Opto-mechanical designs for the HARMONI adaptive optics systems
Proceedings of SPIE SPIE 10703 (2018)
Abstract:HARMONI is a visible and near-infrared integral field spectrograph equipped with two complementary adaptive optics systems, fully integrated within the instrument. A Single Conjugate AO (SCAO) system offers high performance for a limited sky coverage and a Laser Tomographic AO (LTAO) system provides AO correction with a very high sky-coverage. While the deformable mirror performing real-time correction of the atmospheric disturbances is located within the telescope itself, the instrument contains a suite of state-of-the-art and innovative wavefront sensor systems. Laser guide star sensors (LGSS) are located at the entrance of the instrument and fed by a dichroic beam splitter, while the various natural guide star sensors for LTAO and SCAO are located close to the science focal plane. We present opto-mechanical architecture and design at PDR level for these wavefront sensor systems.
Corrigendum to: Further Evidence of a Brown Dwarf Orbiting the Post-Common Envelope Eclipsing Binary V470 Cam (HS 0705+6700)
Open Astronomy (2018)
Abstract:© 2018 D. Bogensberger, published by De Gruyter. "Eclipse times for HS 0705+6700 which Bogensberger et al. (2017, Open Astronomy 26, 134, their table 2) list are exposure-start times; times of mid-exposure are obtained by adding thirty seconds (0.00035 days) to each entry. Third body orbital parameterswhich Bogensberger et al. deduce are superseded by the analysis of more recent data, to be the subject of a future publication".
Further evidence of a brown dwarf orbiting the post-common envelope eclipsing binary V470 cam (HS 0705+6700)
Open Astronomy De Gruyter 26:1 (2017) 134-138
Abstract:Several post-common envelope binaries have slightly increasing, decreasing or oscillating orbital periods. One of several possible explanations is light travel-time changes, caused by the binary centre-of-mass being perturbed by the gravitational pull of a third body. Further studies are necessary because it is not clear how a third body could have survived subdwarf progenitor mass-loss at the tip of the Red Giant Branch, or formed subsequently. Thirty-nine primary eclipse times for V470 Cam were secured with the Philip Wetton Telescope during the period 2016 November 25thto 2017 January 27th. Available eclipse timings suggest a brown dwarf tertiary having a mass of at least 0.0236(40) M, an elliptical orbit with an eccentricity of 0.376(98) and an orbital period of 11.77(67) years about the binary centre-of-mass. The mass and orbit suggest a hybrid formation, in which some ejected material from the subdwarf progenitor was accreted on to a precursor tertiary component, although additional observations would be needed to confirm this interpretation and investigate other possible origins for the binary orbital period change.
CASTAway: An asteroid main belt tour and survey.
Advances in Space Research Elsevier 62:8 (2017) 1998-2025
Abstract:CASTAway is a mission concept to explore our Solar System’s main asteroid belt. Asteroids and comets provide a window into the formation and evolution of our Solar System and the composition of these objects can be inferred from space-based remote sensing using spectroscopic techniques. Variations in composition across the asteroid populations provide a tracer for the dynamical evolution of the Solar System. The mission combines a long-range (point source) telescopic survey of over 10,000 objects, targeted close encounters with 10 – 20 asteroids and serendipitous searches to constrain the distribution of smaller (e.g. 10 m) size objects into a single concept. With a carefully targeted trajectory that loops through the asteroid belt, CASTAway would provide a comprehensive survey of the main belt at multiple scales. The scientific payload comprises a 50 cm diameter telescope that includes an integrated low-resolution (R = 30 – 100) spectrometer and visible context imager, a thermal (e.g. 6 – 16 μm) imager for use during the flybys, and modified star tracker cameras to detect small (~10 m) asteroids. The CASTAway spacecraft and payload have high levels of technology readiness and are designed to fit within the programmatic and cost caps for a European Space Agency medium class mission, whilst delivering a significant increase in knowledge of our Solar System.
Sensing and control of segmented mirrors with a pyramid wavefront sensor in the presence of spiders
Adaptive Optics for Extremely Large Telescopes, 2017 AO4ELT5 2017-June (2017)