Unique Challenges
Communications for deep space missions are complicated by the extreme distances between the spacecraft and Earth, with lengthy intervals required for transmission and return of signals; a wide range of environments in which spacecraft must operate; and unusual navigation scenarios such as gravity-assist trajectories, aerocapture, and aerobraking. Locating the spacecraft's signal over vast distances, commanding the spacecraft, verifying that the transmission has been correctly understood, and receiving and decoding the faint transmitted signal are fundamental challenges the DSN must meet.
These challenges have become increasingly complex, with continuing needs for high capacity and new technologies. Because large portions of spacecraft resources are devoted to communications, spacecraft design affects the data results. Challenging new types of missions have been flown or are being developed - precision landing on or orbiting small bodies, studying cometary features during flybys, two or more spacecraft flying in formation for coordinated observations or interferometry, long-traverse rover missions, in situ studies carried out by spacecraft functioning individually or in networks, sample-return missions, long-duration studies of the outer planets, and exploration of largely unknown and extreme environments.
Meeting the telecommunications bandwidth requirements of high-resolution instruments returning information at unprecedented data rates is an essential need for the future DSN. Mission designers have moved to higher radio frequencies, which use a narrower, more focused beam to provide higher data rates. At the same time spacecraft designers have optimized and miniaturized spacecraft components. Additionally, the DSN is currently moving toward meeting Consultative Committee for Space Data Systems (CCSDS) international standards and is requiring new missions to be compliant with these standards. Looking further into the future, optical communications, using light instead of radio waves, hold the promise of even higher telecommunications performance.