SVN49 Tip of the Iceberg?

After looking into the details of the SVN49 anomaly we have now discovered
that more GPS Block IIR and IIR-M satellites may be suffering from the same
root cause. Have a look at the latest information on my blog or on
InsideGNSS

My blog: http://gnss.servolux.nl/gnss_blog.html

InsideGNSS: http://www.insidegnss.com/node/1599

wrote:
d
me

SVN49 problem was caused by impedance miss match with the L5
demonstration payload. It is a unique configuration. The elevation
dependent pseudorange error is not seen on other satellites.


Tom

Tom, sorry but I have to disagree with you. Have a look at the residuals
picture shown on our InsideGNSS article and judge for yourself if this is an
anomaly or not....

For completeness, here once more the link InsideGNSS:
http://www.insidegnss.com/node/1599

Tim.

wrote:
red
same

Tom,
From the referenced article,

"(Independent sources have confirmed to Inside GNSS that a classified
payload has been connected to the J2 port on several satellites.
However, unlike SVN49, these classified packages include a component
designed to negate or dampen the secondary-path signal.) "

Shades of Hubble.

I was very surprised to read that the IIR had an extra J2 port. It is
quite possible that the other IIR satellites are showing a very small
reflection off this port that has only come to light because people
went looking for it. It might prove to be useful if the Kalman filter
can take advantage of this fact to adjust the measurement data coming
from the monitor stations to improve the zero age of data estimates
for the IIR birds. That is out of my league.

wrote:
red
same

I don't disagree that each SV has its own variations, as does each
receiving antenna/filter/receiver set, my point is SVN-49 has a
problem due to the installation of the L5 demonstration payload. The
other SVs do not have the same problem. SV transmit amplifier and
filter characteristics, the characteristics of the satellite antenna
array, the PRN codes themselves, the type of correlator used, the RF
section of the receiver, the antenna, the radome, and LNA all
introduce small (usually) biases. Antennas, radomes, and AGC
introduce a lot of elevation dependence. Heck, there is not even a
universally accepted definition of the exact point of the pseudorange
measurement (i.e. which is right? a full chip correlator or a narrow
correlator?) Whether or not the carrier windup correction is applied
will also make a elevation like dependent difference in high accuracy
applications.


Tom