The flight also tested an advanced heatpipe radiator for potential use on the then-future space station and conducted a variety of medical and materials science investigations.Secondary payloads were Space Station Heat Pipe Advanced Radiator Element (SHARE II); Shuttle Solar Backscatter Ultra-Violet (SSBUV) instrument; Tank Pressure Control Equipment (TPCE) and Optical Communications Through Windows (OCTW).The TDRS network of satellites provides the vital communication link between Earth and low-orbiting spacecraft such as the Space Shuttle.One test showed that optical fibers could provide video and audio links between the flight deck and the payload bay.Crew members in space and flight controllers on the ground demonstrated their ingenuity when they adapted a camera part to replace one that had not been packed for the mission.On August 9, 1991, astronauts Lucid and Adamson used AppleLink to write an email from a Macintosh Portable addressed to Marsha S. Ivins at Johnson Space Center.Hasta la vista, baby, ... we'll be back!The crew experienced some minor problems, none of them critical to the safety or success of the mission.