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How to compute a distance between 2 satellites if I know its orbit altitude?

I know LEO-LEO satellite distance is from 1000 km until ~7000 km. But it should have a calculation equation?

EDIT 1

S1, S2, .... are satellites in a constellation. I am asking about a distance between, for example S1 and S2

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Noel Miller
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1 Answers1

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Inter-satellite range: how to compute max. range?

How to compute a distance between 2 satellites if I know its each of their orbit altitude(s)?

Let's say their altitudes $h_1, h_2$ are 500 and 1200 km.

If the satellites share the same orbital plane, then you can add the two altitudes plus twice the equatorial radius of the Earth $r_{eq} = 6378$ km:

$$d_{max} = h_1 + h_2 + 2 \times 6,378 \text{ km} = 14,456 \text{ km}$$

h1, h2 = 500, 800 km

uhoh
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  • i am not sure we can calculate it like this. 15000 km between two LEO satellites...seems wrong – Noel Miller Nov 25 '21 at 10:57
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    @NoelMiller which part of the calculation do you disagree with? – Organic Marble Nov 25 '21 at 12:24
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    @NoelMiller it's not wrong given the question that was asked, but i would guess what you actually meant was, "what is the greatest distance at which their view of each other is not blocked by having the Earth in the way?" If you do mean that, please change the question accordingly, or accept this as the answer to the question you asked by accident. making that rigorous with regard to max range at which they can communicate then requires some modeling of what the atmosphere in the way does to your chosen signal frequency. – Ryan C Nov 25 '21 at 19:16
  • @OrganicMarble 15 000 km between two satellite? It seems for me wrong for satellites in LEO constellation. Lets take Iridium LEO satellite constellation. 66 satelllite and ~15 000 km between them. The radius of Earth should be than 10 or more bigger than it is – Noel Miller Dec 07 '21 at 12:14
  • You disagree with the value of the Earth's radius used in the calculation? – Organic Marble Dec 07 '21 at 12:50
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    @NoelMiller the question's title asks "how to compute *max. range?*" and this is how to calculate the maximum possible range for two satellites in LEO. I can see now that the body of the question doesn't match the title. Exactly what range to you want? Average nearest-neighbor distance for a well distributed constellation near the equator? (Starlink and Iridium have very different constellation architecture. Iridium get really close to each otherat the poles for example, but are very nice and evenly spaced at the equator. Starlinks have a different behavior. – uhoh Dec 07 '21 at 12:52
  • @NoelMiller Iridium looks like this and Starlink looks like this. Let's keep working on this until we can nail down exactly what it is you're after. I think it's something like "average nearest-neighbor distance" but maybe it's something else. – uhoh Dec 07 '21 at 12:54
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    @OrganicMarble see above; I answered the "max" in title but it turns out the OP probably is not interested in the maximum at all. – uhoh Dec 07 '21 at 12:55
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    @NoelMiller also you didn't mention a constellation in your original question, you just ask for "How to compute a distance between 2 satellites if I know its orbit altitude?" That sentence is still there, but now later you change to a constellation. Basically your question is sloppily written and conflicts with itself. I'd say go back and delete all the contradictory stuff and just write a few sentences that clearly state exactly what you want to know. Don't try to keep everything there. Thanks! – uhoh Dec 07 '21 at 13:10