Satellite footprints - a replicatable experiment

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Satellite footprints - a replicatable experiment
« on: May 17, 2012, 06:41:10 PM »
There has been lots of discussion of satellites, pseudolites, stratellites (I'll just call them 'lites in this post), and the like on this forum. One question that has, AFAIK, not yet been brought up, is the issue of 'lite beam footprints.

As you may know, if you shine a point light on the surface of a sphere, the boundary of the lit area will be a circle. The farther the point light is from the sphere, the bigger the circle will be - a point light at infinity distance will light up an entire hemisphere (the boundary will be a great circle), while a point light directly on the surface of the sphere will light only a single point.

In an equirectangular projection, a circle centered on the equator of a sphere will appear as a superellipse commonly known as a "squircle". The Azimuthal stereographic projection, on the other hand, renders all circles as circles.

With that said, here is an equirectangular footprint map of the Intelsat 10-02 'lite's "Global" beam:


A feature of this 'lite is that it is essentially an isotropic "point" microwave source - if you can "see" it, you can receive transmissions from it. The shape of the footprint is a squircle, as predicted by the model of a point light shining at a sphere. To further prove this point, here is the same map in azimuthal stereographic projection (centered on the equator, at longitude 0 - the bounds of the original map are 85N-84S, 177W-177E, for those wishing to reproduce the other projections):


Indeed, the footprint is a circle.

Yet, here is the same image in the flat-Earth projection commonly used on this forum:


I've yet to see any explanation for the shape of this footprint on a flat Earth.

And now, how to actually confirm these footprints.

You will need:
-A parabolic dish reflector with a diameter of at least 3m (7ft). Limited success should be expected with a smaller dish.
-A C-band LNB converter that supports circular polarization.
-A DVB-S tuner. This can be a conventional set-top-box with free-to-air reception support, or a computer with an add-in card.
-A GPS receiver (optional, used for obtaining geographical coordinates).

What you need to do is set up your equipment (dish+LNB+tuner) at a location near the edge of reception as shown on the map.
Install the LNB on the dish, connect the tuner to the LNB, then align your dish as suggested by http://www.satlex.de/en/azel_calc-params.html?satlo=17.0&user_satlo=1&user_satlo_dir=W&location=6.33,-10.76&la=6.33&lo=-10.76&country_code=lr&diam_w=180&diam_h=180 - set your coordinates according to the values from the GPS receiver.

Now, tune your DVB-S receiver to 4084 MHz, left circular polarization, symbol rate 3906, FEC 3/4 (some DVB-S tuners can auto-detect the FEC) and scan for channels. If you are lucky, and there is nothing blocking the path between the 'lite and your receiver, you will see a signal from Senegal TV station "RTS". The farther you are (inside) from the edge of reception, the more likely you will get a signal, and the higher you will need to align your dish.

The alignment calculator I posted uses RE math to calculate the dish settings from your coordinates - oddly enough (for FE'ers at least), it works.

Re: Satellite footprints - a replicatable experiment
« Reply #1 on: May 21, 2012, 10:12:48 AM »
I think you forgot a few things about the FE model like where the Sun and Moon are, the satellites footprint would be wasted by the radiation coming from the Sun because the satellites are way past the distance from FE to the Sun. In other words your dish antenna would only see the Sun The noise from the Sun would overload your LNA or LNB making reception useless.

Re: Satellite footprints - a replicatable experiment
« Reply #2 on: May 23, 2012, 05:45:31 PM »
Yet, we do not in real life observe solar interference when receiving Intelsat 10-02.

Also, I don't understand why being farther from the Sun is a problem for reception - as long as the Sun and the 'lite are separated by a wide-enough angle, there should be no interference. In other words, for solar noise to be a problem, Intelsat 10-02 would have to be directly behind the Sun (or at least very close to it), not merely higher than it.

Re: Satellite footprints - a replicatable experiment
« Reply #3 on: June 12, 2012, 01:58:51 PM »
Depending on the position of the satellite and the month of the year synchronous satellites eclipse the sun at some part of the year depending where you are on the earth. Synchronous satellites are at about 23,000 mile so called orbit, to match the so called earths' revolution around it's so called axis.

You are also assuming there is no distortion of the EMF from the satellite by the so called atmosphere or dark matter.  The air itself can distort EMF, so can Dark Matter.
To wit the earth is flat and can't be illuminated in totality because of the effects of a flat earth dark matter, and air posses on the EMF and the type of antenna the satellite uses.

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Re: Satellite footprints - a replicatable experiment
« Reply #4 on: June 12, 2012, 02:04:07 PM »
This is a fascinating experiment, but I don't see how this proves anything other than the reception of a signal.

Re: Satellite footprints - a replicatable experiment
« Reply #5 on: June 12, 2012, 02:37:25 PM »
This is a fascinating experiment, but I don't see how this proves anything other than the reception of a signal.

You don't see. That's the problem with you.
It proves of course a lot of things beyond your grasp.
The Earth looks flat, therefore it is FEers wisdom.

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Son of Orospu

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Re: Satellite footprints - a replicatable experiment
« Reply #6 on: June 12, 2012, 03:51:24 PM »
You don't see. That's the problem with you.
It proves of course a lot of things beyond your grasp.

Almost 1900 posts, and still an angry noob.  How sad.

Re: Satellite footprints - a replicatable experiment
« Reply #7 on: June 12, 2012, 04:09:06 PM »
You don't see. That's the problem with you.
It proves of course a lot of things beyond your grasp.

Almost 1900 posts, and still an angry noob.  How sad.

2700 posts and not any understanding of anything. How sad.
The Earth looks flat, therefore it is FEers wisdom.

Re: Satellite footprints - a replicatable experiment
« Reply #8 on: June 13, 2012, 07:32:52 PM »
@raypsi: Lack of reception due to distortion, interference or "the type of antenna the satellite uses" is easy to tell apart from a below-the-horizon condition. In the first case, as you move toward the proper reception area of the 'lite, when you do eventually enter the reception area, you will receive your first signal with a dish clearly pointed towards the sky. OTOH with an actual below-the-horizon condition, your first reception will be with a horizontally pointing dish.

Also, you still haven't explained why your supposed solar interference doesn't manifest in real life for those receiving Intelsat 10-02.

@Irushwithscvs: Because we are dealing with extremely directional antennas, reception of the signal is proof that the source of the signal is located in the direction the antenna is pointing to. The correct direction is highly dependent on your location on Earth. And if you compare the directions you need to use for receiving Intelsat 10-02 from various points on Earth, you will find that these directions diverge on the surface of a flat Earth, but converge on a round Earth. In other words, measuring the reception angles (azimuth/elevation) on different points of Earth gives a consistent location for the 'lite on a round Earth, but conflicting locations on a flat Earth.