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A comment on SpaceX Sells 10% Stake to Google, Fidelity for $1B. Parent comment

Re:SpaceX Sells 10% Stake to Google, Fidelity for $1B by Cogito on Tuesday January 20, 2015 @06:58PM (#8920572)
Down thread there are a lot of numbers thrown about, some slightly wrong or only in miles, so let me summarise them! The values are taken mostly from wikipedia, with some data double checked against [1]

Low Earth Orbit (LEO)

altitude: 160 to 2,000 kilometers (99 to 1,200 miles)

orbital period: ~88 to ~127 minutes

latency: 20 to 40 msecs

Geosynchronous Earth Orbit (GEO)

altitude: 42,164 km (26,199 mi)

orbital period: 1 day (approximately 23 hours 56 minutes and 4 seconds)

latency: 240 milliseconds

[1] http://iml.jou.ufl.edu/projects/Fall99/Coffey/INDEX.HTM

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Re:SpaceX Sells 10% Stake to Google, Fidelity for $1B by benihana on Tuesday January 20, 2015 @08:05PM (#8920852)
So if the orbital period is about an hour and a half to two hours, does that mean that you can expect to hold on to a single satellite's signal for about 40-50 minutes? Longer? I wonder how much power a cell phone will have to use to track a satellite that's moving through the sky - if the tracking will dominate power usage, or sending and receiving the signal will and we won't see much change.

I wonder how this will be different (if at all) from GEO satellites when it's cloudy. Could you presumably find a satellite near the horizon to use to bypass the clouds?

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Re:SpaceX Sells 10% Stake to Google, Fidelity for $1B by jacquesm on Tuesday January 20, 2015 @08:13PM (#8920883)
The magic words are 'phased array antennae'.
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Re:SpaceX Sells 10% Stake to Google, Fidelity for $1B by azernik on Wednesday January 21, 2015 @12:31AM (#8921648)
Much less - these satellites are low, so you're not going to have line-of-sight for anything near half the orbital period. Not sure about the precise numbers, but I know Iridium was really challenged by the requirement for clients to roam between satellites on the order of once a minute. As they demonstrated, though, it's a solvable problem.
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