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1. Upgrading the Submillimeter Array: wSMA and beyond

Author

Grimes, Paul K., Keating, Garrett K., Blundell, Raymond, Christensen, Robert D., Gurwell, Mark, Kovacs, Attila, Norton, Timothy, Paine, Scott N., Rao, Ramprasad, Tong, Edward C. -Y., Weintroub, Jonathan, Wilner, David, Wilson, Robert W., Zeng, Lingzhen, and Zhang, Qizhou

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The Submillimeter Array (SMA) is an array of 8 antennas operating at millimeter and submillimeter wavelengths on Maunakea, Hawaii, operated by the Smithsonian Astrophysical Observatory and Academia Sinica Institute of Astronomy and Astrophysics, Taiwan. Over the past several years, we have been preparing a major upgrade to the SMA that will replace the aging original receiver cryostats and receiver cartridges with all new cryostats and new 230 and 345 GHz receiver designs. This wideband upgrade (wSMA) will also include significantly increased instantaneous bandwidth, improved sensitivity, and greater capabilities for dual frequency observations. In this paper, we will describe the wSMA receiver upgrade and status, as well as the future upgrades that will be enabled by the deployment of the wSMA receivers., Comment: To be published in the proceedings of SPIE Astronomical Telescopes + Instrumentation 2024, paper number 13096-122

Published
2024

2. The Black Hole Explorer: Instrument System Overview

Author

Marrone, Daniel P., Houston, Janice, Akiyama, Kazunori, Bilyeu, Bryan, Boroson, Don, Grimes, Paul, Haworth, Kari, Lehmensiek, Robert, Peretz, Eliad, Rana, Hannah, Sinclair, Laura C., Kumara, Sridharan Tirupati, Srinivasan, Ranjani, Tong, Edward, Wang, Jade, Weintroub, Jonathan, and Johnson, Michael D.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The Black Hole Explorer (BHEX) is a space very-long-baseline interferometry (VLBI) mission concept that is currently under development. BHEX will study supermassive black holes at unprecedented resolution, isolating the signature of the "photon ring" - light that has orbited the black hole before escaping - to probe physics at the edge of the observable universe. It will also measure black hole spins, study the energy extraction and acceleration mechanisms for black hole jets, and characterize the black hole mass distribution. BHEX achieves high angular resolution by joining with ground-based millimeter-wavelength VLBI arrays, extending the size, and therefore improving the angular resolution of the earthbound telescopes. Here we discuss the science instrument concept for BHEX. The science instrument for BHEX is a dual-band, coherent receiver system for 80-320 GHz, coupled to a 3.5-meter antenna. BHEX receiver front end will observe simultaneously with dual polarizations in two bands, one sampling 80-106 GHz and one sampling 240-320 GHz. An ultra-stable quartz oscillator provides the master frequency reference and ensures coherence for tens of seconds. To achieve the required sensitivity, the front end will instantaneously receive 32 GHz of frequency bandwidth, which will be digitized to 64 Gbits/sec of incompressible raw data. These data will be buffered and transmitted to the ground via laser data link, for correlation with data recorded simultaneously at radio telescopes on the ground. We describe the challenges associated with the instrument concept and the solutions that have been incorporated into the baseline design., Comment: SPIE Astronomical Telescopes + Instrumentation, 2024

Published
2024

3. The Black Hole Explorer Cryocooling Instrument

Author

Rana, Hannah, Akiyama, Kazunori, Canavan, Edgar, DiPirro, Michael, Freeman, Mark, Galison, Peter, Grimes, Paul, Honma, Mareki, Houston, Janice, Johnson, Michael, Kimball, Mark, Marrone, Daniel, and Tong, Edward

