[Spice_discussion] Questions about the Two-Body Propagator, PROB2B.f
sdupree at speakeasy.net
Tue Mar 14 20:25:44 PDT 2017
I have some question concerning the two-body propagator PROP2B. I'd like
to use it in performing an initial validation the DIVA (from MATH77) and
TOMS Algorithm 670 (from the ACM Transactions On Mathematical Software)
numerical integrators using the two-body problem. My questions follow.
1. How was PROP2B validated?
2. In reviewing the code I saw that PROP2B uses a modified version of
the method documented in Danby's book on celestial mechanics. I'm
also reviewed the methods developed by Goodyear (documented in the
Astronomical Journal and elaborated in a NASA report) and by
Shepperd (documented in the journal Celestial Mechanics). The
question I have here is what are the "pros" and "cons" when each
method is compared against the others?
3. What kind of numerical precision (8 digits, 10 digits, 12 digits ,
etc.) can I expect from PROP2B over a one day propagation? two days?
propagation out to 8 days?
4. Lastly, are there any "gotchas" I need to pay attention to when
using PROP2B to compare two-body propagated position and velocity
vectors with their counterparts from a numerical integration? For
example, does one get better numerical accuracy by by propagating
from the epoch point to each later time point in turn, or is it
better to use PROP2B to propagate from each time point to the next?
Any run-time trade-offs between these two approaches to pay
Looking forward to hearing from you.
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