Telecommunications technologies serve as the "walkie-talkies" that enable spacecraft operators on Earth to send commands and receive data faster and in greater amounts. Below are examples of the way in which the Mars Science Laboratory mission benefits from past technological development.
The Mars Science Laboratory rover, Curiosity, is able to "talk" to Earth using any one of three antennas. During the mission, the rover's primary means of communication is via UHF frequencies -- similar to those used for television broadcasts. During "conversations" scheduled twice each day, NASA's Mars Reconnaissance Orbiter, now in flight above Mars, will serve as intermediary and record the information for transmission to Earth. Each conversation will last about 15 minutes, the length of time it takes for the orbiter to pass from horizon to horizon. The orbiter will then relay the information to Earth.
In a pinch, NASA's Odyssey spacecraft, also in orbit above Mars, will serve as a backup for relaying information in the same manner. Odyssey has transmitted most of the data from NASA's two Mars Exploration Rovers since they landed on the red planet in 2004. On occasion, the European Space Agency's Mars Express may also serve as intermediary.
The rover has two other antennas for communicating directly with Earth, similar to those used on the Viking landers in the 1970s, the Pathfinder mission in the 1990s, and the Mars Exploration Rovers. One is the Low-Gain Antenna, the other the High-Gain Antenna. Both are similar in appearance to satellite television dishes but transmit signals at much higher frequencies known as X-band frequencies. These higher frequencies can transmit more data in the same amount of time using smaller, shorter wavelengths, but the transmissions must be more narrowly focused to be received at the other end.
The Low-Gain Antenna, transmitting broader, less focused signals, serves as the rover's primary link to Earth for the first several sols, or Martian days, after landing. These signals spread out as they leave the antenna, so that no matter which way the antenna is pointed, the signal will reach the Earth. Once mission controllers have determined the rover's precise location and attitude -- that is, which way its various parts are oriented relative to the Sun and Earth -- they will switch communications to the High-Gain Antenna. The High-Gain Antenna sends a more efficient signal focused directly at Earth, to be detected, like all transmissions from Mars, by NASA's Deep Space Network of antennas.
Another way the Mars Science Laboratory rover can communicate is via the Electra experiment on board the Mars Reconnaissance Orbiter. Electra has a very important role in helping determine the precise location of the rover as well as any other spacecraft on or above Mars.