[IGSMAIL-7126] igs08_1854.atx: Update including Galileo, BeiDou, QZSS and IRNSS satellites

Ralf Schmid schmid at tum.de
Tue Jul 21 00:37:19 PDT 2015


Dear IGS colleagues!

The present release (called igs08_1854.atx) of the IGS antenna phase 
center model is the first to incorporate satellite antenna phase center 
corrections for the new GNSS (Galileo, BeiDou, QZSS, IRNSS). In order to 
facilitate a smooth transition, parallel files with and without the MGEX 
extension (called igs08_wwww.atx and igs08_wwww_woMGEX.atx, 
respectively) will be offered over a limited period of about 2-3 months.

Previous igs08.atx users should verify that their software to read 
and/or convert the model is ready for the following new satellite 
antenna types:

> +----------------------+-------------------------------------------------------+
> | Satellite Antennae   |                                                       |
> | IGS Codes-20 columns |                      Description                      |
> | XXXXXXXXXXXXXXXXXXXX |                                                       |
> +----------------------+-------------------------------------------------------+
> | BEIDOU-2G            |  BeiDou-2 GEO                                         |
> | BEIDOU-2I            |  BeiDou-2 IGSO                                        |
> | BEIDOU-2M            |  BeiDou-2 MEO                                         |
> | BEIDOU-3I            |  BeiDou-3 IGSO                                        |
> | GALILEO-0A           |  Galileo In-Orbit Validation Element A (GIOVE-A)      |
> | GALILEO-0B           |  Galileo In-Orbit Validation Element B (GIOVE-B)      |
> | GALILEO-1            |  Galileo IOV     : GSAT 0101-0104                     |
> | GALILEO-2            |  Galileo FOC     : GSAT 0201-0222                     |
> | IRNSS-1GEO           |  IRNSS-1 GEO                                          |
> | IRNSS-1IGSO          |  IRNSS-1 IGSO                                         |
> | QZSS                 |  QZSS            : SVN 01                             |
> +----------------------+-------------------------------------------------------+
defined in ftp://ftp.igs.org/pub/station/general/rcvr_ant.tab

The corresponding frequency codes (e.g., "E01") can be found in the 
ANTEX format description available at
ftp://ftp.igs.org/pub/station/general/antex14.txt
For IRNSS (not yet contained in the format specification), the system 
identifier "I" will be used in accordance with the upcoming RINEX 3.03 
standard. The corresponding frequency codes are "I05" (L5 band) and 
"I09" (S band). As regards BeiDou, duplicate entries for "C01" and "C02" 
are provided for the B1 frequency band taking into account different 
signal specifications in RINEX 3.01/03 and RINEX 3.02.

So far, the new ANTEX model provides only phase center offsets (PCOs) 
for the respective satellites, while phase center variations (PCVs) are 
set to dummy (zero) values over the required range of nadir/boresight 
angles. The PCO values are partly based on provider-supplied calibration 
values and partly conventional values as agreed upon for the IGS 
Multi-GNSS Experiment (MGEX):

a) Galileo:
conventional MGEX values for Galileo IOV/FOC satellites; ESA-supplied 
frequency-specific values for GIOVE-A/B (Zandbergen and Navarro, 2008: 
Specification of Galileo and GIOVE space segment properties relevant for 
satellite laser ranging, ESA-EUING-TN/10206); PRN numbers E51/E52 were 
adopted for GIOVE-A/B in accordance with previous MGEX practice and the 
majority of RINEX observation files
b) BeiDou:
conventional MGEX values; inofficial space vehicle numbers (SVNs) were 
assigned in the order of the launch dates
c) QZSS:
JAXA-supplied frequency-specific values; provided by Satoshi Kogure
d) IRNSS:
ISRO-supplied values; provided by Aiylam S. Ganeshan; inofficial SVNs 
were assigned in the order of the launch dates

In accordance with recommendations of the IGS Workshop 2014 in Pasadena, 
the IGS has introduced an IGS-specific convention for the labeling of 
spacecraft axes, which is not necessarily identical to 
manufacturer-specifc coordinate systems used for other purposes (e.g., 
satellite laser ranging). Similar to GPS and GLONASS, the IGS-specific 
axis convention for Galileo, BeiDou, QZSS, and IRNSS has been chosen 
such as to allow a uniform modeling of the spacecraft attitude for all 
satellites applying a yaw-steering attitude control:

* The +z-axis is the principal body axis closest to the antenna 
boresight direction (i.e., the direction of the maximum beam intensity).
* The y-axis is parallel to the rotation axis of the solar panels. The 
positive y-direction is defined through the corresponding x-axis 
orientation.
* The +x-direction is chosen such that the +x-panel is permanently 
sunlit during nominal yaw-steering, while the -x-panel remains dark at 
all times.

Detailed definitions of the IGS-specific axis conventions are provided in

   Montenbruck O., Schmid R., Mercier F., Steigenberger P.,
   Noll C., Fatkulin R., Kogure S., Ganeshan A.S. (2015)
   GNSS satellite geometry and attitude models. Adv Space Res,
   doi 10.1016/j.asr.2015.06.019

for all supported satellites and constellations along with a description 
of the relevant attitude modes. This Open Access publication is 
available at http://doi.org/10.1016/j.asr.2015.06.019.

As further discussions and/or format modifications will be necessary, 
phase center information for the following frequencies/signals has not 
yet been considered for the igs08.atx model:

a) GPS L5 (transmitted by SVN 49 and all Block IIF satellites)
b) GLONASS G3 (transmitted by certain GLONASS-M and all GLONASS-K1 
satellites)
c) QZSS SAIF signal (transmitted by the auxiliary LS-ANT antenna)

According to Hugo Fruehauf (Chief Engineer at Rockwell International in 
the 1970s), the helix array antenna of the initial five Block I 
satellites was centered on the front panel of the space vehicle. 
Therefore, the x-offset value for these satellites was corrected to 
zero. However, as all these Block I satellites were already 
decommissioned prior to 1993, IGS products are not affected by this update.

The updated antenna correction model is available at
ftp://ftp.igs.org/pub/station/general/igs08_1854.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_1854_woMGEX.atx

With best regards,
Oliver Montenbruck and Ralf Schmid
on behalf of the Multi-GNSS and the Antenna WG


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