Reprocessing of the Parkes Multibeam Pulsar Survey has resulted in the discovery of five previously unknown pulsars and several as-yet-unconfirmed candidates. PSR J0922−52 has a period of 9.68 ms and a DM of 122.4 pc cm −3 . PSR J1147−66 has a period of 3.72 ms and a DM of 133.8 pc cm −3 . PSR J1227−6208 has a period of 34.53 ms, a DM of 362.6 pc cm −3 , is in a 6.7 day binary orbit, and was independently detected in an ongoing high-resolution Parkes survey by Thornton et al. and also in independent processing by Einstein@Home volunteers. PSR J1546−59 has a period of 7.80 ms and a DM of 168.3 pc cm −3 . PSR J1725−3853 is an isolated 4.79-ms pulsar with a DM of 158.2 pc cm −3 . These pulsars were likely missed in earlier processing efforts due to the fact that they have both high DMs and short periods, and also the large number of candidates that needed to be looked through. These discoveries suggest that further pulsars are awaiting discovery in the multibeam survey data.
In this paper, a multi-antenna Global Navigation Satellite System (GNSS), multi-sensor attitude estimation algorithm is outlined, and its sensitivity to various error sources is assessed. The attitude estimation algorithm first estimates attitude using multiple GNSS antennas, and then fuses a host of other attitude estimation sensors including tri-axial magnetometers, Sun sensors, and inertial sensors. This work is motivated by the attitude determination needs of the Antarctic Impulse Transient Antenna (ANITA) experiment, a high-altitude balloon-lofted science platform. In order to assess performance trade-offs of various algorithm configurations, the attitude estimation performance of various approaches is tested using a simulation that is based on recorded ANITA III flight data. For GNSS errors, attention is focused on multipath, receiver measurement noise, and carrier-phase breaks. For the remaining attitude sensors, different grades of sensor are assessed. Through a Monte-Carlo simulation, it is shown that, under typical conditions, sub-0.1 degree attitude accuracy is available when use multiple antenna GNSS data only, but that this accuracy can degrade to degree-level in some environments warranting the inclusion of additional attitude sensors to maintain the desired level of accuracy.
We present various performance trades for multiantenna global navigation satellite system (GNSS) multisensor attitude estimation systems. In particular, attitude estimation performance sensitivity to various error sources and system configurations is assessed. This study is motivated by the need for system designers, scientists, and engineers of airborne astronomical and remote sensing platforms to better determine which system configuration is most suitable for their specific application. In order to assess performance trade-offs, the attitude estimation performance of various approaches is tested using a simulation that is based on a stratospheric balloon platform. For GNSS errors, attention is focused on multipath, receiver measurement noise, and carrierphase breaks. For the remaining attitude sensors, different performance grades of sensors are assessed. Through a Monte Carlo simulation, it is shown that, under typical conditions, sub-0.1-degree attitude accuracy is available when using multiple antenna GNSS data only, but that this accuracy can degrade to degree level in some environments warranting the inclusion of additional attitude sensors to maintain the desired level of accuracy. Further, we show that integrating inertial sensors is more valuable whenever accurate pitch and roll estimates are critical.
Characterization and Flight Test of a Multi-Antenna GNSS, Multi-Sensor Attitude Determination Algorithm Nathan Tehrani A multi-antenna Global Navigation Satellite System (GNSS), multi-sensor attitude estimation algorithm is outlined, and its sensitivity to various error sources is assessed. The attitude estimation algorithm first estimates attitude using multiple GNSS antennas, and then fuses a host of other attitude estimation sensors including tri-axial magnetometers, Sun sensors, and inertial sensors. This work is motivated by the attitude determination needs of the Antarctic Impulse Transient Antenna (ANITA) experiment, a high-altitude balloon-suspended science platform. In order to assess performance trade-offs of various algorithm configurations, the attitude estimation performance of various approaches is tested using a simulation that is based on recorded ANITA III flight data. For GNSS errors, attention is focused on multipath, receiver measurement noise, and carrier-phase breaks. For the remaining attitude sensors, different grades of sensor are assessed. Through a Monte-Carlo simulation, it is shown that, under typical conditions, sub-0.1 degree attitude accuracy is available when using multiple antenna GNSS data only, but that this accuracy can degrade to degree-level in some environments warranting the inclusion of additional attitude sensors to maintain the desired level of accuracy. This algorithm was validated in a flight test. A WVU Phastball unmanned aerial vehicle was outfitted with GNSS receivers, an IMU, a magnetometer, and a Sun sensor to collect flight data. To determine the wing flex during flight, and correct the body-centric antenna coordinates, a computer vision algorithm was developed to use aircraft-mounted camera data to track markers along the wing surface and estimate the wing deflection. First and foremost, I must thank my advisor, Dr. Jason Gross, for providing the many hours of guidance, motivation, and technical assistance that made this work possible. I also thank the members of my committee, Dr. John Christian and Dr. Yu Gu, for providing the extra help and guidance that I often needed while working on this project. I must give special thanks to Scott Harper, who provided technical guidance on the Phastball Zero instrumentation. And to Stefane D'Urso for designing several of the mount points for the instruments and helping me with all aspects of the aircraft. Thank you for teaching me all that you did about the aircraft and about aircraft in general.
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