How does DS1's communications system work?
The general term for all data sent back by a spacecraft is "telemetry." DS1 is sending back two different types of telemetry.
"Engineering" or "health" data is the first type. It is an update on the status of the spacecraft. Spacecraft engineering or health data is composed of a wide range of measurements, from switch positions and subsystem states to voltages, temperatures, and pressures. Literally thousands of these measurements of data are collected and inserted into the telemetry.
The other type of telemetry is referred to as "science" data. These data are made up of readings taken from the scientific equipment on board. Except in really unusual cases or during critical tests, the science data are always given a higher priority than engineering data. This is because the science data are a mission's end product while the engineering data are collected mostly so that a spacecraft stays healthy in order to obtain the science data. DS1 is a little different from other space missions in that regard because its primary mission is to test new technologies. DS1's health data gives engineers on the ground valuable information on how well they have done thier job and how well DS1's experimental systems are functioning.
Interestingly, we will also learn more things from DS1 than just what information it sends back. There is a whole branch of science interested in studying the radio signal itself. These "radio scientists" are interested in refraction, Doppler shifts, and other modifications of the signal as it is changed by the atmosphere of a planet, moons, or by structures such as planetary rings. Amazing amounts are learned by these scientists just by studying how the signal got to us without even looking at what data was sent.
What is telemetry?
How is data put on radio waves?
How much time on the Deep Space Network is DS1 getting?
What interferes with communications?
How often is DS1 in communication with Earth?
How do the instruments and sensors coordinate sending signals?
How much data is DS1 able to transfer?
How is data processing managed?
What is the Doppler effect?