Temperatures of three fumaroles on the west summit crater of Mount Rainier, Washington, were monitored over a 5-week period by satellite telemetry. Upon interrogation by the Nimbus 4 satellite, the temperature transducer voltages were converted to digital signals and transmitted to the satellite. The information was stored on board until the Nimbus 4 came in view of the Alaska ground station, where the data were read out and forwarded via land lines to Goddard Space Flight Center.