It's Saturday morning. I've got a need to send a command to the spacecraft I work on, but here I sit at home, unshowered and in a robe, listening to my children make a lot of noise in the other room. But this isn't a problem, you see, because we live in the 21st century. Here's how it works:
-- The spacecraft sends data from Mars, which currently is 11 minutes and 44 seconds away from Earth when traveling at the speed of light. This is how long the data takes to reach the giant, 70-meter wide antenna in the desert up in Goldstone, California.
-- The antenna receives the data and it is converted into bits (ones and zeroes) to be sent across dedicated "telephone" lines between the antenna and where I work.
-- Where I work has machines that receive the data and process it into meaningful information, where it makes it available via a broadcast.
-- I have logged in via the internet, to have this data sent to my home from where I work using my DSL line.
-- My laptop is connected to my DSL via a wireless modem, and the data flows across that connection to my display.
This data contains information regarding the spacecraft. Where are the solar arrays pointed? How much power is available from the solar panels? How much processing time is being used on the onboard computer? What are the temperatures on the electronics boxes? What instruments are collecting data at this time? How much data is back-logged, needing to be sent to Earth? What commands are currently being issued by the spacecraft? Over 10,000 points of information about the spacecraft are transmitted from Mars within mere seconds. At best, the spacecraft can transmit data at a rate of over 6 million bits per second -- depending on the distance between Mars and Earth (right now they're pretty close together).
So, here I sit, in my home, unshowered and in a robe, while data is being transmitted directly from Mars into my home. I looked at this data a moment ago and concluded that all is well, so I called somebody at work and gave them a "go" for sending the command to the spacecraft. It's on it's way to Mars right now. And I know this is true as I sit in my home, unshowered and in a robe.
Isn't modern technology wonderful?
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