IceTop, the surface component of IceCube Neutrino Observatory at the South Pole, studies cosmic ray air showers with an array of ice Cherenkov detectors typically referred to as “IceTop Tanks.” In November 2009, collaborators from the University of Delaware, UW River Falls, and Uppsala University loaded an insulated shipping container containing an IceTop Tank on the icebreaker Oden which traversed the Atlantic Ocean from Helsingborg, Sweden to McMurdo, Antarctica, and return. Over an approximately 6-month interval, Oden carried the IceTop Tank through a wide range of geomagnetic cut-offs. The data obtained will allow the energy dependent effective area (yield function) to be determined using the Earth as a magnet spectrometer. The ultimate goal of the project is to calibrate the IceTop Tanks to study cosmic rays in the GeV primary energy range. We will report preliminary results for determining the yield functions.