Table of Contents

Data Downlink: Configuring Antennae

Accessing Components

In the tutorial blueprint, accessing components from a spacecraft can be done in a couple of ways. Since the components added were child components, they will need to be casted to the correct type when attempting to find the objects. Instead, it is best practice to use the Get Child function on the spacecraft to find the objects of the correct type. Create a function called Configure Antennae and call the function on the child, looking for an object of type Transmitter.

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Note

When dealing with inherited classes, the base class is always just the name of the component. The BP_NS indicates it is a Blueprint asset (with a mesh) and part of the Nominal Systems standard library. It is best practice to store the reference to the lowest level component when dealing with simulation Blueprints, and only use the Blueprint references if there are variables or objects needed that are not present in the base class.

Changing Frequency

The TT&C system uses the frequency of transmitters and receivers in the simulation as a way of communication. In the back end, a system tracks all of the antennae and each time the frequencies change, it determines which antennae are on the same frequency and adds them to a map. This allows two antennae (provided one is a transmitter and one is a receiver) to communicate with each other provided the other conditions are met, such as distance or angle. For this tutorial, we will assume both the transmitter on the spacecraft and the receiver on the ground station will have a frequency of 900 MHz (which is 900,000,000 Hz). This can be done by using the Set Frequency function on both antennae.

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The bandwidth property on the antennae specifies the range of frequencies about the desired mean frequency it can listen to. If the transmitting frequency is not the same, provided it is within a suitable range of the bandwidth, the antennae may still be able to communicate. A normal distribution curve is applied to this frequency range. In this example, as the two frequencies match, there is no requirement for the bandwidth to change from the default.