Recursos de colección

Caltech Authors (142.336 recursos)

Repository of works by Caltech published authors.

Group = Keck Institute for Space Studies

Mostrando recursos 1 - 20 de 277

  1. The Bimodal Color Distribution of Small Kuiper Belt Objects

    Wong, Ian; Brown, Michael E.
    We conducted a two-night photometric survey of small Kuiper Belt objects (KBOs) near opposition using the wide-field Hyper Suprime-Cam instrument on the 8.2 m Subaru Telescope. The survey covered about 90 deg^2 of sky, with each field imaged in the g and i bands. We detected 356 KBOs, ranging in absolute magnitude from 6.5 to 10.4. Filtering for high-inclination objects within the hot KBO population, we show that the g − i color distribution is strongly bimodal, indicative of two color classes—the red and very red subpopulations. After categorizing objects into the two subpopulations by color, we present the first...

  2. Small Near-Earth Asteroids in the Palomar Transient Factory Survey: a Real-Time Streak-detection System

    Waszczak, Adam; Prince, Thomas A.; Laher, Russ; Masci, Frank; Bue, Brian; Rebbapragada, Umaa; Barlow, Tom; Surace, Jason; Helou, George; Kulkarni, Shrinivas
    Near-Earth asteroids (NEAs) in the 1–100 meter size range are estimated to be ~1,000 times more numerous than the ~15,000 currently cataloged NEAs, most of which are in the 0.5–10 kilometer size range. Impacts from 10–100 meter size NEAs are not statistically life-threatening, but may cause significant regional damage, while 1–10 meter size NEAs with low velocities relative to Earth are compelling targets for space missions. We describe the implementation and initial results of a real-time NEA-discovery system specialized for the detection of small, high angular rate (visually streaked) NEAs in Palomar Transient Factory (PTF) images. PTF is a 1.2-m...

  3. Monthly trends of methane emissions in Los Angeles from 2011 to 2015 inferred by CLARS-FTS observations

    Wong, Clare K.; Pongetti, Thomas J.; Oda, Tom; Rao, Preeti; Gurney, Kevin R.; Newman, Sally; Duren, Riley M.; Miller, Charles E.; Yung, Yuk L.; Sander, Stanley P.
    This paper presents an analysis of methane emissions from the Los Angeles Basin at monthly timescales across a 4-year time period – from September 2011 to August 2015. Using observations acquired by a ground-based near-infrared remote sensing instrument on Mount Wilson, California, combined with atmospheric CH_4–CO_2 tracer–tracer correlations, we observed −18 to +22 % monthly variability in CH_4 : CO_2 from the annual mean in the Los Angeles Basin. Top-down estimates of methane emissions for the basin also exhibit significant monthly variability (−19 to +31 % from annual mean and a maximum month-to-month change of 47 %). During this period, methane emissions consistently peaked in...

  4. The stratigraphy and evolution of lower Mount Sharp from spectral, morphological, and thermophysical orbital data sets

    Fraeman, A. A.; Ehlmann, B. L.; Arvidson, R. E.; Edwards, C. S.; Grotzinger, J. P.; Milliken, R. E.; Quinn, D. P.; Rice, M. S.
    We have developed a refined geologic map and stratigraphy for lower Mount Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mount Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1–3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate-bearing unit, (5) a hematite-capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible near-infrared wavelengths, and (7) a...

  5. The faint intergalactic-medium red-shifted emission balloon: future UV observations with EMCCDs

    Kyne, Gillian; Hamden, Erika T.; Lingner, Nicole; Morrissey, Patrick; Nikzad, Shouleh; Martin, D. Christopher
    We present the latest developments in our joint NASA/CNES suborbital project. This project is a balloon-borne UV multi-object spectrograph, which has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies. One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (¡ 1e-). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with the CCD Controller for Counting Photons (CCCP) from Nüvü. This optimisation also includes methods for reducing...

  6. Remote sensing of solar induced Chlorophyll Fluorescence from satellites, airplanes and ground-based stations

    Frankenberg, C.; Drewry, D.; Geier, S.; Verma, M.; Lawson, P.; Stutz, J.; Grossmann, K.
    With the advent of existing high resolution spectrometers in space (GOSAT, GOME-2, OCO-2), global observations of solar induced chlorophyll fluorescence (SIF) became feasible for the first time. The potential of SIF is to provide an independent and more direct proxy for photosynthetic activity and, depending on retrieval methodology, be less susceptible to atmospheric scattering. Empirically, strong linear correlations between SIF and gross primary production (GPP) have been shown in several studies, albeit with somewhat different slopes per biome type. Here, we show the first full year of data acquired by the Orbiting Carbon Observatory-2, which provides unprecendendet spatial resolution (1.3·2.3...

  7. W.M. Keck Institute for Space Studies Postdoctoral Fellowship Final Report

    Fraeman, Abigail A.

