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Caltech Authors (108,052 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 4,825

1. The Infrared Imaging Spectrograph (IRIS) for TMT: Volume Phase Holographic Grating Performance Testing and Discussion - Chen, Shaojie; Meyer, Elliot; Wright, Shelley A.; Moore, Anna M.; Larkin, James E.; Maire, Jérôme; Mieda, Etsuko; Simard, Luc
Maximizing the grating efficiency is a key goal for the first light instrument IRIS (Infrared Imaging Spectrograph) currently being designed to sample the diffraction limit of the TMT (Thirty Meter Telescope). Volume Phase Holographic (VPH) gratings have been shown to offer extremely high efficiencies that approach 100% for high line frequencies (i.e., 600 to 6000l/mm), which has been applicable for astronomical optical spectrographs. However, VPH gratings have been less exploited in the near-infrared, particularly for gratings that have lower line frequencies. Given their potential to offer high throughputs and low scattered light, VPH gratings are being explored for IRIS as...

2. Non-parametric stochastic subset optimization for design problems with reliability constraints - Jia, G.; Taflanidis, A. A.; Beck, J. L.
The Non-Parametric Stochastic Subset Optimization (NP-SSO) is a recently developed algorithm appropriate for optimization problems that use the system reliability as objective function and involve computationally expensive numerical models. This paper discusses its extension to reliability-based design optimization (RBDO) applications involving the system reliability as a design constraint. The foundation of NP-SSO is the formulation of an augmented problem where the design variables are artificially considered as uncertain. In this context, the system reliability is proportional to an auxiliary probability density function related to the design variables. NP-SSO is based on simulation of samples from this density and approximates the system reliability through kernel density estimation...

3. Enhancement of the Spitzer Infrared Array Camera Distortion Correction for Parallax Measurements - Lowrance, Patrick J.; Carey, Sean J.; Ingalls, James G.; Surace, Jason; Capak, Peter; Stauffer, John; Beichman, Chas; Shupe, David; Kirkpatrick, J. Davy
The Spitzer Space Telescope Infrared Array (IRAC) offers a rare opportunity to measure distances and determine physical properties of the faintest and coldest brown dwarfs. The current distortion correction is a 3rd order polynomial represented by TAN-SIP parameters within the headers. The current correction, good to 100 mas, was derived from deep imaging, using marginally resolved galaxies in some cases, and has remained stable throughout both the cryogenic and warm mission. Using recent Spitzer calibration observations mapped to HST/ACS calibration observations of 47 Tuc with an absolute accuracy good to 1 mas, we are working towards a possible 5th order...

4. Studying Extragalactic Background Fluctuations with the Cosmic Infrared Background ExpeRiment 2 (CIBER-2) - Lanz, Alicia; Arai, Toshiaki; Battle, John; Bock, James; Cooray, Asantha; Hristov, Viktor; Korngut, Phillip; Lee, Dae Hee; Mason, Peter; Matsumoto, Toshio; Matsuura, Shuji; Morford, Tracy; Onishi, Yosuke; Shirahata, Mai; Tsumura, Kohji; Wada, Takehiko; Zemcov, Michael
Fluctuations in the extragalactic background light trace emission from the history of galaxy formation, including the emission from the earliest sources from the epoch of reionization. A number of recent near-infrared measure- ments show excess spatial power at large angular scales inconsistent with models of z < 5 emission from galaxies. These measurements have been interpreted as arising from either redshifted stellar and quasar emission from the epoch of reionization, or the combined intra-halo light from stars thrown out of galaxies during merging activity at lower redshifts. Though astrophysically distinct, both interpretations arise from faint, low surface brightness source populations...

5. Using drift scans to improve astrometry with Spitzer - Ingalls, James G.; Carey, Sean J.; Lowrance, Patrick J.; Grillmair, Carl J.; Stauffer, John R.
The Spitzer Space Telescope Infrared Array Camera (IRAC) is the only space-based instrument currently capable of continuous long duration monitoring of brown dwarfs to detect variability and characterize their atmospheres. Any such studies are limited, however, by the accuracy to which we know the positions and distances to these targets (most of which are newly discovered and therefore do not yet have multiple epochs of astrometric data). To that end, we have begun a new initiative to adapt the astrometric drift scanning technique employed by the Hubble Space Telescope to enhance Spitzer measurements of parallaxes and proper motions of brown...

