Capacity challenged
Paul Hertz, senior scientist in NASA’s Office of Space Science, said the space agency, in collaboration with other nations, is investigating the feasibility of augmenting the DSN. Japanese, Australian, European, as well as Russian dishes are being reviewed, he said.
"We’ve recognized that we have a capacity challenge," Hertz said.
"There are two parts of the study. We want to identify any assets that might potentially be useful. Then, study what kind of investment is needed to make them compatible, not just with the DSN, but more importantly, to the spacecraft systems they have to be talking to," Hertz said.
An immediate concern is the crisis at Mars. That takes place in the November 2003 to May 2004 time frame, made all the worse by demands on the DSN by a bunch of non-Mars spacecraft.
"For the near-term, we need capacity in place to handle the over-subscription during that time period," Hertz said.
Banding together
Early electronic bandaging of the DSN is underway. A new antenna in Madrid, Spain is being built, for example. Also, some transmitters on existing dishes are being upgraded, not only allowing them to upload commands to various spacecraft but also to listen to more than one probe at a time.
In addition, JPL has come up with new navigation techniques that significantly reduce the amount of DSN time needed to query each craft to determine its exact whereabouts and velocity in the solar system, Hertz said.
Barry Geldzahler, program executive for space operations in NASA’s Office of Space Science, said shifting to higher frequencies is also being considered. Moving into what’s called the Ka-band offers a factor of four in capacity than now available, he said.
Geldzahler said that interlinking radio dishes on a worldwide basis is already in practice within radio astronomy circles. Scheduling and coordinating time on a spread out array of dishes, however, can be troublesome, he said.
"There’s a lot of ability to work these issues out if you start working them early enough," Hertz added.
All-for-one, one-for-all
There is a blossoming of new and large antennas, said Rich Miller, manager of JPL’s Office of Plans and Commitments responsible for NASA’s Deep Space Network.
Miller said the European Space Agency is constructing a big dish outside Perth, Australia. Also, France’s space agency, the Centre National D’etudes Spatiales, just gave a go-ahead to build a large antenna, planted in either Tahiti, Kourou, French Guiana, or perhaps in South Africa, he said.
The Italian space agency is building a giant dish on Sardinia, Miller said, mostly for radio astronomy work, but also capable of tracking spacecraft.
There’s a loud and clear signal evident from this sprouting of powerful dishes. "They have taken the decision to be spacefaring and to extend their spacefaring into deep space," Miller said. Being self-reliant also gives rise to independence from NASA’s DSN network, he said.
At the same time, NASA may be able to call upon these assets during a time of peak load, Miller said. Furthermore, in the event of a sick spacecraft needing tender loving care, a DSN dish goes down, or just providing backup to one another during critical maneuvers, the coordination of global antennas would benefit all concerned, he said.
Various groups are looking at technical and managerial practicalities for any all-for-one, one-for-all international Deep Space Network, Miller said. For instance, an International Operations Advisory Group, as well as an Interagency Coordination Group — each a confab of spacefaring countries — are now delving into a host of antenna networking issues. Another group, a Consultative Committee for Space Data Tracking has long wrestled with formats and standards for handling telemetry and commanding spacecraft, he said, and is now studying how best to extend links between control centers.
"We’re all in the same game today now that we’re all spacefaring," Miller said.
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