Questions tagged [radio-communication]

Using radio wavelengths to communicate between multiple spacecraft or between a spacecraft and the Earth.

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7
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1answer
340 views

Deep Space Network time budgets per spacecraft - is such statistics available?

Is statistics available about time consumed by different spacecraft for communication wint NASA Deep Space Network (DSN)? It would be interesting to compare which space missions are more downlink-...
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1answer
116 views

Which is stronger per Hz, radio signals from a Mars spacecraft, or Mars' blackbody radiation?

It just occurred to me that while Mars is cold from a human's perspective, from a radio engineer's perspective it's still kind-of hot. When even the largest DSN antennas are pointed at Mars to ...
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619 views

What is the highest non-optical frequency used or tested for use in deep space communication?

For dish antennas used to transmit a signal over large distances, the on-axis gain scales as $D^2/ \lambda^2$ or $D^2 f^2 / c^2$ where $\lambda$ and $f$ are the wavelength or frequency and $c$ is the ...
4
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1answer
62 views

Is it practical for HF skywave propagation to be utilized for space exploration robot telecommand when outside of microwave/mm wave range?

Is it practical for HF skywave propagation to be utilized for space exploration robot telecommand when outside of microwave/mm wave range? Currently it appears that only the C band and UHF is used in ...
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3answers
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How did NASA prevent third parties from spoofing Apollo communications?

The Apollo crews transmitted footage to Earth using SSTV, a ham radio technique that amateurs and pirates can use to send similar messages around the world. Did NASA have any technical ...
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1answer
199 views

The appearance of TESS' dish seems to be evolving, what will be the final configuration?

The question Why is TESS' high gain antenna made of undulating BLACK fabric rather than metal? has had three bounties, and is probably the recipient of this sites longest answer. My personal pet ...
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2answers
199 views

Feasibility of Interstellar Probe Communication

So, I understand that to transmit information across interstellar distances, you need to use a lot of power (or less bandwidth?), something for example a small space probe wouldn't exactly have. If we ...
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1answer
259 views

Juno RF power output

What is the RF Power Output from Juno into its Parabolic dish, and the RF radiated out from the dish and the eventual power received say at the dish in Canberra which obviously then would need to be ...
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1answer
500 views

Have deep-space spacecraft always used some form of spread-spectrum for data downlink?

tl;dr: Question: Have deep-space spacecraft always use some form of spread-spectrum for data downlink? note: I'm looking for some insight into why, and any possible exceptions, not just a "yes" or "...
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3answers
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Do satellite uplink/downlink signals spread or leak into space?

Satellite communication generally involves three types of nodes: the ground station (also known as teleport), the satellite in geosynchronous orbit, and the satellite receiver/transceiver. I am ...
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2answers
241 views

Are sun outages having more limited impact in some cases?

Sun outages occur when a satellite, usually one in a geostationary orbit, passes between a ground station and the sun. Seen from the point of view of the ground station, the sun looks like it passes ...
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1answer
754 views

Is there really a radio on Elon Musk's solar-orbiting Tesla Roadster? Can we communicate with it? [closed]

Various media have reported that there is a radio on Elon Musk's Tesla Roadster, now in orbit around the Sun, and that this radio is playing music (for example: BBC reporting that David Bowie's ...
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1answer
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Why is TESS' high gain antenna made of undulating BLACK fabric rather than metal?

above: from Facebook, then annotated. There is an excellent review of the design of the TESS spacecraft in G. R. Richter et al. Journal of Astronomical Telescopes, ...
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1answer
413 views

How does the Satellite Networked Open Ground Station operate? How is it used?

SatNOGS, the Satellite Networked Open Ground Station (mentioned in this answer) appears to be a distribution of independently maintained amateur DIY satellite receiving ground stations, linked by a ...
6
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1answer
862 views

Why such a large observed doppler shift from Apollo 17 orbiting the moon?

Following the links in this comment by @Uwe I've found some interesting sources of information on Ham (amateur) radio operators trying to listen in on Apollo transmissions. One of them is Sven Grahn's ...
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How much power do missions to other planets use for radio transmissions?

