Santiago Navarro - Academia.edu (original) (raw)

Papers by Santiago Navarro

Research paper thumbnail of A 3mm band dual polarization MMIC receiver for the 30-m Pico Veleta Radio Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI, 2012

ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for th... more ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for the 3 mm band (84-116 GHz). The receiver cryogenic module consists of a single corrugated feed horn cascaded with an Ortho Mode Traducer (OMT) that splits the two incoming linear polarized signals in two independent single-mode rectangular waveguides. Low noise MMIC HEMT amplification modules, attached to the OMT WR10 waveguide outputs, amplify the signal of each polarization channel. Outside the dewar, each signal is filtered, down-converted, and further amplified to provide a final 8 GHz IF bandwidth across 4-12 GHz. The receiver was installed on the Pico Veleta 30 m telescope in August 2010 where it was used to perform spectral line surveys of astronomical sources. The measured receiver noise temperature was below 75 K with an average value of ~55 K for both polarization channels across 84-116 GHz.

Research paper thumbnail of Variables associated with nonadherence in clinically stable patients with bipolar disorder

Actas españolas de psiquiatría, 2016

Nonadherence is an important and highly prevalent issue in bipolar disorder, which may have serio... more Nonadherence is an important and highly prevalent issue in bipolar disorder, which may have serious consequences. Surprisingly, few studies have been carried out in patients with clinical stability to explore risk factors for nonadherence. Adherence was assessed in 76 bipolar disorder patients with clinical stability using objective and subjective methods, both with a cross-sectional approach and a 3-year retrospective period. Possible associations between nonadherence and sociodemographic, clinical, treatment-related, psychopathological, psychological-subjective and result variables were also assessed. 36.8% of patients were nonadherent. These patients showed greater concerns about medicines, worse functionality, a greater number of episodes and depressive episodes, higher prevalence of psychiatric comorbidities, present and/or past substance use or abuse and a history of depressive episodes with psychotic symptoms. A multivariate analysis revealed that concern about medicines, pre...

Research paper thumbnail of Obesity and health related quality of life in the general adult population of the Canary Islands

Quality of Life Research, 2008

Purpose To explore the relationship between excess weight and health related quality of life (HRQ... more Purpose To explore the relationship between excess weight and health related quality of life (HRQL) in the general population by means of the EuroQol-5D questionnaire. Methods The relationship between excess weight and HRQL was explored by the 2004 Canary Islands Health Survey. Survey participants from 16 years of age and older were classified according to their body mass index (BMI). The relationship between excess weight and the dichotomized EuroQol-5D was examined by multiple logistic regression analysis, adjusting by socio-demographic variables, smoking status, alcohol consumption, and selfreported disease status. Results People with excess weight were older, less educated, and had more associated diseases than the population without excess weight. Excess weight and HRQL are inversely correlated. Severely obese participants showed EuroQol-5D index scores significantly lower than those of normal weight participants (0.65 vs. 0.87). The adjusted odds ratio for the lower HRQL is 3.17 for severely obese people compared to normal weight people.

Research paper thumbnail of Hopelessness and suicidal risk in bipolar disorder. A study in clinically nonsyndromal patients

Comprehensive Psychiatry, 2012

Attempted suicide and death due to suicide are not uncommon among patients with bipolar disorder.... more Attempted suicide and death due to suicide are not uncommon among patients with bipolar disorder. Although some risk factors for suicidality in bipolar patients have been identified, little is known about hopelessness and other possible trait or diathesis-related factors. Consequently, the objective of this study was to investigate variables associated with suicidal risk in clinically nonsyndromal bipolar patients. A sample of 102 outpatients with a diagnosis of bipolar disorder according to International Classification of Diseases, 10th Revision criteria during nonsyndromal stage were evaluated. On the basis of suicidal history, patients were divided into suicide attempt, suicidal ideation, and nonsuicidal groups. Sociodemographic, clinical, and psychopathological variables were assessed. As compared with the nonsuicidal group, female sex, combined psychopharmacologic treatment, and hopelessness were independently associated with suicide attempt. Hopelessness and insight into having a mental disorder were independently associated with history of suicidal ideation. Patients with bipolar disorder and suicidal history are characterized by the presence of hopelessness, which probably confers greater vulnerability for suicidal behavior in the presence of stress factors. This identification of the risk profile for suicidal behavior in nonsyndromal bipolar patients adds complementary information to risk factors established for suicidality during acute phases of the disease, allows for differentiated preventive and treatment approaches of patients at risk, and suggests psychotherapy as an advisable intervention in this group of patients.

