Stability of BIMA antenna positions

J. R. Forster
Hat Creek Radio Observatory, University of California, Berkeley, CA, 94720

This memo discusses temporal changes of up to 3mm in the positions of
BIMA antennas observed at HCRO.  The motions occur on timescales of days
to months, and appear to be related to seasonal temperature changes. 
Position changes observed over a three month period in the spring of
2001 are shown for illustration, and possible sources of the instability
are discussed.  Ground stability at the 0.1mm level will be required at
Cedar Flat in order to avoid regular monitoring and correction of
initial pointing and baseline solutions for CARMA.