6. Improving our understanding of the Spitzer Space Telescope's pointing drifts - Grillmair, Carl J.; Carey, Sean J.; Stauffer, John R.; Ingalls, James G.
Spitzer observations of exoplanets routinely yield photometric accuracies of better than one part in 10,000. However, the attainable precision is limited in part by pointing drifts, which have the effect of moving the target to less stable or less-well characterized regions of Spitzer’s IRAC detector arrays. Here we examine a large sample of observing sequences in an effort to identify the causes of these pointing drifts. We find that short term and higher order drifts are correlated on various time scales to the temperatures of components in and around the spacecraft bus, and are most likely due to very slight...

7. Preliminary Design Study of the TMT Telescope Structure System: Overview - Usuda, Tomonori; Ezaki, Yutaka; Kawaguchi, Noburu; Nagae, Kazuhiro; Kato, Atsushi; Takaki, Junji; Hirano, Masaki; Hattori, Tomoya; Tabata, Masaki; Horiuchi, Yasushi; Saruta, Yusuke; Sofuku, Satoru; Itoh, Noboru; Oshima, Takeharu; Takanezawa, Takashi; Endo, Makoto; Inatani, Junji; Iye, Masanori; Sadjadpour, Amir; Sirota, Mark; Roberts, Scott; Stepp, Larry
We present an overview of the preliminary design of the Telescope Structure System (STR) of Thirty Meter Telescope (TMT). NAOJ was given responsibility for the TMT STR in early 2012 and engaged Mitsubishi Electric Corporation (MELCO) to take over the preliminary design work. MELCO performed a comprehensive preliminary design study in 2012 and 2013 and the design successfully passed its Preliminary Design Review (PDR) in November 2013 and April 2014. Design optimizations were pursued to better meet the design requirements and improvements were made in the designs of many of the telescope subsystems as follows: 1. 6-legged Top End configuration...

8. Design and construction of a carbon fiber gondola for the SPIDER balloon-borne telescope - Soler, J. D.; Bock, J. J.; Crill, B. P.; Doré, O. P.; Filippini, J. P.; Golwala, S.; Hristov, V. V.; Mason, P. V.; Moncelsi, L.; Morford, T.; Tucker, R. S.
We introduce the light-weight carbon fiber and aluminum gondola designed for the Spider balloon-borne telescope. Spider is designed to measure the polarization of the Cosmic Microwave Background radiation with unprecedented sensitivity and control of systematics in search of the imprint of inflation: a period of exponential expansion in the early Universe. The requirements of this balloon-borne instrument put tight constrains on the mass budget of the payload. The Spider gondola is designed to house the experiment and guarantee its operational and structural integrity during its balloon-borne flight, while using less than 10% of the total mass of the payload. We...

9. Measuring transmission and forces from observatory equipment vibration - Thompson, Hugh; MacMartin, Douglas G.; Byrnes, Peter W. G.; Tomono, Daigo; Terada, Hiroshi
We describe measurements of both the vibration forces imparted by various types of observatory equipment, and the transmission of these forces through the soil, foundations and telescope pier. These are key uncertainties both in understanding how to mitigate vibration at existing observatories and for developing a vibration budget in the design of future observatories such as the Thirty Meter Telescope. Typical vibration surveys have measured only the resulting motion (acceleration); however, this depends on both the source and the system being excited (for example, isolating equipment results in less force being transmitted, but greater motion of the equipment itself). Instead,...

10. A new zero-ripple switching dc-to-dc converter and integrated magnetics - Ćuk, Slobodan
A new switching dc-to-dc converter is synthesized which consists of the least number of storage elements (inductive and capacitive) and switches, and yet truly emulates the ideally desired dc-to-dc transformer having both input and output currents as pure dc quantities with no ripple. This result was facilitated by implementation of a new concept termed integrated magnetics, which leads in some special switching structures to the integration of otherwise independent and separate magnetic components (inductors and transformers) into a single magnetic circuit.

