# Tag Info

71

The signal from the Moon was received using giant parabolic antennas, e.g. the 64-m dish at the Parkes observatory. These have very good sidelobe rejection so they won't pick up any Earthbound signals. Despite the space race, relations with their biggest enemy were good enough that the Russians shared Luna 15's flight plan with the Americans when this ...

62

GPS isn't affected by demand, as it is transmitting only from satellites, and the receivers only receive, they do no transmit to the satellite at all. At best, there is a slight degradation by having antennas in really close proximity. A million man march, each with a GPS device, might cause some degradation as each device will absorb a bit of the energy ...

43

Yes. The space shuttle could. I recall in shuttle ascent abort training, when the crew was executing an East Coast Abort Landing to an airbase / airport on the East Coast, the commander would communicate with the tower on "guard" as they were approaching the site. These airports included civilian airports such as St. Johns, Wilmington, Stephenville, etc. ...

39

As PearsonArtPhoto says, it's not the GPS protocol itself that causes the problem. Cell phones use Assisted GPS, where cellular data is used to speed up obtaining a GPS fix. This should be just a few kb per session though. Many mapping applications also download map data as you go along, again causing lots of network traffic. This may be an ...

37

He replied that we actually received the signals in just 1-2 seconds with the help of MarCO CubeSats. Later on followed up with confusion from other users with his statement and asked for clarification, he then mentioned that it is relating to quantum entanglement for communications. This is nonsense; the MarCOs received the signals in 1-2 seconds, but ...

28

Those were called Quindar tones and they were used for in-band signaling in the ground communications network to key the transmitters at the ground stations. An "intro" tone is generated when CapCom in Houston presses his/her push-to-talk (PTT) button. This triggers the high power amplifiers at the MSFN ground station (often on the other side of the world) ...

28

It depends on what you mean by "broadcast to the whole world". According to the annotated transcript (h/t to Organic Marble for finding it) John Young said it into a "hot mike", i.e. with the air-to-ground communications loop open: [In the following, John doesn't realize he still has a hot mike. Charlie is only faintly audible through John's mike and ...

27

Yes. The Soyuz Escape Capsule Responding Instructions explicitly document 121.5 MHz capability, including voice: c. Morse code: “AN” (dot, dash, dash, dot) broadcast on VHF 121.5 during descent. d. Emergency Locator Transmitter warble on VHF 121.5 interrupted only by crew broadcasts. e. Crew has a survival radio with beacon and voice capability on VHF 121....

26

According to NASA's Space Educator's Handbook: As the men in Apollo 13 experienced what no men had undergone before, millions followed the developing drama by radio and television in public squares, private homes, schools, offices and factories. Pope Paul, at an audience in St. Peter's Basilica for 10,000 Romans and tourists, said "We cannot forget at ...

25

First you lock on to energy at (or near) the expected frequency. That’s carrier lock. Then you start to look for patterns in how the phase changes. The transmitter is coding groups of bits as phase-change “symbols”, and you want to find the time-pattern of those: symbol lock. But those are not yet bits because the coding works in blocks of bits. Once you ...

24

The difference between 10 W at 350,000km, and 1,000 W at 1km is 131 dB. If the pranksters on Earth used a directional antenna like the Ham radio operators shown below, the ratio would be even higher because that thing has much more gain than the Apollo antennas from the orbit and surface of the Moon. It would only take a tiny bit of random or isotropic ...

23

Apparently not: I like this Quora answer. Here's part of it, the rest is worth reading as well: No experiment conducted using entangled photons has ever demonstrated faster than light communication! There have been many such experiments. They were not looking for faster than light communication. They were testing quantum mechanics against Einstein's ...

22

It's a great question! Trajectory To get a few decades more out of them, you can launch Voyagers 3 and 4 sometime around now and get by with a maximally-boosting flyby of Jupiter since you wouldn't target Saturn as well. If you had to wait for Jupiter and Saturn to line up with the original pair's trajectories again, it would be too long of a wait. ...

19

No. Communication latency (the time between sending a bit and receiving it on the other end) between Earth and Mars probes is limited almost entirely by the speed of light, as they are radio waves on a direct path in vacuum. (There are also plans for optical communications, but as far as I know no Martian orbiter has yet been launched with that capacity. It ...

18

Check the DSN Now page when it will show any of its stations communicating with Voyager 1 (code VGR1) or Voyager 2 (VGR2), select that dish and then expand the side column on the right to show all the data. It will show transmit power under up signal section. I'll update this answer as soon as I see that happen (see below for updates), but it would be in the ...

