ARLA/CLUSTER: NASA reforça pedido de participação aos radioamadores na missão Juno em 10m

[João Costa > CT1FBF]

  SAY “HI� TO JUNO EVENT BEGINS IN 6H00
NASA's Juno mission is inviting amateur radio operators around the world to
transmit a coordinated message on the 28 MHz band to the Juno spacecraft

NASA's Juno spacecraft will fly past Earth on October 9, 2013 to receive a
gravity assist from our planet, putting it on course for Jupiter.

To celebrate this event, the Juno mission is inviting amateur radio
operators around the world to say "HI" to Juno in a coordinated Morse Code
message. Juno's radio and plasma wave experiment, called Waves, should be
able to detect the message if enough people participate.

Juno will have a better chance of detecting the signal from many operators
if the signal is spread out across the spectrum. The Juno Waves instrument
is a broadband receiver, and the detector being used for this event has a
band width of 1 MHz. It is better for detection of the signal to have a
broadband signal coming in.

For this experiment, we would like to ask those participating to spread out
in frequency across the 10 meter band. We have supplied a table of
suggested frequencies between 28 and 29 MHz, based on the last letter of
your call. When the HFR receiver is tuned to 28MHz, the center frequency is
28.5 MHz. A 50 kHz high pass filter limits low frequencies hitting the
detector, so the frequency table excludes 28.5 MHz ±50 kHz. The natural
signals we expect to measure at Jupiter will consist of a large number of
discrete tones, so spreading the signals out in this manner is a good
approximation to the signals we expect to detect. But at Jupiter, we don't
expect to be able to decode CW in our telemetry!

The 28 MHz band was chosen for this experiment for several reasons. The
Waves instrument is sensitive to radio signals in all amateur bands below
40 MHz, but experience with the University of Iowa instruments on the
Galileo and Cassini earth flybys shows significant shielding by the
ionosphere at lower frequencies. As sad as it sounds, we hope for lousy
band conditions on October 9, so an appreciable fraction of the radiated
energy escapes the ionosphere into space, and is not refracted back down to
the ground somewhere else on the planet.

Juno's antenna consists of a pair of tapered 2.8 meter long titanium tubes,
deployed from the bottom deck of the spacecraft under the +X solar array
and magnetometer boom. A high impedance radiation resistant preamp sits at
the base of the antenna and buffers the signals from 50 Hz to 45 MHz. The
elements are deployed with an opening angle of about 120 degrees. Ten
meters is above the resonant frequency of the antenna and NEC analysis
indicates a lobe generally along the spin axis of the spacecraft. This will
be good for detection on the inbound part of closest approach to Earth.

The Waves instrument uses four receivers to cover the frequency range of 50
Hz to 41 MHz. Signals up to 3 MHz are bandpass filtered, sampled by A/D
converters and FFT processed into spectra using a custom FFT processor
developed by The University of Iowa under a grant from the Iowa Space Grant
Consortium.

Please join in, and help spread the word to fellow amateur radio
enthusiasts!

NASA - Say "HI" to Juno!
http://www.jpl.nasa.gov/hijuno/

See How do I participate ? for the frequency list.


[image: transmit frequency table]
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