the numbers in Wikipedia for peri and apo you'd call this a 567 x 515 km orbit. It's a simple way to express roughly the size and shape.
The linked de.Wikipedia page says
Umlaufzeit:       95,3 min[1]
Bahnhöhe:         572 km
Bahnneigung:      97.7°
Apogäumshöhe:     567 km
Perigäumshöhe:    515 km

[1]  Bahndaten nach [TES](https://www.n2yo.com/satellite/?s=26957). N2YO, 18. November 2017, abgerufen am 18. November 2017

I don't know what Bahnhöhe means, google translates it as "track height", so I've asked What exactly would a distance labeled Bahnhöhe mean in the context of a satellite's orbit around the Earth? in German SE.
While the data might be static, the mentioned n2yo link says:
NORAD ID:           26957 
Int'l Code:         2001-049A 
Perigee:            513.2 km 
Apogee:             564.0 km 
Inclination:        97.7 ° 
Period:             95.3 minutes 
Semi major axis:    6909 km 

and looking it up in Celestrak gives the two line element set or TLE as
TES                     
1 26957U 01049A   20269.88561907  .00000195  00000-0  15464-4 0  9995
2 26957  97.7413  31.7408 0036778 246.8588 112.8763 15.11565287 39121

The TLE is also shown in n2y0.
Here's a link direct to Celestrak for this object. They are always changing, the orbits of Earth satellites are never really fixed.
Atmospheric drag tends to lower them and Earth's lumpy gravity causes them to precess, just for starters.
Many satellites have small thrusters to raise their orbit after atmospheric drag lowers it, so we can't expect numbers in static Wikipedia data fields to be accurate.


---

