The unpiloted Progress 53 cargo ship undocks from the aft port of the Zvezda service module at 3:58 a.m. (CDT) on April 23 and begins its relative separation from the International Space Station for tests on its upgraded Kurs automated rendezvous system that were delayed from last November. The Russian resupply vehicle will move to a distance of some 300 miles from the complex before it begins to phase back in, testing the Kurs-NA rendezvous hardware and its associated software. The enhanced Kurs system will be incorporated into future Progress vehicles to reduce weight by eliminating several navigational antennas, thus enabling the Progress to carry additional supplies to the station. The Progress is scheduled to redock to Zvezda around 7:15 a.m. (CDT) April 25.