11. Transition State Theory and Experiments in Chemical Reactions - Marcus, R. A.
The transition state theory of chemical reactions has proven to be a formidable tool for analyzing chemical reaction rates of a wide variety of reactions. In the present article some of its developments, extensions, and applications are described. Transition state theory was developed in its current form by Eyring and Evans and Polanyi in 1935, only about a half a dozen years after the quantum mechanical description of potential energy surfaces by London for chemical reactions. The advances in the understanding of the dynamics in the 1930s were rapid, particularly by Hirschfelder, Wigner, and O.K. Rice, among others. A number...

12. Theory and Experiment in Photosynthetic Electron Transfer - Marcus, Rudolph A.
The recent determination of the crystallographic structure of a bacterial photosynthetic reaction center has provided an important framework for treating electron transfers in these systems. As in electron transfers in simpler systems, a knowledge of both the structure and the thermodynamics is needed for understanding the experimental results on reaction rates at the fundamental level. In this lecture we first describe the theory of simple electron transfer reaction rates, and then consider how the resulting interaction between theory and experiment may assist us in treating electron transfers in the photosynthetic reaction center. In the final portion of this talk we summarize a view of the current state of knowledge in...

13. Anti-reflection coatings for submillimeter silicon lenses - Wheeler, Jordan D.; Koopman, Brian; Gallardo, Patricio; Maloney, Philip R.; Brugger, Spencer; Cortes-Medellin, German; Datta, Rahul; Dowell, C. Darren; Glenn, Jason; Golwala, Sunil; McKenney, Chris; McMahon, Jeffrey J.; Niemack, Mike; Parshley, Steven; Stacey, Gordon
Low-loss lenses are required for submillimeter astronomical applications, such as instrumentation for CCAT, a 25 m diameter telescope to be built at an elevation of 18,400 ft in Chile. Silicon is a leading candidate for dielectric lenses due to its low transmission loss and high index of refraction; however, the latter can lead to large reflection losses. Additionally, large diameter lenses (up to 40 cm), with substantial curvature present a challenge for fabrication of antireflection coatings. Three anti-reflection coatings are considered: a deposited dielectric coating of Parylene C, fine mesh structures cut with a dicing saw, and thin etched silicon...

14. Design, fabrication and testing of active carbon shell mirrors for space telescope applications - Steeves, John; Laslandes, Marie; Pellegrino, Sergio; Redding, David; Bradford, Samuel Case; Wallace, James Kent; Barbee, Troy
A novel active mirror concept based on carbon fiber reinforced polymer (CFRP) materials is presented. A nanolaminate facesheet, active piezoelectric layer and printed electronics are implemented in order to provide the reflective surface, actuation capabilities and electrical wiring for the mirror. Mirrors of this design are extremely thin (500-850 µm), lightweight (~ 2 kg/m^2) and have large actuation capabilities (~ 100 µm peak- to-valley deformation per channel). Replication techniques along with simple bonding/transferring processes are implemented eliminating the need for grinding and polishing steps. An outline of the overall design, component materials and fabrication processes is presented. A method to...

15. Thermal design and performance of the balloon-borne large aperture submillimeter telescope for polarimetry BLASTPol - Soler, J. D.; Moncelsi, L.
We present the thermal model of the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). This instrument was successfully own in two circumpolar flights from McMurdo, Antarctica in 2010 and 2012. During these two flights, BLASTPol obtained unprecedented information about the magnetic field in molecular clouds through the measurement of the polarized thermal emission of interstellar dust grains. The thermal design of the experiment addresses the stability and control of the payload necessary for this kind of measurement. We describe the thermal modeling of the payload including the sun-shielding strategy. We present the in-flight thermal performance of the instrument and compare...

