That’s because of the very high gain receivers at the other end. You have to account for free space loss. There’s no free ride. I used to do radar data analysis for NASA. I also did satellite link budget analysis for the military. The same sort of idea applies to Hubble Space Telescope being able to detect and photograph galaxies at the edge of the universe, I.e., from pretty soon after the Big Bang.
Some interesting points(a verbatim quote), regarding, "the edge of the universe"(including theory/opinion/speculation, of course), from the source linked:
"Because space is expanding, it’s possible for the galaxies to appear as if they are moving faster than light, without violating relativity — which says that nothing can go faster than light in a vacuum. The actual size of the observable universe is 46 billion light-years in any direction, even though the universe began only 13.8 billion years ago, Mack said. But that still sets a limit on the size of the universe humans can see, called the observable universe. Anything outside of that radius of 46 billion light-years is not visible to Earthlings, and it never will be. That’s because the distances between objects in the universe keep getting bigger at a rate that’s faster than the light beams can get to Earth.
And on top of that, the rate of expansion has not been uniform. For a brief fraction of a second after the Big Bang, there was a period of accelerated expansion called inflation, during which the universe grew at a much faster pace than it is growing now. Whole regions of space will never be observable from Earth for that reason. Mack noted that assuming inflation happened, the universe is actually 1023 times bigger than the 46 billion light-years humans can see. So if there is an edge to the universe, it’s so far away Earthlings can’t see it, and never will." [Big Bang, Deflated? Universe May Have Had No Beginning]quoted from: (https://www.livescience.com/33646-universe-edge.html)
I dunno who that dude is but he’s way out of whack with what we actually know about the universe. Hey, Mack rhymes with Whack. Coincidence?
In physical cosmology, the age of the universe is the time elapsed since the Big Bang. The current measurement of the age of the universe is 13.799±0.021 billion (109) years within the Lambda-CDM concordance model.
In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10−36 seconds after the conjectured Big Bang singularity to sometime between 10−33 and 10−32 seconds after the singularity. Following the inflationary period, the universe continues to expand, but at a less rapid rate.
(The expression 10-36 is equal to 10 to the minus 36 power.)
There are just too many universes to keep up with(well, theories, anyway). I’m still deciding whether to color, name and arrange my quarks, then fire a few hadrons into each other and weigh the bosons, or just pluck my cosmic strings, vibrate up a nice, informational hologram and entangle myself the hell out of here. Trying to contemplate, at what speeds the very first matter/energy, whatever form it may have taken, and how that would have affected, "time", since there is no time, at the speed of light(Relativity, of course, IF that was relevant, in the beginning, however THAT looked), will just have to take the back seat......oh, wait....I threw my brain back there, somewhere. You think Macky might be whacky? Could be, by cracky!
Convert you to what, a beam of dark? Can you tell me, whether the universe, is one in need of dark matter, to reach a mathematical equilibrium, just one in a multiverse, or(lately) a hologram, created through information generated by vibrating strings? All the prior vastly simplified, of course. I really thought it was funny, when they expected the weight of the Higgs Boson, to lend credence to either of the first two of the theories and it weighed pretty much dead center of the two expected parameters. I’m simply pointing out that no one can tell me, with certainty(YET), much of anything, regarding this universe. Everyone can’t be correct, can they? It’s not that I can’t be convinced. Just difficult to, given the possibilities. I didn’t intend to turn this thread into another soap. Won’t happen again(I may have said that before). Just trying to have some fun in here(for a change) and it backfired.
"I’m simply pointing out that no one can tell me, with certainty(YET), much of anything, regarding this universe. Everyone can’t be correct, can they?"
Even though science seems to have explained away the existence of God and the Heavens, cosmological thinking is, ironically, like theology in that it is wide open to hypothesis---like religion, only so much is knowable.
A little refresher course in cosmology wouldn’t hurt, guys. The word is cosmology, not astrology. Nothing to get all hung up about.
Science explained away the existence of God and Heaven? Whoa! That’s seems a little extreme. That’s what is known as a misconception. Ye olde us vs them mentality. How do you explain the fact that many scientists believe in God? Betcha can’t.
Here’s something you can sink your teeth 🦷 into, the observation of gravity waves 2 years ago.
rodman999993,336 posts12-04-2018 9:24pmConvert you to what, a beam of dark? Can you tell me, whether the universe, is one in need of dark matter, to reach a mathematical equilibrium, just one in a multiverse, or(lately) a hologram, created through information generated by vibrating strings? All the prior vastly simplified, of course. I really thought it was funny, when they expected the weight of the Higgs Boson, to lend credence to either of the first two of the theories and it weighed pretty much dead center of the two expected parameters. I’m simply pointing out that no one can tell me, with certainty(YET), much of anything, regarding this universe. Everyone can’t be correct, can they? It’s not that I can’t be convinced. Just difficult to, given the possibilities. I didn’t intend to turn this thread into another soap. Won’t happen again(I may have said that before). Just trying to have some fun in here(for a change) and it backfired.
>>>>I honestly don’t know what you’re hyperventilating about. I just gave examples of things that are known about the universe. I never said we know everything. Cut me some slack, Jack.
That’s because of the very high gain receivers at the other end. You have to account for free space loss.
Wrongo Geoffy. Terrestrial GNSS receivers detect the unique pseudo random code that modulates the L1 carrier to ensure they are tracking the same satellite(s) consistently. Others use DSP to lower the noise floor. Hel-loo! High gain signal amplification will (rpt will) amplify noise as well as the signal, a self-defeating means to an end. Get on the knowledge train Geoffy 🚂 🚂 🚂 Toot! Toot!
TBF, antennas are often described as "high gain" so I’m not sure Geoff was speaking purely about active amplification.
With up to 70m wide dishes, I’m sure those antennas are of extremely high gain, not to mention the digital signal processing and at least some electronic gain that occurs down the pipeline.
The Arecibo antenna is a radio telescope though, not really used for routine satellite monitoring, is it?
Good news, after Hurricane Maria damaged it, it will now get a 5.8 million dollar upgrade.
I use Arecibo to illustrate the point I was trying to make about the link power budget. You know, if you do not have a lot of power at the transmit end or you have a LOT OF FREE SPACE LOSS you must have a great receiver (high gain) on the other end. Satellites are space limited and power limited, so obviously you have to calculate the gain at the receiver to support the link. In the case of Hubble the received signal is optical, I.e., light. Arecibo is looking for a radio signal, no? Ditto the radio antenna array out west as seen in the movie Contact. Jodie Fosters SETI group in Contact picked up a radio signal. A radio signal just like a satellite signal, with EIRP. The only difference is the radio waves received by radio telescopes are from astrological sources, not satellites. The received signal are not (visible) light. Which brings us to the dodgy subject of light and electromagnetic waves and photons.
Geostationary satellites are not tracked. They’re uh, stationary. GPS satellites are not geosynchronous. So, they are tracked. But satellites that aren’t geosynchronous are tracked by radar, not stationary satcom terminals or receivers. The radar antennas have to be rotatable. I used to be a range rat at NASA.
As of April 2018, there were 548 satellites, listed as being in geosynchronous Earth orbit. (https://en.wikipedia.org/wiki/List_of_satellites_in_geosynchronous_orbit) There were 1886 satellites in orbit, as of the same time frame(April 2018). (https://www.ucsusa.org/nuclear-weapons/space-weapons/satellite-database#.XA0iunRKg1J) Slightly over one third is NOT, "most"(at least not in THIS universe).