However, three possible solutions are emerging. The first is the logical reduction of repetitive data transmission, with mission project managers being a lot more thoughtful when it comes to deciding
However, three possible solutions are emerging. The first is the logical reduction of repetitive data transmission, with mission project managers being a lot more thoughtful when it comes to deciding exactly what information needs to be transmitted. The second is to pour more money into developing increasingly autonomous, self-navigating spacecraft, thus reducing the amount of data that needs to be transmitted at all. The third, and most interesting, is to make the change from the current default S-Band (2GHz) and X-Band (8GHz) frequencies to the higher frequency Ka-Band (32GHz). Essentially, the higher the frequency, the more data you can move, so the move up to Ka-Band would mean four times as much data transmitted in one-quarter of the time of X-Band. As previously mentioned, the Cassini mission is already using Ka-Band, as was the Mars Polar Lander, but perhaps the less said about that the better.
Unfortunately, there are no plans for its widespread use in the immediate future because it is harder to use, requiring more accurate tracking and pointing. The lure of being able to cram more missions into the available bandwidth is compelling, though, and the JPL is expected to be making regular use of Ka-Band within the next five years or so.
Being Internet obsessed, as I am, I prefer to think that there could be yet another answer to the problems of future off-planet communications,
namely an IPN (Inter-Planetary Net). NASA, together with some impressive names in the network business including the father of the Internet, Vinton Cerf himself, are already working hard to extend the Internet into outer space. Although the timescale isnt exactly imminent, Cerf has been quoted as saying that he hopes a stable interplanetary backbone could be in situ by 2040. Its certainly within sight, with funding coming from both NASA and the DARPA (Defense Advanced Research Projects Agency) Next Generation Internet project. In addition, one has to expect private sector commercial funding to enter the equation, and that combined with the rate of developing technological advance means that the 40-year plan could easily be cut short by a decade or two in reality.
Indeed, plans are already afoot to wire up the first planet in the network -
not surprisingly, that planet will be Mars. A team of scientists and engineers are working at JPL on a scheme to circle Mars with a constellation of navigation satellites, at least six in the first instance, that will act both as a Mars version of a GPS (Global Positioning System) and as communications relays. The hope is that such a system could enable a near-constant communications stream
between Earth and Mars at a data rate of an average 11,000bits/sec - fast enough to support the sending of a high-resolution panorama of the planet every day. With the first multipurpose spacecraft that could carry such satellites due for launch in 2003, and missions planned for every two years following, the clock is most definitely ticking.
A perfect example of why communications systems will play such a vital role in achieving this aim was the Mars Pathfinder mission. The atmosphere of Mars meant that only limited sunlight could reach the solar panels of the spacecraft, and therefore produce the power to send signals back to Earth. Whats more, the communications signals took some 11 minutes to travel back to this planet, limiting productivity of the mission rover, Sojourner. If Sojourner hit a rock or some other obstacle it would have to wait for further instructions before moving on, a wait that could often take up to a day.
On a 90-day mission, if each of the mission rovers moves took as long as this, it wouldnt take a genius to realise it could soon develop into a logistical nightmare. Indeed, with data being transmitted from Pathfinder to Earth at a rate of just 300bits/sec, the data from a $US150 million mission would be hard pressed to fill your average desktop PCs hard drive. So the move has to be towards automated, robot-driven missions, and communications technology will be at the heart of their success. Taking the somewhat broader view, if truly useful interplanetary exploration is something thats to be taken seriously in the future, such a communications infrastructure is imperative.