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The engineering behind the SKA

The resources below were developed by the Jodrell Bank Discovery Centre team with SKAO’s help and provide a set of activities that aim to illustrate some of the engineering principles behind the SKA such as structural integrity for the dishes, optical fibres, radio-frequency interference, sampling, etc. This project was funded by the Royal Academy of Engineering, part of their Ingenious award scheme.

The full set of activities, including instructions and list of material necessary and where to find it is available here. In some cases some of the material may no longer be available from its original supplier and should be sourced from alternative providers.

 

 

 

 

How do you make a light but solid structure?

The cheapest and most accessible activity in this set, you just need marshmallows and spaghetti! The SKA dishes support structure must be strong enough to hold up the 15 metre steel dish itself, as well as stand up to the harsh environment. However, it must do this using the least amount of materials possible and it must be relatively quick and easy to construct, in order to keep the project costs down (with 200 dishes to install for SKA1, costs could quickly spiral out of control if this was not taken into account).

In this activity, participants are challenged to create a structure that can support a weight, out of very simple materials. We suggest dried spaghetti and marshmallows. The spaghetti acts as girders, the marshmallows as joints, to demonstrate how structures can be reinforced to be the most stable!

What you’ll need: spaghetti and marshmallows.

 
How will the SKA transport data? 

A very simple demonstration. The SKA dishes and antennae will be connected by a vast network of fibre optic cables. These will carry the data from the individual detectors to a central processing unit, where the data is combined; making the SKA work as a single instrument, and eventually distribute over thousands of kilometres. How is that possible?

Information is transported down fibre optic cables as visible light. This can be demonstrated by firing a laser into a fibre optic cable and seeing it shine out the other end. Simply insert one end of the fibre optic cable into the recess of the laser pen bulb and turn it on. 

what you’ll need: a laser pointer and a strand of optical fibre.

Note: be careful never to point the laser into someone’s eye! 

 
Understanding why dishes have a parabolic shape

The shape of the bowl focuses sound waves to the microphone in the centre. This amplifies sound so that listeners wearing the headphones can hear conversations from quite a distance away (when they depress the trigger button on the underside).

The bowl is a 3D parabola. This shape reflects the sound to a point, called the focal point. The focal point is where the microphone sits. This is similar to how radio or satellite dishes work, with a receiver at the focal point. 

What you’ll need: a parabolic microphone.

 

Showing invisible signals exist

The RF (radio frequency) detector picks up radio waves, as the SKA will do. This can be used to demonstrate the existence of radio waves (which can be an abstract concept, since they are undetectable by the human body).

By bringing the antenna close to a source of radio waves (e.g. an active mobile phone, walkie-talkie, or radio mic), more bars will light up.

What you’ll need: an RF detector.

 

Demonstrating radio noise

Have an iPad? Then this activity is for you. The WiPry-Pro spectrum analyser is similar to the RF detector, in that it picks up radio waves; however it displays a real-time map of the radio frequencies. These frequencies are used for wireless communications, such as Wi-Fi networks, mobile phone signals and Bluetooth.

Like the RF detector, this can be used to demonstrate the existence of radio waves, but it can also be used to demonstrate the need to build the SKA in remote locations like remote areas of South Africa and Australia. Modern humans produce a lot of ‘radio noise’ due to wireless technology. In order to detect the (much fainter) radio signals from space, the SKA detectors must be built far from populated areas.

What you’ll need: a spectrum analyser for iPad.

 

Understanding different telescopes see different things, including invisible ones!

The FLIR Systems C2 Pocket Thermal Imaging System is a mobile-phoned sized camera that is sensitive to infrared radiation. This is a type of electromagnetic radiation (similar to light and radio waves). Although humans cannot see infrared waves, our skin can feel them as heat. This camera demonstrates that it is possible to build devices to see otherwise invisible types of electromagnetic radiation. It is analogous to how the SKA will create radio pictures of the universe; a type of light that is completely undetectable to the human eye. However, seeing these other forms of electromagnetic radiation show us hidden things in the universe.

Alternative infrared cameras exist that can be plugged into your mobile phone directly.

what you’ll need: an infrared camera

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