kevin willoughby wrote:
If two of three versions agree, that doesn't mean those two are correct.

Though in this case you do get feedback by observing where exactly the
satellite's orbit ended up in reality versus what one or more programs
predicted.
Subtle problems in a program may not manifest themselves fully until
something in the program is pushed out to the edge of its abilities.*
Tell them to figure out the launch trajectory into a orbit with a apogee
of 500 miles and a perigee of 450 miles and most all of the programs
will probably give you almost the same exact answer.
Toss one with a apogee of 1,000,000 miles and a perigee of 50 miles at
them and have them figure in the influence of the gravity of the Moon
and Sun during each orbit, as well as air drag at the perigee and that's
influence on future orbits...and I'll bet different answers start to
emerge from different programs.

* A tragic example of this was trying to use the "Crater" program to
determine the probable impact damage Columbia suffered, even though
"Crater" was never designed to deal with foam impacts of that severity.

Pat