16. Argus: A 16-pixel Millimeter-Wave Spectrometer for the Green Bank Telescope - Sieth, Matthew; Devaraj, Kiruthika; Voll, Patricia; Church, Sarah; Gawande, Rohit; Cleary, Kieran; Readhead, Anthony C. S.; Kangaslahti, Pekka; Samoska, Lorene; Gaier, Todd; Goldsmith, Paul F.; Harris, Andrew I.; Gundersen, Joshua O.; Frayer, David; White, Steve; Egan, Dennis; Reeves, Rodrigo
We report on the development of Argus, a 16-pixel spectrometer, which will enable fast astronomical imaging over the 85–116 GHz band. Each pixel includes a compact heterodyne receiver module, which integrates two InP MMIC low-noise amplifiers, a coupled-line bandpass filter and a sub-harmonic Schottky diode mixer. The receiver signals are routed to and from the multi-chip MMIC modules with multilayer high frequency printed circuit boards, which includes LO splitters and IF amplifiers. Microstrip lines on flexible circuitry are used to transport signals between temperature stages. The spectrometer frontend is designed to be scalable, so that the array design can be...

17. The Status of MUSIC: The Multiwavelength Sub/millimeter Inductance Camera - Sayers, Jack; Duan, Ran P.; Golwala, Sunil R.; Hollister, Matt I.; Lam, Albert; Miller, David A.; Schlaerth, James A.; Siegel, Seth R.; Vayonakis, Anastasios; Zmuidzinas, Jonas
The Multiwavelength Sub/millimeter Inductance Camera (MUSIC) is a four-band photometric imaging camera operating from the Caltech Submillimeter Observatory (CSO). MUSIC is designed to utilize 2304 microwave kinetic inductance detectors (MKIDs), with 576 MKIDs for each observing band centered on 150, 230, 290, and 350 GHz. MUSIC’s field of view (FOV) is 14′ square, and the point-spread functions (PSFs) in the four observing bands have 45′′, 31′′, 25′′, and 22′′ full-widths at half maximum (FWHM). The camera was installed in April 2012 with 25% of its nominal detector count in each band, and has subsequently completed three short sets of engineering...

18. Preliminary design of the wavefront sensor for CCAT - Naylor, David; Gom, Brad; Leclerc, Mélanie; Legros, Mathieu; Padin, Stephen; Serabyn, Eugene
CCAT1 is a submillimeter telescope currently under development that will be located at an altitude of 5600 meters in the Andes mountains of northern Chile. The atmospheric transmission at this site will allow CCAT to achieve high sensitivity over a wide field of view and a broad wavelength range to provide an unprecedented capability for deep, large area multicolor submillimeter surveys. In order to achieve high aperture efficiencies out to frequencies of ~ 1 THz, the 162 individual panels that form the 25 meter aperture of CCAT must be aligned to a tolerance of a few microns rms. The design...

19. Inflight performance and calibration of the NuSTAR CdZnTe pixel detectors - Kitaguchi, Takao; Bhalerao, Varun; Cook, W. Rick; Forster, Karl; Grefenstette, Brian W.; Harrison, Fiona A.; Madsen, Kristin K.; Mao, Peter H.; Miyasaka, Hiromasa; Rana, Vikram R.
The Nuclear Spectroscopic Telescope Array (NuSTAR) satellite is a NASA Small Explorer mission designed to operate the first focusing high-energy X-ray (3-79 keV) telescope in orbit. Since the launch in June 2012, all the NuSTAR components have been working normally. The focal plane module is equipped with an 155Eu radioactive source to irradiate the CdZnTe pixel detectors for independent calibration separately from optics. The inflight spectral calibration of the CdZnTe detectors is performed with the onboard 155Eu source. The derived detector performance agrees well with ground-measured data. The in-orbit detector background rate is stable and the lowest among past high-energy...

20. High efficiency CCD detectors at UV wavelengths - Hamden, Erika T.; Jewell, April D.; Gordon, Samuel; Hennessy, John; Hoenk, Michael E.; Nikzad, Shouleh; Schiminovich, David; Martin, D. Christopher
The Faint Intergalactic Redshifted Emission Balloon (FIREBall) is a NASA/CNES balloon-borne ultraviolet multi-object spectrograph designed to observe the diffuse gas around galaxies (the circumgalactic medium) via line emission redshifted to ~ 205 nm. FIREBall uses a ultraviolet-optimized delta doped e2v CCD201 with a custom designed high efficiency five layer anti-re ection coating. This combination achieves very high quantum efficiency (QE) and photon-counting capability, a first for a CCD detector in this wavelength range. We also present new work on red blocking mirror coatings to reduce red leak.

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