[IGSMAIL-6634] igs08_1699.atx: Update including R801 (R26)

[Robert Khachikyan]

Dear IGS colleagues!

The absolute IGS antenna correction file (igs08_wwww.atx) has been 
updated. The new release is called 'igs08_1699.atx'. It contains the 
following changes:

1) According to Stefan Schaer (CODE), GLONASS-K1 satellite R801 was 
reactivated utilizing almanac slot 26 in March 2012. Therefore, the 
following satellite has been added to igs08.atx:

R26 (R801)

This change in the GLONASS constellation was announced in [IGSMAIL-6581]:
 > GLONASS-801, the first GLONASS-K1 satellite, launched on February 26,
 > 2011, has been reactivated on frequency channel -5. The designation of
 > this (25th active) GLONASS satellite is R26.
http://igscb.jpl.nasa.gov/pipermail/igsmail/2012/006573.html

2) Upon request from Rusnavgeoset/Trimble, robot calibration values were 
copied from "TRM57971.00     NONE" to the following antenna type:

RNG80971.00     NONE

The agreement of the phase center behavior between the two antenna types 
could be confirmed by the colleagues from Geo++ who calibrated one 
single Rusnavgeoset antenna.


The updated antenna correction model is available at
ftp://igs.org/pub/station/general/igs08_1699.atx
or
ftp://igs.org/pub/station/general/igs08.atx

Following discussions at the recent IGS Workshop in Olsztyn, the 
following changes of igs08.atx have to be expected in the near or far 
future:
- conventional phase center offset values for new GNSS
- extension of the GPS satellite antenna phase center variations for 
nadir angles > 14°
- azimuthal satellite antenna phase center variations

With best regards,
Ralf Schmid and Robert Khachikyan
on behalf of the IGS Antenna Working Group