[IGSMAIL-7239] igs08_1881.atx: Update including reactivated Block IIR-M satellite SVN49/PRN04

[Ralf Schmid]

Dear IGS colleagues!

The absolute IGS antenna correction file (igs08_wwww.atx) has been 
updated. The new release is called 'igs08_1881.atx'. It contains the 
following changes:

1) According to NANU 2016009, Block IIR-M satellite SVN49 will resume 
transmitting L-band utilizing PRN04 on approximately 2 February 2016. 
Therefore, the following satellite has been added to igs08.atx:

G04 (G049)

NANU message 2016009:
> NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2016009 NANU TYPE: GENERAL
> *** GENERAL MESSAGE TO ALL GPS USERS ***
> ON APPROXIMATELY 02 FEB 2016, SVN49 WILL RESUME TRANSMITTING L-BAND UTILIZING PRN04. AT L-BAND ACTIVATION, SVN49/PRN04 WILL BE UNUSABLE UNTIL FURTHER NOTICE. ADDITIONALLY, NO BROADCAST ALMANACS WILL INCLUDE SVN49/PRN04 UNTIL FURTHER NOTICE.
http://www.navcen.uscg.gov/?Do=gpsShowNanu&num=2016009

2) A decommission date for the following satellite has been added:

G32 (G023): 25 January 2016

NANU message 2016008:
> NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2016008
> SUBJ: SVN23 (PRN32) DECOMMISSIONING JDAY 025/2200
> 1. NANU TYPE: DECOM
> NANU NUMBER: 2016008
> NANU DTG: 252232Z JAN 2016
> REFERENCE NANU: 2016006
> REF NANU DTG: 201928Z JAN 2016
> SVN: 23
> PRN: 32
> UNUSABLE START JDAY: 025
> UNUSABLE START TIME ZULU: 1536
> UNUSABLE START CALENDAR DATE: 25 JAN 2016
> DECOMMISSIONING JDAY: 025
> DECOMMISSIONING TIME ZULU: 2200
> DECOMMISSIONING CALENDAR DATE: 25 JAN 2016
>
> 2. CONDITION: GPS SATELLITE SVN23 (PRN32) WAS UNUSABLE AS OF JDAY 025 (25 JAN 2016)
> AND REMOVED FROM THE GPS CONSTELLATION ON JDAY 025 (25 JAN 2016).
http://www.navcen.uscg.gov/?Do=gpsShowNanu&num=2016008


The updated antenna correction model is available at
ftp://ftp.igs.org/pub/station/general/igs08_1881.atx
or
ftp://ftp.igs.org/pub/station/general/igs08.atx

Those who don't cope with the MGEX extension can use the following model 
instead:
ftp://ftp.igs.org/pub/station/general/igs08_1881_woMGEX.atx

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