Iridium operates 66 active LEO satellites in a cross-linked constellation, providing truly global coverage including the poles. Inmarsat uses 3–4 GEO satellites at about 36,000 km altitude to cover most of the globe from roughly 70°N to 70°S, and its IsatPhone 2 offers 8 hours of talk time. Globalstar runs about 48 LEO satellites to…
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