RocketSTEM Issue #9 - October 2014 | Page 6

The Goldstone complex is located on the U.S. Army’s Fort Irwin Military Reservation, approximately 72 km (45 miles) northeast of the desert city of Barstow, California. Credit: Doug Ellison/NASA/JPL-Caltech An interplanetary communications network These giant dishes do more than act as a cell phone network for distant missions. Some are also active in mapping asteroids via radar as well as radio astronomy. Radar experiments in 1961 helped define the astronomical unit (the average distance between the Earth and Sun), a critical measurement used by astronomers. There is even science in the radio waves themselves. Changes in those waves transmitted back to Earth are helping scientists reveal the interiors of moons and planets and even test Einstein’s theory of relativity. DSN data types: • Tracking: Communication sessions start with an exchange of carrier waves between the antenna on Earth and on the spacecraft. Pure tones which are used to track the position, the lifeblood of engineers responsible for spacecraft navigation. Ranging data helps determine (within 1 meter) the distance to spacecraft. Doppler shift measured on the downlink carrier wave determines velocity within fractions of a millimeter per second. • Telemetry: Greek for “far off measurements”, telemetry is the digital engineering data gathered. Temperatures of key spacecraft parts, science data, as well as all those great images of places like Saturn and Titan from the Cassini mission and the surface of Mars from the Curiosity rover • Command: Orders sent to spacecraft. Instructions for new science or course corrections for spacecraft en route. • Radio Science: Signals change slightly as they pass through the atmosphere of a planet, moons, or the sun The Deep Space Network is our connection to space. Since 1963, it has directed NASA’s intrepid explorers on their journeys to the planets and all the way to the edge of our solar system, capturing their sights, sounds and discoverie. View the full-size infographic at our website. Credit: Kim Orr/NASA/JPL-Caltech 04 04 www.RocketSTEM .org