[IGSMAIL-7252] igs08_1885.atx: Update considering changes in the GLONASS constellation

[Ralf Schmid]

Dear IGS colleagues!

The absolute IGS antenna correction file (igs08_wwww.atx) has been 
updated. The new release is called 'igs08_1885.atx'. It contains the 
following changes:

1) According to the Information Analytical Centre (IAC), the second 
GLONASS-K1 satellite (R802, 2014-075A) replaced GLONASS-M satellite R736 
in almanac slot 9. Therefore, the following satellite has been added:

R09 (R802)

source:
> According to GLONASS System Control Centre: SC Glonass-K #702 (orbital slot 9) was included into GLONASS operational constellation at 21:30 MT (UTC+3) 15.02.2016
https://www.glonass-iac.ru/en/content/news/?ELEMENT_ID=1563

2) According to the Information Analytical Centre (IAC), GLONASS-M 
satellite R714 replaced GLONASS-K1 satellite R802 in almanac slot 17. 
Therefore, the following satellite has been added:

R17 (R714)

source:
> According to GLONASS System Control Centre: SC Glonass-M #714 (orbital slot 17) was included into GLONASS operational constellation at 00:00 MT (UTC+3) 17.02.2016
https://www.glonass-iac.ru/en/content/news/?ELEMENT_ID=1565

Analyses performed by Richard Langley have shown that R714 was already 
active in almanac slot 17 on 16 February.

3) The following decommission dates have been added:

R09 (R736): 15 February 2016
R17 (R802): 15 February 2016

4) According to an IGS Workshop recommendation, the following satellites 
have been renamed:

R18: R754 --> R854
R21: R755 --> R855

IGS Workshop recommendation:
> In order to guarantee unique IGS space vehicle numbers for GLONASS, GLONASS numbers "701..." (GLONASS-K) and "750..." (GLONASS-M) are converted to "R801..." and "R850...", respectively.


The updated antenna correction model is available at
ftp://ftp.igs.org/pub/station/general/igs08_1885.atx
or
ftp://ftp.igs.org/pub/station/general/igs08.atx

Many thanks to Richard Langley for his help and sorry for the delay of 
that update!

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