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The Black Hole Explorer (BHEX) is a space-based very-long baseline interferometry (VLBI) mission aimed at precision black hole measurements, detecting the photon ring around black holes, exploring spacetime, spin, and mass properties, and validating predictions of General Relativity. These objectives are achieved using cryogenic receivers with quantum-limited sensitivities across a broad frequency range. Dual-band receivers at 80-106 GHz and 240-320 GHz require operating temperatures of 20 K and 4.5 K, respectively. A cryocooling system with two cold stages will be employed: a 20 K stage handling a 125 mW heat load and a 4.5 K stage handling a 10 mW heat load. To design the cryocooling system, the mission leverages existing space industry technology at high Technology Readiness Levels (TRLs), informed by missions such as Planck, JEM/SMILES, Hitomi, and XRISM, and advancements from the ACTDP/JWST program. Integrating the cryocooler with the receivers and broader instrument involves careful consideration of thermal challenges, including linking the cold ends of each cooling stage to minimize heat losses and ensuring adequate passive cooling for the cryocooler warm end heat rejection. Key challenges and trade-offs include sizing the mass and reducing power consumption while meeting the receiver cold temperature requirements, which impact the scientific objectives. This paper addresses efforts to balance the scientific requirements with the limitations of technical cryocooling capabilities within the framework of a small-class (SMEX) space mission, presenting an overview of cooling needs, initial design considerations, a survey of 4 K spaceflight cryocooler developments, and trade-offs.

Published
2024

4. The Black Hole Explorer: Motivation and Vision

Author

Johnson, Michael D., Akiyama, Kazunori, Baturin, Rebecca, Bilyeu, Bryan, Blackburn, Lindy, Boroson, Don, Cardenas-Avendano, Alejandro, Chael, Andrew, Chan, Chi-kwan, Chang, Dominic, Cheimets, Peter, Chou, Cathy, Doeleman, Sheperd S., Farah, Joseph, Galison, Peter, Gamble, Ronald, Gammie, Charles F., Gelles, Zachary, Gomez, Jose L., Gralla, Samuel E., Grimes, Paul, Gurvits, Leonid I., Hadar, Shahar, Haworth, Kari, Hada, Kazuhiro, Hecht, Michael H., Honma, Mareki, Houston, Janice, Hudson, Ben, Issaoun, Sara, Jia, He, Jorstad, Svetlana, Kauffmann, Jens, Kovalev, Yuri Y., Kurczynski, Peter, Lafon, Robert, Lupsasca, Alexandru, Lehmensiek, Robert, Ma, Chung-Pei, Marrone, Daniel P., Marscher, Alan P., Melnick, Gary J., Narayan, Ramesh, Niinuma, Kotaro, Noble, Scott C., Palmer, Eric J., Palumbo, Daniel C. M., Paritsky, Lenny, Peretz, Eliad, Pesce, Dominic, Plavin, Alexander, Quataert, Eliot, Rana, Hannah, Ricarte, Angelo, Roelofs, Freek, Shtyrkova, Katia, Sinclair, Laura C., Small, Jeffrey, Kumara, Sridharan Tirupati, Srinivasan, Ranjani, Strominger, Andrew, Tiede, Paul, Tong, Edward, Wang, Jade, Weintroub, Jonathan, Wielgus, Maciek, Wong, George, and Zhang, Xinyue Alice

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract

We present the Black Hole Explorer (BHEX), a mission that will produce the sharpest images in the history of astronomy by extending submillimeter Very-Long-Baseline Interferometry (VLBI) to space. BHEX will discover and measure the bright and narrow "photon ring" that is predicted to exist in images of black holes, produced from light that has orbited the black hole before escaping. This discovery will expose universal features of a black hole's spacetime that are distinct from the complex astrophysics of the emitting plasma, allowing the first direct measurements of a supermassive black hole's spin. In addition to studying the properties of the nearby supermassive black holes M87* and Sgr A*, BHEX will measure the properties of dozens of additional supermassive black holes, providing crucial insights into the processes that drive their creation and growth. BHEX will also connect these supermassive black holes to their relativistic jets, elucidating the power source for the brightest and most efficient engines in the universe. BHEX will address fundamental open questions in the physics and astrophysics of black holes that cannot be answered without submillimeter space VLBI. The mission is enabled by recent technological breakthroughs, including the development of ultra-high-speed downlink using laser communications, and it leverages billions of dollars of existing ground infrastructure. We present the motivation for BHEX, its science goals and associated requirements, and the pathway to launch within the next decade., Comment: Proceedings for SPIE Astronomical Telescopes and Instrumentation

