Experiment M403: Electrostatic charge

Experiment M403 was flown on the Gemini 4 and 5 spacecraft in an effort to discover whether the spacecraft could accumulate sufficient excess electric charge to constitute a hazard for later Gemini-Agena rendezvous missions. An attempt was made to measure the electric field terminating on a small area of the spacecraft retrograde adapter section and to calculate the total spacecraft charge from this measured field value. The Gemini 5 instrument was inhibited from responding to electric fields that corresponded to a charge on the spacecraft. However, readings were obtained on the Gemini 5 mission that were of as great or greater magnitude than those obtained on the Gemini 4 mission. This could be interpreted as an indication that the contribution of a net spacecraft charge to the Gemini 4 measurements was negligible. An operational measurement that was performed on a later rendezvous mission was indicative of a very small exchange of charge between the Gemini spacecraft and the Agena vehicle.