Polar motion program of the Earth Physics Branch

The Polar Motion Group was established in 1973 as part of the newly organized Geodynamics Section within the Gravity Division to carry on studies of polar motion, earth's rotation and crustal plate movements. This long term program includes the operation of the two Canadian PZT observatories located near Ottawa and Calgary which have been accumulating astronomical data on latitude and longitude variations since 1951 and 1968 respectively. Both PZT which appear to be capable of detecting secular notions greater than 10 cm, contribute data regularly to the international time (BIH) and polar motion (IPMS) services. In 1974 two Doppler satellite tracking stations were collocated with the PZT observatories to compare polar motion as determined by the the two independent techniques. It is hoped that the Doppler satellite method will increase the accuracy and time resolution of pole determinations to facilitate studies of short-term variations of polar motion. A mini-computer system is being used to automate the satellite data acquisition, processing and comraunication. As part of the world-wide TRANET satellite tracking network the Doppler stations contribute data to the Dahlgren Polar Monitoring Service.