Published
2024

5. The Japanese Vision for the Black Hole Explorer Mission

Author

Akiyama, Kazunori, Niinuma, Kotaro, Hada, Kazuhiro, Doi, Akihiro, Hagiwara, Yoshiaki, Higuchi, Aya E., Honma, Mareki, Kawashima, Tomohisa, Kolev, Dimitar, Koyama, Shoko, Masui, Sho, Ohsuga, Ken, Sano, Hidetoshi, Takami, Hideki, Tsunetoe, Yuh, Uzawa, Yoshinori, Akahori, Takuya, Akiyama, Yuto, Galison, Peter, Hayashi, Takayuki J., Hirota, Tomoya, Inoue, Makoto, Iwata, Yuhei, Johnson, Michael D., Kino, Motoki, Kofuji, Yutaro, Mizuno, Yosuke, Moriyama, Kotaro, Nagai, Hiroshi, Nakamura, Kenta, Notsu, Shota, Ono, Fumie, Oya, Yoko, Oyama, Tomoaki, Rana, Hannah, Saida, Hiromi, Saito, Ryo, Saito, Yoshihiko, Sasada, Mahito, Sawada-Satoh, Satoko, Takahashi, Mikiya M., Takamura, Mieko, Tong, Edward, Tsuji, Hiroyuki, Yoshioka, Shogo, and Watanabe, Yoshimasa

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The Black Hole Explorer (BHEX) is a next-generation space very long baseline interferometry (VLBI) mission concept that will extend the ground-based millimeter/submillimeter arrays into space. The mission, closely aligned with the science priorities of the Japanese VLBI community, involves an active engagement of this community in the development of the mission, resulting in the formation of the Black Hole Explorer Japan Consortium. Here we present the current Japanese vision for the mission, ranging from scientific objectives to instrumentation. The Consortium anticipates a wide range of scientific investigations, from diverse black hole physics and astrophysics studied through the primary VLBI mode, to the molecular universe explored via a potential single-dish observation mode in the previously unexplored 50-70\,GHz band that would make BHEX the highest-sensitivity explorer ever of molecular oxygen. A potential major contribution for the onboard instrument involves supplying essential elements for its high-sensitivity dual-band receiving system, which includes a broadband 300\,GHz SIS mixer and a space-certified multi-stage 4.5K cryocooler akin to those used in the Hitomi and XRISM satellites by the Japan Aerospace Exploration Agency. Additionally, the Consortium explores enhancing and supporting BHEX operations through the use of millimeter/submillimeter facilities developed by the National Astronomical Observatory of Japan, coupled with a network of laser communication stations operated by the National Institute of Information and Communication Technology., Comment: Submitted to SPIE Conference Series, 17 pages for the main text, 33 pages for the references, 4 figures, SPIE Astronomical Telescopes + Instrumentation 2024

Published
2024

6. A Prospective ISRO-CfA Himalayan Sub-millimeter-wave Observatory Initiative

Author

Sridharan, T. K., Bialy, Shmuel, Blundell, Raymond, Burkhardt, Andrew, Dame, Thomas, Doeleman, Sheperd, Finkbeiner, Douglas, Goodman, Alyssa, Grimes, Paul, Imara, Nia, Johnson, Michael, Keating, Garrett, Lada, Charles, Gal, Romane Le, Myers, Philip, Narayan, Ramesh, Paine, Scott, Patel, Nimesh, Raymond, Alexander, Tong, Edward, Wilner, David, Zhang, Qizhou, and Zucker, Catherine

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The Smithsonian Astrophysical Observatory (SAO), a member of the Center for Astrophysics | Harvard and Smithsonian, is in discussions with the Space Applications Centre (SAC) of the Indian Space Research Organization (ISRO) and its partners in the newly formed Indian Sub-millimetre-wave Astronomy Alliance (ISAA), to collaborate in the construction of a sub-millimeter-wave astronomy observatory in the high altitude deserts of the Himalayas, initially at the 4500 m Indian Astronomical Observatory, Hanle. Two primary science goals are targeted. One is the mapping of the distribution of neutral atomic carbon, and the carbon monoxide (CO) molecule in higher energy states, in large parts of the Milky Way, and in selected external galaxies. Such studies would advance our understanding of molecular hydrogen present in the interstellar medium, but partly missed by existing observations; and characterize Galaxy-wide molecular cloud excitation conditions, through multi-level CO observations. Stars form in interstellar clouds of molecular gas and dust, and these observations would allow research into the formation and destruction processes of such molecular clouds and the life cycle of galaxies. As the second goal, the observatory would add a new location to the global Event Horizon Telescope (EHT) network, which lacks a station in the Himalayan longitudes. This addition would enhance the quality of the images synthesized by the EHT, support observations in higher sub-millimeter wave bands, sharpening its resolving ability, improve its dynamic imaging capability and add weather resilience to observing campaigns. In the broader context, this collaboration can be a starting point for a wider, mutually beneficial scientific exchange between the Indian and US astronomy communities, including a potential future EHT space component., Comment: Internal white paper prepared in support of the initiative, 32 pages, 7 figures

