Fernando Garfias

Co-phasing of segmented mirror telescopes with curvature sensing

The applicability of the curvature method for co-phasing of segmented mirrors is investigated by means of simulations for the case of strongly defocused images. The simulations are performed for both the monochromatic and the white light as well. A simple wavefront reconstruction from curvature signal was made. The reconstruction quality of the piston modes and the aberrations up to the fourth order is analyzed. The dependence of the Central Intensity Ratio for a segmented mirror as a function of the rms segments aberrations is presented. The effect of turbulence-induced distortions on the quality of mirror co-phasing is analyzed. It is shown that the local pistons and the local tip-tilts can be measured directly from the curvature signal without any phase recovering procedure. The results obtained show that, even in the presence of the atmospheric turbulence, the curvature method is sensitive enough to detect the errors of segmented mirrors.

Curvature equation for a segmented telescope

We demonstrate that the curvature equation can be modified using some properties of Distributions theory for segmented mirror techniques. It is shown that, additionally to the individual segment aberrations, the modified equation contains the information about the relative pistons and tip- tilts among the segments. The validity of the equation is verified by numerical simulations and by a laboratory experiment as well.

San Pedro Mártir: astronomical site evaluation

The Observatorio Astronomico Nacional at San Pedro Martir is situated on the summit of the San Pedro Martir Sierra in the Baja California peninsula of Mexico, at 2800m above sea level. For as long as three decades, a number of groups and individuals have gathered extremely valuable data leading to the site characterization for astronomical observations. Here we present a summary of the most important results obtained so far. The aspects covered are: weather, cloud coverage, local meteorology, atmospheric optical extinction, millimetric opacity, geotechnical studies, seeing, optical turbulence profiles, wind profiles and 3D simulations of atmospheric turbulence. The results place San Pedro Martir among the most favorable sites in the world for astronomical observations. It seems to be particularly well-suited for extremely large telescopes because of the excellent turbulence and local wind conditions, to mention but two characteristics. Long-term monitoring of some parameters still have to be undertaken. The National University of Mexico (UNAM) and other international institutions are putting a considerable effort in that sense.

UNAM scanning Fabry-Perot interferometer (PUMA) for the study of interstellar medium

The system called PUMA is an instrument consisting of a focal reducer coupled to a scanning Fabry-Perot interferometer (SFPI), which is being developed for the Observatorio Astronomicao Nacional at San Pedro Martir, B.C. It will be installed at the 2.0 m Ritchey-Chretien telescope with a focal ratio of F/7.9. It has interference filters, a calibration system, and field diaphragms. The SFPI can be moved out of the optical path in order to acquire direct images. The images produced by this instrument will be focused on an optoelectronic detector, a CCD, or a Mepsicron, depending on the spectral range used.

OSIRIS tunable imager and spectrograph for the GTC: from design to commissioning

OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) was the optical Day One instrument for the 10.4m Spanish telescope GTC. It is installed at the Observatorio del Roque de Los Muchachos (La Palma, Spain). This instrument has been operational since March-2009 and covers from 360 to 1000 nm. OSIRIS observing modes include direct imaging with tunable and conventional filters, long slit and low resolution spectroscopy. OSIRIS wide field of view and high efficiency provide a powerful tool for the scientific exploitation of GTC. OSIRIS was developed by a Consortium formed by the Instituto de Astrofísica de Canarias (IAC) and the Instituto de Astronomía de la Universidad Nacional Autónoma de México (IA-UNAM). The latter was in charge of the optical design, the manufacture of the camera and collaboration in the assembly, integration and verification process. The IAC was responsible for the remaining design of the instrument and it was the project leader. The present paper considers the development of the instrument from its design to its present situation in which is in used by the scientific community.

Dual infrared camera for near and mid infrared observations

We present the dual IR camera CID for the 2.12 m telescope of the Observatorio Astronomico Nacional de Mexico, IA-UNAM. The system consists of two separate cameras/spectrographs that operate in different regions of the IR spectrum. In the near IR, CID comprises a direct imaging camera with wide band filters, a CVF, and a low resolution spectrograph employing an InSb 256 x 256 detector. In the mid IR, CID uses a BIB 128 x 128 detector for direct imaging in 10 and 20 microns. Optics and mechanics of CID were developed at IR-Labs (Tucson). The electronics was developed by R. Leach (S. Diego). General design, construction of auxiliary optics (oscillating secondary mirror), necessary modifications and optimization of the electronics, and acquisition software were carried out at OAN/ UNAM. The compact design of the instruments allow them to share a single dewar and the cryogenics system.

Site acceptance of the commissioning instrument for the Gran Telescopio Canarias

In March 2004, the Commissioning Instrument (CI) for the GTC was accepted in the site of The Gran Telescopio Canarias (GTC) located in La Palma Island, Spain. During the GTC integration phase, the CI will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature Wave-front sensing (WFS), and high resolution Shack-Hartmann WFS. The imaging mode permits to qualify the GTC image quality. The Pupil Mode permits estimate the GTC stray light. The segments figure, alignment and cophasing verifications are made with both WFS modes. In this work we describe the Commissioning Instrument and show some tests results obtained during the site acceptance process at the GTC site.

The commissioning instrument for the Gran Telescopio Canarias: made in Mexico

In March 2004 was accepted in the site of Gran Telescopio Canarias (GTC) in La Palma Island, Spain, the Commissioning Instrument (CI) for the GTC. During the GTC integration phase, the CI will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature Wave-front sensing (WFS), and high resolution Shack-Hartmann WFS. This instrument was built by the Instituto de Astronomia UNAM in Mexico City and the Centro de Ingenieria y Desarrollo Industrial (CIDESI) in Queretaro, Qro under a GRANTECAN contract after an international public bid. Some optical components were built by Centro de Investigaciones en Optica (CIO) in Leon Gto and the biggest mechanical parts were manufactured by Vatech in Morelia Mich. In this paper we made a general description of the CI and we relate how this instrument, build under international standards, was entirely made in Mexico.

Commissioning instrument for the Gran Telescopio Canarias

During the GTC integration phase, the Commissioning Instrument (CI) will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature WFS, and high resolution Shack-Hartmann WFS. After the GTC Commissioning we also plan to install a Pyramid WFS. This instrument can therefore serve as a test bench for comparing co-phasing methods for ELTs on a real segmented telescope. In this paper we made a general instrument overview.

PUMILA: A Near-infrared Spectrograph for the Kinematic Study of the Interstellar Medium.

We are developing an instrument to study the morphology and kinematics of the molecular gas and its interrelationship with the ionized gas in star forming regions, planetary nebulae and supernova remnants in our Galaxy and other galaxies, as well as the kinematics of the IR emitting gas in starburst and interacting galaxies. This instrument consists of a water-free fused silica scanning Fabry-Perot interferometer optimized in the spectral range from 1.5 to 2.4 micrometers with high spectral resolution. It will be installed in the collimated beam of a nearly 2:1 focal reducer, designed for the Cassegrain focus of the 2.1 m telescope of the San Pedro Martir National Astronomical Observatory. Mexico, in its f/7.5 configuration, yielding a field of view of 11.6 arc-min. It will provide direct images as well as interferograms to be focused on a 1024 X 1024 HAWAII array, covering a spectral range from 0.9 to 2.5 micrometers .