Semester

Summer

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Yu Gu

Committee Co-Chair

Guilherme Pereira

Committee Member

Guilherme Pereira

Committee Member

Hang Woon Lee

Abstract

Although Venus and Earth began as twins, possessing comparable size, mass, and composition, past exploration missions have revealed that Venus is now hellishly hot, devoid of oceans, and enveloped in a carbon dioxide-filled atmosphere. To understand when and why this evolutionary divergence occurred, further exploration is required. Today, there is a growing interest in the use of aerial platforms to circumvent the harsh conditions at the surface, which limit the lifetime of landed instruments. In this concept, a single balloon, propelled by the ambient wind field, would operate in the atmosphere at an altitude between 50 and 70 km, where the temperature and pressure are akin to those on Earth. Concurrently, a single satellite would be deployed in a well-defined orbit to provide real-time positioning updates. During the balloon's operation, it would encounter persistent cloud cover, super-rotation winds, and intermittent satellite communication.

Localization, defined as the ability to estimate position and orientation in relation to one's surroundings, is a fundamental aspect of the balloon's mission. While proprioceptive sensors, such as an inertial measurement unit, can provide continuous data regarding the balloon’s internal state, they are insufficient for accurate long-term localization due to the integration of sensor error over time. In contrast, exteroceptive sensors measure the state of the surrounding environment. For this specific problem, a barometric altimeter and radar altimeter could be used to measure the ground elevation and compare it against a known topographic map, in a form of map-aided navigation. However, due to the self-similarity in natural terrains, this may not provide a unique solution. Alternatively, single-satellite positioning offers direct position measurements, but only when communication is possible.

In this thesis, a novel solution to balloon localization in the atmosphere of Venus is proposed. Initially, a Rao-Blackwellized Particle Filter (RBPF), which is capable of handling multi-modality, integrates map-aided navigation with the inertial solution in real time. Following intermittent observations of the orbiter, factor graph optimization smooths single-satellite positioning with the preliminary RBPF result. Through a MATLAB simulation, the algorithm was shown to enhance localization performance in comparison to its inertial counterpart. Furthermore, a sensitivity analysis demonstrates the algorithm’s performance with varying sensor quality, map resolution, observation frequency, and operational height.

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