[en] To achieve the goals of cosmic ray astrophysics, an ultraheavy cosmic ray experiment on an LDEF reflight should be in an orbit with high inclination (approximately 57 deg) at approximately 230 nm for approximately 2 years near solar minimum (approximately 1986). It should fill 61 trays. Each tray should contain 4 modules of total active area 0.7 sq m, with a thermal blanket, thermal labyrinth mounts, aluminum honeycomb mechanical support, and total weight approximately 100 kg. Each module should contain interleaved CR39, Lexan, and thin copper sheets plus one event-thermometer canned in a thin metal cannister sealed with approximately 0.2 atm dry O2. The CR39 and Lexan should be manufactured to specifications and the sheet copper rolled to specifications. The event-thermometer should be a stiffened CR39 sheet that slides via bimetal strips relative to fixed CR39 sheet so that stack temperature can be read out for each event. The metal cannister can be collapsed at launch and landing, capturing the sliding assembly to prevent damage. An engineering study should be made of a prototype LDEF tray this will include thermal and mechanical tests of detectors and the event thermometer