Linköping, Sweden
Linköping, Sweden

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Chauvin M.,KTH Royal Institute of Technology | Chauvin M.,The Oskar Klein Center | Floren H.-G.,Albanova University Center | Jackson M.,KTH Royal Institute of Technology | And 24 more authors.
Experimental Astronomy | Year: 2015

In the 50 years since the advent of X-ray astronomy there have been many scientific advances due to the development of new experimental techniques for detecting and characterising X-rays. Observations of X-ray polarisation have, however, not undergone a similar development. This is a shortcoming since a plethora of open questions related to the nature of X-ray sources could be resolved through measurements of the linear polarisation of emitted X-rays. The PoGOLite Pathfinder is a balloon-borne hard X-ray polarimeter operating in the 25-240 keV energy band from a stabilised observation platform. Polarisation is determined using coincident energy deposits in a segmented array of plastic scintillators surrounded by a BGO anticoincidence system and a polyethylene neutron shield. The PoGOLite Pathfinder was launched from the SSC Esrange Space Centre in July 2013. A near-circumpolar flight was achieved with a duration of approximately two weeks. The flight performance of the Pathfinder design is discussed for the three Crab observations conducted. The signal-to-background ratio for the observations is shown to be 0.25 ±0.03 and the Minimum Detectable Polarisation (99 % C.L.) is (28.4 ±2.2) %. A strategy for the continuation of the PoGOLite programme is outlined based on experience gained during the 2013 maiden flight. © 2015 Springer Science+Business Media Dordrecht

Pearce M.,Albanova University Center | Floren H.-G.,Albanova University Center | Jackson M.,Albanova University Center | Kamae T.,Stanford University | And 7 more authors.
IEEE Nuclear Science Symposium Conference Record | Year: 2012

PoGOLite is a hard X-ray polarimeter operating in the 25-100 keV energy band. The instrument design is optimised for the observation of compact astrophysical sources. Observations are conducted from a stabilised stratospheric balloon platform at an altitude of approximately 40 km. The primary targets for first balloon flights of a reduced effective area instrument are the Crab and Cygnus-X1. The polarisation of incoming photons is determined using coincident Compton scattering and photo-absorption events reconstructed in an array of plastic scintillator detector cells surrounded by a bismuth germanate oxide (BGO) side anticoincidence shield and a polyethylene neutron shield. A custom attitude control system keeps the polarimeter field-of-view aligned to targets of interest, compensating for sidereal motion and perturbations such as torsional forces in the balloon rigging. An overview of the PoGOLite project is presented and the outcome of the ill-fated maiden balloon flight is discussed. © 2012 IEEE.

Stromberg J.-E.,DST Control
European Space Agency, (Special Publication) ESA SP | Year: 2011

The paper describes a modular solution for science platform stabilisation. The solution was developed for project PoGOLite and is based on technology developed by DST CONTROL over the last 20 years. PoGOLite is a balloon-borne X-ray polarimeter with an energy range of 25-80 keV. To meet the scientific objectives, the platform must be capable of absolute angular positioning to within 0.1° or better. This requirement must be met without the support from star trackers. The solution combines a distributed control system with intelligent bus nodes, a high speed bus for wide band width servo loops, and a graphical design tool with an automatic code generator. All the bus nodes conform to a simple standardised bus interface and are equipped with powerful FPGAs providing enough computational power for advanced distributed signal processing. The presented modular solution is capable of meeting a wide range of scientific applications and budgets.

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