Date	Speaker	Topic
28.09.2018 (11hrs, MPIA Hoersaal)	Prashant Pathak (ESO)	Closed-loop correction of atmospheric dispersion for high-contrast coronography and astrometry On ground-based telescopes employing adaptive optics (AO) systems, atmospheric dispersion compensation is essential to deliver high-quality imaging, and critical for coronagraphy and high-precision astrometry. Imperfect compensation by an atmospheric dispersion compensator (ADC) can be addressed with a high-precision on-sky measurement of residual dispersion in a closed-loop control scheme. In this talk, Prashant Pathak will present a focal plane based technique, which utilizes the chromatic scaling of speckles to measure residual dispersion (atmospheric and optical) in the final science image. The residual dispersion can be accurately measured and subsequently corrected in a closed-loop control. On-sky residual dispersion of < 1 mas across H-band was demonstrated, which reduced from 8.4 mas before closing the loop. Presentation: English Slides: English Questions: German, English
05.10.2018
12.10.2018 (11hrs, MPIA Hoersaal)	Hans-Ulrich Kaeufl (ESO)	NEAR - Planet search around Alpha Centauri with VISIR ESO, in collaboration with the Breakthrough Initiatives, modifies the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability this instrument has, by adding a dedicated coronagraph. This enables a meaningful search for potentially habitable planets around both Alpha Cen1 and 2. Meaningful here means, achieving a contrast of ~10-6 within ~0.8arcsec from the star while maintaining basically the normal sensitivity of VISIR. For risk mitigation all components are being tested and qualified under realistic conditions in the lab at ESO headquarters before integration into the instrument. Hans-Ulrich Kaeufl will give an overview of - the optical changes to VISIR - the implementation of wave front sensing - the Dicke switch (fast chopping for noise suppression) design and laboratory testing - the Annular Groove Phase Mask design and laboratory testing - non common path error control with a ZELDA mask - sensitivity and contrast estimates - data flow and analysis - the overall project status, plan and outlook Needless to say that this project is of critical interest for future infrared instrumentation at the next generation of extremely large telescopes aiming at surveying the solar neighbourhood for terrestrial planets by detecting and characterizing them based on their mid-IR fluxes. Therefore some emphasis will be put on the verification of the novel chopper system, the Dicke switch. Presentation: German Slides: English Questions: German, English
19.10.2018
26.10.2018 (11hrs, MPIA Hoersaal)	Armin Huber	Slide-Show: Life at the VLT - Part 2 of the famous photo reportage Today, Armin Huber will present us some impressions of how installation work at the Very large Telescope (VLT) looks like. To make it a complete story, he certainly will also talk about the trip to Chile, the accommodation and food options, and last but not least the recreation possibilities. And while part 1 about the LBT included Native Americans and Red Squirrels, this time we will hear about James Bond and a swimming pool at a height of 2400m ASL. Lots of photos - only a little text. Presentation: German
02.11.2018	--	Bridging day after All Saints's Day
09.11.2018 (11hrs, MPIA Hoersaal)	Faustine Cantalloube	Peering through the SPHERE high contrast images When looking at the VLT/SPHERE images we can already infer a few error terms that were expected when designing the instrument. But when going deeper in contrast there may arise some new error terms that were not expected. This talk presents a review of all these terms, based on what we can now see in the focal plane images. Faustine Cantalloube will then focus on one of the main killers of high contrast imaging: the wind driven halo which appears in the images when the turbulence is evolving faster than the AO correction loop frequency could account for. For detection of extended features, this effect is affecting the detection capabilities at short separation (below 300mas), which is the region of interest for most science cases. This talk is a short review of this effect, including its recently acknowledged asymmetry and potential solutions to get over it. Presentation: English Slides: English Questions: German, English
16.11.2018
23.11.2018
30.11.2018
07.12.2018 (11hrs, MPIA Hoersaal)	Wolfgang Brandner	Surveying the galactic center of our Milky way with VLTI Hidden behind dense dark clouds of dust and gas, and hence optically invisible, a super massive black hole populates the center of our Milky Way. Since September 2016 the interferometric instrument GRAVITY and the MPIA provided Coudé Infrared Adaptive Optics (CIAO) allow for the very first time the simultaneous interferometric observation of the galactic center with all four 8m telescopes of ESO's Very Large Telescope Interferometer (VLTI). Goal is to better understand the physical effects in this central region. After a short introduction of interferometry with GRAVITY+CIAO, Wolfgang Brandner will give an overview of the observational results of the first two years at VLTI. The prime science cases were the tracking of a star during its passage at smallest distance to the galactic center and the investigation of brightness fluctuations at the closest proximity to the black hole. The motion of the star allows to determine the mass of the black hole and the distance to the sun with high precision. Furthermore, the measured data allow for a comparison with effects of Einstein's special and general theorie of relativity. The results indicate that Einstein's predictions are also valid in the direct vicinity of the super massive black hole in the center of our Milky Way. Presentation: German Slides: English Questions: German, English
14.12.2018 (11hrs, HdA Auditorium)	Bernd Carsten Sander (ZARM)	The Drop-Tower in Bremen - Weightless on Earth The drop-tower in Bremen is a unique research facility in Europe, where everyday since 1990 scientific and technological experiments at zero gravity conditions are conducted. During the free fall from a height of 120m inside the tower, zero gravity is given for 4,74 seconds. Since 2004 a catapult-system allows to double this duration to 9,3 seconds. The possible experiments span the complete range from knowledge-based and application-oriented fundamental research up to product design, especially in fluid mechanics, rheology, combustion and thermodynamics, as well as in material research, physics and biology. In addition, the proper functionality of spaceborne instruments is verified in this zero gravity environment before their nominal use in space. Presentation: German Slides: English Questions: German, English
21.12.2018
28.12.2018	--	Christmas Break