How much power did the voice and data radios have on the Apollo missions? Additionally how much broadcast power is used on data transmissions from the surface of Mars?
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Satellite Intra link [closed]

I read there are sometimes intra-satellite links. Is it already used or just a project in the future ? How is is used and why ? and for what services ? thanks david thanks for interesting answers. ...
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1answer
240 views

What was the modulation used in the Space Shuttle Ku-band comm system?

The Ku-band system consisted of a directional antenna mounted in the orbiter payload bay and provided high BW communication with a ground station. This page: KU-BAND SYSTEM describes the system as ...
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2answers
281 views

Is the utility PREDICT good enough for operational orbital prediction?

I'm looking for a cheap and cheerful, but ultimately working utility or library for tracking a cubesat and predicting link windows. I've been looking at using Orekit. I'm a student, so a lot of its ...
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3answers
9k views

Why would GPS availability be reduced by high demand (or solar eclipse)?

This Newsweek article states that "GPS...will likely be nonexistent near the eclipse zone" because of all the people going to that area. While it makes sense that cell towers might be overloaded and ...
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329 views

How do satellites communicate with a relay satellite?

Although the exact usage of the system is classified, NASA has a system called TDRS which is used by other government agencies for relaying data to ground stations. To maintain communications with a ...
2
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1answer
1k views

Real time communications in space

Today we use audio and video communications (using UDP protocol) over IP networks (VoIP) for communicating (Skype, Whatsapp, FB messenger). This works fine on planet Earth (although there are various ...
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1answer
485 views

Faster than light communications in space [closed]

Today communication with different spacecraft is limited to speed-of-light. Around the Earth it is not such a problem, but when you have to work with a spacecraft on the surface of Mars, it becomes an ...
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2answers
1k views

Is it possible for small satellites to orbit in MEO or GEO?

I am researching satellite technology, and in particular I am looking at the rise and implications of smallsat technology. As far as I know, there are currently no satellites beyond LEO that would be ...
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1answer
329 views

Characteristics of the modern satelite radio transmitters

I'm trying to find some data concerning current Earth-satellite radio communication systems, namely general characteristics of the equipment currently used on satellites. Specifically, I'm interested ...
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2k views

Why were the two Quindar tones so close in frequency and not apodized?

This and this answer explain the function of the Quindar_tones within Apollo mission comms. At 2525 and 2475 HZ they are only 50Hz or 2% apart in frequency, and the duration is 250 ms or 0.25 seconds....
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What purpose serve the audible “bip” on apollo radio communications? [duplicate]

When looking at moonwalk videos, we can hear bips. What are those bips? Why are there bips? Do this bips still exist in nowaday space missions?
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Why were there beeps punctuating the voice communications during missions such as Apollo?

Voice communication between ground and spacecraft during missions such as Apollo seemed to be always punctuated by beeps. What was the origin of these beeps? Were they some sort of unavoidable ...
9
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1answer
383 views

With the correct antenna and transmitter, could the Sojourner rover be reactivated?

The Sojourner rover was deployed as part of the Mars Pathfinder mission. At the end of the mission, the Sojourner rover was still operable. But the base station that the Mars Pathfinder carried failed....
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2answers
229 views

Details of Apollo 11 video transmission [duplicate]

NASA has the video of Neil Armstrong on the moon. I'm interesting in the technology how the signal was created and transmitted. There are some details about it in Wikipedia but I'd like to know in-...
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1answer
881 views

Has DSS-43 ever been used in high power mode (>>20 kW) for an emergency situation?

This answer notes that while most Deep Space Network transmitters are 20 kW of power or less, one dish (DSS-43 in Canberra) is equipped with a transmitter capable of 400 kW. As described in 101, 70-m ...
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1answer
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Did USSR discontinue radio transmissions, relocate ships, to aid the US in response to Apollo 13?

In this article there is following statement by Dr. Ernst Stuhlinger: Let me only remind you of the recent near-tragedy of Apollo 13. When the time of the crucial reentry of the astronauts ...
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Could a smartphone really transmit to satellites in a space based internet system?

Space based internet systems, like the one recently proposed by SpaceX and Google, are said to use satellites to communicate directly with end users, without using cellular ground stations. But how ...
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4answers
348 views

What exactly do they look for when searching for extraterrestrial intelligence?