Research paper thumbnail of New doublets in IRC+10216 - Vibrationally excited C4H?

Astronomy and Astrophysics

Research paper thumbnail of A 3mm multipixel SIS receiver for IRAM 30-m Pico Veleta Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI, 2012

ABSTRACT A 3mm band focal plane array heterodyne receiver is being developed for Nasmyth focus of... more ABSTRACT A 3mm band focal plane array heterodyne receiver is being developed for Nasmyth focus of the IRAM 30-m Pico Veleta Radio Telescope located in the Sierra Nevada Mountains, south of Spain. This receiver will comprise 25 dual linear polarization pixels operating across the 80-116GHz nominal band. Design efforts are being made to enlarge the band to cover the full 3mm atmospheric transmission window available at Pico Veleta, i.e. 72-116GHz. The instrument will be coupled to the Pico Veleta Telescope via a purely reflective low-loss optical system that includes a de-rotator. The receiver will be based on 5 x 5 cryogenically cooled dual-linear polarized feed horns cascaded with Ortho Mode Transducers (OMT) and side band separating SIS mixers, a technology which offers state-of-the-art performances for millimeter and sub-millimeter receivers.

Research paper thumbnail of GISMO: A 2-millimeter bolometer camera for the IRAM 30 m telescope - art. no. 62751D

Millimeter and Submillimeter Detectors and Instrumentation for Astronomy III, 2006

We are building a bolometer camera (the Goddard-Iram Superconducting 2-Millimeter Observer, GISMO... more We are building a bolometer camera (the Goddard-Iram Superconducting 2-Millimeter Observer, GISMO) for operation in the 2 mm atmospheric window to be used at the IRAM 30 m telescope. The instrument uses a 8x16 planar array of multiplexed TES bolometers which incorporates our newly designed Backshort Under Grid (BUG) architecture. Due to the size and sensitivity of the detector array (the NEP of the detectors is 4 × 10 −17 W/ √ Hz), this instrument will be unique in that it will be capable of providing significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for this instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high-z ULIRGs and quasars, even in the summer season. The 2 mm spectral range provides a unique window to observe the earliest active dusty galaxies in the universe and is well suited to better confine the star formation rate in these objects. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. The observational efficiency of a 2 mm camera with respect to bolometer cameras operating at shorter wavelengths increases for objects at redshifts beyond z ∼ 1 and is most efficient at the highest redshifts, at the time when the first stars were re-ionizing the universe. Our models predict that at this wavelength one out of four serendipitously detected galaxies will be at a redshift of z > 6.5.

Research paper thumbnail of <title>Instrument performance of GISMO, a 2 millimeter TES bolometer camera used at the IRAM 30 m Telescope</title>

Millimeter and Submillimeter Detectors and Instrumentation for Astronomy IV, 2008

We have developed key technologies to enable highly versatile, kilopixel bolometer arrays for inf... more We have developed key technologies to enable highly versatile, kilopixel bolometer arrays for infrared through millimeter wavelengths. Our latest array architecture is based on our Backshort Under Grid (BUG) design, which is specifically targeted at producing kilopixel-size arrays for future ground-based, suborbital and space-based X-ray and far-infrared through millimeter cameras and spectrometers.

