Communication with Mars

I’ll write this post in English as my ‘international’ posts tend to get a lot of, well, international readers. Naturally. Mars_RoverAs you all may know, the second mission to land on Mars is now in the books. The landing was a huge success for NASA, and they have already received the first pictures from their onsite companion, Curiosity. –Which made me think; Is it possible to stream realtime video from Mars to Earth? After all, it’s a pretty fucking huge distance! There must be some latency? And yes. There is latency. And no, it’s not possible to stream anything realtime over that distance.     First of all, radio waves are electromagnetic radiation with wavelenghts longer than infrared light. Like all electromagnetic waves, they travel at the speed of light, close to 300.000 km per second (actually 299.792.458 meters per second). And, depending on the wavelength (frequency), they can travel over short or very long distances. Typically, radiowaves used for communication travels on Very High Frequency, because this betters the quality of the audio, but it has limited range, so one needs to amplify and repeat the signal with antennas and radiotowers all over the place. Obviously, this cannot be done in space. Therefore, radiocommunication in space use either X-band (8.4 GHz) or Ka-band (32 GHz) to travel over great distances. The distance from Earth to Mars vary from unthinkable insanely far (401.000.000 km) to just frickin’ far (54.600.000 km). Obviously, the mission to land on Mars was conducted when the distance between the two planets was at a minimum, 54,6 million km. Therefore we can, with some basic math, find how much latency we’re talking about when communicating from Earth to Mars. The formula is pre-school easy: Latency = Distance / Speed of Light. Which gives: 54600000 / 300000 = 182 seconds. Or just over 3 minutes. So there you have it. 3 minutes latency. Also, because of suntime, energy consumption, uplink, arrays in Mars orbit and such, the Curiosity rover cannot upload more than 8,5 MB of data per Mars day (24h 37m). And this only takes 8 minutes to complete. Anyway, if I were on Mars, and you still on Earth, this could very well be our conversation:   Me: Hello? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . You: HI!! How are you?? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Me: Fine!! And you?? . . . . . ….. -You get the point? But it IS possible to communicate. Just be patient…!

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