Complex sentence: Guidance was to be a simple radio control manual command to line of sight (MCLOS) system for use against daytime targets, but night-time use was considerably more complex because neither the target nor the missile would be easily visible.
Split into simpler sentences: Guidance was to be a simple radio control manual command to line of sight (MCLOS) system for use against daytime targets. Night-time use was considerably more complex because neither the target nor the missile would be easily visible.