On Tue, January 3, 2012 6:33 am, Chris McSweeny wrote: > On Tue, Jan 3, 2012 at 9:54 AM, wrote: >> Do they still use ELF? I had been given to understand that they use >> lasers from spacecraft these days, green blue lasers penetrate the water >> quite well apparently, and the resultant data rate is much faster than >> ELF, and has a potentially bidirectional path. > > It's been a little while since I did any work with UW comms (and if I > had done anything more recent which changed anything I don't suppose I > could discuss it freely on here!) but certainly until very recently > VLF/ELF was what they were doing. I just can't see using lasers > between spacecraft and subs being practical in terms of spacecraft > location/availability, pointing accuracy, gain etc. I do know a bit > about why you might not pick up the VLF/ELF signals easily, but that > definitely comes under things I can't talk about. ELF is still the primary method to communicate with near-surface (but not close enough to put up an antenna) submarines. Lasers might work, the downside is that it would negate the real reason why we have the submarines out there- it would make them almost trivially easy to spot.=20 While the patrol area is fixed, I believe the exact position is only known to certain members of the ships crew- a satellite orbit wouldn't know exactly where to point. Matt Bennett Just outside of Austin, TX 30.51,-97.91 The views I express are my own, not that of my employer, a large multinational corporation that you are familiar with. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .