Information Request

Allan

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Hello my Orbiter friends,

I'm working through another novel and have come across some sciences related areas that need clarification. I've been researching subject matter for some practical questions and have found myself ending up with more questions than answers. I'm hoping you guys can come through for me again,

Radio Waves. I understand that radio waves can move at the speed of light (approx 300Km/sec).
Do radio waves (electromagnetic waves), without obstruction, slow down when moving across unoccupied in space?

Are radio waves the preferred communication method between Earth and satellites or between satellites or is there another technology?


Sensors. Exploration of space has to have some degree of remote surveying capability to assess an object from a distance. I've come across these [ame="http://en.wikipedia.org/wiki/Remote_sensing"]http://en.wikipedia.org/wiki/Remote_sensing[/ame]. All of the technologies have some earth oriented use. I would like to know if these technologies are whats being used today in space exploration? If so, are they projected to be used for long term future exploration? If not, what technologies are being used?

Any direct feedback or links would be greatly helpful.

As always thank you for allowing me to use you guys as a resource.

Allan
 

Krikkit

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No, radio waves do not slow down.

Radio waves are the preferred means of communication, though collimated visible light has been used. So far the band width has been pretty low for optical comunications, but NASA is pushing the technology. You can read about some of that here http://opticalcomm.jpl.nasa.gov/

I don't know where to begin on remote sensing systems, there are so many methods. I would start by looking up all the various types of instruments which have flown on various space probes over the years.
 

fsci123

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Im not an expert at this but...

Radio waves are currently the preferred medium of communications... However for high bandwidth comm you may have to shift into the microwave, infrared or visible spectrum. I think microwaves are being used for a lot of comm sats now.
 

Allan

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Thanks to you both. The issue I'm having is like Krikket said, so much information. I can't be sure what information to project from in writing sci-fi novel.
 

Unstung

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Radio Waves. I understand that radio waves can move at the speed of light (approx 300Km/sec).
Do radio waves (electromagnetic waves), without obstruction, slow down when moving across unoccupied in space?
Radio waves are light like the visible light that you see, but just have longer wavelengths and thus lower energy. Energy is directly related to the frequency of the light, so higher frequency = higher energy. (The equation is E = hf, or Energy = Planck's constant * frequency.) Unobstructed, radio waves travel at the speed of light like any other electromagnetic wave, all the way up to gamma rays.

Are radio waves the preferred communication method between Earth and satellites or between satellites or is there another technology?
Radio waves cannot transmit as much data as optical communication (using higher energy visible light, which has been tested at the moon and at the ISS). One problem with using visible light is that it can be obstructed by clouds, while radio waves simply pass through the entire atmosphere (and many other obstacles) without a problem. It also seems easier to transmit and detect radio waves from extremely long distances, like Cassini at Saturn. Radios have been around for a long time, after all.

Sensors. Exploration of space has to have some degree of remote surveying capability to assess an object from a distance. I've come across these http://en.wikipedia.org/wiki/Remote_sensing. All of the technologies have some earth oriented use. I would like to know if these technologies are whats being used today in space exploration? If so, are they projected to be used for long term future exploration? If not, what technologies are being used?
Spectroscopy is very important in astronomy and planetary science. Just splitting the light reflected from an object into its component colors can reveal its composition (visible/ultraviolet spectroscopy) to its bonds (infrared spectroscopy). Looking at the instrument suite for Cassini in particular, a spacecraft that carries infrared to ultraviolet spectrometers, is a good way to see some applications of remote sensing. The Mars Exploration Rovers create photographs using infrared filters all the time to reveal the mineralogy of the surrounding area.

---------- Post added at 07:59 PM ---------- Previous post was at 07:49 PM ----------

A good example can be presented in a single image:
The image combines exposures taken through Pancam filters centered on wavelengths of 753 nanometers (near-infrared), 535 nanometers (green) and 432 nanometers (violet). The view is presented in false color to make some differences between materials easier to see.
720741main_pia16704-43_946-710.jpg
 

Allan

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Thanks Unstung, very helpful. I don't shy away from reading but sometimes the comprehension needs an assist. The sensor info should prove helpful!

I wrote in multi-spectral sensors to be generic but wanted to add something more concrete for my more scientific readers (yep, I have more than a few).
 
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