18

As someone deeply involved in quantum information/entanglement research: You cannot, under any circumstance, use entanglement to communicate faster than lightspeed. Ever. The "no-signalling principle" says that no information can be transferred faster than lightspeed, even using all the tricks in the quantum book. If it were to be violated, a bunch of ...

15

Radio may reduce some complexity, but it will introduce problems that wiring doesn't have. Limited bandwidth. Interference. You can separate wiring so it doesn't influence each other. Can't do that with radio: each receiver can hear all transmitters. You're introducing new points of failure. A radio transmitter or receiver contains loads of active ...

15

OK let's first understand units. The decibel (dB) is a base-10 log scale without units and dBm is a similar decibel scale for power referenced to 1 milliwatt. They also include a factor of 10, so for example 10 dB is a ratio of 10^1, 20 dB is a ratio of 10^2, etc, while 10 and 20 dBm would be 10 mW and 100 mW. But in the block quote, they use dBW instead of ...

15

You have a few problems with doing that which @uhoh unit has already elaborated. Even if you could surmount those you have a bigger problem, which is the Voyager probes will have to shut down their science instruments due to power constraints before a probe launched now would be able to get in a position to do any good. There are 4 instruments running on the ...

13

Let's think about what it would take to do what you're suggesting. The DSN uses some pretty large antennas, so you're talking about putting a 70 meter dish like this (and a power supply to run it) in space: (Source: NASA) You could put it in LEO (because that's much closer and cheaper), but then you have to deal with the Earth occluding it frequently. You ...

13

They have to spread their signal. Also, it requires a really big dish to not spread your signal at all. Imagine that there was no spreading at all. The dish would have to be pointed exactly at the satellite, to the margin of the size of the dish. That is far beyond the technology of today! DSS has it's dishes pointed to 0.1 degrees. At the distance of ...

13

It's a very simple phased array antenna. Other examples include cell phone antennas, this French satellite tracking antenna, and the famous Very Large Array (VLA) in New Mexico. You create a phased array by spacing more than one antenna at regular intervals. The individual antennas can be almost any type: dipole rods (cell tower), helical (French ...

12

I submitted a FOIA request for every contact made by the DSN from 2010 onward (I received contacts from Jan 1, 2010, till Sep 1, 2018) Here is a summary of the contact time for all 86 Missions contacted by the DSS in that time sorted by total time (in hours). +------------------------------------------------------+---------+---------+---------+---------+---...

11

Assuming that by signal you mean radio signals, there were many attempts. All this has already been described in detail on Wikipedia, so I'm not inclined to repeat it. What you are looking for is available in these two pages: Active Search for Extra-Terrestrial Intelligence (Active SETI) Communication with Extraterrestrial Intelligence (CETI). Probably ...

11

While power requirements are higher than for regular GSM service, they are not as high as one might think. Current satellite telephones use handsets of the size of 2000-era mobile phones and are able to transmit 15 kBit/s to geosynchronous satellites (the Thuraya system). These satellites are more than 30 times farther from Earth than the planned SpaceX ...

11

If the question is that if spacecraft independently initiate communications with random civilian ATC unit, the answer seems to be no. Civilian ATC units operate on VHF frequencies (118-136MHz) with AM modulation. Besides that, spacecraft should be able to tune in any frequency within the range that an ATC unit is using. Or they could use universal emergency ...

10

The first message in the history of humanity was: "Мир, Ленин, СССР". The English translation being, "World, Lenin, USSR". A lot of people will try to bring up that "мир" actually has two meanings, the second one being "peace". My opinion is, that in this case, it only means "world", or in stricto sensu "Universe". It was long ago, in 1962, when this radio ...

10

If it were still working and you have a powerful enough transmitter and sensitive enough receiver on your orbiter (likely requiring a high-gain antenna), then I suppose. However there is no way that it's still working. The modem on the Sojourner rover is designed to communicate with a companion modem on the Mars Pathfinder lander no more than a few meters ...

10

When discussing radio antennae, radio astronomers usually describe things in terms of temperatures. We can convert between power and temperature simply by multiplying (or dividing) by Boltzmann's Constant: $P=k_BT$. We define the antenna's System Temperature, $T_{sys}$, as the sum of all the temperature contributing factors. The most important contributor ...

9

A wire would be needed to get any real amount of data out. Wikipedia has the state of the art communication with submarines. There are basically 2 ways to communicate with them. Using sound waves could work for short period distance, and that might be possible to use from a surface component to the underwater submarine. Very low frequency (3-30 kHz) can ...

Only top voted, non community-wiki answers of a minimum length are eligible