Millimetric ground-based observations of CMB anisotropy

Resultados del experimento Bartol-IAC sobre medidas de la anisotropía en el Fondo Cósmico de Microondas. Estas observaciones se realizaron en los meses de Junio y Julio de 1994 en el Observatorio del Teide. Se observó la región del cielo a delta=+40 grados en cuatro bandas a lamda=3,3; 2,1; 1,3 y 1,1 mm. En la tesis e han desarrollado técnicas sofisticadas de eliminación del ruido atmosférico mostrando por primera vez la posibilidad de observar en estas longitudes de onda con experimentos desde la superficie terrestre. Se analizó estadísticamente la región observada a alta latitud galáctica mostrando la existencia de una señal astronómica en una escala angular correspondiente a l=53. Estos resultados son compatibles con los de otros experimentos en similares escalas angulares y con lo que se espera de los modelos de materia oscura frí

Pre-distortion adaptive optics for optical feeder links: simulations and performance analyses

Optical feeder links offer immense utility in meeting future communication demands—however, atmospheric turbulence limits their performance. This work targets this challenge through analyses of a bidirectional free-space optical communication (FSOC) link that incorporates pre-distortion adaptive optics (AO) between the next-generation optical ground station at the German Aerospace Center (DLR) Oberpfaffenhofen and the laser communications terminal on Alphasat—a satellite in geostationary orbit (GEO). The analyses are performed via end-to-end Monte Carlo simulations that provide realistic performance estimates of the bidirectional FSOC link for a GEO feeder link scenario. We find that applying pre-distortion AO reduces the total uplink losses of the bidirectional FSOC link by up to 10 dB and lessens the scintillation at the GEO satellite by an order of magnitude. Moreover, applying pre-distortion AO eases the link budget requirements needed for maintaining 99.9% link uptime by as much as 20-40 dB, while its use with a laser guide star shows an additional performance improvement of up to 8 dB. These findings demonstrate the desirability and feasibility of utilizing pre-distortion AO for the realization of optical feeder links

Three years of harvest with the vector vortex coronagraph in the thermal infrared

For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 {\mu}m). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications.Comment: To appear in SPIE proceedings vol. 990

A near-infrared tip-tilt sensor for the Keck I laser guide star adaptive optics system

The sky coverage and performance of laser guide star (LGS) adaptive optics (AO) systems is limited by the natural guide star (NGS) used for low order correction. This limitation can be dramatically reduced by measuring the tip and tilt of the NGS in the near-infrared where the NGS is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We present the design of a near-infrared tip-tilt sensor that has recently been integrated with the Keck I telescope’s LGS AO system along with some initial on-sky results. The implementation involved modifications to the AO bench, real-time control system, and higher level controls and operations software that will also be discussed. The tip-tilt sensor is a H2RG-based near-infrared camera with 0.05 arc second pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2×2 to 16×16 pixels, centered on an NGS anywhere in the 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beamsplitters located in front of the OSIRIS integral field spectrograph

Suppressing stellar residual light on extremely large telescopes by aperture modulation

Efficient suppression of the residual stellar light is paramount to the success of exoplanet imaging efforts. We present a new approach to diffraction suppression on extremely large telescopes. The method is based on the realization that by obscuring part of the wavefront in the Lyot stop we can change the shape of the corresponding PSF. This obscuration is then modulated leading to modulated Airy pattern, while image of a planet - if present - is only slightly affected. The modulation could then be removed from the set of images, leading to better SNR of the possible planets. Simulation of the European Extremely Large Telescope has been used to test this approach

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