Inversion of the Loss Tangent of Martian Regolith From Echoes of Ultrawideband Ground Penetration Radar in the Tianwen-1 Mission

In the Tianwen-1 Mars exploration mission, ultrawideband radar is carried by the Zhurong Martian rover. The exponential attenuation at the center frequency was applied to invert the loss tangent of Mars regolith in previous studies. Ignoring the frequency-dependent absorption in the ultrawideband might cause a large error in the inversion results. Considering the transmitted linear frequency-modulated (LFM) waves, in this letter, an analytical formula for the attenuation of ultrawideband waves to invert the loss tangents of Martian regolith is derived with the accumulation of the frequency-dependent attenuated spectrum. The newly inverted loss tangent is much larger than the inverted values with the center frequency. In addition, the inversion of the loss tangent from the ultrawideband radar data obtained in the Chang’e-5 lunar program is discussed. This letter presents a corrected inversion method for the loss tangent of regolith from ultrawideband radar echoes.