/sci/ - Science & Math

>>10735804

To let the astronauts know that they're RIGHT THERE, and that they can take appropriate action (kill the DPS engine). Seconds counted and descent-fuel was used almost to its last drop, and so if you can gently let the thing plop straight down a few feet if you know your attitude is good, then that's the thing to do.

The sensing probes were on all four legs for Apollo 9's Spider (pic related), which was only a test of the complete spacecraft in low Earth orbit. For lunar landings, the sensing probe was omitted from the ladder-leg - to avoid a possible suit-puncturing safety hazard.