Surveyor 3 Spacecraft, Credit NASA
A large part of the success of the Surveyor programme can be attributed to the selection of a simple and reliable mission architecture that had a pragmatic and incremental approach to solving the most critical engineering challenges of the time, namely the closed-loop terminal descent guidance and control system, throttleable engines, and the radar systems required for determining the Lander’s altitude and velocity. The Surveyor missions were the first time that NASA tested such systems in the challenging thermal and radiation environment near the Moon.
Key features of the missions were the choice of wide flat landing areas, a two-stage design (the first stage using a solid motor for braking), and the use of a 'direct-descent' trajectory that did not enter Moon orbit before landing. The main advantages of this approach were the relatively simple design of the engines for the landing stage, and the fact that a complex precision landing system was not needed. In the years following Surveyor, NASA developed more advanced landing technologies building upon Surveyor's critical systems and components, as well as the lessons learned during the programme.
Embedded below is a detailed PhotoSynth of the Surveyor spacecraft at the Smithsonian National Air and Space Museum on the National Mall in Washington, D.C., created by one of the White Label Space team members in 2008.