  8. Charge-coupled devices detectors with high quantum efficiency at UV wavelengths

    Hamden, Erika T.; Jewell, April D.; Shapiro, Charles A.; Cheng, Samuel R.; Goodsall, Tim M.; Hennessy, John; Hoenk, Michael; Jones, Todd; Gordon, Sam; Ong, Hwei Ru; Schiminovich, David; Martin, D. Christopher; Nikzad, Shouleh
    We report on multilayer high efficiency antireflection coating (ARC) design and development for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of single-layer coatings, which achieve >50% quantum efficiency (QE) in four bands from 130 to 300 nm. We now present multilayer coating designs that significantly outperform our previous work between 195 and 215 nm. Using up to 11 layers, we present several model designs to reach QE above 80%. We also demonstrate the successful performance of 5 and 11 layer ARCs on silicon and fused silica substrates. Finally, we present a...

  9. Ultralight Structures for Space Solar Power Satellites

    Arya, Manan; Lee, Nicolas; Pellegrino, Sergio
    The design of a deployable spacecraft, measuring 60 m × 60 m, and with an areal density 100 g m^(−2) , is described. This spacecraft can be packaged into a cylinder measuring 1.5 m in height and 1 m in diameter. It can be deployed to a flat configuration, where it acts as a stiff, lightweight support framework for multifunctional tiles that collect sunlight, generate electric power, and transmit to a ground station on Earth.

  10. Architecture for in-space robotic assembly of a modular space telescope

    Lee, Nicolas; Backes, Paul; Burdick, Joel; Pellegrino, Sergio; Fuller, Christine; Hogstrom, Kristina; Kennedy, Brett; Kim, Junggon; Mukherjee, Rudranarayan; Seubert, Carl; Wu, Yen-Hung
    An architecture and conceptual design for a robotically assembled, modular space telescope (RAMST) that enables extremely large space telescopes to be conceived is presented. The distinguishing features of the RAMST architecture compared with prior concepts include the use of a modular deployable structure, a general-purpose robot, and advanced metrology, with the option of formation flying. To demonstrate the feasibility of the robotic assembly concept, we present a reference design using the RAMST architecture for a formation flying 100-m telescope that is assembled in Earth orbit and operated at the Sun–Earth Lagrange Point 2.

  11. A co-crystal between benzene and ethane: a potential evaporite material for Saturn’s moon Titan

    Maynard-Casely, Helen; Hodyss, Robert; Cable, Morgan; Hoang Vu, Tuan; Rahm, Martin
    Using synchrotron X-ray powder diffraction, the structure of a co-crystal between benzene and ethane formed in situ at cryogenic conditions has been determined, and validated using dispersion-corrected density functional theory calculations. The structure comprises a lattice of benzene molecules hosting ethane molecules within channels. Similarity between the intermolecular interactions found in the co-crystal and in pure benzene indicate that the C— H network of benzene is maintained in the co-crystal, however, this expands to accommodate the guest ethane molecules. The co-crystal has a 3:1 benzene:ethane stoichiometry and is described in the space group R3 with a = 15.977 (1) A˚ and c = 5.581 (1) A˚ at 90 K,...

  12. Polymorphism and electronic structure of polyimine and its potential significance for prebiotic chemistry on Titan

    Rahm, Martin; Lunine, Jonathan; Usher, David; Shalloway, David
    The chemistry of hydrogen cyanide (HCN) is believed to be central to the origin of life question. Contradictions between Cassini–Huygens mission measurements of the atmosphere and the surface of Saturn’s moon Titan suggest that HCN-based polymers may have formed on the surface from products of atmospheric chemistry. This makes Titan a valuable “natural laboratory” for exploring potential nonterrestrial forms of prebiotic chemistry. We have used theoretical calculations to investigate the chain conformations of polyimine (pI), a polymer identified as one major component of polymerized HCN in laboratory experiments. Thanks to its flexible backbone, the polymer can exist in several different polymorphs, which are relatively close in energy. The electronic and structural...

  13. Using VSWIR Microimaging Spectroscopy to Explore the Mineralogical Diversity of HED Meteorites

    Fraeman, Abigail A.; Ehlmann, Bethany L.; Northwood-Smith, Geraint W. D.; Liu, Yang; Wadhwa, Meenakshi; Greenberger, Rebecca N.
    We use VSWIR microimaging spectroscopy to survey the spectral diversity of HED meteorites at 80-μm/pixel spatial scale. Our goal in this work is both to explore the emerging capabilities of microimaging VSWIR spectroscopy and to contribute to understanding the petrologic diversity of the HED suite and the evolution of Vesta. Using a combination of manual and automated hyperspectral classification techniques, we identify four major classes of materials based on VSWIR absorptions that include pyroxene, olivine, Fe-bearing feldspars, and glass-bearing/featureless materials. Results show microimaging spectroscopy is an effective method for rapidly and non-destructively characterizing small compositional variations of meteorite samples and...

