Planets

From this one can compute for the individual planets

Planet:	Mercury	Venus	Mars	Jupiter	Saturn	Uranus	Neptune	Pluto
Diameter	4240	10170	6750	142800	120800	47200	44600	3000	km
Distance	0.61..1.39	0.28..1.72	0.52..2.52	4.2..6.2	8.5..10.5	19.2	30	39	AU
Ω	22..4.2	660..17	59..2.5	440..185	7....4.6	2.1	0.77	0.008	10-10sterad
Flux (10GHz)	4.7..0.9	152...4	5.4..0.2	20..9.4	2.9..1.9	0.065	0.018	0.0002	Jy
(S+N)/N	0.001..0.0002	0.04..0.001	0.001..0.0001	0.004..0.002	0.0007..0.0005	0.000015	0.000004	0.00000004	dB

(Some of the surface temperateures are estimates only) The S/N ratios are computed for our 7 m antenna on 10 GHz with a system temperature of 150 K. They show that Venus and Jupiter are the best candiates, whenever they are closest to the Earth.

On 1 Jan. 2014 the Solar System offered a rather favourable situation: Jupiter would be in opposition to the Sun on 5 Jan. and Venus would pass through lower conjunction on 12 Jan.

Venus

	The Record of 25 Jan. shows the observational method: The 10 GHz antenna tracks alternatingly Venus for a while and a position nearby to measure the background from sky and receiver. The background level rises by about 0.2 dB within a quarter of an hour. The signal from Venus is only 0.03 dB above the background.
	The slow change of the background level can be filtered out by FFT, and one can determine the average signal from Venus ...
	The individual measurements show a good agreement with the predictions. Unfortunately, no flux calibrations could be done, but as the 10 GHz system has proven to be rather stable, one may assume that the system temperature kept close to 150 K.
	The 10 GHz radio flux perdicted for the next few years: Venus gets closest to us every 585 days, at about 0.3 AU. In the meantime it may go as far away as 1.7 AU. Hence the signal level varies over a large range, from 10 times that of Jupiter's to only one half.

Jupiter

The outer layers of the giant gas planet Jupiter consist of hydrogen and helium gas. Under the existing pressures and temperatures hydrogen acts as a liquid and is electrically highly conductive. The planet's rapid rotation (about 10 hrs period) then produces a strong magnetic field. Quite similar to the Earth, a large magnetosphere is formed which can deflect the charged particles of the solar wind. The volcanos of the moon Io eject gas, which is ionized by the solar ultraviolet radiation and forms a doughnut-sheped ring around Jupiter and supplies plasma which is trapped in the magnetic field as radiation belts, like the Van Allen belts of the Earth. The movement of Io in the magnetic field causes large currents to flow. These charged particles have to follow the magnetic field lines towards Jupiter's magnetic poles where they cause auroral emission in the upper atmosphere, like on Earth.

A picture taken in ultraviolet light by the Hubble Space Telescope shows the polar region of Jupiter with aurorae: they are produced by electrons which can only spiral along the magnetic field lines and thus are funneled towards the magnetic poles. Here they collide with the dilute gas of the upper atmosphere and excite the atoms to give off optical emission. Apart from the permanent auroral ring which may vary in intensity, there are emission spots linked to the Jovian moons. The brightest is associated with Io, whose sulphur volcanos eject gas which is ionized by sunlight and thus constitute a source of charged particles.

Aurorae are also accompanied with radio emission: Early in 1955 B.Burke and K.Franklin picked up on 22 MHz sporadic radio signals from Jupiter. After extendive observations it became clear that burst-type emissions occurred when a certain Jovian longitude faces the Earth. This indicates that the sources of these noise storms are fixed with respect to Jupiter's rotating magnetic field. In 1964 E.K.Bigg found that the location of the moon Io on its orbit also influences the probability of detecting radio emissions. The details of how the radio bursts are generated is not yet completely clear. The plot below summarizes the statistics of occurance of radio bursts.

Probability of Jovian decametric radio emission as a function of the central meridian longitude (CML) and the orbital phase of the moon Io (C.Higgins, 1966). While it is impossible to predict when a noise storm actually occurs, these data permit to predict when a storm would be detectable by a terrestial observer.

These radio bursts can be observed with rather simple equipment: NASA's RadioJove Project has produced a inexpensive receiver on 20.1 MHz, software to predict observability of possible radio storms, software to record and inspect observational data, and provides all the instructions for a successful operation.

However, one very important requirement to pick up bursts from Jupiter is to have a electronically quiet location: In a city or on a campus this is rather difficult, but observations of solar radio bursts are also possible with this equipment. Being located on a computer-infested site, during DF3GJ's operations Jupiter was never detected, but nontheless it provided a lot of interesting experiences and great fun!

	Since electrons can only move along or spiral around a magnetic field line, the energetic electrons from the radiation belts are forced on helical paths around the field lines, thereby radiating synchrotron radiation, in a broad spectrum from 100 MHz to 10 GHz. This radio image taken at 22 cm wavelength indicates the radiation belts in the equatorial plane ...
	... while the image at the shorter wavelength of 13 cm (2.3 GHz) already shows some thermal emission from Jupiter itself.

The spectrum above about 10 GHz is dominated by thermal emission from the planet and its atmosphere. Below this frequency there is a component of non-thermal emission from the magnetosphere, viz. the layers high above the planet, in which strong magnetic fields trap electrons and protons in radiation belts - as the Van Allen belts around the Earth. The electrons can only move on helical orbits around the magnetic field, producing the non-thermal synchrotron radiation.

Our Observations

	The observation of 21 Jan. shows that it is much more difficult, but still possible. The signal is only 0.015 dB above the background!
	FFT allows to get rid of the slow changes in the signal level ...
	The difficult measurements, the weather, and some problems with the receiver allowed only a few observations. The measured flux initally is significantly above the predicted level, but eventually appears to converge on it. Unfortunately no flux calibrations could be done, but as the measurements of Venus, done at the same time, agree well with predictions, and the 10 GHz system is known to be rather stable, it seems well possible that the observed discrepancies are genuine. Although one would not expect non-thermal emission reaching as far high up as 10 GHz, it might be possible that we caught the tail of a radio eruption. If this is a rare phenonmenon or if it does happen occasionally, only future observations will reveal.
	Predicted 10 GHz radio flux for the next few years: Since the distance varies only between 4.2 and 6.2 AU, the low level flux varies only by a factor of 2, due to the yearly movement of the Earth.