Self-Deploying Antennas for Proof-of-Concept Radio Astronomy Science Satellite

In this paper the usage of Shape Memory Alloy (SMA) is presented as building material for deployable antennas. Using this material a Yagi-Uda and horn antenna are realized. For research towards space-based low frequency radio astronomy between 80 kHz - 30 MHz, sensitive antennas are needed to receive signals originating from the Dark Ages (13 billion years ago). A solution for the design of such antennas having an advanced shape or structure is by using Shape Memory Alloy. This metal can be trained to ‘remember’ a certain shape. After cooling down, SMA is known by its ability to be deformed and to recover to its pre-trained shape by heating it to a certain transition temperature, which in space can be achieved by the radiation of the sun. These frequencies (80 kHz - 30 MHz) are challenging to mea-sure on Earth due to the radio opaqueness of the ionosphere. Therefore, two antennas were simulated, constructed, deployed and measured for a proof-of-concept satellite; a Yagi-Uda an-tenna and an horn antenna. Both antennas fit within 0.5U ( $10\times 10\times 5\ \text{cm}$ ) when stowed. Experiments were done on these novel antennas. In terms of deployment, the Yagi-Uda antenna shows a deployment from 50 mm to slightly less than the pre-designed 400 mm, meaning a recovery of over 95%. Measurements show that the realized gain compared to simulations (10.1 dBi) is only 2 and 2.2 dBi less for the ideal and deployed antenna, respectively. The horn antenna, on the other hand, with an full height of 200 mm was deployed and measured in steps as the plate material for the sides was determined to be unreliable in deployment. Only a recovery of around 60% is achieved. An average gain difference over the band between ideal and full deployment was around 4 dB. This was decreased to 2.5 dB by further improvements. The results show that there is great potential in the usage of Shape Memory Alloy for radio astronomy, but also for antenna design and reconfigurability in general.