|
Communications SystemHow does NASA communicate with spacecraft? |
Dish-shaped high-gain antennas (HGAs) are the spacecraft antennas principally used for communications with Earth. The amount of gain achieved by an antenna refers to the amount of incoming radio power it can collect and focus into the spacecraft's receiver.
The larger the collecting area of an HGA, the higher the gain, and the higher the rate of data transfer it will support. However, the higher the gain, the more highly directional it is. When using an HGA, it must be pointed to within a fraction of a degree of Earth for communications to work. Once this is achieved, communications may take place at a high rate over the highly focused radio signal.
This is like using a telescope, which provides magnification (gain) of a very distant and small object (a weak source), but it requires accurate pointing. No magnification is achieved with the naked eye, but you have a much wider field of view and don't need to be pointed with great accuracy.
Low-gain antennas (LGAs) provide wide-angle coverage (the "naked eye," to continue the comparison) at the expense of gain. LGAs are designed to be useable for relatively low data rates as long as the spacecraft is within relatively close range. DS1 is using an LGA to send simple health data back to Earth.
How does reflection affect radio waves?
