The SGP maintains many programs. Four major packages are available for distribution:

  • GEODYN - orbit determination and geodetic parameter estimation
  • SKED - creation of geodetic schedules
  • Calc/Solve - VLBI data analysis package
  • nuSolve - newest VLBI data analysis package

GEODYN is used to generate orbit predictions for satellite tracking (particularly for Satellite Laser Ranging) and to process the tracking data for geodetic parameter estimation and related science investigations. The other programs fit into the chain of generating and analyzing geodetic VLBI sessions as follows:

  • SKED is used to schedule a VLBI observing session.
  • Correlator hardware and software is used to process the recorded signals and to compute arrays of the complex cross-correlation function.
  • The Haystack Observatory Post-processing System (HOPS) is used to process these arrays, find fringes, and calculate VLBI observables for each scan, for each processed baseline: the narrow-band group delay, the wide-band group delay, and the phase and the amplitude of the coherence function.
  • Calc/Solve is used to archive the output of HOPS into databases, compute theoretical delays and delay rates, find adjustments to the parameters of models by least squares estimation, calculate solution statistics, and generate tables and plots of the final results. Used to process single or multiple sessions.
  • nuSolve is being developed as a replacement for Calc/Solve. Currently it handles single sessions.