SWOrD SoftWare for Oceansat2 Orbit Determination. S. Casotto, P. Zoccarato, A. Nardo, M. Bardella CISAS – University of Padua. ASI/EUMETSAT Meeting ASI Space Geodesy Center — Matera, 04-05 February 2009. SWOrD : Software purposes.
SWOrDSoftWare for Oceansat2 Orbit Determination
S. Casotto, P. Zoccarato, A. Nardo, M. Bardella
CISAS – University of Padua
ASI Space Geodesy Center — Matera, 04-05 February 2009
ROSAROSSA(Research and OperationalSatelliteand SoftwareActivities)data flow
SWOrD: Programming paradigms
TAI 1958 -
19 s fixed
OOP advantages (1/2)
UTC: Coordinated Universal Time
UT: Universal time
ET: Ephemeris Time. Was used 1960-1983
TDT: Terrestrial Dynamical Time. Was used 1984-2000
TT: Terrestrial Time
TAI: International Atomic Time (Temps Atomique International)
GPS time = TAI - 19 seconds
the Time_Tag class
UTC 1972 -
delta-UT = UT1-UTC
(max 0.9 sec)
delta-T = TT-UT1
An example of inheritance usage: the GroundStation and Satellite classes
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Two main kinds of operational blocks: interface classes and application classes.
The first called application class triggers the reading interface classes to acquire the input data.
During this process the input data are manipulated to obtain a complete set of information that will be later used by the other application classes.
SWOrDcontains a mathematical model of the world used to process observational data. The functional model of the system can be decomposed into several components, which are the counterpart to the physical model to be developed
There exist several kinematic orbit determination techniques based on either undifferenced, doubly-differenced or triply-differenced observables, but also on time-differenced phase observables.
All of the kinematic approaches to GPS-based LEO OD, including the one adopted here, make use of the fundamental contribution of data provided by the IGS. These data include GPS SV’s orbits, clock solutions for both SV’s and ground stations, EOP and tropospheric zenith delay (TZD) solutions. All these parameters are held fixed in the solution process.
The strategy adopted in the SWOrD OD system is based on the use of a combination of pseudorange and phase observables differenced in time. The procedure is illustrated on the left