Implementation of the frequency-modulated sideband search method for gravitational waves from low mass X-ray binaries

We describe the practical implementation of the sideband search, a search for periodic gravitational waves from neutron stars in binary systems. The orbital motion of the source in its binary system causes frequency-modulation in the combination of matched filters known as the $\mathcal{F}$-statistic. The sideband search is based on the incoherent summation of these frequency-modulated $\mathcal{F}$-statistic sidebands. It provides a new detection statistic for sources in binary systems, called the $\mathcal{C}$-statistic. The search is well suited to low-mass X-ray binaries, the brightest of which, called Sco X-1, is an ideal target candidate. For sources like Sco X-1, with well constrained orbital parameters, a slight variation on the search is possible. The extra orbital information can be used to approximately demodulate the data from the binary orbital motion in the coherent stage, before incoherently summing the now reduced number of sidebands. We investigate this approach and show that it improves the sensitivity of the standard Sco X-1 directed sideband search. Prior information on the neutron star inclination and gravitational wave polarization can also be used to improve upper limit sensitivity. We estimate the sensitivity of a Sco X-1 directed sideband search on 10 days of LIGO data and show that it can beat previous upper limits in current LIGO data, with a possibility of constraining theoretical upper limits using future advanced instruments.Comment: 20 pages, 5 figure

A technique for improving conflict alerting performance in the context of runway incursions

An effective solution to the problem of runway incursions is long overdue. To date, an average of a thousand incursions are registered yearly in the United States alone, with similar figures registed in Europe. Installing a system on-board aircraft capable of providing an alert in the case of a runway incursion has the potential of significantly reducing this. As with any conflict detection and alerting system, the difficulty lies in the fine-tuning of the parameters which define a conflict, in effect resulting in finding the right trade-off between false and missed detections and associated alerts. This is an important consideration in the design of any conflict detection system and is key in the context of runway incursion alerting where aircraft would be travelling at high speed and in close proximity of eachother. This paper addresses this problem by providing an assessement on the effects of false and missed detections in the event of a runway incursion and provides mathematical tools for tuning the conflict detection boundaries.peer-reviewe

A 6 DoF navigation algorithm for autonomous underwater vehicles

US

6-DoF Navigation Systems for Autonomous Underwater Vehicles

Austri

Design and development of a reduced form-factor high accuracy three-axis teslameter

Acknowledgments: The authors would like to thank Reuben Debono for his useful guidance and help in the PCB assembly of the instruments at the Electronic Systems Lab at the Faculty of Engineering at University of Malta. The authors would like to thank R. Ganter, project leader of the Athos undulator beamline and H-H. Braun, SwissFEL machine director, for their constant support throughout the entire project. The authors would like to thank Sasa Spasic and his team at Sentronis facilities for their fruitful discussions and their guidance during testing.A novel three-axis teslameter and other similar machines have been designed and developed for SwissFEL at the Paul Scherrer Institute (PSI). The developed instrument will be used for high fidelity characterisation and optimisation of the undulators for the ATHOS soft X-ray beamline. The teslameter incorporates analogue signal conditioning for the three-axes interface to a SENIS Hall probe, an interface to a Heidenhain linear absolute encoder and an on-board high-resolution 24-bit analogue-to-digital conversion. This is in contrast to the old instrumentation setup used, which only comprises the analogue circuitry with digitization being done externally to the instrument. The new instrument fits in a volumetric space of 150 mm × 50 mm × 45 mm, being very compact in size and also compatible with the in-vacuum undulators. This paper describes the design and the development of the different components of the teslameter. Performance results are presented that demonstrate offset fluctuation and drift (0.1–10 Hz) with a standard deviation of 0.78 µT and a broadband noise (10–500 Hz) of 2.05 µT with an acquisition frequency of 2 kHz.peer-reviewe

Performance analysis of a reduced form-factor high accuracy three-axis teslameter

