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

[Paulo Nuno]

Em 09/10/2013 13:03, "João Costa &gt; CT1FBF" <ct1fbf  gmail.com> escreveu:

>   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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