scope:

Description of Driving Event:

The first United States Microgravity Laboratory (USML-1) located in the Spacelab of the shuttle (STS-50) was not continuously monitored due to insufficient notification of the latest flight procedures. The contingency flight procedures allow for Spacelab power-up in the event of system low temperature and power-down when the orbiter proceeds to ground cooling. Due to an anomaly with the orbiter ammonia boiler system, the flight procedures were altered the day before landing with the decision to power-up Spacelab. The flight procedures were altered again on the landing day with the decision to leave Spacelab powered after the orbiter proceeded to ground cooling. The Spacelab was left in this condition when the orbiter was turned over to KSC. Since KSC-Payloads Group was not informed of the condition, they did not monitor Spacelab's activation nor the several hours of power-on operation.