Research paper thumbnail of <title>ALMA front-end optics</title>

Ground-based Telescopes, 2004

The ALMA telescope will be an interferometer of 64 antennas, which will be situated in the Atacam... more The ALMA telescope will be an interferometer of 64 antennas, which will be situated in the Atacama desert in Chile. Each antenna will have receivers that cover the frequencies 30 GHz to 970 GHZ. This frequency range is divided into 10 frequency bands. All of these receiver bands are fitted on a cartridge and cooled, with bands 1 and 2

Research paper thumbnail of <title>Versatile IF polarimeter at the IRAM 30m telescope</title>

Polarimetry in Astronomy, 2003

We report on the commissioning of a polarimeter operating at the intermediate frequency (150 MHz)... more We report on the commissioning of a polarimeter operating at the intermediate frequency (150 MHz) of the IRAM 30m telescope. The polarimeter adds, with suitable phase shifts, the amplitudes of two orthogonally linearly polarized heterodyne receivers, and determines from these signals all four Stokes parameters. The polarimeter allows continuum as well as spectral line observations in all millimeter atmospheric windows

Research paper thumbnail of Determination of the Ortho to Para Ratio of H 2 Cl + and H 2 O + from Submillimeter Observations

The Journal of Physical Chemistry A, 2013

The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection... more The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection of new interstellar molecular ions, H2O(+), H2Cl(+), and HCl(+), which are important intermediates in the synthesis of water vapor and hydrogen chloride. In this paper, we report new observations of H2O(+) and H2Cl(+) performed with both Herschel and ground-based telescopes, to determine the abundances of their ortho and para forms separately and derive the ortho-to-para ratio. At the achieved signal-to-noise ratio, the observations are consistent with an ortho-to-para ratios of 3 for both H2O(+) and H2Cl(+), in all velocity components detected along the lines-of-sight to the massive star-forming regions W31C and W49N. We discuss the mechanisms that contribute to establishing the observed ortho-to-para ratio and point to the need for a better understanding of chemical reactions, which are important for establishing the H2O(+) and H2Cl(+) ortho-to-para ratios.

Research paper thumbnail of XPOL—the Correlation Polarimeter at the IRAM 30-m Telescope

Publications of the Astronomical Society of the Pacific, 2008

XPOL, the first correlation polarimeter at a large millimeter telescope, uses a flexible digital ... more XPOL, the first correlation polarimeter at a large millimeter telescope, uses a flexible digital correlator to measure all four Stokes parameters simultaneously, i.e. the total power I, the linear polarization components Q and U, and the circular polarization V . The versatility of the backend provides adequate bandwidth for efficient continuum observations as well as sufficient spectral resolution (40 kHz) for observations of narrow lines. We demonstrate that the polarimetry specific calibrations are handled with sufficient precision, in particular the relative phase between the Observatory's two orthogonally linearly polarized receivers.

Research paper thumbnail of GISMO, a 2 mm Bolometer Camera Optimized for the Study of High Redshift Galaxies

Journal of Low Temperature Physics, 2008

The 2 mm spectral range provides a unique terrestrial window enabling ground based observations o... more The 2 mm spectral range provides a unique terrestrial window enabling ground based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We have built GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), a 2 mm, 128 element superconducting Transition Edge Sensor (TES) based bolometer camera for the IRAM 30 m telescope in Spain. The camera uses an 8x16 planar array of multiplexed TES bolometers, which incorporates our recently designed Backshort Under Grid (BUG) architecture, described elsewhere. The optical design incorporates a 100 mm (4 inches) diameter silicon lens cooled to 4 K, which provides the required fast beam of 0.9 λ/D. With this spatial sampling, GISMO will be very efficient at detecting sources serendipitously in large sky surveys, while the capability for diffraction-limited observations is preserved. With the background limited performance of the detectors, the camera provides significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for the instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high -z Ultra Luminous Infrared Galaxies (ULIRGs) and quasars, even in the summer season. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Our source count models predict that GISMO will serendipitously detect one galaxy every four hours on the blank sky, and that one quarter of these galaxies will be at a redshift of z 6.5. We expect to install GISMO at the 30 m telescope in the second half of 2007. Here we present the design and instrument characterization from the first tests of GISMO. PACS numbers: 07.57.Kp, 95.55.Jz, 98.70.Lt, 95.85.Bh, 98.80.Es

