A thermistor implanted in the brain measured deep body temperature every 10 seconds. Thermistors attached to the leg, ankle, and head measured skin temperature every 10 seconds. Ambient temperature in the capsule was also measured at 10 second intervals. Flown monkeys (with the exception of #357) were used for post-flight control studies at R+17 and R+45.

Results:

Data were pooled across 6 Bion missions, using a total of 12 monkeys. In 8 out of 12 animals, a gradual decrease in mean deep body temperature (DBT) by 0.3-0.8 degrees Celsius was observed. DBT reached a minimum on flight days 4-8, then began to increase. Values of head temperature and leg temperature in space and on the ground were not significantly different. Out of the three skin temperatures measured, only ankle temperature (Tank) suggested that the skin region participates in physiologically controlled heat release; Tank usually varied inversely to DBT. An unusually high Tank increase versus DBT was seen at night during space flight; this may be due to blood redistribution in microgravity. Overall, the pooled data shows that the system of thermal regulation is adequate to support the normal range of DBT, even during high ambient temperatures.