A communications system, apparatus, method, and computer program product for inter-satellite and inter-spacecraft crosslinks (ISL) with non-ISL optimized antennas on spacecraft. The system includes a mobile communications platform that includes an ISL antenna configured to transmit information to a target satellite through a non-ISL antenna of the target satellite. The mobile communications platform is configured to relay transmissions through the non-ISL antenna of the target satellite to another communications platform. The mobile communications platform includes a controller configured to determine a location of the mobile platform; determine whether the target satellite is within communications range; and prepare a signal for relayed transmissions through a non-ISL antenna of the target satellite to another communications platform in a signal format that is decipherable by this other communications platform.