Because of the two-month delay, the STS 41-F mission was cancelled (STS 41-E had already been cancelled) and its primary payloads were included on the STS 41-D flight. The combined cargo weighed over 47,000 pounds, a Space Shuttle record up to that time.
The primary cargo consisted of three communications satellites, SBS-D for Satellite Business Systems, TELSTAR 3-C for Telesat of Canada and SYNCOM IV-2, or Leasat-2, a Hughes-built satellite leased to the Navy. Leasat-2 was the first large communications satellite designed specifically to be deployed from the Space Shuttle. All three satellites were deployed successfully and became operational.
Life sciences experiments performed during the STS-41D mission were those classified as Detailed Supplementary Objectives (DSOs). A DSO is a NASA-sponsored investigation performed by Space Shuttle crewmembers, who also serve as test subjects. These studies are designed to require minimal crew time, power and stowage. Biomedical DSOs focus on operational concerns, including space motion sickness, cardiovascular deconditioning, muscle loss, changes in coordination and balance strategies, radiation exposure, pharmacokinetics and changes in the body's biochemistry.
Other payloads were the IMAX cargo bay camera, flown for the second time; Radiation Monitoring Equipment; Cloud Logic to Optimize Use of Defense Systems; Continuous flow Electrophoresis System; an Air Force experiment; a Shuttle Student Involvement Program experiment; and the Office of Application and Space Technology solar wing (OAST-1), the largest structure ever extended from a manned spacecraft. OAST-1 demonstrated the feasibility of large lightweight solar arrays for future application to large facilities in space, such as the International Space Station.
STS-41D landed safely at Edwards Air Force Base in California on September 5, 1984. Landing was scheduled for Edwards desert runway because it was Discovery's first flight.