[IGSMAIL-7308] igs08_1899.atx: Update including C017 and I007

[Ralf Schmid]

Dear IGS colleagues!

The absolute IGS antenna correction file (igs08_wwww.atx) has been 
updated. The new release is called 'igs08_1899.atx'. It contains the 
following changes:

1) The latest BeiDou-2 satellite (BeiDou IGSO 6) launched on 29 March 
2016 has been added with conventional MGEX phase center offset values:

C15 (C017)

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

2) The latest IRNSS satellite (IRNSS-1G) launched on 28 April 2016 has 
been added with ISRO-supplied phase center offset values:

I07 (I007)

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

3) According to Oliver Montenbruck, observation data with nadir angles 
above 15 degrees are available for the two Galileo satellites in 
elliptical orbits (E201, E202). Therefore, the maximum nadir angle has 
been increased from 15 to 16 degrees for these satellites.


The updated antenna correction model is available at
ftp://ftp.igs.org/pub/station/general/igs08_1899.atx
or
ftp://ftp.igs.org/pub/station/general/igs08.atx

Many thanks to Simon Lutz, Zhiguo Deng and Peter Steigenberger for their 
help!

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