Published
2020

7. The Greenland Telescope (GLT): Antenna status and future plans

Author

Raffin, Philippe, Algaba-Marcos, Juan Carlos, Asada, Keichi, Blundell, Raymond, Burgos, Roberto, Chang, Chih-Cheng, Chen, Ming-Tang, Christensen, Robert, Grimes, Paul K., Han, C. C., Ho, Paul T. P., Huang, Yau-De, Inoue, Makoto, Koch, Patrick M., Kubo, Derek, Leiker, Steve, Liu, Ching-Tang, Martin-Cocher, Pierre, Matsushita, Satoki, Nakamura, Masanori, Nishioka, Hiroaki, Nystrom, George, Paine, Scott N., Patel, Nimesh A., Pradel, Nicolas, Pu, Hung-Yi, Shen, H. -Y., Snow, William, Sridharan, T. K., Srinivasan, Ranjani, Tong, Edward, and Wang, Jackie

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The ALMA North America Prototype Antenna was awarded to the Smithsonian Astrophysical Observatory (SAO) in 2011. SAO and the Academia Sinica Institute of Astronomy & Astrophysics (ASIAA), SAO's main partner for this project, are working jointly to relocate the antenna to Greenland to carry out millimeter and submillimeter VLBI observations. This paper presents the work carried out on upgrading the antenna to enable operation in the Arctic climate by the GLT Team to make this challenging project possible, with an emphasis on the unexpected telescope components that had to be either redesigned or changed. Five-years of inactivity, with the antenna laying idle in the desert of New Mexico, coupled with the extreme weather conditions of the selected site in Greenland have it necessary to significantly refurbish the antenna. We found that many components did need to be replaced, such as the antenna support cone, the azimuth bearing, the carbon fiber quadrupod, the hexapod, the HVAC, the tiltmeters, the antenna electronic enclosures housing servo and other drive components, and the cables. We selected Vertex, the original antenna manufacturer, for the main design work, which is in progress. The next coming months will see the major antenna components and subsystems shipped to a site of the US East Coast for test-fitting the major antenna components, which have been retrofitted. The following step will be to ship the components to Greenland to carry out VLBI and single dish observations. Antenna reassembly at Summit Station should take place during the summer of 2018., Comment: 10 pages, 8 figures

Published
2014
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8. Mixture models for consumer credit risk

Author

Tong, Edward N. C. and Mues, Christophe

Subjects
658, HF Commerce, HG Finance
Abstract

The three papers in this thesis comprise the development of three types of Basel models – a Probability of Default (PD), Loss Given Default (LGD) and Exposure at Default (EAD) model for consumer credit risk, using mixture model methods. Mixture models consider the underlying population as being composed of different sub-populations that are modelled separately. In the first paper (Chapter 2), mixture cure models are introduced to the area of PD/credit scoring. A large proportion of the dataset may not experience the event of interest during the loan term, i.e. default. A mixture cure model predicting (time to) default on a UK personal loan portfolio was developed and its performance compared to industry standard models. The mixture cure model's ability to distinguish between two subpopulations can offer additional insights by estimating the parameters that determine susceptibility to default in addition to parameters that influence time to default of a borrower. The second paper (Chapter 3) considers LGD modelling. One of the key problems in building regression models to estimate loan-level LGD in retail portfolios such as mortgage loans relates to the difficulty in modelling its distribution, which typically contains an extensive amount of zeroes. An alternative approach is proposed in which a mixed discrete-continuous model for the total loss amount incurred on a defaulted loan is developed. The model simultaneously accommodates the probability of zero loss and the loss amount given that loss occurs. This zero-adjusted gamma model is shown to present an alternative and competitive approach to LGD modelling. The third paper (Chapter 4) considers EAD models for revolving credit facilities with variable exposure. The credit conversion factor (CCF), the proportion of the current undrawn amount that will be drawn down at time of default, is used to calculate the EAD and poses modelling challenges with challenging bimodal distributions. We explore alternative EAD models which ignore the CCF formulation and target the EAD distribution directly. We propose a mixture model with the zero-adjusted gamma distribution and compare performance with CCF based models. We find the mixture model to be more accurate in calibration than the CCF models and that segmented approaches offer further performance improvements.

