A miniaturized impedance probe for ionospheric sensing

Abstract

Space weather refers to “conditions on the Sun and in the solar wind, magnetosphere, ionosphere, and the thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health” [National Space Weather Program, 1995]. Of particular interest are the effects caused by the ionosphere, which is an ionised region of the upper atmosphere, ranging from approximately 90 to 1500 km. The ionosphere can degrade the performance of many radio systems; these include satellite navigation systems (i.e. GPS), satellite communications and space based radar. Measurements of the electron density in the ionosphere can be used to improve empirical ionospheric models or as inputs into assimilative ionospheric models, thereby permitting the development of better techniques to mitigate the impact of the ionosphere on radio systems. Ground-based radar systems may be used to make measurements of the bottom-side of the ionosphere (i.e. below the height of the peak density), and GPS provides a means of making integrated measurements of total electron content between a satellite and a receiver. However, for measurements of the top-side of the ionosphere, satellite based instrumentation is required. A radio frequency ionospheric impedance probe (ImP) is being developed by the Space Environment and Radio Engineering group at the University of Birmingham, UK, to provide in-situ measurements of the top-side electron density. ImP will measure this density by exciting an antenna embedded in the ionosphere – the frequencies at which the antenna resonates can then be used to estimate the electron density. ImP can be hosted on a dedicated very small spacecraft, such as a PocketQube. A PocketQube is a small spacecraft typically measuring 5x5x5 cm. Alternatively, it could be hosted as a secondary payload on a larger platform, such as a CubeSat or larger. Effective ionospheric measurements will require several ImPs to be installed on satellite constellations to provide measurements with high spatial and temporal resolution. A PocketQube platform is being developed by the Astrionics group at the University of Malta, with a target of launching a complete spacecraft with an ImP in March 2018. The platform is being developed to meet the design constraints imposed by ImP. ImP requires both orbital positioning data and attitude determination, which is to be provided by the platform. ImP measurements also require a magnetically clean environment as it is susceptible to local magnetic fields. This poster paper will describe the principle of operation behind ImP, as well as the design of the instrument itself. It will also describe the challenges involved in designing a versatile PocketQube spacecraft architecture that can accommodate a scientific payload.