[IGSMAIL-7412] BRDC Rinex 2 glonass files

[Nacho Romero]

Author: Nacho Romero

Dear all,

Since the start of 2017 the "17g" Glonass navigation files have been 
reporting epochs with an incorrect epoch, always wrong by "1.0" second, 
this is due to an old version of teqc being used for the generation of 
the "17g" files.

This comes about because the Glonass navigation files are in UTC ... 
(thanks to Lou Estey for the explanation)
see Table A11 ... https://igscb.jpl.nasa.gov/igscb/data/format/rinex211.txt

  |                                  TABLE 
A11                                 |
  |         GLONASS NAVIGATION MESSAGE FILE - DATA RECORD 
DESCRIPTION          |
  +--------------------+------------------------------------------+------------+
  |    OBS. RECORD     | DESCRIPTION |   FORMAT   |
  +--------------------+------------------------------------------+------------+
|PRN / EPOCH / SV CLK| - Satellite number:                      |     
I2,    |
  |                    |       Slot number in sat. constellation 
|            |
  |                    | - Epoch of ephemerides             (UTC) 
|            |
  |                    |     - year (2 digits, padded with 0, |   
1X,I2.2, |
  |                    |                if necessary) |            |
  |                    |     - month,day,hour,minute, |  4(1X,I2), |
  |                    |     - second |    F5.1,   |

i.e. the ephemeris time for a GLONASS navigation ephemeris is in UTC.  
So if an older
version of teqc is being used, it does not know about recent leap second 
insertions into
UTC.

If you operate a station with Glonass data and generate Rinex 2 Glonass 
navigation files please update your teqc version to the latest one as 
found here;

https://www.unavco.org/software/data-processing/teqc/teqc.html


the affected stations in the CDDIS repository is as follows for a recent 
day, if you see your station PLEASE update the teqc ASAP since its 
affecting everyone using the "brdc..17g" files each day;

cebr0150.17g
cedu0150.17g
coco0150.17g
darw0150.17g
faa10150.17g
hob20150.17g
kat10150.17g
kiru0150.17g
kour0150.17g
mac10150.17g
mas10150.17g
mgue0150.17g
mobs0150.17g
naur0150.17g
nnor0150.17g
redu0150.17g
str10150.17g
sydn0150.17g
tlsg0150.17g
tow20150.17g
vill0150.17g
yar20150.17g
yel20150.17g


Thanks !!

-- 
Best regards,
Nacho
_______________________________________________________________

Ignacio (Nacho) Romero
Aerospace Engineer, PhD
CSC Ltd @ ESA/ESOC/OPS-GN
Satellite Navigation Engineer @ ESOC Navigation Support Office
IGS Infrastructure Committee Chair
www.navigation-office.esa.int
www.canaryspaceconsulting.co.uk
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