Hi The sat needs to transmit at the GPS frequencies and have an uplink that works exclusively with those frequencies. (or at least that sub band). A "normal" transponder probably would not radiate at the GPS allocation, simply to be a good citizen. I believe the "specialization" is simply a frequency mod to allow WAAS to pass through. There is no mention of a space qualified Cs and / or Rb flying on those birds and no indication that the ground segment is controlling such a payload. If all that *was* present, then including them in the normal navigation solutions would be a "zero cost" next step.
Bob On Jul 4, 2013, at 11:16 PM, Dennis Ferguson <[email protected]> wrote: > > On 3 Jul, 2013, at 21:05 , Bob Camp <[email protected]> wrote: >> If the WAAS sats were purpose designed to provide a high accuracy carrier, >> then yes there are ways to do it. The fundamental design concept of a "bent >> pipe" is that you don't do any of that. You do not care what's going through >> the bird, it just maps the input frequencies to the output and amplifies >> them (a lot). Again, the WAAS signal is simply piggybacking on existing >> hardware. The conversion oscillator is not locked to the GPS carrier (or to >> any other carrier). It's simply a free running quartz based oscillator, >> running into a synthesizer to get the appropriate microwave frequency. > > I'm not sure about the "Again, ..." part. All three WAAS satellites are > commercial > satellites but they were all launched recently enough (2 in 2005, 1 in 2008) > to have > had WAAS-specific payload added. The solicitation for the 2008 satellite is > here > > > <https://www.fbo.gov/index?s=opportunity&mode=form&id=f5aacd4bba2ef67b0c59b586900499b6&tab=core&_cview=1> > > and is dated 2002; this isn't looking for service on a satellite already in > orbit. For > the 2005 satellites, the Telesat one is mentioned here > > http://www.telesat.com/services/government-services > > which says > > Telesat’s Anik F1R includes a specialized payload for the Wide Area > Augmentation > System > > while you look at the Orbital Sciences blurb on the last three satellites it > built for > PanAmSat, here > > http://www.orbital.com/newsinfo/publications/galaxy_fact.pdf > > you'll see that they are all exclusively satellite TV things, with 24 active > C-band transponders and 8 spares, except for Galaxy 15 which weighs 350 pounds > more than the other two and about which it says: > > The Galaxy 15 satellite, which features a unique hybrid payload > configuration, was launched on October 13, 2005. In addition to C-band > commercial communications, the spacecraft also broadcasts Global > Positioning System (GPS) navigation data using L-band frequencies as > part of the Geostationary Communications and Control Segment (GCCS) > implemented by Lockheed Martin for the U.S. Federal Aviation > Administration (FAA). > > I don't think they can use any old satellite for WAAS, they added payload > for it. Note that when Galaxy 15 went awol it took the WAAS service with it > for most of a year even though it was replaced in its orbital slot for TV > service > by a spare within a week or so (though Wikipedia says the replacement was > Galaxy 12 > so I guess that's predictable from the blurb above). > > So I've been assuming that while the WAAS satellites are commercial the WAAS > transmitters are specialized to the service and included for its exclusive > use. > I hence guess they could have been designed to work however they needed to. > > Dennis Ferguson > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
