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How do spacecraft communicate?
How do spacecraft communicate?
Spacecraft need to communicate with scientists on Earth in order to relay data they've collected or communicate their conditions or even to allow control from the ground. In order to do this, there are two essential parts: a transmitter and a receiver. The transmitter modulates electromagnetic waves to represent the data and sends it in the direction of a receiver, which then receives the information and interprets it by demodulating the wave. This works in a similar manner to the Wi-Fi in your home, except designed specifically to travel long distances through space.
NASA has a variety of ground antennae to receive and transmit data from anywhere on Earth. Additionally, some satellites are built with the purpose of communicating with spacecraft elsewhere.
Unfortunately, there's a lot of factors which determine the strength and quality of connections, including frequency bands used, interference from Earth, and the equipment used.
Frequency
Frequency
Electromagnetic waves are like a pattern that largely differs from wave to wave, but all of them have a specific wavelength, which is one of their most important aspects. Wavelength is the distance between the highest part of a wave and the next, and it is directly correlated to its frequency. Fun fact: between wavelengths of approximately 380 to 700nm is the spectrum of visible light! Spacecraft, of course, use radio frequency bands.
High frequency bands are able to carry more data per second, but should be used on shorter distances. Low frequency bands carry less but are significantly stronger for longer distances.
In this case, we require both: high frequency specialized antennae for communication between the satellite and the lander, which has an absurdly smaller distance and less potential interference due to the atmosphere, and low frequency antennae for the communication between the satellite on Enceladus and our network here on Earth.
Communciations Diagram
Communciations Diagram
As our satellite orbits Enceladus and passes over the lander, it will collect data that the lander must transmit, especially from the instruments. This will be sent through the software, which routes it through the antennae to modulate and transmit. The satellite receives this information, which they will then interpret, and if necessary send the scientific data or any errors or issues back to Earth through the same method, except on lower frequencies.
This same path can be used for Earth to send guidance information to the satellite, specific instructions for the lander, as well as any communications that need to be sent between these devices. In short, these communications systems keep the mission held together.
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