In September and October 2010, 19 balloons were deployed from McMurdo, 6 with a scientific payload sounding the stratosphere, and 13 of the driftsonde type. From the 13 driftsondes, around 640 dropsondes were dropped over Antarctica and the surrounding seas. Most of these were transmitted in real-time on the Global Telecommunication System, for use by the Numerical Weather Prediction centres.
Here are maps of the balloon trajectories and of the dropsondes released, at the end of November.