Thermal probes can carry instrumentation packages into polar ice sheets for geophysical investigations and long-term observations by remote measurement methods. They are self-contained surface-controlled devices. The development work at U.S. Army CRREL solved problems of materials, fabrication and heat-transfer analysis. The Philberth probe, named after its inventor, has demonstrated its performance capability in Greenland. The pendulum probe is a further development with increased performance and versatility. The probes are a tool to widen Man’s knowledge in glaciology and geophysics, and to increase his capability in seismics and possibly communications.