Subject: "Dawn" Achieves Ceres Orbit
From: Daniel Adamo <[email-masked]>
Date: Sun, 08 Mar 2015 21:45:51 -0700

ATIG Members-

About the time most of us in the U.S. were arising on Friday morning, March
6, the Dawn spacecraft was achieving orbit about dwarf planet asteroid (1)
Ceres.  Because Dawn uses solar electric propulsion (SEP), its thrust duty
cycles are highly flexible and equally uncertain because of the low
accelerations exerted.

The attached plot of Dawn's Ceres-centered motion depicts orbit capture, but
SEP thrusting doesn't appear to be modeled much after March in the
associated ephemeris posted March 6 to http://ssd.jpl.nasa.gov/?horizons.
According to http://dawnblog.jpl.nasa.gov/2015/03/06/dawn-journal-march-6/,
Dawn should be in its circular RC3 orbit about Ceres (13,500 km altitude,
polar inclination, ascending node at local midnight) on April 23.  I'll
attempt to pass along subsequent plots reflecting SEP thrusting leading to
RC3 as they become available.

-Dan