There are some experiments and projects that are searching for extraterrestrial intelligence.(SETI) I want to know what signs exactly are they looking for? Do they just look for monotone sinusoidal ...
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2answers
330 views

Earth-Mars Radio Blackout: Is it possible to define an extended solar radius to solve this as a geometric problem?

Solar atmosphere causes difficulties in communication during opposition (when Mars is almost behind the sun w.r.t. Earth). The question is: is it possible to define an extended radius for the sun, ...
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3answers
10k views

How much RF transmit power does DSN need to send commands to Voyager?

I recently looked up how weak the Voyager signals are when they get to Earth from the 22 W transmitters (as of September 2013, it was roughly -245 dBm). But that got me wondering how many watts of ...
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2answers
721 views

Would an orbital Deep Space Network be more efficient?

Deep Space Network sites in California, Madrid and Canberra perform an excellent job, for example receiving from Voyager 2 (16+ billion km) at -150 dBm power. However, would it be more advantageous ...
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1answer
542 views

How much power would an Alpha Centauri probe require for communication?

Project Longshot report (1988) says: A laser with an input power of 250 kilowatts would allow for a data rate of 1000 bits per second at maximum range." Yet Breakthrough Starshot website (2016) ...
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380 views

Do you need a “wire” on a Europa submarine to phone home?

In regards to Europa, what are the limitations regarding current data transmission technology. Say we were to have an orbiter circling Jupiter, a lander on the surface of Europa and a "swimmer" [...
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1answer
661 views

How does NASA communicate to spacecrafts? [duplicate]

In Our communication systems we have limitations like signal strength to achieve communication between two points in the same country we have to build towers / etc .. my question is how does NASA ...
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1answer
2k views

What is the advantage of QPSK over FSK or ASK for satellite data transmission?

I am wondering what are the big advantages and disadvantages using QPSK, FSK,and ASK in satellite communication. In our project, which is in phase 3, are we supposed to work with QPSK modulation for ...
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0answers
190 views

How to build an antenna to receive VHF or UHF? [closed]

I am trying to build a cubesat using a Raspberry Pi. I am now figuring out how to communicate with it. As far as I know, I understand I will have to use VHF or UHF to do so. How do I decide on the ...
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1answer
953 views

Why has the Earth's motion carried it out of view of Pioneer 11's antenna?

According to The Pioneer Missions, my emphasis, The Pioneer 11 Mission ended on 30 September 1995, when the last transmission from the spacecraft was received. There have been no communications ...
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1answer
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When is a phased array antenna not a phased array?

This question is inspired by an answer to this question, where it is stated that: The real power of phased arrays is their ability to be steered electronically. This set me wondering about the ...
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2answers
1k views

How are phased array antennas used in spaceflight? Benefits and limitations

It would seem to me that a phased array antenna would be great for spacecrafts since it removes the need to turn the entire spacecraft around in order to point the radio dish towards Earth. Many ...
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0answers
80 views

Why are space probes / satellites data rates so low? [duplicate]

The New Horizon's data transfer rate is only about 2kbps right now. At its peak the rate was 38kbps. Why is this transfer rate so slow? Is this due to using radio waves, limitations in the data relay, ...
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1answer
835 views

How is a space probe's antenna directed toward Earth?

I wonder how is it possible to direct the probe's antenna from enormous distances (like Pluto) toward the Earth. Because if even an extremely small inclination in antenna direction emerge, it will ...
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1answer
630 views

What is the highest practical data rate for a downlink from a spacecraft at a distance such as Pluto to Earth?

An answer to this question states that the expected downlink rate for New Horizons at Pluto encounter will be about 1,000 bits/sec. Understanding the issues of distant transmitters and data rates as ...
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1answer
526 views

Were the Voyager Golden Record / Arecibo message tested for decodability

I was wondering if the microgroove golden records they put on the Voyager spacecraft, or the Arecibo message, along with instruction on how to decode it, were first put to the test with the subjects ...
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3answers
425 views

Does man send any signal to attract aliens?

Does man send any signal (such as electromagnetic radiation) to space to attract aliens?