This report determines the maximum and minimum solar and terrestrial thermal energy incident and absorbed by Saturn IB/V vehicles in earth orbit and translunar travel. The influence' of this external energy on the Instrument Unit Thermal Conditioning System performance, and consequently its adequacy to maintain the electronic packages at acceptable temperature limits is ascertained. Conclusions are: a) Methanol/water coolant temperature will deviate from 111 specifications only during translunar cold flights. However, adequate thermal conditioning of the electronic equipment would still be maintained. b) Instrument Unit missions exceeding 6 1/2 hours, or electronic packages heat dissipation magnitudes lower than 3 kw or higher than 8.5 kw, should be reviewed to ascertain thermal compatibility.
