|Established on 1963 December 24, the Deep Space Network (DSN) has played an integral role in science and exploration from the beginnings of the space program. Receiving the data from the robotic Ranger spacecraft, the DSN helped provide the first high resolution images of the surface of the Moon, the first human exploration target. During the Apollo program, the DSN downlinked both a wealth of scientific data and provided the critial communications with the astronauts. Later, the Goldstone radar observations helped provide early indications of water in the lunar polar regions, an observation subsequently confirmed by the LCROSS mission.
Today, the DSN continues the tradition of providing science measurements and advanced reconnaissance for robotic and human missions. Radio science links between spacecraft and the DSN are used to probe the atmospheres, gravity fields, and interior structures of bodies, and the Goldstone radar system is used to measure the rotation rates, sizes, shapes, surface features, and precision orbits for asteroids. Highlights of the precision of radio science measurements include recent results from Mars Express-DSN links and the GRAIL mission. During recent Mars Express close fly-bys of Phobos, radio science measurements on the Mars Express-DSN link indicate that the interior of Phobos is highly porous and suggesting that this Martian satellite re-accreted in place. The GRAIL mission used both spacecraft-spacecraft and spacecraft-DSN links to provide an unparalled gravity field and near sub-surface structure map of the Moon. Highlights of Goldstone radar observations include the asteroid (101955) Bennu, which is the target of the forthcoming OSIRIS-REx mission, and imaging and precision orbit determination of the close-approaching asteroids 99942 Apophis and 2012 DA14.
Looking toward the future, the existing suite of science measurement techniques both will continue and is likely to expand with higher resolution radar imaging and the inclusion of laser communications. In addition to even higher precision link science to spacecraft for probing interior structures, the laser communication infrastructure is likely to allow ``opportunistic'' use of laser ranging to the Moon and other bodies in the inner solar system.
Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics & Space Administration.