With four spacecraft from three space agencies on the way to Mars, a communications crunch at the Red Planet is hardly unexpected. But managers of NASA's Deep Space Network (DSN) believe they are ready to handle the traffic.

"We've made all of our transmitters uniform to spread the [communications] load out better," said Rich Miller, manager of Office of Plans and Commitments NASA's Jet Propulsion Laboratory in Pasadena California. "And we're perfecting a way to track the Mars missions in particular." Miller's office is part of JPL’s Interplanetary Network Directorate responsible for the DSN.

Ground controllers are using two DSN tracking stations - one in Goldstone, California and the other in near Madrid, Spain - to communicate with the Mars-bound spacecraft. The European Space Agency (ESA) expects its Mars Express probe and lander to arrive in December, closely followed by Japan's Nozomi orbiter and later by NASA's twin Mars Exploration Rovers (MERs). ESA and Japan are using some of their own ground stations to track their missions, which may alleviate some DSN traffic.

Miller told SPACE.com that most of the current space missions, Mars included, are using X-band radio waves for at least part of their communications systems. X-band signals are high-frequency waves in the eight gigahertz range, much higher than those you hear out of your FM radio.

ESA's Mars Express, an orbiter that also carries the British landing probe Beagle 2, is expected to reach the Mars sometime around Dec. 25. Like the other Mars-bound probes, Mars Express is using the DSN as its communications lifeline with Earth. It is not, however, ESA's only means of deep space communication.

Earlier this year, the agency unveiled its first dedicated deep space tracking station in Australia, a 114-foot (35-meter) dish set up in New Norcia about 93 miles (150 kilometers) north of Perth.

"The Europeans have really expanded their space communications capabilities," explained space scientist Everett Gibson of NASA's Johnson Space Center. Researchers with the Jodrell Bank Observatory in the United Kingdom will also try and pick up Mars Express signals, adding to the ESA and DSN efforts, Gibson added. Gibson was chosen by ESA to work with Beagle 2 as the sole U.S. interdisciplinary scientist on the Mars Express mission.

Meanwhile, ESA officials are building a second tracking installation, dubbed the Cebreros ground station, just outside Avila, Spain, which should be operational by September 2005. The Cebreros and New Norcia installations are the are the beginnings of worldwide European version of the DSN, they added.

ESA's communication efforts won't just benefit Mars Express either, Gibson said. The improvements are also meant to prepare for future missions like Rosetta and Venus Express, the direct descendant of Mars Express, set to launch in 2004 and 2005, respectively.

The boxy Mars Express, ESA's first planetary probe, uses a (40-centimeter) low gain antenna for near-Earth communications. Once the probe reaches Mars, it will send and receive data or instructions with the 5.2-foot (1.6-meter) antenna taking up a full side of the cube-shaped craft.

Unlike Mars Express, Beagle 2 cannot communicate directly with Earth and will relay signals via the orbiting Mars Express and the aid of two NASA satellites, Mars Odyssey and Mars Global Surveyor (MGS), already circling the planet. Once Beagle 2 lands on the surface of Mars' Isidis Planitia, for example, it will begin broadcasting a nine-tone call sign composed by the rock group Blur until Odyssey receives and relays it back to Earth.

Communication with the Nozomi space probe is primarily handled through the Usuda Tracking Station in Japan, a 209-foot (64-meter) antenna that receives the spacecraft's X-band and S-band transmissions.

"When they can't receive it, which is about one-third of the time, we use [DSN's] Goldstone or Madrid antennas," explained Albert Chang, Nozomi telecommunications and mission systems manager

Nozomi researchers said scientific data has taken a back seat to tracking information since the April 2002, when a solar flare crippled its power supply and rendered it unable to control its temperature or send telemetry.

Controllers have been using signals from the craft's ON/OFF radio beacon to receive telemetry and control the craft, said professor Ichiro Nakatani, Nozomi project leader, in an e-mail interview. Power system repairs have been underway since July and should be completed by November, he added.

Nozomi should swing into Mars orbit sometime in mid-December, though Nozomi managers have agreed to wait awhile before they start using NASA's DSN for communication.

"We know there's going to be a high contention for communication time," Chang told SPACE.com. "So until Mars orbit insertion we will be doing almost nothing."

Rounding out the Mars mission mayhem are NASA's two identical MER rovers, Spirit and Opportunity, expected to land in January 2004. Both rovers contain two methods of communication, one for Mars-Earth messages and another for Mars-Mars orbit.

"In cruise and prior to arrival at Mars, the rovers use only the X-band system and broadcast with high and low gain antennas," said Matt Wallace, surface mission manager for Opportunity. Once on the Martian surface, the rovers can communicate with Earth directly with their onboard X-band systems, or up to MGS of Odyssey using a UHF antenna. "We get four chances to reach the orbiters each day; two for MGS and two for Odyssey," Wallace said.

Direct Mars to Earth communications will be reserved for critical MER mission data, such as rover health and engineering, as well as any information or images useful to the ground controllers planning out the next day's science mission. Data from science instruments and cameras, however, will be routed to Earth via MGS and Odyssey since they're not as time critical as ensuring the health of the rover.

The only drawback to relaying scientific data through MGS and Odyssey is the time lag, Wallace said. Direct Mars-Earth communications is only hampered by the time it takes light to traverse the millions of miles between the red planet and ground controllers, which only 10 minutes or so, he added. But going the MGS or Odyssey route will delay signals by as little as 90 minutes to as long as 24 hours because if the way each orbiter works and communicates with Earth.

But a communications traffic jam caused by a data flood from multiple Mars-bound spacecraft is preferable to steady stream from a solitary probe, Wallace said.

"It's true that DSN is going to have an awful lot of Mars assets to deal with this winter," he added. "But we hoped that we would be in this situation -- with all of our missions on the way -- and I think it will go just fine."