All computations are done using my own programs which I developed in the past 10+ years. The most important and comprehensive program is the n-body program 'ssd' (solar system dynamics) which allows to do several computations like pure integration (ephemerides , osculating elements etc.), differential orbit correction of asteroids and comets, solving for additional parameters (unknowns) like nongravitational force parameters of comets (using different models), cometary fragmentation parameters (Sekanina model), the mass of perturbing bodies, etc..
The implemented integrator is a multi-step, variable order, predictor-corrector (PECE) method with self-adjusting stepsize. The dynamical model includes the perturbations of the major planets (+ our moon), major asteroids, relativistic motion terms, etc..