Engineering topics
Hussein, Yasser
Publications and source records attributed to Hussein, Yasser.
VHF antenna far-field pattern measurements at 60 MHz using an outdoor antenna range for Europa Clipper mission
Improvements to measurements of a VHF folded dipole operating at 55-65 MHz to be used as part of a radar for a mission to one of Jupiter’s moons, Europa, are presented. Previous measurements using an unmanned aerial vehicle (UAV) or small unmanned aerial system (sUAS) are improved upon by reducing systematic errors and more accurately tracking distances within the measurement system on an outdoor measurement range at Jet Propulsion Laboratory (JPL). Details of the measurement system setup are presented along with a brief discussion of error sources. Comparing previously collected measurement data with the new measurements reveal an improvement of approximately 0.4 dB in accuracy with an improvement in over 1 dB for error budgets.
Far-Field Pattern Measurement and Simulation of VHF Antenna at 60 MHz for Europa Clipper Mission
This paper presents measurements and simulations of a linearly polarized VHF folded dipole operating at 60 MHz for NASA’s upcoming Europa Clipper mission. The spacecraft contains a ground penetrating radar, consisting of an array of four VHF antennas, that will characterize the surface of Jupiter’s icy moon Europa. Measured far-field radiation patterns and reflection coefficients above a 50×80m perfect ground plane are compared to predicted results using commercial software. Normalized Far-Field radiation pattern cuts are measured utilizing a biconical antenna and receiver mounted on a flying drone. Simulations of the radiation pattern show that the number of lobes increases with the distance of the antenna from the ground due to the ground-bounce phenomenon. In addition, the measured and simulated reflection coefficients stay unchanged for height above 2 meters, which matches the predicted calculation of the reactive-near field region of this antenna. However, the antenna electrical parameters are optimized for use on the spacecraft and become detuned in the presence of a ground plane. Simulated and measured return loss discrepancy less than 0.5 dB is presented. Radiation pattern comparisons show similar agreement when taking into account the effect of far-field measurement uncertainties.
Far-Field Pattern Measurement and Simulation of VHF Antenna at 60 MHz for Europa Clipper mission
UNKNOWN