GNSS Attitude Determination for Long Duration HAPS Missions

M. Turner and T. Reynolds

Peer Reviewed

Abstract: The class of Unmanned Aerial Systems (UAS) which operate at high altitude and have very long flight endurance are termed as High Altitude Pseudo Satellites (HAPS). These are being developed to carry a variety of payloads including communications, navigation and earth observation missions. This paper considers the needs of the Zephyr, which is the Airbus HAPS offering. To accurately determine the location of a target at maximum range requires accurate knowledge of the attitude of the platform. This is particularly true when there are very few other points of reference e.g. maritime surveillance or forestry protection. One of the driving requirements for equipment fitted to HAPS is the size weight and power (SWaP), coupling this with the very long flight endurance which can be several months, rules out traditional INS navigation systems. Accurate, low drift INS are too heavy & low SWaP MEMS INS suffer from excessive drift over the flight duration. This means that only GNSS can provide the attitude performance over the full duration of the mission. An analysis of the maritime surveillance use case has shown that the attitude determination requirement is in the order of 0.05°. This is needed to sufficiently pinpoint a ships location at maximum sensor range. The maximum practical GNSS sensor baseline available on the Zephyr HAPS under consideration is 1m. To be able to achieve the accuracy needed means a significant improvement in the GNSS receiver carrier performance. A block processing approach is proposed which provides the most likely estimate of the carrier phase over the observation period. The observation period of a block processing algorithm can be much longer than a typical PLL loop bandwidth thereby providing a much better estimate of the carrier phase. The block processing approach can provide as much as 10 times more accuracy than a conventional DLL/ PLL. In this way the accuracy needs of the HAPS can be met.
Published in: Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018)
September 24 - 28, 2018
Hyatt Regency Miami
Miami, Florida
Pages: 2695 - 2702
Cite this article: Turner, M., Reynolds, T., "GNSS Attitude Determination for Long Duration HAPS Missions," Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018), Miami, Florida, September 2018, pp. 2695-2702.
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