Research paper thumbnail of Astigmatism in reflector antennas: measurement and correction

IEEE Transactions on Antennas and Propagation, 1994

Investigates astigmatism is Cassegrain antennas from cross scans through in-and-out-of-focus diff... more Investigates astigmatism is Cassegrain antennas from cross scans through in-and-out-of-focus diffraction images of extended radio sources. The use of extended sources is of interest for large (mm-wavelength) telescopes where the bright planets subtend a substantial fraction of the beam. The experimental and theoretical results presented refer to the IRAM 30-m telescope and measurements at 7.3 mm-1.3 mm wavelength; however, extrapolation

Research paper thumbnail of The EMIR multi-band mm-wave receiver for the IRAM 30-m telescope

Astronomy & Astrophysics, 2012

ABSTRACT Aims: The prime motivation of this project was to design and build a state-of-art mm-wav... more ABSTRACT Aims: The prime motivation of this project was to design and build a state-of-art mm-wave heterodyne receiver system to enhance the observing throughput of the IRAM 30-m radiotelescope. More specifically, the requirements were i) state-of-art noise performance for spectroscopic observations; ii) simultaneous dual polarization and dual-frequency observing; iii) coverage of the atmospheric transmission windows from 83 to 360 GHz; iv) compact footprint and minimal maintenance. Methods: Key elements for low noise performance of heterodyne mixers are the superconducting Niobium junctions, operating at ≃4 K. These junctions are embedded in carefully designed coupling structures; furthermore, since atmospheric radiation is a significant contributor to the system noise budget, all mixers are either sideband separating or sideband rejecting. To achieve low noise, it is also essential to maximize the coupling of the receiver to the astronomical source, and to minimize the coupling to thermal radiation from the ground-based environment; this is achieved through mirror optics that realize a wavelength-independent coupling to the telescope. A flexible configuration of mirrors and frequency selective surfaces permits various combinations of frequency bands, as well as dual-load radiometric calibration. Low noise intermediate frequency amplifiers and bias electronics also play an important role in the system performance. Results: The EMIR receiver in operation at the 30 m telescope offers four frequency bands: B1: 83-117 GHz, B2: 129-174 GHz, B3: 200-267 GHz, and B4: 260-360 GHz. In each band, the two orthogonal polarizations are observed simultaneously. Dual-band combinations B1/2 B1/3, and B2/4 are available. Bands 1 and 4 (also 3 as of Nov.-2011) feature sideband separation. In dual-band configuration, including sideband separation and polarization diplexing, up to eight IF channels are delivered to the spectrometers, totaling up to 64 GHz of signal bandwidth (of which 32 GHz can be transported and processed by spectrometers, status Nov.-2011). The EMIR receiver has been in continuous operation for more than two years and has allowed, through a qualitative jump in performance, observations not possible before, as shown by a few selected examples of astronomical results. This article is dedicated to the memory of our colleague Matt who initiated and played a key role in this project.

Research paper thumbnail of A 3mm band dual polarization MMIC receiver for the 30-m Pico Veleta Radio Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI, 2012

ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for th... more ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for the 3 mm band (84-116 GHz). The receiver cryogenic module consists of a single corrugated feed horn cascaded with an Ortho Mode Traducer (OMT) that splits the two incoming linear polarized signals in two independent single-mode rectangular waveguides. Low noise MMIC HEMT amplification modules, attached to the OMT WR10 waveguide outputs, amplify the signal of each polarization channel. Outside the dewar, each signal is filtered, down-converted, and further amplified to provide a final 8 GHz IF bandwidth across 4-12 GHz. The receiver was installed on the Pico Veleta 30 m telescope in August 2010 where it was used to perform spectral line surveys of astronomical sources. The measured receiver noise temperature was below 75 K with an average value of ~55 K for both polarization channels across 84-116 GHz.

