RF characterization of the Mars Exploration Rover radar altimeter antennas-airbag interaction

Presents results of the Mars Exploration Rover-03 (MER) radar altimeter antennas-airbag interaction. The objective of this work is to determine the impact of the MER airbag on the radiation properties and mutual coupling and return loss of the radar altimeter antennas at the design frequency of 4.3 GHz and over a frequency band of 25 MHz. This is done to ultimately assess any impacts or risks to the radar altimeter system performance. Because the radar altimeter antennas are close (near-field region) to the airbag when it is inflated, we have considered several configurations to characterize the antennas´ performance. These characterizations should allow us to determine the proper link budget for the radar altimeter in terms of signal lock during MER descent to the Martian surface. It is shown that the mutual coupling between radar altimeter antennas may be affected when the airbag is on top or in the close proximity to the antennas, 0 to 15.24 cm (or 2.18λ), and the radar may not function properly for certain orientations and positions within this region. It is demonstrated that as the airbag is withdrawn away from the antennas (toward the far-field region of the antennas), the antenna´s performance will be decoupled from the airbag.