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?


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

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1 Answer 1


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

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    $\begingroup$ @NoelMiller which part of the calculation do you disagree with? $\endgroup$ Nov 25, 2021 at 12:24
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    $\begingroup$ @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. $\endgroup$
    – Ryan C
    Nov 25, 2021 at 19:16
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    $\begingroup$ @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. $\endgroup$
    – uhoh
    Dec 7, 2021 at 12:52
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    $\begingroup$ @OrganicMarble see above; I answered the "max" in title but it turns out the OP probably is not interested in the maximum at all. $\endgroup$
    – uhoh
    Dec 7, 2021 at 12:55
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    $\begingroup$ @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! $\endgroup$
    – uhoh
    Dec 7, 2021 at 13:10

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