# Where to find the network topology of Iridium-Next?

This is my first post on Space Exploration. I'll preface this by saying that I just started learning how satellite communications work from a technical perspective. Until a few days ago I had never heard of phased array antennas or a Ka-band and all I'm learning comes from the Internet.

I need to find the network topology of Iridium-Next and any constraints on its inter-satellite connections such as maximum number of links per satellite, maximum distance between two satellites in order to establish a link and the average bit rate. From what I have read, Iridium-Next satellites are arranged in blocks [1] and each satellite is connected to up to 4 neighbors via Ka-band links [2]. Unfortunately, I can't find the information I need: which satellites are connected to each other? I found the TLE data on celestrak and I could analyse the orbits to identify satellite subgroups, but with this data I could only guess at the connections. Also, in this article the authors talk about exceptions in links, so I really need an official network topology:

Most satellites maintain four ISLs (two intra-plane ISLs and two inter-plane ISLs) with neighboring satellites, except those at high latitudes whose inter-plane ISLs are turned off.

Consider for example the following images (from CelesTrak Orbit Visualization).

1. Satellites Iridium 107, 165, 163, 114 moved southward and I guess they are in the same group, thus they are always connected in adjacent pairs. Rather than having to look at orbits I would prefer a list of these fixed connections.

2. Iridium 149 (on the right) moved northward so it is in a different group and has fixed connections with other satellites. Iridium 114 and Iridium 149 approach each other and then move away: I guess that they establish a temporary link to connect the two groups of satellites to which they belong. What are the distances at which this temporary connection begins and ends ?

## 2022-04-03 22:01:47Z

• Hi Wippo. I think you may need to clarify. Where you ask " which satellites are connected to each other?": what is it you want there that is not answered by the quote and the Figure 4 diagram in the RG link? Do you want to know which precise real-world satellite identifiers connect with each other. The latter sounds like an orbit visualisation problem rather than a networks question. Apr 3, 2022 at 20:27
• Hi @Puffin. As I understand it, there are satellites that are always connected to each other via fixed links. Satellites are arranged in groups that move along two opposite directions (question link [1]): satellites on the edge of different groups can establish temporary links. I would like to have 1) for each real satellite X, the set of satellites always connected to X 2) the distances that determine the beginning and end of a temporary link between two satellites that belong to different groups Apr 3, 2022 at 23:13