Bernese GPS Software Version 5.0 - Bernese GNSS Software

7.7 Special Applications
(8) The screening procedure should be performed iteratively repeating the processing
steps (5) to (7).
Introduce the improved orbit from the previous iteration to MAUPRP. You may now
reduce the screening level for the zero-difference observations. Make sure that you
reset the marking flags in the observation files from the previous run (disable the
option “Mark if marking flags in observation file”).
Due to technical reasons, GPSEST can handle standard orbit and radiation pressure
files only if no stochastic pulse parameters are included. For that reason, the LEO a
priori orbit for GPSEST has to be the initial orbit (from processing step (4)) together
with the corresponding radiation pressure file for all iterations.
Usually, after the second iteration the screening is finalized.
(9) The reduced-dynamic orbit resulting from the last update from ORBGEN is already of
good quality. In order to generate a reduced-dynamic orbit with a shorter interval for
the stochastic pulse parameters, it is necessary to run GPSEST again with an increased
“Number of parameter sets per day”. It is important to pay attention that the interval
between subsequent pulses is a multiple of the integration step size for the equation
of motion previously specified in ORBGEN.
The determination of a kinematic trajectory works in an analogue way as for a roving
ground station (see Section 10.4). The reduced-dynamic orbit generated with the procedure
described above may be selected as a priori information and the screened phase observation
files may also be used for the determination of the kinematic trajectory.
7.7.1.3 Import of LEO Attitude Files
Each LEO has its own attitude characteristics and in most cases the real attitude behavior is
measured with star cameras onboard the satellite. These measurements are then distributed
in special attitude files with different file formats for each satellite mission. Besides the
Bernese attitude file format (description in Section 22.7.13) the Bernese GPS Software,
Version 5.0 supports at the moment the CHAMP (auxiliary) data format and the JASON
format from CNES (Centre Nationale d’ Études Spatiales).
All attitudes files have the default extension ATT. The files in CHAMP data format may
also be transformed to the Bernese attitude file format with the program LEOAUX (using
the RUNGPS command, see Section 18.8). This makes sense, e.g., if you would like to extract
the accelerometer and maneuver data from the CHAMP auxiliary files.
If you have attitude files available for other LEOs you would like to process, you have to
implement these new attitude file formats in the subroutine ${LG}/READATT.f90. Within
this subroutine you find two sections corresponding to each of the supported formats.
The first section is to distinguish between the supported formats looking at the first line of
the attitude file. The variable iAuxFlg(if) is set according to the decision (for the Bernese
attitude format called ”pre-preprocessed attitude” this flag stays zero). In addition, the
number of lines in the file are counted for the allocation of the corresponding variables later
in the subroutine.
Bernese GPS Software Version 5.0 Page 159