In the framework of the SwissFEL project at the Paul Scherrer Institute (PSI), a Hall probe bench is being developed for the high-precision magnetic characterization of the insertion devices for the ATHOS soft X-ray beamline. For this purpose, a novel three-axis teslameter has been developed, which will be placed between the undulator and its outer shell in a very limited volumetric space of 150 × 50 × 45 mm. Together with a SENIS® 3-axis Hall probe at the center of the cross sectional area of the undulator, the setup will traverse along the undulator length on a specifically designed rig with minimal vibrations. This teslameter has all the analog signal conditioning circuitry for the Hall probe and also has on board 24-bit digitization. The instrument also handles an interface to a linear absolute encoder. The old instrumentation used only had analog signal conditioning circuitry whilst digitization was done off board. The new instrument also provides a very accurate magnetic field map in the µT range with simultaneous readings from the position encoder at an accuracy of ±3 µm. In this paper, a series of tests are described, which were performed at PSI in order to establish the measuring precision and repeatability of the instrument.peer-reviewe

Calibration and characterization of a reduced form-factor high accuracy three-axis teslameter

A new reduced form-factor three axes digital teslameter, based on the spinning current technique, has been developed. This instrument will be used to characterize the SwissFEL insertion devices at the Paul Scherrer Institute (PSI) for the ATHOS soft X-ray beamline. A detailed and standardized calibration procedure is critical to optimize the performance of this precision instrument. This paper presents the measurement techniques used for the corrective improvements implemented through non-linearity, temperature offset, temperature sensitivity compensation of the Hall probe and electronics temperature compensation. A detailed quantitative analysis of the reduction in errors on the application of each step of the calibration is presented. The percentage peak error reduction attained through calibration of the instrument for reference fields in the range of ±2 T is registered to drop from 1.94% down to 0.02%.peer-reviewe

Towards optimized profile descents at Malta International Airport through revised approach procedures

The work presented in this paper was conducted as part of the CLEAN-FLIGHT project which is financed by the Malta Council for Science and Technology through the National Research and Innovation Programme 2011 (Grant Agreement R&I-2011-021).Traditionally, aircraft descend from cruise level towards the aerodrome in a stepped manner as directed by Air Traffic Control to ensure safe separation between aircraft, particularly in the terminal area. A descent methodology that is now being preferred is that of optimised profile descents (OPD). In OPDs, the aircraft descends from the top-of-descent (TOD) point towards the aerodrome following a smooth, continuous descent profile that is optimal from an operational perspective of choice, until it intersects the final approach glide path such as that of the Instrument Landing System (ILS). OPDs are advantageous because they consume less fuel and generate fewer emissions than their stepped counterparts. This paper presents a proposal of new approach procedures for use in the approaches to Malta International Airport (MIA) that will facilitate the introduction of OPDs. With around 28,000 aircraft movements per annum at MIA, this can be achieved by giving Air Traffic Control Officers (ATCOs) a selection of approach procedures on which to direct in-trail inbound and outbound aircraft without imposing altitude constraints. The discussion includes a study of current procedures, a statistical analysis of historical radar plots, the presentation of the proposed approaches, and a forecast of the potential gains in terms of fuel burn and emissions expected through fast-time simulation.peer-reviewe

A traffic surveillance function and conflict detection method for runway manoeuvres

Runway conflicts continue to occur regularly in commercial aviation. There have been several initiatives worldwide to implement new systems capable of detecting such conflicts. For example, ground based systems have been implemented in several airports improving the air traffic controller situational awareness. Unfortunately, however, these systems fail to provide support in situations where the time to conflict is very short. This paper discusses the implementation of an algorithm for traffic surveillance and runway conflict detection on board the aircraft to provide the necessary information directly to the crew. The rules on which the detection algorithm is based and the alert suppression logic to reduce the number of nuisance alerts are discussed. A description of the multi-threaded software architecture is also included