9/17/02

This fileset contains the integrator.f package, which
evolves a system of n gravitating bodies forward in time using a
Bulirsch-Stoer integrator.

The file "input" contains the epoch 2000.0 ephemeris for the solar
system (Sun + 9 planets). The input file also contains parameters which
determine how the code will run. Output is in the form of data files
for each planet which chart the orbital elements as a function of time.

In order to run the code for n different than 9 bodies, one should change
the parameter nb=9 to nb=whatever in the main routine, and also in
the subroutines "derivs" and "Energysum". The code is currently opening
up data files for 9 possible planets. For other n, delete or insert more
"open" statements. It is also necessary to add or delete lines with the additional
orbital elements for the additional planets in the "input" file.
These extra lines would go in in exact analogy to the lines for 
9 planets for which the code is currently configured.