Communications with the Cassini spacecraft are conducted through radio transmissions received and sent through the biggest antennas in the world – those of NASA's Deep Space Network. Deep Space Network complexes are strategically located around the globe in California, Spain and Australia. As Earth rotates, a spacecraft in deep space can always be in touch with at least one of the antenna complexes.
Mission control activities for Cassini are conducted from the Space Flight Operations Facility at JPL, where the project is headquartered.
Scientists and engineers at JPL write sequences of commands that tell the spacecraft what to do for large blocks of time – hours, days or weeks. These commands are encoded into a radio signal that can be "heard" by Cassini's onboard radio receiver. The powerful antennas of the Deep Space Network then transmit, or "uplink" this encoded radio signal to the spacecraft.
When it's time for Cassini to return scientific data to Earth, the communications process is reversed. Cassini's own computers encode images and measurements into a radio signal, which is then transmitted by the spacecraft's radio system to the Deep Space Network antennas. A 70-meter (260-foot) diameter antenna – larger than a football field -- is often used capture Cassini's radio signal, either alone or in concert with smaller, 34-meter (110-foot) diameter antennas to boost the amount of signal received. About half the time, though, the smaller ones are used alone.
The incoming signal is decoded, stored and distributed to Cassini's engineers and scientists. Instrument teams receive raw data ready for scientific analysis and interpretation . Findings by Cassini scientists are published in scientific journals, and ultimately, data from the mission are made available for use by scientists around the world.
Raw images from Cassini's cameras are one high-visibility, instantly available example of the scientific data returned by the spacecraft. Through Cassini's "raw images" link, anyone with a connection to the Internet can see fresh images from Saturn at the same time that Cassini's scientists see them.