Say “Hi” to Juno! The NASA spacecraft en route to Jupiter

The 9th of October will be a special day for amateur radio operators around the world. NASA, the US space agency, will promote an unprecedented event in tribute to the many contributions in the field of space exploration during the past several decades.

The Juno spacecraft, traveling to Jupiter, will make a transit around the earth and NASA has asked for our assistance in taking part in a fascinating experiment.

Before going into the details of the event, we’ve been asked to focus for a moment on Juno’s mission and turn to the expertise of a passionate amateur astronomer and physics student, Simone Garrappa:

“Juno, certainly one of the most interesting NASA missions in recent years, is in fact part of a series of missions grouped in the “New Frontiers” program, which includes highly specialized missions in the exploration of the solar system with a moderate cost (less than 700 million) in respect to expenditures which required of a space mission. The goal will be to closely study the planet Jupiter, thanks to eight sophisticated instruments that will allow Juno to conduct experiments related to the magnetic field, gravitational field and on the chemical and the dynamics of the atmosphere of the planet.

The Juno spacecraft was launched August 5, 2011 and on October 9, after more than 2 years, will be involved in a close pass to our planet, to make a “maneuver” incredibly fascinating. If we have in mind the structure of our solar system, observing the orbits of the planets around the sun, we see immediately that the star of the incredible gravitational pull exerted on them, the same is true for any body in this system.  So, for a probe traveling from the earth to Jupiter, it would need an enormous amount of energy for the engines, which automatically translates into huge costs. And it is here that the charm of the flight plan of the Juno spacecraft, where the most convenient route does not match that of the shorter one..

From the scheme provided by NASA in the figure, allows ua toretrace the various stages of trajectory carefully analyzed by experts of the agency. The probe, after the launch, started to follow an orbit that led it to a distance greater than that of Mars. And August 30th and September 3rd of last year, two “deep space maneuvers” were carried out, during which the main propulsion unit of the probe was put into operation for 30 minutes in order to correct the trajectory and make sure that the next October 9 flyby would happen, during which the probe will perform a maneuver commonly referred to as a gravitational slingshot (also known as gravity assist) to take advantage of the gravitational pull of a nearby planetary mass utilizing its speed and the motion of revolution around the sun to then be accelerated to tremendous speeds. It is not the first time  this maneuver has been used. The first spacecraft to use it to achieve a secondary objective using the planet Mercury. Mariner 10 utilized the gravity assist of Venus. The probes of the Pioneer Mission, Voyager and Ulysses, sent to explore the boundaries of the solar system, have carried out these maneuvers as well. Thus this technique is very useful, which will allow Juno to reach, as planned, the planet Jupiter, on July 5, 2016.. Juno will then remain in orbit for about a year and then plunge into the atmosphere of the planet.

Just what will the scientists be doing during this long period of space travel to reach the planet?  First of all, during the close encounter they will have the opportunity to check the status of the instruments on board,and during the journey scientists will verify that the probe meets the expected trajectory. And why not conduct some useful experiments during the trip, while waiting for Juno to reach its final goal, that of the exploration of Jupiter. “

 

This transit across of the face of planet earth marks the real start of the mission with NASA wanting to dedicate this particular moment to the worldwide amateur community.

On board the probe are to be found specially designed receivers, developed and assembled by the University of Iowa Department of Physics and Astronomy for the study of radio and plasma waves emitted by Jupiter. In this context we should specify that the region of Aurore Jupiter emits signals on decametric HF bands. It’s for this purpose that these receivers have been developed for the express purpose of studying this phenomenon.

These receivers constitute the entire equipment lineup for the so-called “Waves Instrument.” Let’s take a detailed look at two identical HFR receivers (High Frequency Receiver). They are broad spectrum receivers capable of receiving from 3MHz to 41MHz in 38 steps. Each step is 1MHz with each single conversion receiver capable of selecting seven different filters on the front end depending on the sampled frequency bands; a quadrature mixer allows to obtain two IQ output channels followed by a low pass filter at 500Hz to get a 1MHz bandwidth. This type of analysis will subject the entire emission spectrum of Jupiter to its RF probes..

The second copy of these receivers play a backup role when at its destination. However, as the spacecraft passes in front of the earth, the receiver will be assigned a different role: it will be the HFWBR (High Frequency Wideband Receiver), which will be centered on 6.25MHz and will tune in terrestrial broadcast stations. This test will be used to study the ionosphere and terrestrial emissions into the universe. A similar test will be provided us by using the first amateur radio receiver!

The experts who have worked on the project have chosen the 10 meter band, a decametric band less subject to the ionization of the ionosphere, to test the receiver HFR as relating to its broadband characteristics. All of us are invited to submit, during the passage of Juno, a greeting in CW to the spacecraft. A table of frequencies in the CW portion of the band  of 10 meters was created and a specific frequency is assigned  to every amateur radio operator depending on the final letter of your call.

In order to transmit a message, precise rules must be followed: first, to keep the clocks of the station synchronized with a standard time, the message must be “HI” or 4 points (H) followed by 2 points (I) in Morse code. Of course, according to national and international regulations, you need to anticipate and follow the message with your call. The speed, if we can call it that, should be 30 seconds per element, 1/25th word per minute; basically you can use this pattern:

So Each greeting will last ten minutes. Our call will be repeated between two messages at higher speeds!

In the position closest to earth, the distance of Juno will be 50,000Km, not a small distance; any amateur who wants to participate will have to follow the orbit of the spacecraft to capture the best angles, considering the characteristics of its antennas. We hope, however, for relative low solar activity, so that there is less possible ionization of the ionosphere. As absurd as it might seem at first, we need that there be no propagation in order to get our signals through the atmosphere and out into space.

It will not, therefore, be a simple experiment, but for this reason the incentive to participate is certainly more compelling. Our very own signals will be part of a NASA space experiment, nice recognition to hams around the world! And don’t forget to ask for the special QSL card by sending an e-mail within one month following transit of the spacecraft to: juno_outreach@jpl.nasa.gov; at the same address you can ask questions regarding the event.

Further information and additional details are regularly made available via Juno’s official website: http://www.jpl.nasa.gov/hijuno/.

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