NASA Jet Propulsion Laboratory California Institute of Technology JPL HOME EARTH SOLAR SYSTEM STARS & GALAXIES SCIENCE & TECHNOLOGY JPL Email News RSS Mobile Video
Follow this link to skip to the main content
JPL banner - links to JPL and CalTech
left nav graphic Overview Science Technology The Mission People Spotlights Events Multimedia All Mars
Link to Mars for Kids
link to mars for students
link to mars for educators
link to mars for press
+ Mars Home
+ Rovers Home
link to the mission page
link to summary page
link to rover update page
link to the Month in Review page
link to mission team page
link to launch vehicle page
link to spacecraft page
link to mission timeline
link to communications with earth
Summary
Antennas Size and Strength
Preventing Busy Signals
Navigation
Special Signal Tones
Communication
X-band Radio Waves
How Fast and How Much Data
Communications With Earth

Preventing "busy signals"

The Deep Space Network (DSN) communicates with nearly all spacecraft flying throughout our solar system. Dozens of spacecraft are cruising in space, observing Jupiter, the sun, asteroids, and comets, and even more spacecraft are traveling to Saturn and the outer reaches of our solar system. The DSN antennas are extremely busy trying to track all of these space missions at once. The Mars Exploration Rover spacecraft must therefore share time on the DSN antennas. A sophisticated scheduling system with a team of hundreds of negotiators around the world ensures that each mission´s priorities are met.

During critical mission events, such as landing on Mars, multiple antennas on Earth and the MGS orbiter will track the signals from the spacecraft to minimize risk of loss of communication. During the landing operations phase on the martian surface, the Mars Exploration Rovers are expecting to utilize the Multiple Spacecraft Per Aperture (MSPA) capability of the DSN, which allows a single DSN antenna to receive downlink from up to two spacecraft simultaneously.

The rovers´ downlink sessions (when the rovers send information back to Earth) will generally be limited to a couple of hours at a stretch, with perhaps two downlink sessions per martian day (sol) per rover. MSPA allows only one spacecraft at a time to have the uplink, and it is expected that the rovers will command early in each sol (martian day) for roughly an hour each to provide the instructions for that sol's activities. The rovers share DSN resources with many other missions.

USA.gov
PRIVACY    |     FAQ    |     SITEMAP    |     CREDITS