Research paper thumbnail of A 3mm band dual polarization MMIC receiver for the 30-m Pico Veleta Radio Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI, 2012

ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for th... more ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for the 3 mm band (84-116 GHz). The receiver cryogenic module consists of a single corrugated feed horn cascaded with an Ortho Mode Traducer (OMT) that splits the two incoming linear polarized signals in two independent single-mode rectangular waveguides. Low noise MMIC HEMT amplification modules, attached to the OMT WR10 waveguide outputs, amplify the signal of each polarization channel. Outside the dewar, each signal is filtered, down-converted, and further amplified to provide a final 8 GHz IF bandwidth across 4-12 GHz. The receiver was installed on the Pico Veleta 30 m telescope in August 2010 where it was used to perform spectral line surveys of astronomical sources. The measured receiver noise temperature was below 75 K with an average value of ~55 K for both polarization channels across 84-116 GHz.

Research paper thumbnail of Variables associated with nonadherence in clinically stable patients with bipolar disorder

Actas españolas de psiquiatría, 2016

Nonadherence is an important and highly prevalent issue in bipolar disorder, which may have serio... more Nonadherence is an important and highly prevalent issue in bipolar disorder, which may have serious consequences. Surprisingly, few studies have been carried out in patients with clinical stability to explore risk factors for nonadherence. Adherence was assessed in 76 bipolar disorder patients with clinical stability using objective and subjective methods, both with a cross-sectional approach and a 3-year retrospective period. Possible associations between nonadherence and sociodemographic, clinical, treatment-related, psychopathological, psychological-subjective and result variables were also assessed. 36.8% of patients were nonadherent. These patients showed greater concerns about medicines, worse functionality, a greater number of episodes and depressive episodes, higher prevalence of psychiatric comorbidities, present and/or past substance use or abuse and a history of depressive episodes with psychotic symptoms. A multivariate analysis revealed that concern about medicines, pre...

Research paper thumbnail of Obesity and health related quality of life in the general adult population of the Canary Islands

Quality of Life Research, 2008

Purpose To explore the relationship between excess weight and health related quality of life (HRQ... more Purpose To explore the relationship between excess weight and health related quality of life (HRQL) in the general population by means of the EuroQol-5D questionnaire. Methods The relationship between excess weight and HRQL was explored by the 2004 Canary Islands Health Survey. Survey participants from 16 years of age and older were classified according to their body mass index (BMI). The relationship between excess weight and the dichotomized EuroQol-5D was examined by multiple logistic regression analysis, adjusting by socio-demographic variables, smoking status, alcohol consumption, and selfreported disease status. Results People with excess weight were older, less educated, and had more associated diseases than the population without excess weight. Excess weight and HRQL are inversely correlated. Severely obese participants showed EuroQol-5D index scores significantly lower than those of normal weight participants (0.65 vs. 0.87). The adjusted odds ratio for the lower HRQL is 3.17 for severely obese people compared to normal weight people.

Research paper thumbnail of Hopelessness and suicidal risk in bipolar disorder. A study in clinically nonsyndromal patients

Comprehensive Psychiatry, 2012

Attempted suicide and death due to suicide are not uncommon among patients with bipolar disorder.... more Attempted suicide and death due to suicide are not uncommon among patients with bipolar disorder. Although some risk factors for suicidality in bipolar patients have been identified, little is known about hopelessness and other possible trait or diathesis-related factors. Consequently, the objective of this study was to investigate variables associated with suicidal risk in clinically nonsyndromal bipolar patients. A sample of 102 outpatients with a diagnosis of bipolar disorder according to International Classification of Diseases, 10th Revision criteria during nonsyndromal stage were evaluated. On the basis of suicidal history, patients were divided into suicide attempt, suicidal ideation, and nonsuicidal groups. Sociodemographic, clinical, and psychopathological variables were assessed. As compared with the nonsuicidal group, female sex, combined psychopharmacologic treatment, and hopelessness were independently associated with suicide attempt. Hopelessness and insight into having a mental disorder were independently associated with history of suicidal ideation. Patients with bipolar disorder and suicidal history are characterized by the presence of hopelessness, which probably confers greater vulnerability for suicidal behavior in the presence of stress factors. This identification of the risk profile for suicidal behavior in nonsyndromal bipolar patients adds complementary information to risk factors established for suicidality during acute phases of the disease, allows for differentiated preventive and treatment approaches of patients at risk, and suggests psychotherapy as an advisable intervention in this group of patients.

