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GPS satellites are right in the outer Van Allen radiation belt (a little above 20,000 km). Communications satellites in GEO are higher, but still in it.

If I recall correctly, both the inner and outer Van Allen belts have increased levels of radioactivity and can damage satellites.

So why are there so many satellites in an area which is such a bad place for them to be orbiting in? Is there some major benefit making it all worth it?

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  • $\begingroup$ The title of your question doesn't reflect what you are really asking $\endgroup$ – Olivier Aug 16 '15 at 6:10
  • $\begingroup$ @Olivier It got changed by TidalWave, was the original more appropriate or does it need a new one altogether? $\endgroup$ – Mast Aug 16 '15 at 11:29
  • $\begingroup$ I don't know what was the previous title. But the current one is about radiation level and it seems you are really asking about satellites orbits and their usefulness. If your question is "why are satellites close to the radiation belt given the danger", it hasn't much to do with the title. $\endgroup$ – Olivier Aug 16 '15 at 11:45
  • $\begingroup$ @Olivier The biggest thing I know about the Van Allen belt is they are dangerous to satellites. So out of all useful orbits we know, this one must be pretty important to take the risk. More advanced tracking would tackle the need for 'easy' orbits AFAIK and reduce the cost of producing/launching one. Does that clear things up? $\endgroup$ – Mast Aug 16 '15 at 11:57
  • $\begingroup$ What about the current answer ? Is it what you are looking for ? $\endgroup$ – Olivier Aug 16 '15 at 12:08
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The Van Allen belts, while damaging to satellites, aren't fatal to them. Basically, if there's a justifiable reason to orbit at a particular location, then satellites will orbit at that location, even if additional damage could result. The satellites will simply be hardened to take advantage of that. There is a whole slew of factors involved in orbit determination, including some of the following:

  • Coverage
  • Launch availability
  • Time of day on Earth (Earth observing)
  • Customer locations
  • Lifetime of satellite.

The bottom line is though, it might add a small amount to protect against additional radiation, but the cost of the satellite won't be drastically more for orbiting in the Van Allen belts.

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The main reason for satellites to be in the Van Allen belts is because the synchronous orbits are located there.

The GPS satellites orbit at around 20,200 km altitude above MSL because the orbital period at this altitude is 12 hours and the satellite returns to the same place on earth twice a day.

At the other end is the geosynchronous orbit at 35,786 km above MSL, where the satellites have an orbital period of 24 hours, thus returning to the same place once a day.

An important thing about the synchronous satellites is that they trace the same ground track every day (since their rotation matches with that of the earth's) and this makes tracking easy. For example, the geostationary satellites make satellite broadcasting to individual households possible. This also means that they can used to cover the same areas everyday.

Though it is possible to locate the satellites in an active geosynchronous orbit, it requires continuous expenditure of some form of energy. Since lifting payload to space cost astronomical sums of money, it is better to safeguard the satellites against any radiation rather than getting more fuel there.

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