A Mars Riometer: Antenna Considerations

This is the final report on NASA Grant NAG5-9706. This project explored riometer (relative ionospheric opacity meter) antenna designs that would be practical for a Mars surface or balloon mission. The riometer is an important radio science instrument for terrestrial aeronomy investigations. The riometer measures absorption of cosmic radio waves by the overhead ionosphere. Studies have shown the instrument should work well on Mars, which has an appreciable daytime ionosphere. There has been concern that the required radio receiver antenna (with possibly a 10 meter scale size) would be too large or too difficult to deploy on Mars. This study addresses those concerns and presents several antenna designs and deployment options. It is found that a Mars balloon would provide an excellent platform for the riometer antenna. The antenna can be incorporated into the envelope design, allowing self-deployment of the antenna as the balloon inflates.