In testing, it was found that the IR guidance signals were blocked by rain, fog or snow, and could be confused by sunlight shining through the rocket exhaust which caused it to scintillate like the command signals. A 25 GHz radio link was proposed to replace the IR system, but never proceeded with as the project "ran into the sand."
The IR guidance signals were obstructed by rain, fog, or snow, and could be confused by sunlight shining through the rocket's exhaust, causing it to shimmer like the command signals. A 25 GHz radio link was proposed as a replacement for the IR system but never implemented due to project setbacks.