  With the Navy Prototype Optical Interferometer (NPOI), the binary system
Theta 1 Orionis C, the most massive member of the Trapezium, was spatially
resolved over a time period extending from February 2006 to March 2007. The
data show significant orbital motion over the 14 months, and, after combining
the NPOI data with previous measurements of the system from the literature, the
observations span 10 years of the orbit. Our results indicate that the
secondary did not experience an unusually close periastron passage this year,
in contradiction to the prediction of a recently published, highly eccentric
~11 year orbit. Future observations of this source will be required to improve
the orbital solution. Possible implications of the results in terms of system
distance are discussed, although a main conclusion of this work is that a
definitive orbit solution will require more time to obtain sufficient phase
coverage, and that the interaction effects expected at periastron did not occur
in 2007.
