Throughout his polar trek, Mr. Uemura's progress – or, on some stormy days, lack of it – was
link tracked by the Nimbus meteorological satellite, which passes over the pole every 108 minutes. Signals from a radio transmitter mounted
link on the
link sled were received by the satellite and relayed to the Goddard Space Flight Center at Greenbelt, Md., where Mr. Uemura's position could be pinpointed several times a day.