# Tag Info

9

@Arne is right in his answer about two things, that the most suitable frequency for Jovian amateur radio is 20.1 MHz, and that this is a 15 meter wavelength. However, the antenna can actually be half the wavelength, and amateur radio astronomers have had good results listening to all kinds of Jovian sounds, including detecting occultations of its many moons ...

8

Interesting idea. I think the answer is both yes and no -- yes with a manufactured dish but no in the crater's raw state. The Arecibo telescope sits in a natural crater, but adds a dish which has a couple of important things required by a radio dish: a radio-reflective surface a specific curvature, classically parabolic, but also shaped low surface ...

6

All electromagnetic radiation from a point source - which a normal radio transmitter is - propagates according to the inverse square law which means that the intensity of the signal is inversely proportional to the square of the distance. This happens on earth and in deep space equally. So this will mean that for any signal there will be a distance at which ...

4

The resolution/error box. Radioastronomy has always been hindered by the resolution, because it is inversely proportional to the size of the telescope and making larger telescopes (even with interferometry) is not always easy. No amount of modern technology can substitute for a large effective diameter. (When I say effective I'm including interferometry ...

4

I think the image you posted is not quite reallistic. On it, objects are just inverted from some radius on, while what you can expect from a real black hole seen from near enough is a combination of these: a) an accretion disc b) a companion being sucked c) Hawking's radiation d) X-Ray burst from the poles (really starting out of the event horizon) You ...

4

The StarGazers lounge featured a radio kit article for Jupiter radio astronomy. The same article is also featured over at the Radio Group of BritAstro. It seems that 20.1 MHz is the suitable frequency for amateurs observing Jupiter. I am far from being an expert for radio astronomy, but for a small source such as Jupiter, I would assume that you need a big ...

4

A parabola does indeed focus over a broad frequency range. The lower limit is determined by the dish diameter, the upper by the construction (mesh size, parabolic accuracy etc.). The collector placed at the focal point may be a simple dipole or other fixed frequency antenna, or more commonly, a waveguide that leads the collected signals to a low noise ...

4

The first thing to consider is that the area of a beam will, over long distances, diffuse. The best situation we can hope for is a diffraction-limited system, where this diffusion is minimized thus maximizing our received signal. That is, in theory we have a perfectly collimated transmission beam that neither diverges nor converges. In practice, we are ...

3

Since the astronomers are using radio telescopes and not optical telescopes, I'd like to point out why they are doing so - The centre of the Milky Way is a very dusty place. Wavelengths from the millimeter to optical get easily absorbed by all this dust, so it's very difficult to see the centre of the galaxy in the optical spectrum. But radio waves do not ...

3

The first thing to notice is that the Local Interstellar Cloud, in which the Sun is evolving right now, is a fairly diffuse region, with a typical density of about one to a few particles per cubic centimeters. Clouds with such low density are actually mostly atomic; as you can see on this plot (Snow & McCall 2006, adapted from Neufeld et al. 2005): It ...

2

1MW of transmitted power is very modest by RADAR terms, to give one example. Thus, you probably need to establish what exactly your professor means by "brightest" (may it be a specific wavelength or point in time, or some other definition). Otherwise, there's no reason to believe that Arecibo transmission was any special or outstanding from radio engineering ...

2

The pointing is not a fundamental problem with the suggested design: The suggested trajectory is designed to include a Sun flyby as the last flyby. This ensures an asymptotically radial trajectory away from the sun after the flyby, hence maintaining the pointing relative to the sun. The proper motion of the observed object may be some challenge, but the ...

2

2SB is Dual Sideband, as opposed to DSB - Double Sideband. Here are a couple of papers you might find relevant and interesting: a 2SB upgrade replacing a DSB a paper that mentions the advantages of 2SB over DSB

2

Could large craters on the moon be used as reflective lenses for radio signals? You'd have to line the surface with something reflective to microwaves, like a metallic mesh, or similar materials. Secondly, the shape of the crater is probably not quite ideal, so it would have to be adjusted a little, carved up a bit in various places. But it's a good ...

2

Tired light has been used as an explanation before, whereby light loses energy whilst travelling through space---a sort of drag effect. I don't think anyone actually supports it nowadays, though.

