Two optical disk "jukebox" mass memory storage systems have been developed that provide access to any data in a store of 1013 bits (1250 Gbytes) within six seconds. These engineering models have been developed under a program sponsored by the Air Force and NASA ana have recently been delivered to testbed facilities -- one to NASA Marshall Space Flight Center and one to the AF Rome Air Development Center. Each system contains a library of 125 optical disks with mechanisms for retrieving any disk, and recording or playing digital data at 50 Mb/s. Disks in protective cartridges are moved from the store to a load station, which then mounts the disks onto a precision turntable. Still in the cartridge, they are spun up to speed and data is recorded or played back via focused laser beams. The major emphasis in both the NASA and Air Force jukebox optical disk systems has been reliability of operation. Enhancements of the mechanical, electrical, and software designs have been implemented to minimize the user downtime in an operating scenario. The NASA system will interface to a database management system using a fiber optics data bus, while the Air Force system will interface to a DEC VAX 11/750 minicomputer. Both systems will store digitized imagery and provide fast access to a huge store of such images.