As one of three stations (along with sites at Goldstone in the Mojave Desert, 200kms north of Los Angeles, and Robledo, 60kms west of Madrid in Spain) forming the Deep Space Network (DSN), the Canberra Deep Space Communication Complex (CDSCC), is responsible for maintaining Earths' links to distant spacecraft.

Engineers, here, have developed a new technology for receiving and sending greater amounts of radio data from multiple spacecraft simultaneously, on just one antenna. They have also developed a new system for automating the pre-calculation process that must be made prior to tracking and 'talking' to each craft.

"Over the years, it's been a case of one antenna, one spacecraft, to receive in a single signal frequency, coming from what ever planet or spacecraft we're talking to", says Glen Nagle, Manager, Education & Outreach, for Raytheon Australia, which provide operations and maintenance to the NASA site.

"A new system that was developed here now allows us to split the signal, being able to bring in two signals simultaneously. A lot of the spacecraft are in the same general location, so if you've got two spacecraft in orbit around Mars, you could bring in both of those signals, and have a software system that could split those signals to recognize them as two separate frequencies."

The system is known as MSPA, or Multiple Spacecraft Per Aperture. It continues to be developed and tested, and eventually DSN controllers will be able to communicate with three spacecraft simultaneously, receiving signals from two, and being able to transmit to a third, or receive from three, and so forth.

This increases the capacity of the antennas, so that as more and more spacecraft are launched, rather than having to build more antennas, antennas will have the capability, instead, to talk to more spacecraft at the same time.

"Every scientist would like us to talk to their spacecraft 24 hours a day, 7 days a week- but you can't do that, because you've got lots of other spacecraft you need to talk to, so to give them maximum coverage, you need to talk to more than one at a time- and that's the system were developing here", says Nagle.

Another system developed at CDSCC that has made operations more efficient is called TSA2 (Telemetry Simulation Assembly 2), which concerns the time taken to reconfigure an antenna, and radio translation software, each time tracking for a spacecraft commences again.

"It's like building up a little computer database � to put together the antennas, and the individual components that each mission will need- whether it's a set of receivers or transmitters, or mechanical systems that are needed to move an antenna to a specific point to track a particular object- you build up this on a computer, like Lego blocks, dragging and dropping in each component, and then saying "well, that's set up, that's the system we need for communication, to translate from the spacecraft to the antenna to the systems, to translate it, process it, and then send it off to NASA", says Nagle.

"And that's different for every spacecraft, and it takes time, to set up each of those things- all the pre-calculations that need to be done. Anything that will help to streamline that, and to make it quicker and easier to do, is just better, in terms of efficiency. So this is another system were developing", Nagle continues.

Operators at CDSCC have been training for two years for the Huygens mission-set to begin on January 14- which will require some unique configurations of the Network.

"Cassini is going to be at an interesting angle- there are some interesting communication challenges brought up by just where Cassini will be at the time its transmits back to Earth, in relation to Titan, and in relation to the spacecraft and the Saturn and Earth positions."

"When the spacecraft was sent out they realized fairly soon that the angle that they're going to be communicating at, is going to present some interesting Doppler shifts in the signal; the speed , direction, and distance of the spacecraft makes it slightly more challenging to receive those signals, because the frequency will shift."

"Scientists knew these weren't the most favourable conditions you could put Cassini on, but for the mission it's the only way you could do it," says Nagle.

The Cassini signals received from Saturn are only at a twenty billionth of a watch battery power type of energy, or minus one hundred and eighty micro decibels signal strength. With such weak signals, Nagle says CDSCC still has 99.997% accuracy with the data it sends and receives from Saturn.

"We are absolutely ready for this. There were unique communications challenges when we arrived at Saturn, keeping communications with the spacecraft as it flew through the rings, past the planet, and as it came out the other side, but it all happened like out of a textbook".

Among the 35 spacecraft that Canberra DSCC tracks, and talks to daily, are Voyager 1 and Voyager 2, which have been out in space for 27 years.

"They still return amazing information, says Nagle. "Nobody expected Voyager to last this long. They were designed to last maybe seven years. It's getting to explore a region of space we never thought we'd get to this early, where the influence of our sun runs out, where from Voyagers' point of view of our sun will be indistinguishable from any other star that's out there".

"We believe we'll still have contact with Voyager up to about 2020, and then its transmitter simply isn't strong enough any more to transmit, and it will disappear behind the background noise generated by the universe, and all the other stars out there."

"Voyager will travel a long away from our planet, reaching the next closest star in about one hundred and fifteen thousand years from now. So it's got a big voyage ahead of it, and in the meantime we have our voyage in the solar system to continue with".

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NASA's Deep Space Network
Raytheon Australia
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