MKO Provides Measurements of Comet's Position
Astrometry is the branch of astronomy that is concerned
with measurements of the celestial bodies, especially those made to
determine their positions and movements.
Measuring the precise position of an asymmetrical object at a distance
of 83 million miles away is not an easy task. The Deep Impact Navigation
Team at the Jet Propulsion Laboratory (JPL) in Pasadena needed accurate
data on the position of Comet Tempel 1, and Mauna Kea Observatories (MKO)
and IfA personnel played a key role in this.
A total of 5171 position measurements were made of Comet Tempel
1 since 1994, according to Steven Chesley, who did the orbit calculations
for the mission at JPL. MKO provided 374 of these measurements. Of the
total observations, only 951 were of high enough quality to be used in
these calculations, including nearly all of the MKO data, so Mauna Kea
provided 40 percent of the astrometry for the final orbit calculation.
During the active phase of the comet, Mauna Kea data comprised 74 of the
671 observations, or about 11 percent.
IfA astronomer Karen Meech made most of the Mauna Kea observations, and
graduate student Nick Moskovitz did most of the astrometric measurements
on them, with some help from postdoctoral researcher Jana Pittichová.
IfA astronomers Yanga Fernández and David Tholen also contributed
some of the observations and astrometric measurements, respectively, in
the final days before impact.
The time of the impact was only 10 seconds early, well under JPL's
17-second uncertainty estimate.