2

Take for instance radio, when listening to radio you gather static on the frequency. A passband filters the static which in turn provides a clearer signal. Objects radiate in multiple frequencies/wavelengths, for instance heat/thermal (infrared) and visible. Not all object radiate in a range of frequencies, humans for example can be seen well in infrared and ...

2

LOFAR does not go 'through the ionosphere' as it's ground based. Rather, it is able to receive signals from outside the ionosphere due to the very low frequencies involved. These frequencies (naturally) have very long wavelengths, which means that LOFAR must be very large to obtain a decent level of resolution. The number of antennae will affect sensitivity ...

2

Radio telescopes are frequently used to observe the births of stars and their planetary systems. The longer wavelengths are able to penetrate from beneath the envelope of gas and dust that shrouds any attempts to view these events at optical or infrared wavelengths. Unfortunately, the smallest angular resolution of a telescope goes as $\lambda/D$, where $D$ ...

1

Some radio telescopes have been used to observe young stars and protoplanetary disks, if that counts. Atacama Large Millimeter Array (ALMA): Though it's used for a variety of things, ALMA was used in late 2014 to observe a young star, HL Tau. Among the data gathered was information about HL Tau's circumstellar disk. It found a series of gaps in the disk. ...

1

You may be looking for the "water hole". See http://www.setileague.org/general/waterhol.htm.

1

Space is not quiet at all and is actually very noisy when listening via a radio telescope. There are many sources of radio emissions in the universe, with pulsars being a very common one. They can be quite interesting to listen when the signals are converted into sound frequencies we can hear. They range from slow clicks every few seconds to high pitched ...

1

No, except in the sense that national broadcasting and so on is regulated. Our location can be fixed, as you suggest, from simply looking at where the signals come from. Perhaps, though, you mean is it sent out "regularly" (i.e., at specified intervals). In truth we have been sending very powerful signals continuously into space since the dawn of the ...

1

See http://en.wikipedia.org/wiki/HALCA and http://en.wikipedia.org/wiki/Spektr-R. HALCA was a Japanese 8 meter radio telescope satellite used for Very Long Baseline Interferometry (VLBI) from 1997 to 2003. Spektr-R is a Russian 10 m dish launched into space in 2011 with apogee nearly as far away as the moon, and still going. So, yes a radio telescope in ...

1

Ashley's comments are all fine. I'll add that homogenisation just means that where you have results from different instruments at the same frequency, they have been averaged in some way. The reference code refers to something like this 1995MNRAS.273..559J That can be used to look up the paper referred to at somewhere like the NASA ADS catalogue. Can you ...

1

If you're talking about the electromagnetic radiation (in the radio spectrum) produced by the planets themselves, then the answer is no. BTW, not all planets generate a lot of radio EM. Jupiter does generate some amount, but the other planets are quite a bit more quiet. Still, a very small amount is probably generated by most planets out there. In any ...

1

I see two problems. 1) Any particular source in the sky is above the horizon for a limited region of the Earth at a given time, so one would need to relay the signal around the globe. 2) It is hard to think of an astronomical source that is truly random all of the time. Astronomical sources are physical systems reacting to internal and environmental ...

1

I agree that the crater needs to be lined, but you also have the problem of maintaining a satellite in stationary orbit above the crater. Nearly impossible unless the crater is on the equatorial plane. Also, a stationary satellite around the moon would be influenced by the Earth, so you would need to burn fuel to keep the satellite in position.

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This can actually mean a couple of different things, but in the case of steering an MWA tile, Jeremy is quite correct. Each tile has a 'beamformer' box that all of the individual antenna cables plug into. This box physically delays each signal appropriately (by having a longer path to go through for more delay) based on the signals sent to it for each ...

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Check out the Design Overview and the Antenna/Beamformer page on the MWA website. The basic idea is that the signal arriving at an antenna is delayed in the circuitry, which makes it seem to the processing engine like the tile is being tilted in a particular direction.

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It cannot be said correctly, since we humans have hardly traveled to the moon and sent space probes to explore other planets in our solar system. So, theoretically anything might be possible. I'm trying to be a bit practical here. The only man made object that has gone really far is Voyager 1, which is at a distance of 18.7 billion kilometers (125.3 AU) from ...

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