Enormous bowl-shaped antennas point into the desert sky nonstop every day, beaming commands or collecting data and images from unmanned spacecraft millions of miles from Earth.
Pictures from Mars. Directions to Saturn. An analysis of Jupiter's clouds. NASA's Deep Space Network, this planet's link to two dozen probes scattered throughout the solar system and beyond, is busier than ever. Perhaps too busy.
"When we look at the overall capacity of the network, we invariably have about 20 to 50 percent more requirements than we have the capacity," said Gene Burke, who oversees network scheduling at NASA's Jet Propulsion Laboratory.
Today's crunch is expected to be dwarfed by future demands as the space agency plans to launch 27 more missions by 2008. In an era of tight dollars, researchers are looking for ways to expand the overbooked system without losing a pricey probe or busting the budget with more $35 million antennas.
"We're trying to do it less expensively yet return even more exciting results," said Marc Rayman, deputy mission manager of the Deep Space 1 spacecraft.
The network stations, spread around the Earth so spacecraft can be tracked continuously, can detect signals at the edge of the solar system from a transmitter no more powerful than a light bulb.
One way to ease pressure on the network is to make spacecraft more self-sufficient. The Voyager probes launched in 1977 required daily contact with ground controllers. Cassini, which is now on its way to Saturn, normally needs only weekly contact.
The Deep Space 1 probe, launched in October, tested automatic navigation and artificial intelligence software. Both technologies could make future spacecraft less reliant on orders from Earth.
Researchers also are exploring ways to expand the network's capacity by packing more information into the signals.
Deep Space 1 included a radio that can transmit at a higher frequency than most of today's probes. The frequency, called Ka band, is expected to speed up communications by four fold over current transmitters.
Much of the research into expanding the network's capacity with Ka band is taking place at the Goldstone tracking station in California's Mojave Desert, where the antennas stand like massive exotic desert flowers.
The remote location shields the station from Earth-based radio interference, but the desert heat and wind also make it more difficult to point the antennas, which range from 36 feet to 230 feet in diameter.
Goldstone researchers are developing a system that would automatically adjust the antennas depending on wind speeds and temperatures.
Even with a capacity crunch, NASA has yet to lose a mission because of problems with the network, Burke said.
"All that massive amount of steel just has to move to an intricate level of detail when you talk about a spacecraft being out there," he said. "It's a really immense ask."