X-band communication is the primary means of communication between the Mars Reconnaissance Orbiter and the 34-meter-diameter (112-foot) Deep Space Network antennas in California, Spain, and Australia.
The X-band communication system on the orbiter uses a 3-meter-diameter (10-foot) high-gain antenna and a 100-watt X-band radio traveling wave tube amplifier to transmit signals to Earth. Each of these devices is more than twice as powerful as those used by most Mars missions. As a result, Mars Reconnaissance Orbiter is able to send data back to Earth more than 10 times faster than previous missions.
At its maximum distance from Earth of about 250 million miles, the orbiter sends data at a rate of at least 500 kilobits per second. At closer ranges, the signal strength is greater, making higher data rates possible. For several months when Mars Reconnaissance Orbiter is at its closest range of about 60 million miles, the orbiter sends data to Earth at 3 to 4 megabits per second. That is several times greater than a cable modem or DSL internet connection at home.
During the science phase, Mars Reconnaissance Orbiter schedules 8 hours of transmission time per day on two 34-meter (112-foot) Deep Space Network antennas. Occasionally, the orbiter also requests time on the 70-meter (230-foot) antennas.