3 ms·
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,
by Cogito 12y ago
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 http://iml.jou.ufl.edu/projects/Fall99/Coffey/INDEX.HTM
- benihana 12y agoSo 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?
- jacquesm 12y agoThe magic words are 'phased array antennae'.
- azernik 12y agoMuch 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.