Published
2015

9. Evidence for Dynamically Important Magnetic Fields in Molecular Clouds

Author

Li, Hua-bai, Blundell, Raymond, Hedden, Abigail, Kawamura, Jonathan, Paine, Scott, and Tong, Edward

Subjects
Astrophysics - Astrophysics of Galaxies, Physics - Plasma Physics
Abstract

Recent observational evidence that magnetic fields are dynamically important in molecular clouds, compared to self-gravity and turbulence, is reviewed and illustrated with data from the NGC 2024 region. One piece of evidence, turbulence anisotropy, was found in the diffuse envelope of a cloud (Av~1; Heyer et al. 2008); our data further suggests turbulence anisotropy in the cloud (Av >7) and even near the cloud core (Av~100). The data also shows that magnetic fields can channel gravitational contraction even for a region with super-critical N(H2)/2Blos ratio (the ratio between the observed column density and two times the line-of-sight observed field strength), a parameter which has been widely used by observers to estimate core mass-to-flux ratios. Although the mass-to-flux ratio is constant under the flux-freezing condition, we show that N(H2)/2Blos grows with time if gravitational contraction is anisotropic due to magnetic fields., Comment: accepted by MNRAS

Published
2010
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17. Heterodyne Receiver for Origins

Author

Wiedner, Martina C., primary, Aalto, Susanne, additional, Amatucci, Edward G., additional, Baryshev, Andrey M., additional, Belitsky, Victor Y., additional, Cooray, Asantha, additional, De Beck, Elvire, additional, Delorme, Yan, additional, Ellison, Brian N., additional, Eggens, Martin J., additional, Gallego-Puyol, Juan D., additional, Gerin, Maryvonne, additional, Goldsmith, Paul F., additional, Herpin, Fabrice, additional, Hunt, Leslie K., additional, Krieg, Jean-Michel, additional, Kroes, Gabby, additional, Laporte, Philippe, additional, Laurens, André, additional, Leisawitz, David T., additional, Lis, Dariusz C., additional, Meixner, Margaret, additional, Melnick, Gary J., additional, Milam, Stefanie N., additional, Neufeld, David A., additional, Nguyen-Tuong, Napoléon, additional, Plume, Réné, additional, Risacher, Christophe, additional, Staguhn, Johannes G., additional, Tong, Edward, additional, Viti, Serena, additional, Origins Space Telescope Mission Concept Study Team, The, additional, Battersby, Cara, additional, Bergin, Edwin, additional, Borgo, Bruno, additional, Carter, Ruth C., additional, Caux, Emmanuel, additional, Corsetti, James A., additional, Desmaris, Vincent P., additional, DiPirro, Michael J., additional, Di Giorgio, Anna Maria, additional, Goldstein, Christophe, additional, Helmich, Frank P., additional, Hills, Richard E., additional, Hogerheijde, Michiel, additional, Jellema, Willem, additional, Keizer, Geert, additional, Martins, Gregory E., additional, Mehdi, Imran, additional, Pontoppidan, Klaus, additional, Quertier-Dagorn, Benjamin, additional, and Wyrowski, Friedrich, additional

Published
2021
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21. Far-Infrared Heterodyne Array Receivers

Author

Mehdi, Imran, Goldsmith, Paul, Lis, Dariusz, Pineada, Jorge, Langer, Bill, Siles, Jose, Kawamura, Jon, Karasik, Boris, Chattopadhay, Goutam, Pearson, John, Kooi, Jacob, Samoska, Lorene, Groppi, Chris, Williams, Ben, Heyer, Mark, Melnick, Gary, Wolfire, Mark, Koda, Jin, Yorke, Hal, Pontoppidan, Klaus, Tong, Edward, Grimes, Paul, Zeng, Lingzhen, Wiedner, M. C., Gerin, M., Baryshev, A., Belitsky, V., Desmaris, V., Gallego, J. D., Helmich, F., Jellema, W., Risacher, C., Gao, J. R., Cherednichenko, S., Wiedner, Martina, Astronomy, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), ESO, European Southern Observatory (ESO), Department of Microtechnology and Nanoscience (MC2), and Chalmers University of Technology [Gothenburg, Sweden]

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Galaxy Astrophysics, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

Astro 2020 Decadal Survey APC White paper; Heterodyne spectroscopic instruments are currently the only practical technical approach for obtaining velocity-resolved spectra in the far infrared. Moreover, to produce the large-scale maps of molecular clouds envisioned for future missions, large-format (100’s pixels) array receivers are required, which is the focus of this whitepaper.

