GNSS Yaw-Attitude Estimation: Results for QZSS Block-II Satellites Using Single- or Triple-Frequency Signals from two Antennas

Abstract

The QZSS constellation has added three new Block-II satellites. Two of these satellites have been launched into inclined geosynchronous orbits and one into a geostationary orbit. All three spacecraft broadcast ranging signals on GPS L1, L2 and L5 frequencies from their main L-band antenna together with the centimeter-level Augmentation service (CLAS) signal L6 (formerly LEX) on the Galileo E6 frequency band. Like QZS-1, a sub-meter level Augmentation service (SLAS) signal is transmitted from a separate antenna on the GPS L1 frequency. A new feature is the addition of the position technology verification service (PTV) signal on the L5 frequency from yet another antenna. Differential processing of measurements from different observations allow for an estimation of the satellite’s yaw attitude after determination of the antenna baseline vector. The L1 SLAS and the L1 C/A-code signals have been used to estimate the yaw attitude with an accuracy of less than 1°. Differential carrier-phase center variation maps have been derived for this signal combination. Yaw estimation results are presented for period of special interest, for example 360° yaw rotations, orbit correction maneuvers and the satellite’s eclipse period, where a special pseudo yaw steering attitude mode is applied. The second part of the paper introduces a new concept using triple-frequency signals from two different antennas for attitude determination. This method is demonstrated with QZSS measurements, but is also applicable to other satellite navigation system, like the enhanced GLONASS-M satellites with L3 signal capabilities