This directory contains the AIUB (Astronomical Institute, University of Bern)
contributions to the CHAMP orbit campaign of the IGS LEO Pilot Project

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The following files are included:

* chpYYDDD_NN.sp3.Z   CHAMP orbit solutions in SP3 format.
                      Solution ID NN see below.
* readme.txt          This file
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NN = 01: Kinematic Orbit

The POD solution is based on a kinematic approach using undifferenced
pseudorange and time-differenced phase observations of the GPS data. The GPS
orbits and clocks are fixed to the corresponding CODE (Center for Orbit
Determination in Europe) contributions to the IGS. CHAMP real attitude is used
for the correction to center of mass. CHAMP clock corrections
are included but no velocity vectors. Vector intervals are 10 seconds.

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NN = 02: Reduced-dynamic Orbit

The POD solution is based on a reduced-dynamic orbit fit using kinematic
positions and position differences as pseudo-observations. 
The kinematic positions are derived from the pseudorange observations and the
position differences are derived from time-differenced phase observations of
the GPS data of CHAMP. The GPS orbits and clocks are fixed to the
corresponding CODE (Center for Orbit Determination in Europe) contributions to
the IGS.

The parametrization of the reduced-dynamic orbit is the following:
  - six initial osculating elements
  - 15 dynamical parameters (R,S,W)
  - stochastic pulse in R,S,W every 10 minutes

Nominal attitude is used for the correction to center of mass. No CHAMP clock
corrections are included but velocity vectors. Vector intervals are 
60 seconds. 


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NN = 03: GPS Zero-difference Reduced-dynamic Orbit

The POD solution is based on a zero-difference reduced-dynamic approach
using GPS phase observations. The GPS satellite orbits and high-rate clock
corrections are fixed to the corresponding CODE (Center for Orbit
Determination in Europe) contributions to the IGS. CHAMP attitude files
provided by GFZ Potsdam are used for the correction to the center of mass.
No CHAMP clock corrections are included in the SP3c files.

The parametrization of the reduced-dynamic orbit is the following:
  - six initial conditions (osculating elements)
  - 3 dynamical parameters (R,A,O)
  - piecewise constant accelerations in R,A,O over 6 minutes

				      
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Each orbit file spans a 24-hour period starting at 0:00.

Kinematic orbits may contain undefined position and clock values which are
given as 0.000000 and 999999.999999, respectively.

Contact:      Heike Bock                     (Solutions NN=01 and 02)
              heike.bock@aiub.unibe.ch

              Adrian Jaeggi                  (Solutions NN=03)
              adrian.jaeggi@aiub.unibe.ch

              Urs Hugentobler
              urs.hugentobler@aiub.unibe.ch