Published
2019

22. Observations in the 1.3 and 1.5 THz atmospheric windows with the Receiver Lab Telescope

Author

Marrone, Daniel P, Blundell, Raymond, Tong, Edward, Paine, Scott N, Loudkov, Denis, Kawamura, Jonathan H, Luhr, Daniel, and Barrientos, Claudio

Subjects
Electronics And Electrical Engineering
Abstract

The Receiver Lab Telescope (RLT) is a ground-based terahertz telescope; it is currently the only instrument producing astronmical data between 1 and 2 THz. We report on our first measurements o the high CO transitions, which represent the highest frequency detection ever made from the ground. We also present initial observations of {N II} and discuss the implications of this non-detection for the standard estimates of the strength of this line.

Published
2005

23. Heterodyn receiver for the Origins Space Telescope concept 2

Author

Belitsky, Victor, Desmaris, Vincent, Di Giorgio, Anna Maria, Goldstein, Christophe, Ellison, Brian, Gallego, Juan-Daniel, Herpin, Fabrice, Huet, Jean-Michel, Krieg, Jean-Michel, Laporte, Philippe, Quertier-Dagorn, Benjamin, Plume, René, Risacher, Christophe, De Beck, Elvire, Goldsmith, Paul, Hogerheijde, Michiel, Hunt, Leslie, Lis, Darek, Aalto, Susanne, Viti, Serena, Wyrowski, Friedrich, Neufeld, David, Melnick, Gary, Bergin, Edwin, Battersby, Cara, Milam, Stefanie, Borgo, Bruno, Carter, Ruth, Cooray, Asantha, Corsetti, James, Delorme, Yan, Dipirro, Michael, Eggens, Martin, Hills, Richard, Keizer, Geert, Kroes, Gabby, Leisawitz, David, Meixner, Margaret, Nguyen Tuong, Napoléon, Pontoppidan, Klaus, Staguhn, Johannes, Martins, Gregory, Wiedner, Martina, Baryshev, Andrey, Laurens, André, Gerin, Maryvonne, Helmich, Frank, Jellema, Willem, Mehdi, Imran, Amatucci, Edward, MacEwen, Howard, Lystrup, Makenzie, Fazio, Giovanni, Batalha, Natalie, Tong, Edward, Siegler, Nicholas, FORMATION STELLAIRE 2018, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Calgary], University of Calgary, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Max-Planck-Institut für Radioastronomie (MPIFR), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH), Observatoire de Paris, Université Paris sciences et lettres (PSL), and Astronomy

Subjects
Heterodyne, Pixel, Computer science, Astronomy, 7. Clean energy, 01 natural sciences, Focal Plane Arrays, Spitzer Space Telescope, Planet, 0103 physical sciences, HERO, Satellite, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], 010306 general physics, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS
Abstract

The Origins Space Telescope (OST) is a NASA study for a large satellite mission to be submitted to the 2020 Decadal Review. The proposed satellite has a fleet of instruments including the HEterodyne Receivers for OST (HERO). HERO is designed around the quest to follow the trail of water from the ISM to disks around protostars and planets. HERO will perform high-spectral resolution measurements with 2x9 pixel focal plane arrays at any frequency between 468GHz to 2,700GHz (617 to 111 μm). HERO builds on the successful Herschel/HIFI heritage, as well as recent technological innovations, allowing it to surpass any prior heterodyne instrument in terms of sensitivity and spectral coverage.