  14. The Stratigraphy and Evolution of Lower Mt. Sharp from Spectral, Morphological, and Thermophysical Orbital Datasets

    Fraeman, A. A.; Ehlmann, B. L.; Arvidson, R. E.; Edwards, C. S.; Grotzinger, J. P.; Milliken, R. E.; Quinn, D. P.; Rice, M. S.
    We have developed a refined geologic map and stratigraphy for lower Mt. Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mt. Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1-3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate-bearing unit, (5) a hematite-capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible-near infrared wavelengths, and (7) a...

  15. The Stratigraphy and Evolution of Lower Mt. Sharp from Spectral, Morphological, and Thermophysical Orbital Datasets

    Fraeman, A. A.; Ehlmann, B. L.; Arvidson, R. E.; Edwards, C. S.; Grotzinger, J. P.; Milliken, R. E.; Quinn, D. P.; Rice, M. S.
    We have developed a refined geologic map and stratigraphy for lower Mt. Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mt. Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1-3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate-bearing unit, (5) a hematite-capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible-near infrared wavelengths, and (7) a...

  16. Dark census: Statistically detecting the satellite populations of distant galaxies

    Cyr-Racine, Francis-Yan; Moustakas, Leonidas A.; Keeton, Charles R.; Sigurdson, Kris; Gilman, Daniel A.
    In the standard structure formation scenario based on the cold dark matter paradigm, galactic halos are predicted to contain a large population of dark matter subhalos. While the most massive members of the subhalo population can appear as luminous satellites and be detected in optical surveys, establishing the existence of the low mass and mostly dark subhalos has proven to be a daunting task. Galaxy-scale strong gravitational lenses have been successfully used to study mass substructures lying close to lensed images of bright background sources. However, in typical galaxy-scale lenses, the strong lensing region only covers a small projected area...

  17. Architecture for in-space robotic assembly of a modular space telescope

    Lee, Nicolas; Backes, Paul; Burdick, Joel W.; Pellegrino, Sergio; Fuller, Christine; Hogstrom, Kristina; Kennedy, Brett; Kim, Junggon; Mukherjee, Rudranarayan; Seubert, Carl; Wu, Yen-Hung
    An architecture and conceptual design for a robotically assembled, modular space telescope (RAMST) that enables extremely large space telescopes to be conceived is presented. The distinguishing features of the RAMST architecture compared with prior concepts include the use of a modular deployable structure, a general-purpose robot, and advanced metrology, with the option of formation flying. To demonstrate the feasibility of the robotic assembly concept, we present a reference design using the RAMST architecture for a formation flying 100-m telescope that is assembled in Earth orbit and operated at the Sun–Earth Lagrange Point 2.

  18. Constraints on iron sulfate and iron oxide mineralogy from ChemCam visible/near-infrared reflectance spectroscopy of Mt. Sharp basal units, Gale Crater, Mars

    Johnson, Jeffrey R.; Bell, James F., III; Bender, Steve; Blaney, Diana; Cloutis, Edward; Ehlmann, Bethany; Fraeman, Abigail A.; Gasnault, Olivier; Kinch, Kjartan; Le Mouélic, Stéphane; Maurice, Sylvestre; Rampe, Elizabeth; Vaniman, David; Wiens, Roger C.
    Relative reflectace point spectra (400–840 nm) were acquired by the Chemistry and Camera (ChemCam) instrument on the Mars Science Laboratory (MSL) rover Curiosity in passive mode (no laser) of drill tailings and broken rock fragments near the rover as it entered the lower reaches of Mt. Sharp and of landforms at distances of 2–8 km. Freshly disturbed surfaces are less subject to the spectral masking effects of dust, and revealed spectral features consistent with the presence of iron oxides and ferric sulfates. We present the first detection on Mars of a ~433 nm absorption band consistent with small abundances of...

  19. Large wind ripples on Mars: A record of atmospheric evolution

    Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M. J.; Daybell, M.; Gupta, S.; Banham, S. G.; Bridges, N. T.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A.; Herkenhoff, K. E.; Ming, D. W.; Mischna, M. A.; Rice, M. S.; Sumner, D. A.; Vasavada, A. R.; Yingst, R. A.
    Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density...

  20. Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials

    Nikzad, Shouleh; Hoenk, Michael; Jewell, April D.; Hennessy, John J.; Carver, Alexander G.; Jones, Todd J.; Goodsall, Timothy M.; Hamden, Erika T.; Suvarna, Puneet; Bulmer, J.; Shahedipour-Sandvik, F.; Charbon, Edoardo; Padmanabhan, Preethi; Hancock, Bruce; Bell, L. Douglas
    Ultraviolet (UV) studies in astronomy, cosmology, planetary studies, biological and medical applications often require precision detection of faint objects and in many cases require photon-counting detection. We present an overview of two approaches for achieving photon counting in the UV. The first approach involves UV enhancement of photon-counting silicon detectors, including electron multiplying charge-coupled devices and avalanche photodiodes. The approach used here employs molecular beam epitaxy for delta doping and superlattice doping for surface passivation and high UV quantum efficiency. Additional UV enhancements include antireflection (AR) and solar-blind UV bandpass coatings prepared by atomic layer deposition. Quantum efficiency (QE) measurements...

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