Is ISL used for TV carriers?

The information I found is that it is used for IP connectivity. I did not find any information on TV broadcast.

If not, what are the applications of ISL?


1 Answer 1


Television broadcasts will not (generally) use ISL. The ground stations transmit signals to the satellites which they rebroadcast back to Earth.

From Wikipedia

The uplink dish is pointed toward a specific satellite and the uplinked signals are transmitted within a specific frequency range, so as to be received by one of the transponders tuned to that frequency range aboard that satellite.1 The transponder then converts the signals to Ku band, a process known as "translation," and transmits them back to earth to be received by home satellite stations.

In the case of TV broadcast the source (the ground stations) and the recipients (the large number of customers in the area the satellite broadcasts to) are both prearranged so the satellites and ground stations are placed in the correct orbits and locations to reach these areas.

ISL becomes more useful when the locations of the sender and receiver do not permit them to see the same satellite in the sky. But this does not (generally) happen in TV broadcast because the broadcaster has the ability to build a new ground station if needed.

As for what ISL is actually used for? I'm not sure. But situations such as a spy satellite on the other side of the globe seem more likely.

  • $\begingroup$ many thanks for the answer can we think that the ISL is used in case of the Tx station fails, or some xpndr etc...used for redundancy ? $\endgroup$ Commented May 31, 2017 at 14:57
  • $\begingroup$ Ground stations are cheaper to build, by several orders of magnitude, than satellite antennas that are large enough for ISL (you need high directivity, that comes with large antennas, large antennas are heavy, getting heavy things into space is very expensive), so no, please stop inventing use cases. $\endgroup$
    – user17550
    Commented May 31, 2017 at 15:20
  • $\begingroup$ Actually in most cases the ground stations have multiple backups spread over a large area. this is to guard against really bad weather blocking the signal on its way up. for example DirectTv has uplink centers in Castle Rock, Colorado, and Los Angeles $\endgroup$ Commented May 31, 2017 at 15:25
  • $\begingroup$ i was talking about redundancy betwen satellites or transponders.. could it be possible to think about high avaibility for TV signal, using ISL ? Or ISL definitvly does not support TV ? $\endgroup$ Commented May 31, 2017 at 19:59
  • $\begingroup$ @davidmarchioni ISL is not very useful for that either. the ground station is pointed at a particular point in space, and so are the millions of customers. if that satellite stops sending or receiving, a different satellite in a different location is not going to be of mush use. Please open a new question if you have more to ask. $\endgroup$ Commented May 31, 2017 at 21:18

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