Research paper thumbnail of New doublets in IRC+10216 - Vibrationally excited C4H?

Astronomy and Astrophysics

Research paper thumbnail of A 3mm multipixel SIS receiver for IRAM 30-m Pico Veleta Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI, 2012

ABSTRACT A 3mm band focal plane array heterodyne receiver is being developed for Nasmyth focus of... more ABSTRACT A 3mm band focal plane array heterodyne receiver is being developed for Nasmyth focus of the IRAM 30-m Pico Veleta Radio Telescope located in the Sierra Nevada Mountains, south of Spain. This receiver will comprise 25 dual linear polarization pixels operating across the 80-116GHz nominal band. Design efforts are being made to enlarge the band to cover the full 3mm atmospheric transmission window available at Pico Veleta, i.e. 72-116GHz. The instrument will be coupled to the Pico Veleta Telescope via a purely reflective low-loss optical system that includes a de-rotator. The receiver will be based on 5 x 5 cryogenically cooled dual-linear polarized feed horns cascaded with Ortho Mode Transducers (OMT) and side band separating SIS mixers, a technology which offers state-of-the-art performances for millimeter and sub-millimeter receivers.

Research paper thumbnail of GISMO: A 2-millimeter bolometer camera for the IRAM 30 m telescope - art. no. 62751D

Millimeter and Submillimeter Detectors and Instrumentation for Astronomy III, 2006

We are building a bolometer camera (the Goddard-Iram Superconducting 2-Millimeter Observer, GISMO... more We are building a bolometer camera (the Goddard-Iram Superconducting 2-Millimeter Observer, GISMO) for operation in the 2 mm atmospheric window to be used at the IRAM 30 m telescope. The instrument uses a 8x16 planar array of multiplexed TES bolometers which incorporates our newly designed Backshort Under Grid (BUG) architecture. Due to the size and sensitivity of the detector array (the NEP of the detectors is 4 × 10 −17 W/ √ Hz), this instrument will be unique in that it will be capable of providing significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for this instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high-z ULIRGs and quasars, even in the summer season. The 2 mm spectral range provides a unique window to observe the earliest active dusty galaxies in the universe and is well suited to better confine the star formation rate in these objects. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. The observational efficiency of a 2 mm camera with respect to bolometer cameras operating at shorter wavelengths increases for objects at redshifts beyond z ∼ 1 and is most efficient at the highest redshifts, at the time when the first stars were re-ionizing the universe. Our models predict that at this wavelength one out of four serendipitously detected galaxies will be at a redshift of z > 6.5.

Research paper thumbnail of <title>Instrument performance of GISMO, a 2 millimeter TES bolometer camera used at the IRAM 30 m Telescope</title>

Millimeter and Submillimeter Detectors and Instrumentation for Astronomy IV, 2008

We have developed key technologies to enable highly versatile, kilopixel bolometer arrays for inf... more We have developed key technologies to enable highly versatile, kilopixel bolometer arrays for infrared through millimeter wavelengths. Our latest array architecture is based on our Backshort Under Grid (BUG) design, which is specifically targeted at producing kilopixel-size arrays for future ground-based, suborbital and space-based X-ray and far-infrared through millimeter cameras and spectrometers.