Published
2018

24. The ARIEL space mission

Author

Beaulieu, Jean-Philippe, Bowles, Neil, Coudé Du Foresto, Vincent, Coustenis, Athena, Decin, Leen, Drossart, Pierre, Eccleston, Paul, Encrenaz, Therese, Forget, François, Griffin, Matt, Pascale, Enzo, Barstow, Joanna, Güdel, Manuel, Hartogh, Paul, Heske, Astrid, Lagage, Pierre-Olivier, Leconte, J., Malaguti, Pino, Micela, Giusi, Middleton, Kevin, Min, Michiel, Moneti, Andrea, Morales, Juan Carlos, Ollivier, Marc, Pace, Emanuele, Pilbratt, Goran, Puig, Ludovic, Rataj, Miroslaw, Ray, Tom, Ribas, Ignasi, Rocchetto, Marco, Sarkar, Subhajit, Selsis, Franck, Taylor, William, Tennyson, Jonathan, Tinetti, Giovanna, Turrini, Diego, Vandenbussche, Bart, Venot, Olivia, Waldmann, Ingo, Wolkenberg, Paulina, Wright, Gillian, Zapatero Osorio, Maria-Rosa, Zingales, Tiziano, Bezawada, Naidu, Papageorgiou, Andreas, Mugnai, Lorenzo, MacEwen, Howard, Lystrup, Makenzie, Fazio, Giovanni, Batalha, Natalie, Tong, Edward, Siegler, Nicholas, Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Atmospheric, Oceanic and Planetary Physics [Oxford] (AOPP), University of Oxford [Oxford], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institute of Astronomy [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Institut Pierre-Simon-Laplace (IPSL), École normale supérieure - Paris (ENS Paris)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National d'Études Spatiales [Toulouse] (CNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), University College of London [London] (UCL), Paul Scherrer Institute (PSI), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), ECLIPSE 2018, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Palermo (OAPa), Istituto Nazionale di Astrofisica (INAF), Instituto de Investigaciones Químicas, CSIC, Institut de Génomique Fonctionnelle de Lyon (IGFL), École normale supérieure - Lyon (ENS Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), University of Valencia, Consejo Superior de Investigaciones Científicas [Spain] (CSIC), Dipartimento di Informatica [Verona], Università degli Studi di Verona, Cardiff University, Chemistry, Istituto di Fisica dello Spazio Interplanetario (IFSI), Consiglio Nazionale delle Ricerche (CNR), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS), Space Research Centre of Polish Academy of Sciences (CBK), Polska Akademia Nauk (PAN), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris), Max Planck Institute for Solar System Research (MPS), Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ECLIPSE 2017, Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), École normale supérieure de Lyon (ENS de Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Department of Computer Science [Verona] (UNIVR | DI), Università degli studi di Verona = University of Verona (UNIVR), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National d'Études Spatiales [Toulouse] (CNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Lyon (ENS Lyon), and University of Verona (UNIVR)

Subjects
Astronomy, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Space, Astrophysics::Cosmology and Extragalactic Astrophysics, Atmospheric model, Space (commercial competition), 7. Clean energy, 01 natural sciences, law.invention, 010309 optics, Telescope, law, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Transit (astronomy), 010303 astronomy & astrophysics, Instrumentation, Astrophysics::Galaxy Astrophysics, Spectroscopy, ComputingMilieux_MISCELLANEOUS, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Atmosphere, Atmospheric wave, Exoplanets, Exoplanet, Stars, 13. Climate action, Transit, Astrophysics::Earth and Planetary Astrophysics, Geology
Abstract

The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next M4 space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of about 1000 known transiting exoplanets using its metre-class telescope, a three-band photometer and three spectrometers that will cover the 0.5 μm to 7.8 μm region of the electromagnetic spectrum. The payload is designed to perform primary and secondary transit spectroscopy, and to measure spectrally resolved phase curves with a stability of < 100 ppm (goal 10 ppm). Observing from an L2 orbit, ARIEL will provide the first statistically significant spectroscopic survey of hot and warm planets. These are an ideal laboratory in which to study the chemistry, the formation and the evolution processes of exoplanets, to constrain the thermodynamics, composition and structure of their atmospheres, and to investigate the properties of the clouds.

Published
2018

26. Multilayer antireflection coating for silicon optics at millimeter and submillimeter wavelengths (Conference Presentation)

Author

Defrance, Fabien, primary, Chattopadhyay, Goutam, additional, Connors, Jake, additional, Golwala, Sunil, additional, Hollister, Matthew I., additional, Jung-Kubiak, Cecile, additional, Padilla, Estefania, additional, Radford, Simon, additional, Sayers, Jack, additional, Tong, Edward C., additional, and Yoshida, Hiroshige, additional

Published
2018
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28. Performance of a cryogenic test facility for 4 K interferometer delay line investigations

Author

MacEwen, Howard A., Fazio, Giovanni G., Lystrup, Makenzie, Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Veenendaal, Ian, Naylor, David, Gom, Brad, Gunuganti, Sudhakar, Winter, Calvin, Jones, Martyn, and Walker, David D.

