Re: Signal strength trends

On Aug 1, 10:15 am, HIPAR <captc...@xxxxxxxxxxx> wrote:
On Aug 1, 9:30 am, Mike Jr <n00s...@xxxxxxxxxxx> wrote:



On Jul 31, 3:28 pm, Sam Wormley <sworml...@xxxxxxxxx> wrote:

Mike Jr wrote:
In reading about the GPS Anomalous Event Monitor (GAEM) project,
 http://www.countohio.org/currentprojects/documents/GPS/GAEM_project_s...
I became curious about the question of signal degradation of the GPS
constellation due to age.  Solar panels and other gear take a beating
in space.  I wonder if anyone has been tracking signal strengths of
the individual birds over time.  If so, have you seen any trends?

The IIAs are way past their design life.  The oldest IIR was launched
12 years ago and IIRs have a design lifespan of 10 years.  The cost of
SV's are shaven very thin during development.  Spending money to
extend the design life beyond the contracted lifespan would open the
contractor to the charge of "gold bricking".

Assuming that these birds will last forever is a mistake.

--Mike Jr

   Signal strength is a pretty tight design spec. I would doubt
   that the signal would degrade over time. SVs are usually put
   to pasture (higher orbit) the orientation or clock stability
   become a problem.

Sam and Chas,
 All of what you say is true.  But the current constellation is
getting OLD.  These satellites will not last forever.  The IIA's are
way past their design lifespans and the IIRs are getting past their
design lifespans as well.  I was curious if anyone is monitoring
individual satellites so that they could detect any degradation in
service.  If nobody is then somebody should.

The old MCS used to look at precise positioning service data.  I don't
recall if it looked at coarse acquisition data but I think not.

--Mike Jr

I can only guess. Transmitter output power is such an important
parameter of the overall health of a satellite that it surely must be
monitored..

Power output of the individual transmitters might be monitored
directly at the satellite.  It's easily done by a calibrated power
sampler that connects into the telemetry system. You can speculate
about the long term effects of exposing the antenna array to space.

---  CHAS

I don't think that the monitor stations look at coarse acquisition.
Any degradation of C/A might go unnoticed. I am thinking that
somebody ought to be looking at the quality of C/A by satellite just
to make sure. I would be shocked to discover that nobody is.

--Mike Jr
.

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