First Observations of Mars Atmosphere and Ionosphere with Tianwen-1 Radio-Occultation Technique on 5 August 2021

The radio-occultation technique can provide vertical profiles of planetary ionospheric and atmospheric parameters, which merit the planetary-climate and space-weather scientific research so far. The Tianwen-1 one-way single-frequency radio-occultation technique was developed to retrieve Mars ionospheric and atmospheric parameters. The first radio-occultation event observation experiment was conducted on 5 August 2021. The retrieved excess Doppler frequency, bending angle, refractivity, electron density, neutral mass density, pressure and temperature profiles are presented. The Mars ionosphere M1 (M2) layer peak height is at 140 km (105 km) with a peak density of about 3.7 x 10(10) el/m(3) (5.3 x 10(10) el/m(3)) in the retrieved electron-density profile. A planetary boundary layer (-2.35 km similar to 5 km), a troposphere (temperature decreases with height) and a stratosphere (24 km-40 km) clearly appear in the retrieved temperature profile below 50 km. Results show that Tianwen-1 radio occultation data are scientifically reliable and useful for further Mars climate and space-weather studies.

Automated summary

The radio-occultation technique is crucial for studying planetary climate and space weather. The Tianwen-1 mission successfully retrieved Mars ionospheric and atmospheric parameters, providing reliable and valuable data for further research on Mars climate and space weather.