Research paper thumbnail of <title>ALMA front-end optics</title>

Ground-based Telescopes, 2004

The ALMA telescope will be an interferometer of 64 antennas, which will be situated in the Atacam... more The ALMA telescope will be an interferometer of 64 antennas, which will be situated in the Atacama desert in Chile. Each antenna will have receivers that cover the frequencies 30 GHz to 970 GHZ. This frequency range is divided into 10 frequency bands. All of these receiver bands are fitted on a cartridge and cooled, with bands 1 and 2

Research paper thumbnail of <title>Versatile IF polarimeter at the IRAM 30m telescope</title>

Polarimetry in Astronomy, 2003

We report on the commissioning of a polarimeter operating at the intermediate frequency (150 MHz)... more We report on the commissioning of a polarimeter operating at the intermediate frequency (150 MHz) of the IRAM 30m telescope. The polarimeter adds, with suitable phase shifts, the amplitudes of two orthogonally linearly polarized heterodyne receivers, and determines from these signals all four Stokes parameters. The polarimeter allows continuum as well as spectral line observations in all millimeter atmospheric windows

Research paper thumbnail of Determination of the Ortho to Para Ratio of H 2 Cl + and H 2 O + from Submillimeter Observations

The Journal of Physical Chemistry A, 2013

The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection... more The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection of new interstellar molecular ions, H2O(+), H2Cl(+), and HCl(+), which are important intermediates in the synthesis of water vapor and hydrogen chloride. In this paper, we report new observations of H2O(+) and H2Cl(+) performed with both Herschel and ground-based telescopes, to determine the abundances of their ortho and para forms separately and derive the ortho-to-para ratio. At the achieved signal-to-noise ratio, the observations are consistent with an ortho-to-para ratios of 3 for both H2O(+) and H2Cl(+), in all velocity components detected along the lines-of-sight to the massive star-forming regions W31C and W49N. We discuss the mechanisms that contribute to establishing the observed ortho-to-para ratio and point to the need for a better understanding of chemical reactions, which are important for establishing the H2O(+) and H2Cl(+) ortho-to-para ratios.

Research paper thumbnail of XPOL—the Correlation Polarimeter at the IRAM 30-m Telescope

Publications of the Astronomical Society of the Pacific, 2008

XPOL, the first correlation polarimeter at a large millimeter telescope, uses a flexible digital ... more XPOL, the first correlation polarimeter at a large millimeter telescope, uses a flexible digital correlator to measure all four Stokes parameters simultaneously, i.e. the total power I, the linear polarization components Q and U, and the circular polarization V . The versatility of the backend provides adequate bandwidth for efficient continuum observations as well as sufficient spectral resolution (40 kHz) for observations of narrow lines. We demonstrate that the polarimetry specific calibrations are handled with sufficient precision, in particular the relative phase between the Observatory's two orthogonally linearly polarized receivers.

Research paper thumbnail of GISMO, a 2 mm Bolometer Camera Optimized for the Study of High Redshift Galaxies

Journal of Low Temperature Physics, 2008

The 2 mm spectral range provides a unique terrestrial window enabling ground based observations o... more The 2 mm spectral range provides a unique terrestrial window enabling ground based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We have built GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), a 2 mm, 128 element superconducting Transition Edge Sensor (TES) based bolometer camera for the IRAM 30 m telescope in Spain. The camera uses an 8x16 planar array of multiplexed TES bolometers, which incorporates our recently designed Backshort Under Grid (BUG) architecture, described elsewhere. The optical design incorporates a 100 mm (4 inches) diameter silicon lens cooled to 4 K, which provides the required fast beam of 0.9 λ/D. With this spatial sampling, GISMO will be very efficient at detecting sources serendipitously in large sky surveys, while the capability for diffraction-limited observations is preserved. With the background limited performance of the detectors, the camera provides significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for the instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high -z Ultra Luminous Infrared Galaxies (ULIRGs) and quasars, even in the summer season. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Our source count models predict that GISMO will serendipitously detect one galaxy every four hours on the blank sky, and that one quarter of these galaxies will be at a redshift of z 6.5. We expect to install GISMO at the 30 m telescope in the second half of 2007. Here we present the design and instrument characterization from the first tests of GISMO. PACS numbers: 07.57.Kp, 95.55.Jz, 98.70.Lt, 95.85.Bh, 98.80.Es

