The mission was the second shuttle flight totally dedicated to deploying a Department of Defense payload, after STS-51-C. Its cargo was classified, but it was reported that two (USA-11 and USA-12) DSCS-III (Defense Satellite Communications System) satellites were launched into stationary orbits by an Inertial Upper Stage.
Груз был засекречен, однако объявлено о запуске двух военных спутников связи USA-11 и USA-12 типа DSCS-III((), которые были доставлены на целевую орбиту с помощью дополнительной ступени Inertial Upper Stage производства Boeing.