NUTS - NTNU Test Satellite, a Norwegian CubeSat Project

Antennas

The NUTS satellite will use two antennas, one for VHF and one for UHF. Both antennas will be flat turnstile antennas (crossed dipoles).

In order to circumvent unpredictable polarization loss due to Faraday rotation in the atmosphere it has been concluded that the ground station must use circular polarization. In order to minimize the polarization loss it is also preferable with circular polarization on the spacecraft, which is one reason to use turnstile antennas.

Moreover, as the satellite will have a varying elevation angle as it passes the sky, the off-nadir angle will also change, and as a consequence, the antennas should be designed, not to be directive, but to optimize the link margin for as many elevation angles as possible. The turnstile antennas outperforms several other commonly used antennas for CubeSats in this respect.

The antennas will be made of measuring tape wrapped around the satellite and tightened with nylon lines which will be burnt off by NiChrome-wire for deployment such that the measuring tape will restore to its original shape and form the elements of the turnstile antennas. This will be done sequentially to prevent jamming of the antennas.