PostHeaderIcon Communicating With Mars

One of the most basic questions when it comes to Martian expeditions is communication, namely “how long does it take to communicate with Mars?” The simple short answer is 4-20 minutes, depending on where the Earth and Mars are in their orbits. It also gets more difficult when Mars is near or behind the Sun from our point of view.

Interplanetary Internet

You’re probably quite used to looking up the answers to your questions on the internet anytime you want, but with the delay in communication in space, the internet can’t work quite the same way – besides the fact that you’ll be using a connection that feels like a very, very slow modem. The way webpages are designed now that would take forever.

Data Rates

Of the missions currently at the red planet, the Mars Reconnaissance Orbiter (MRO) has the ability to transmit the most data. Its data speed to and from Mars is about 6 megabits per second (about twice as fast as the connection I’m currently on), but that’s not continuous – it is only when MRO can “see” Earth. Since Mars is rotating, the rovers are periodically out of contact, and the satellites lose their connection when they orbit to the far side of the planet.

Eeep! We’re using speed in two different ways. Don’t confuse the speed at which the data is transmitted (the amount of data per second) with how long it takes the data to get to Earth. MRO may transmit at 6 megabits per second, whereas Spirit can only transmit directly to Earth at a maximum of 12,000 bits per second (that’s 0.01 megabits per second – like using a very old dial-up modem!), but still both messages will take the exact same amount of time to get to Earth: between 4 and 20 minutes, depending on the time of year.

Relays

Most messages from space missions go through relay satellites, for example the Mars Rovers often send data through MRO. This in itself might make interplanetary internet a reality, if we can overcome some of the blocks – like the delay causing excessive timeouts among many others. There are some folks studying this problem, and there are even proposed solutions.

Incidentally, the International Space Station just got live internet for the first time – really it’s a connection to a computer in Mission Control – and that computer is connected to the internet. That limits the information that really needs to be transmitted to the Space Station.

Would You Like to Receive a Message from Mars?

Would you like to get some tourist snapshots of Mars? The surface of Mars? Well, your chance to point the HiRISE camera at your favorite part of Mars is here.

More Info:

http://deepspace.jpl.nasa.gov/dsn/

http://marsrovers.nasa.gov/mission/comm_data.html

~ A l i c e !

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