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Communication during Cruise The spacecraft uses radio signals to communicate with Earth. X-band wavelength is used for this purpose. X-band, a high- frequency radio wavelength, allows spacecraft communications with less power and smaller antennas. During the cruise stage, two X-band antennas facilitate this communication. Cruise Low-gain Antenna As explained in altitude control, during travel, the spacecraft is spin stabilized with a spin rate of 2 rpm. It is ensured by periodic updates that the antenna always points towards the earth and the solar panels point towards the sun. The spacecraft will use the low-gain antenna early in cruise since it is close to Earth. The low-gain antenna sends the signals in all directions, so when the spacecraft is close to Earth, the majority of the energy transmitted to Earth reaches Earth. Cruise Medium-Gain Antenna As the spacecraft moves farther from Earth and closer to Mars, much of the energy does not fall on the Earth as before. So we need to use a medium-gain antenna, which direct the energy into a tighter beam to reach Earth. The Deep Space Network receives these signals on the earth.
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