SUBJ: Switch the absolute antenna model within the IGS
DATE: 19 December 2005
Author: Gerd Gendt
Dear colleagues,
At the meeting in San Francisco the IGS Analysis Centers (AC) representatives
have discussed the switch to the new absolute antenna model. We came up with
the following decisions:
1. ANTEX file:
1.1 The new antenna model is accepted by all the ACs. An updated offset for
the PRN17 will be added.
New satellites will be added just after launch with default values (block
mean) and updated as soon as possible.
JPL has agreed to make some more validations with their GRACE-based model.
The final long-term goal should be the generation of a model which
includes also LEO derived PCV maps to have one unique model for ground-
and space-based applications including nadir angles to up to 16 degrees.
1.2. The GLONASS PCV and offsets will be delivered by CODE.
1.3 The ANTEX file name will have the following structure:
base_wwww.atx, e.g. igs05_1325
where
base - basic name which will only be changed if existing values are
changed (one exception is a new launched satellite for which the
initial values will be updated in the first weeks)
wwww - is the GPS-week where the last information were added.
1.4 Satellite antenna x-, y-offsets:
A unified definition for all satellites and systems will be applied.
The definition will be that one used for Block II/IIA namely:
- z-axis points to the geocenter
- y-axis is cross product of z-axis and sat-sun direction (in that order)
- x-axis completes a right-handed system (x is pointing to the sun)
All adaptations will be done by corresponding settings in the ANTEX file.
With the new ANTEX format, having all information in one place, the ACs
have not to maintain different files with x-y-z offset and this way one
source of inconsistency is removed.
2. ANTEX and SINEX-block GPS_PHASE_CENTER
To enable the tracking of information about physically calibrated antennas
in the SINEX file the following proposal should be discussed:
The new SINEX 2.00 already states (Remark 11):
Take value S/N '-----' if the phase center offsets apply to all antennas
of the same type.
The new proposal goes one step further and states:
Take radome 'NONE' if the phase center offsets apply to all antennas of
the same type.
Practically the following sequential test has to be applied to obtain for a
given specific antenna the valid (used) PCV:
1. Check ANT + RADOME + S/N , if not found
2. Check ANT + RADOME + '-----' , if not found
Proposal:
3. Check ANT + NONE + '-----' (valid for all not explicitly given Radomes)
The test is to apply for searching in the atx-file and in the SINEX
block GPS_PHASE_CENTER.
Example:
+SITE/ANTENNA
*SITE P ____DESCRIPTION_____ _S/N_
STA1 A .... ASH701945B_M SCIS 12345 --------
STA2 A .... ASH701945B_M SCIS CR519 ----- |
STA3 A .... ASH701945B_M OSOD 020 -- | |
-SITE/ANTENNA | | |
| | |
+SITE/GPS_PHASE_CENTER | | |
*____DESCRIPTION_____ _S/N_ | | |
ASH701945B_M NONE ----- STA3 <-- | |
ASH701945B_M SCIS ----- STA2 <----- |
ASH701945B_M SCIS 12345 for STA1 <--------
-SITE/GPS_PHASE_CENTER
3. SINEX with SATA_Z
In the new SINEX 2.0 new parameters for satellite antennas are defined. It
is recommended to include as a minimum the SATA_Z parameter in the SINEX
file. The parameter should be constrained so that the submitted solution is
based on the given standards.
4. Satellite clocks
The antenna model used to for generating the clocks is given in the
following comment line:
4.1 SP3:
This information is not only for the clocks of interest.
/* ANTENNA MODEL USED: igs05_1325 CLOCKS ALIGNED TO: igs05_1325
/* ANTENNA MODEL USED: jpl_2005 CLOCKS ALIGNED TO: igs05_1325
4.2 CLK-RINEX:
Following comment lines:
ANTENNA MODEL FOR ANALYSIS : igs05_1325
ANTENNA MODEL FOR CLOCK ALIGNMENT: igs05_1325
[Note these SP3 recommendations were superceded by IGS Mail 5490,
22 November 2006.]
5.The switch to the new APCV model will done in parallel with the switch
to ITRF2005 (November 2006).
Best regards
Gerd Gendt
01 January 2012, originator IGS ACC