[LEAPSECS] Degrees of Accommodating Time Based on Earth Rotation
dfinkleman at agi.com
Tue Nov 2 13:30:42 EDT 2010
A long flight was time to really read Ken Seidelmann's book and part of
Woolard and Clemence, Spherical Astronomy. Subsequent exchanges with
Ken give me a new understanding. (Probably an old understanding for the
rest of you.)
When we solve equations approximating physical processes, we are really
defining our own dynamical time scale. Even with well characterized
initial conditions or observations and a well founded system of units,
the clock in our analysis does not tick at the same rate as those based
on real phenomena. We must correlate time as perceived in our analyses
with the temporal relationships among objects in the universe. For
Earth rotation, time zones are the most coarse correlation. For time
measured in SI seconds, not related to external phenomena, leap seconds
are the next most precise. Finally, DUT, is precise enough for most
astronomical and astrodynamic applications.
It is a hierarchy each level of which is sufficient for a range of
applications. Every time we solve dynamical equations, we are defining
a unique time scale and time interval based on things such as analytical
discretization and computational architecture.
Center for Space Standards and Innovation
Analytical Graphics, Inc.
7150 Campus Drive
Colorado Springs, CO 80920
Phone: 719-510-8282 or 719-321-4780
Discover CSSI data downloads, technical webinars, publications, and
outreach events at www.CenterForSpace.com.
More information about the LEAPSECS