Another major upgrade to the AIM-7 followed, the AIM-7M. The M included a new monopulse radar seeker that allowed it to be shot downward from a higher-altitude aircraft at a target otherwise masked by the ground. The new model also included a completely computerized guidance system that could be updated in the field, as well as further reducing weight for yet another warhead upgrade. The computerized guidance system also included a simple autopilot that allowed the missile to continue flying toward the last known target location even with the loss of a signal, allowing the launch platform to break lock for short periods while the missile was in flight. All of these modifications also improved performance against low-altitude sea-skimming targets as well. The M model entered US operational service in 1983.