Research paper thumbnail of Astigmatism in reflector antennas: measurement and correction

IEEE Transactions on Antennas and Propagation, 1994

Investigates astigmatism is Cassegrain antennas from cross scans through in-and-out-of-focus diff... more Investigates astigmatism is Cassegrain antennas from cross scans through in-and-out-of-focus diffraction images of extended radio sources. The use of extended sources is of interest for large (mm-wavelength) telescopes where the bright planets subtend a substantial fraction of the beam. The experimental and theoretical results presented refer to the IRAM 30-m telescope and measurements at 7.3 mm-1.3 mm wavelength; however, extrapolation

Research paper thumbnail of The EMIR multi-band mm-wave receiver for the IRAM 30-m telescope

Astronomy & Astrophysics, 2012

ABSTRACT Aims: The prime motivation of this project was to design and build a state-of-art mm-wav... more ABSTRACT Aims: The prime motivation of this project was to design and build a state-of-art mm-wave heterodyne receiver system to enhance the observing throughput of the IRAM 30-m radiotelescope. More specifically, the requirements were i) state-of-art noise performance for spectroscopic observations; ii) simultaneous dual polarization and dual-frequency observing; iii) coverage of the atmospheric transmission windows from 83 to 360 GHz; iv) compact footprint and minimal maintenance. Methods: Key elements for low noise performance of heterodyne mixers are the superconducting Niobium junctions, operating at ≃4 K. These junctions are embedded in carefully designed coupling structures; furthermore, since atmospheric radiation is a significant contributor to the system noise budget, all mixers are either sideband separating or sideband rejecting. To achieve low noise, it is also essential to maximize the coupling of the receiver to the astronomical source, and to minimize the coupling to thermal radiation from the ground-based environment; this is achieved through mirror optics that realize a wavelength-independent coupling to the telescope. A flexible configuration of mirrors and frequency selective surfaces permits various combinations of frequency bands, as well as dual-load radiometric calibration. Low noise intermediate frequency amplifiers and bias electronics also play an important role in the system performance. Results: The EMIR receiver in operation at the 30 m telescope offers four frequency bands: B1: 83-117 GHz, B2: 129-174 GHz, B3: 200-267 GHz, and B4: 260-360 GHz. In each band, the two orthogonal polarizations are observed simultaneously. Dual-band combinations B1/2 B1/3, and B2/4 are available. Bands 1 and 4 (also 3 as of Nov.-2011) feature sideband separation. In dual-band configuration, including sideband separation and polarization diplexing, up to eight IF channels are delivered to the spectrometers, totaling up to 64 GHz of signal bandwidth (of which 32 GHz can be transported and processed by spectrometers, status Nov.-2011). The EMIR receiver has been in continuous operation for more than two years and has allowed, through a qualitative jump in performance, observations not possible before, as shown by a few selected examples of astronomical results. This article is dedicated to the memory of our colleague Matt who initiated and played a key role in this project.

Research paper thumbnail of A 3mm band dual polarization MMIC receiver for the 30-m Pico Veleta Radio Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VI, 2012

ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for th... more ABSTRACT We present the design, construction and test results of a prototype MMIC receiver for the 3 mm band (84-116 GHz). The receiver cryogenic module consists of a single corrugated feed horn cascaded with an Ortho Mode Traducer (OMT) that splits the two incoming linear polarized signals in two independent single-mode rectangular waveguides. Low noise MMIC HEMT amplification modules, attached to the OMT WR10 waveguide outputs, amplify the signal of each polarization channel. Outside the dewar, each signal is filtered, down-converted, and further amplified to provide a final 8 GHz IF bandwidth across 4-12 GHz. The receiver was installed on the Pico Veleta 30 m telescope in August 2010 where it was used to perform spectral line surveys of astronomical sources. The measured receiver noise temperature was below 75 K with an average value of ~55 K for both polarization channels across 84-116 GHz.