Time series of variations of heights of VLBI antennas due to thermal 
expansion of antenna mounting. Antenna expansion of two parts of 
antenna are taken into account: concrete foundation and steel pillar.
Expansion coefficient of concrete is set to 1.0D-5
Expansion coefficient of steel is set to 1.2D-5.

Air temperature is taken from numerical weather model. Original
field of air temperature is expanded into B-spline basis. Using,
this expansion, air temperature at antenna reference point is 
computed. The temperature of antenna is set to be equal of air
temperature with a lag of 1.5 hours.

Antenna dimensions are taken from the database maintained by
Axel Nothnagel at http://vlbi.geod.uni-bonn.de/Analysis/Thermal/antenna-info.txt

More details can be found at 
Axel Nothnagel (2009) Conventions on thermal expansion 
modelling of radio telescopes for geodetic and astrometric VLBI;
Journal of Geodesy, Vol. 83(3), 787-792, DOI: 10.1007/s00190-008-0284-z
