Ranger 5 was heat-sterilized like Rangers 3-4 had been, so as to prevent unintended contamination of the Moon with Earth microbes. Rolf Halstrup, who was in charge of the sterilization program, had vocally objected to this procedure as he was convinced that subjecting the probes to a heat dosage was damaging the sensitive electronics in them. He convinced JPL in Pasadena management that sterilization of Ranger 4 had "very likely" damaged the main computer sequencer and timer and that the procedure needed to be stopped to ensure reliability of the spacecraft. Management agreed to stop sterilizing Ranger probes, but only on Ranger 8 and up, as Rangers 6-7 had already been sterilized.