[time-nuts] Speaking of Costas loops

[Bob Camp]

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 <dennis.c.ferguson at gmail.com> wrote:

> 
> On 3 Jul, 2013, at 21:05 , Bob Camp <lists at rtty.us> 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 -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.