Irene Cruz-Gonzales

CAMILA: Infrared Camera/Spectrograph for OAN-SPM

The development of the IR camera and spectrograph (CAMILA) is described. It is based on a NICMOS 3 HgCdTe detector developed by Rockwell with a spectral response of 1 to 2.5 micrometers . The initial configuration of the system was recently concluded and consists of the following components: detector cryostat, detector control electronics, low noise preamplifiers, detector-PC interface, operating system and optics. The characterization of the electronics and the science grade chip are presented. The complete optical configuration allows the following modes of operation: direct imaging (12 filter positions), polarimetry and spectroscopy on three dispersion modes (low, medium, and high resolution). Preliminary spectroscopic results at the H band with R equals 1500 are presented. The project is a collaborative effort of groups from IAUNAM and UMASS (Amherst) and will be used mainly at the 2.1-m telescope of San Pedro Martir, B.C. (Mexico).

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.

Polishing TIM mirror segments with HyDra

We report experimental results and analysis about a new hydrodynamic radial tool (HyDra, patent pending), which expels a suspension of water and polishing particles radially on glass. With this method it is possible to locally shape optical surfaces. The depth of material removed by HyDra grows linearly with the time. The removal rate is independent of the velocity between the tool and the glass element. The HyDra has been used to fabricate successfully an optical flat and Schmidt surface.

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.

Mirror cell and active support system of the Mexican infrared optical telescope (TIM)

We present the conceptual design of the primary mirror support system of the 7.8 m Mexican Infrared-Optical Telescope. The primary mirror consists of 19 hexagonal off- axis parabolic Zerodur segments, which are carried by a tubular, lightweight and high stiffness cell structure. Each segment is actively supported by 19 pneumatic actuators, that cover the whole back area and provide a uniform force distribution. The array of actuators will be able to correct for high order aberrations. Each of these actuators contains a hydraulic damping system to provide a stiff coupling to the tubular cell to sustain the wind buffeting. The tip/tilt and piston control of each segment will be done through three axial, nanometer resolution position defining actuators. The lateral positioning of each segment is performed through 3 independent electro-mechanical actuators. With the combination of the whole set of actuators and differential positioning sensors, the phasing or coherent superposition of images of the segments, will be more feasible. The whole system will be cost effective, since several subsystems have already been tested on our 2.1 m telescope.

Mexican infrared optical new technology telescope (TIM) project

We present the Mexican Infrared-Optical New Technology Telescope Project (TIM). The design and construction of a 7.8 m telescope, which will operate at the Observatorio Astronomico Nacional in San Pedro Martir, B.C. (Mexico), are described. The site has been selected based on seeing and sky condition measurements taken for several years. The f/1.5 primary mirror consists of 19 hexagonal off-axis parabolic Zerodur segments. The telescope structure will be alt-az, lightweight, low cost, and high stiffness. It will be supported by hydrostatic bearings. The single secondary will complement a Ritchey-Chretien f/15 design, delivering to Cassegrain focus instrumentation. The telescope will be infrared optimized to allow observations ranging from 0.3 to 20 microns. The TIM mirror cell provides an independent and full active support system for each segment, in order to achieve both, phasing capability and very high quality imaging (0.25 arcsec).

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 .

Noise reduction in BIB-type detectors

It has been known that in BIB type, Si:As Mid-IR detectors the internal gain can be strongly related to the internal noise. We prove that by modifying the internal gain it is possible to increase the signal-to-noise ratio to a level which is consistent with poissonian statistics only.

Hydrostatic shoe bearing system for the TIM

We present an active, low cost hydrostatic shoe bearing system for the Mexican Infrared Telescope which solves the suspension and motion of a 100 ton, 7.8 m telescope. Different geometries are analyzed to optimize the shoes pressure print. These designs offer a self-adjusting action between the shoes sliding path and the girth track. Different parameters such as pressure, temperature and proximity are measured and implemented into a control system in order to stabilize the bearing from the fluids thermal viscosity effects. A simple method for fluid injection is discussed.

TEQUILA: NIR camera/spectrograph based on a Rockwell 1024x1024 HgCdTe FPA

We describe the configuration and operation modes of the IR camera/spectrograph: TEQUILA based on a 1024 X 1024 HgCdTe FPA. The optical system will allow three possible modes of operation: direct imaging, low and medium resolution spectroscopy and polarimetry. The basic system is being designed to consist of the following: 1) A LN2 dewar that allocates the FPA together with the preamplifiers and a 24 filter position cylinder. 2) Control and readout electronics based on DSP modules linked to a workstation through fiber optics. 3) An opto-mechanical assembly cooled to -30 degrees that provides an efficient operation of the instrument in its various modes. 4) A control module for the moving parts of the instrument. The opto-mechanical assembly will have the necessary provision to install a scanning Fabry-Perot interferometer and an adaptive optics correction system. The final image acquisition and control of the whole instrument is carried out in a workstation to provide the observer with a friendly environment. The system will operate at the 2.1 m telescope at the Observatorio Astronomico Nacional in San Pedro Martir, B.C. (Mexico), and is intended to be a first-light instrument for the new 7.8m Mexican IR-Optical Telescope.