As NASA gears up for the major investments in the hardware and other technology it will need to send astronauts back to the Moon and on to Mars, the agency also must set aside funding to overhaul and expand its communications infrastructure.
The Deep Space Network (DSN), a series of giant dish antennas at three locations across the globe used to communicate with deep space probes, is roughly 40 years old and becoming increasingly expensive to maintain, NASA officials say. At some point, the agency will have to decide whether it can continue to pay those bills or replace the antennas with large arrays consisting of hundreds of smaller dish antennas, these officials said.
To maintain communications with its low- and medium-Earth orbiting spacecraft, NASA relies on the Tracking and Data Relay Satellite System (TDRSS) , which currently consists of nine geostationary-orbiting satellites ranging in age from three to 22 years. NASA will have to begin launching its next-generation of TDRSS satellites sometime between 2012 and 2016, according to John Rush, navigation and communications systems architecture manager in NASA’s Space Operations Mission Directorate .
NASA also will need communications infrastructure in places where currently there is none, potentially including lunar orbit, Rush said. And while NASA and the European Space Agency have spacecraft orbiting Mars that serve as relays for the rovers now operating on the martian surface, far more advanced systems will be needed as robotic exploration of the red planet intensifies.
Rush is leading NASA’s Space Communications Architecture Working Group, which is examining NASA’s space communications requirements out to the year 2030 and identifying architecture and technology options for meeting them. He and some of his NASA colleagues offered a snapshot of where NASA is and where it needs to go in this regard May 31 here at the International Satellite and Communications Conference and Expo, a three-day event sponsored by Hannover Fairs USA Inc.
The working group, Rush said, has identified four major challenges that lie ahead for NASA on the communications front: sustaining existing capabilities, including the DSN and TDRSS systems and other ground-based infrastructure; establishing new capabilities as dictated by the exploration missions NASA chooses to undertake; developing technologies and systems for transmitting data at higher rates over greater distances; and deploying a system that NASA’s international partners can readily plug into.
The shelving of the ambitious Jupiter Icy Moons Orbiter and delay of some planned Mars missions have somewhat eased the urgency of upgrading the DSN. Nonetheless, the aging system will not be able to handle the streams of data that will be coming from the increasingly sophisticated science and exploration missions NASA is likely to launch over the next couple of decades, according to Les Deutsch, chief engineer at the interplanetary networks directorate at the Jet Propulsion Laboratory, the Pasadena, Calif.-based-field center that manages the Deep Space Network and builds and operates spacecraft for NASA.
NASA officials who spoke at the conference were in agreement that the best way to upgrade the DSN is to replace the current 30- to 70-meter diameter dishes with arrays of hundreds of dishes roughly 12 meters across to create a single giant aperture.
“That’s the way to go,” Deutsch said. By using this approach, he added, NASA could take individual antennas off line for maintenance or repairs without affecting the larger system.
NASA has to decide whether to continue putting money into the existing DSN infrastructure or go with the arrays of smaller antennas, said Stephen Lichten, deputy manager of the telecommunications division at the Jet Propulsion Laboratory, which manages the DSN. “I think it’s going to be the latter,” he said.
A handful of contractors have expressed interest in doing the work, Lichten said. One company, Patriot Antenna Systems of Albion, Mich., is building a prototype 12-meter antenna that is expected to be delivered in June, he said.
The three main DSN antenna complexes are located roughly 120 degrees in longitude apart in California, Spain and Australia. Lichten said the new arrays, each consisting of some 400 12-meter antennas, might be located at different sites to take full advantage of the different frequencies they might use.
In general, NASA is likely to increasingly exploit the Ka-band portion of the radio frequency spectrum for its communication needs , agency officials said. For example, the next generation TDRSS system likely will utilize Ka-band frequencies, said Phil Liebrecht, program manager of the Space Communications Program Office at NASA’s Goddard Space Flight Center in Greenbelt, Md.
Laser-optical communications technology also will be exploited, especially as activity at Mars intensifies around the beginning of the next decade, NASA officials said. Because of the great distances and high data rates that will be involved, laser-optical communications really begin to make sense at Mars, said Rush.
One of the pathfinders using optical telecommunications at the red planet is the Mars Telecommunications Orbiter, which is scheduled to launch around the decade. That mission’s payload suite includes the Mars Laser Communications Demonstration, NASA officials noted.
NASA officials also are looking at options to facilitate communications to and from the far side of the Moon, a possible landing site for future astronauts, Rush said. Currently that capability does not exist, he said. Options include a ground-based antenna near the Moon’s south pole and a lunar-orbiting relay spacecraft, he said.
Rush said the cost of the infrastructure deployment and upgrades he and others described at the conference would be consistent with historical spending rates on NASA communications systems in relation to the activities that rely on them.