In recent years, we developed a small, unmanned aerial system (UAS) called OVLI-TA (Objet Volant Leger Instrumenté–Turbulence Atmosphérique) dedicated to atmospheric boundary layer research, in Toulouse (France). The device has a wingspan of 2.60 m and weighed 3.5 kg, including payload. It was essentially developed to investigate turbulence in a way complementary to other existing measurement systems, such as instrumented towers/masts. OVLI-TA’s instrumental package includes a 5-hole probe on the nose of the airplane to measure attack and sideslip angles, a Pitot probe to measure static pressure, a fast inertial measurement unit, a GPS receiver, as well as temperature and moisture sensors in specific housings. In addition, the Pixhawk autopilot is used for autonomous flights. OVLI-TA is capable of profiling wind speed, wind direction, temperature, and humidity up to 1 km altitude, in addition to measuring turbulence. After wind tunnel calibrations, flight tests were conducted in March 2016 in Lannemezan (France), where there is a 60-m tower equipped with turbulence sensors. In July 2016, OVLI-TA participated in the international project DACCIWA (Dynamics-Aerosol-Chemistry-Clouds Interactions in West Africa), in Benin. Comparisons of the OVLI-TA observations with both the 60 m tower measurements and the radiosonde profiles showed good agreement for the mean values of wind, temperature, humidity, and turbulence parameters. Moreover, it validated the capacity of the drone to sample wind fluctuations up to a frequency of around 10 Hz, which corresponds to a spatial resolution of the order of 1 m.

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A simulation analysis has been preformed to quantify the benefits to Mars entry navigation that can be expected if tracking data from Mars based beacons are used. Two types of Mars in situ beacon configurations are analyzed. The primary configuration is a ground based network consisting of beacons, pre-deployed by a mission's orbiter twin to within 50 km of an upcoming lander's anticipated touch down site. The second consists of the aforementioned surface beacons in combination with a single orbiting beacon either on-board a near circular polar orbiter (such as with the Mars Global Surveyor) or alternately on a Mars body-fixed equatorial synchronous, or more appropriately Areosynchronous, orbiter. In either case the tracking beacons would provide pseudo range and range-rate (Doppler) observations, hi this study, the Mars entry configuration is a Mars Path Finder (MPF) type entry reoriented follow along the equator in East-West crossing. For several beacon configuration scenarios, Extend Kalman Filter (EKF) runs are performed and the corresponding trajectory solution analyzed to quantify the benefit from its tracking. Atmospheric, aerodynamic, and other force as well as measurement models are included in this numerical simulation. In each configuration/solution combination, sensitivities to various sets of reasonable beacon location errors and associated measurement degradations (biases and data 'blackout') are presented.

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