They support and facilitate the scientist on the ground working with the scientist on the shuttle to maximize the amount of research accomplished. Among the primary objectives for all shuttle missions are the scientific and technical goals of the onboard payloads. While on orbit, most crew time is occupied with the varied tasks required to meet these goals. A payload may be as simple as a seedling or as complex as a multi-stage deployable satellite. It might be small enough to fit in a middeck locker, or it might fill the entire cargo bay.
Most shuttle missions fly a combination of several payloads of differing size and complexity.
Here is a description of the payloads for this mission. Flight controllers in NASA's Mission Control Center monitor thousands of parameters of data on the performance of the shuttle and its systems during the orbit phase. Here are several streams of telemetry downlinked directly from the shuttle and seen much as flight controllers see them.