Question: Which is the average or maximum speed of a telematically sent message that a space probe can send? Is as simple as radio waves travel at the speed of light in a vacuum?

Context: I have been asked to make a first estimation about how much time is needed to send a space probe and then receive the signal.

I am supposing that the space probe is sent at $15 \ km/s$ but I have not idea of the telematic signal speed.

Thank you in advance!


1 Answer 1


If you refer to the speed of the electromagnetic wave, it is indeed the speed of light - after all light is an electromagnetic wave as well, just of a different wavelength range.

If you refer to the time to send a certain amount of data, it is much more complicated and is referred to as "link budget". It would depend, among others, on the gain of the antennas, the modulation, the coding system, the distance...

Your problem is not clear enough. How much time to send the probe where? It would take a fraction of a second to send the probe if we considered it sent when it took off. Also don't forget that if a space probe is sent from Earth at 15km/s, it will escape the Earth's sphere of influence with less than 4km/s as the escape velocity of the Earth (basically the amount of momentum the earth is eating away by trying to attract it) is 11.2km/s.

  • 1
    $\begingroup$ In fact this was just what I was looking for. I just needed some key works to search of, like the "link budget". I have other data like distances and staff, but I was only curious about the velocity itself. $\endgroup$ Mar 15, 2014 at 19:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.