ESA to Give New Life to Old Satellites

JPNews writes "The European Space Agency is designing a program (www.esa.int) to re-configure dying television transmission satellites to be used as a XM Radio-like satellite radio network. 'Once in position, 35,000 km away in space, TV satellites will remain in orbit forever, but their useful life amounts to 15 years or less... further life can be squeezed from a low-propellant TV satellite switched over to mobile digital radio broadcasting where precision position control is less important.'"

Comments

A Primer on the ESA

[use_compress]

from: http://www.space.com/news/spaceagencies/esa_25year s_000602.html
However, ESA's biggest achievement of all, explained Bonacina, lies not in any one particular space project. Rather, it's the fact that 15 European nations have successfully worked together, and in cooperation with other non-European space programs, to reach a common goal.

It's amazing how little a program this wide in scope accomplishes :)

Just when you thought it was safe

[Anonymous Coward]

Dammit. Where'd I put my tinfoil hat.

To summarize

[mlyle]

Most older communications satelites have what are called "transponders"-- they take everything that comes in on a certain band of frequencies and plays it out on another set.

Because usually relatively high-bandwidth analog signals with high quality requirements are sent through these transponders, and the satelites have a relatively small amount of output power, high gain antennas (big satelite dishes) are required to recover the signal, which must be very precisely pointed.

By using digital signals and audio compression technology, suddenly the signals can be narrower bandwidth. Noise is proportional to bandwidth, and since the signal is narrower, signal/noise ratio is improved. This means high-gain antennas may no longer be strictly necessary, and thus the position of the satelite becomes less critical as the orbit decays.

Note that this does not lock us in to a proprietary standard-- if the spectrum is allocated for this purpose, smarter digital transmitters can be put into space for the same purpose later.

Still important is attitude control-- the satelite's antenna must be pointed down and the solar panels pointed in a useful direction. But this often uses gyroscopes, reaction wheels, and magnetic systems-- which do not use propellant.

Finally, battery life is a question. No communications satelite is constantly receiving solar power, so if the satelite is operated while not in view of the sun, batteries on the satelite discharge. Satelites can withstand a limited number of charge cycles before they fail, and this is likely to form the true upper bound on satelite lifetime.

In all, it's a good idea. I imagine we'll see lots of clever ways to emerge on how to use legacy hardware we've put in space, as launch costs remain so expensive.

Amateur Radio

[sQuEeDeN]

It would be quite cool, depending on the frequencies, if they could open the sattelites up to hams. There are a few sattelites here and there available for amateur use, but something launched by the ESA is probably waay cooler.
Of course, this all depends on the ability of them to switch which frequencies the sattelites use--I imagine they weren't originally designed to use Ham frequencies. As for "sloppy" orbits, we hams typically have fairly sophisticated tracking equipment: a 486 pc, running any one the free tracking wares, connected to a dual-axis antenna rotator. Makes it a challenge!!