Progress of radio occultation exploration of Mars

Mars is the sister star of Earth. Studying Mars is important to understand its evolution as well as that of Earth and even the solar system. Since the launch of American Mariner 4 in 1964 and the first successful use of radio occultation technology to explore the environmental characteristics of Mars, many international missions to Mars have conducted occultation experiments and made important progress. This article investigates Mars probes based on their launch time sequence, which utilized radio occultation techniques for exploration, focusing on groundbreaking missions such as the Mariner series, Mars Global Surveyor, Mars Express, Mars Atmosphere and Volatile Evolution, and Tianwen-1. We review, analyze, and summarize the product information, including the number and distribution of profile measurements, and the methods of acquisition obtained from each mission's radio occultation. Additionally, this article analyzes the limitations of the current Mars radio occultation approaches and explores possible countermeasures. Mars radio occultation can be further improved by considering the mode of star-star occultation combined with star-ground occultation to form occultation constellation, choosing an appropriate signal detection frequency, and improving the inversion algorithm. It can also be combined with the Mars top detection radar and direct detection means to develop multi-source data fusion. With the continuous improvement of detection modes, radio occultation detection will be an important tool for Mars exploration in the future. Detections will grow in number and become increasingly more comprehensive in time and space coverage, and more accurate occultation data for the entire space environment of Mars will be obtained, including large, mesoscale, and even small-scale structure characteristics and evolution laws

Short-Period Variation of the Activity of Atmospheric Turbulence in the MLT Region over Langfang

In this paper, we investigate the activity of atmospheric turbulence in the MLT region and the relationship between the activity of atmospheric turbulence and atmospheric wave activity. We use data from the Langfang MF radar (39.4∘N, 116.7∘E) from July 2019 to June 2020 and NRLMSIS 2.0 to calculate the parameters of atmospheric wave activity and atmospheric turbulence energy dissipation rate (ε). Atmospheric ε is modulated by different periods at different altitudes, and while there are 12 h and 24 h periods at all altitudes, the main period is different at different altitudes. A comparison of the ε with atmospheric tide activity shows that tides have an effect on ε, and the influence of tides on ε may be different at different altitudes. The pattern of variation in ε is similar to that of the atmospheric activity of the gravity wave, with both ε and the atmospheric activity of the gravity wave showing significant semi-annual variation

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 × 1010 el/m3 (5.3 × 1010 el/m3) in the retrieved electron-density profile. A planetary boundary layer (−2.35 km~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

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 × 1010 el/m3 (5.3 × 1010 el/m3) in the retrieved electron-density profile. A planetary boundary layer (−2.35 km~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