On December 15, 1965, the Gemini 6 mission saw the Gemini 7 spacecraft through its hatch window at about 160 miles altitude.

On December 15, 1965, the Gemini 6 mission captured a clear image of the Gemini 7 spacecraft through its hatch window during their rendezvous at around 160 miles altitude. 

This historic achievement marked the first-ever space rendezvous, demonstrating the possibility of spacecraft docking for future lunar missions. 

The Gemini 7 mission, launched earlier on December 4, focused on studying long-duration spaceflight and spacecraft systems. These missions provided critical data on human endurance in space, laying the groundwork for subsequent Apollo missions.