[IGSMAIL-7272] igs08_1888.atx: Update including latest two IRNSS satellites

[Ralf Schmid]

Dear IGS colleagues!

The absolute IGS antenna correction file (igs08_wwww.atx) has been 
updated. The new release is called 'igs08_1888.atx'. It contains the 
following changes:

1) The latest two IRNSS satellites (IRNSS-1E launched on 20 January 2016 
and IRNSS-1F launched on 10 March 2016) have been added with 
ISRO-supplied phase center offset values:

I05 (I005)
I06 (I006)

More information on the IRNSS constellation can be found at
http://mgex.igs.org/IGS_MGEX_Status_IRNS.html

2) One robot calibration provided by Shanghai Huace Satellite Navigation 
Technology Ltd. has been added:

CHCI80          NONE


The updated antenna correction model is available at
ftp://ftp.igs.org/pub/station/general/igs08_1888.atx
or
ftp://ftp.igs.org/pub/station/general/igs08.atx

Many thanks to Oliver Montenbruck for his help!

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