1. How NASA communicates with spacecraft
Lesson 2
Approved for Public Release: NG , 9/15/17

2. Why NASA needs to communicate with spacecraft
Once spacecraft are launched, many of them will never return to Earth.
NASA needs to make sure that the spacecraft is travelling in the right direction.
NASA needs to tell the spacecraft what data to collect.
Once the spacecraft has collected data, the data needs to be transmitted back to NASA?
So, how does NASA communicate with spacecraft?
Approved for Public Release by NASA, 9/26/17; NG

3. Approved for Public Release by NASA, 9/26/17; NG17-1826
The Deep Space Network
The NASA Deep Space Network (DSN) is a network of three huge antennas that allow people on the Earth to communicate with satellites and other spacecraft.
The DSN is used to support scientific spacecraft; it provides coverage from low Earth orbit (about 30,000 miles above the surface of the Earth) to the edge of the solar system and beyond.
Approved for Public Release by NASA, 9/26/17; NG

4. Approved for Public Release by NASA, 9/26/17; NG17-1826
How the DSN works
Three antennas make up the NASA Deep Space Network.
The Antennas are positioned 120 degrees apart (one-third of the way around) on the Earth. They are located:
In Goldstone in California’s Mojave Desert
Outside Madrid, Spain
Outside Canberra, Australia
By positioning the antennas at these locations, NASA can send and receive signals facing any point in space at any time as shown in the illustration.
Approved for Public Release by NASA, 9/26/17; NG

5. How information gets transmitted back to Earth
Copy and paste this URL into your browser to show a video demonstrating how spacecraft transmit information back to Earth
Approved for Public Release by NASA, 9/26/17; NG

6. How information gets back to Earth
Step 1
Instruments on spacecraft collect different kinds of information. Scientists call this information ‘data”
For example, cameras take pictures of Earth or other planets, such as this image of Saturn taken by the Cassini spacecraft.
Approved for Public Release by NASA, 9/26/17; NG

7. How information gets back to Earth
Step 2
Data from the spacecraft instruments are passed to the spacecraft computer
The computer turns the data into little packets of 1’s and 0’s .
Instrument Data Computer (binary) Data
Approved for Public Release by NASA, 9/26/17; NG

8. How information gets back to Earth
Step 3
Computers send the little packets of 1’s and 0’s to a piece of equipment called the transponder.
The transponder codes the packets of 1’s and 0’s into a radio signal
Binary data Radio signal
Approved for Public Release by NASA, 9/26/17; NG

9. How information gets back to Earth
Step 4
The antennae on the spacecraft beams the radio signal into space towards Earth
A big antenna on Earth (one of the three antennae from the Deep Space Network) receives the radio signal from the spacecraft
Approved for Public Release by NASA, 9/26/17; NG

10. How information gets decoded on Earth
Step 5
A receiver on Earth decodes the radio signal from the spacecraft turning the signal back into 1’s and 0’s again.
The receiver sends the 1’s and 0’s to a computer on the ground that turns the 1’s and 0’s into data packets just like the packets the spacecraft created in the first place.
Radio signal Binary data
Approved for Public Release by NASA, 9/26/17; NG

11. How information gets decoded on Earth
Step 6 
Other computers turn the data packets into images or numbers that make sense to people.
Computer (binary)Data Image captured
by the spacecraft 
Approved for Public Release by NASA, 9/26/17; NG

12. To send a signal to the spacecraft
A similar process is followed—binary data is converted into radio waves which is then decoded by computers on the spacecraft.
In this way, NASA is able to communicate with spacecraft that have travelled very far away from Earth.
Approved for Public Release by NASA, 9/26/17; NG