"RVMJ" wrote in message
...

As the result of a deliberate manoeuvre, the Galileo spacecraft
collided with the planet Jupiter at an estimated time of 12:49:36 PDT
on September 21st this year. Signal had been lost at 12:43:14 pm as
Galileo passed behind Jupiter at a height of 5768 miles. Descent angle
was 22 degrees and the impact speed 108,000 mph, a little more than
the 106,500 mph of the Galileo probe, which entered Jupiter's
atmosphere in December 1995.

Galileo's transmitter had an output power of between 15 to 20 watts to
an antenna having 7 db of gain. Received power at the Deep Space Net
was -167 dBm.

The DSN receivers track frequencies with extreme precision. The
frequency gate for Galileo was normally about 0.3 Hz for a carrier
frequency of 2295 MHz, but could be widened to 3 Hz for a moon flyby
or planetary impact.

Normally, Galileo put all the transmitter power into data sidebands
plus or minus 360 kHz from the nominal carrier. This is called
suppressed-carrier working, or a modulation index of 90 degrees.
However, a pure-tone carrier would be less-difficult to track near
impact, so 5.5 hr before impact the modulation index was shifted to 60
degrees. This has the effect of putting more power into the carrier at
the expense of that in the data sidebands.

Four hours before impact the data rate was changed from 20 bps to 32
bps in order to gather as much science. However, Galileo's engineers
noticed that their real-time displays had stopped working.
Wide-spectrum recorders had captured the raw signals, and the
engineers are now using special decoders to find the data, which is 5
dB below the noise level. Obviously a bunch of Amateurs.....NOT.


And all without Gareth's "Big K" ;-)

--
73
Brian
G8OSN
www.g8osn.org.uk
www.amateurradiotraining.org.uk for FREE training material for the UK
Foundation and Intermediate Licences
www.phoenixradioclub.org.uk - a RADIO club specifically for those wishing
to learn more about amateur radio