[time-nuts] Speaking of Costas loops

[Bob Camp]

Hi

Indeed the atomic clocks on sats are set up so they can "tune" far enough to take out the relativistic effects. That (and a bunch of other things) makes them somewhat more expensive than their ground based cousins (like by 10-100X). They also have volume / power / cooling / reliability / weight issues (in addition to cost) that drive you to only use them if you really need to. The default option is to use some form of quartz. 

Bob

On Jul 5, 2013, at 11:44 AM, Bob Stewart <bob at evoria.net> wrote:

> Wouldn't a Cs or Rb clock in orbit be slow due to relativistic effects?  I'm pretty sure there is a relativistic correction to the GPS clocks.
> 
> Bob - AE6RV
> 
> 
> 
> ----- Original Message -----
>> From: Bob Camp <lists at rtty.us>
>> To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>> Cc: 
>> Sent: Friday, July 5, 2013 10:33 AM
>> Subject: Re: [time-nuts] Speaking of Costas loops
>> 
>> 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
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