Subjects
010302 applied physics, Cryostat, Materials science, business.industry, Physics::Instrumentation and Detectors, Nuclear engineering, Instrumentation, Astrophysics::Instrumentation and Methods for Astrophysics, Far-infrared astronomy, Cryogenics, 01 natural sciences, TS, Metrology, Interferometry, Optics, Far infrared, 0103 physical sciences, Astronomical interferometer, business, 010303 astronomy & astrophysics
Abstract

The next generation of space-borne instruments for far infrared astronomical spectroscopy will utilize large diameter, cryogenically cooled telescopes in order to achieve unprecedented sensitivities. Low background, ground-based cryogenic facilities are required for the cryogenic testing of materials, components and subsystems. The University of Lethbridge Test Facility Cryostat (TFC) is a large volume, closed cycle, 4 K cryogenic facility, developed for this purpose. This paper discusses the design and performance of the facility and associated metrology instrumentation, both internal and external to the TFC. Additionally, an apparatus for measuring the thermal and mechanical properties of carbon-fiber-reinforced polymers is presented.

Published
2016

29. A development roadmap for critical technologies needed for TALC: a deployable 20m annular space telescope

Author

MacEwen, Howard, Fazio, Giovanni, Lystrup, Makenzie, Batalha, Natalie, Siegler, Nicholas, Tong, Edward, Sauvage, Marc, Amiaux, Jerome, Austin, James, Bello, Mara, Bianucci, Giovanni, Chesné, Simon, Citterio, Oberto, Collette, Christophe, Correia, Sébastien, Durand, Gilles, Molinari, Sergio, Pareschi, Giovanni, Penfornis, Yann, Sironi, Giorgia, Valsecchi, Giuseppe, Verpoort, Sven, Wittrock, Ulrich, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), CEA, Commissariat à l'Energie Atomique, Gyf Sur Yvette, France, Université Paris Diderot - Paris 7 (UPD7), Università di Pisa - UNIPISA (Pisa, Italy), Laboratoire de Mécanique des Contacts et des Structures [Villeurbanne] (LaMCoS), Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Department of Bio, Electro And Mechanical Systems (BEAMS), Université Libre de Bruxelles [Bruxelles] (ULB), Université libre de Bruxelles (ULB), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and University of Pisa - Università di Pisa

Subjects
Physics, Aperture, business.industry, James Webb Space Telescope, Active optics, Technology readiness level, 7. Clean energy, 01 natural sciences, law.invention, 010309 optics, Telescope, Primary mirror, Optics, [PHYS.MECA.STRU]Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], law, 0103 physical sciences, Scalability, [PHYS.MECA.STRU]Physics [physics]/Mechanics [physics]/Mechanics of the structures [physics.class-ph], Angular resolution, Aerospace engineering, business, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS
Abstract

Astronomy is driven by the quest for higher sensitivity and improved angular resolution in order to detect fainter or smaller objects. The far-infrared to submillimeter domain is a unique probe of the cold and obscured Universe, harboring for instance the precious signatures of key elements such as water. Space observations are mandatory given the blocking effect of our atmosphere. However the methods we have relied on so far to develop increasingly larger telescopes are now reaching a hard limit, with the JWST illustrating this in more than one way (e.g. it will be launched by one of the most powerful rocket, it requires the largest existing facility on Earth to be qualified). With the Thinned Aperture Light Collector (TALC) project, a concept of a deployable 20 m annular telescope, we propose to break out of this deadlock by developing novel technologies for space telescopes, which are disruptive in three aspects: • An innovative deployable mirror whose topology, based on stacking rather than folding, leads to an optimum ratio of collecting area over volume, and creates a telescope with an eight times larger collecting area and three times higher angular resolution compared to JWST from the same pre-deployed volume; • An ultra-light weight segmented primary mirror, based on electrodeposited Nickel, Composite and Honeycomb stacks, built with a replica process to control costs and mitigate the industrial risks; • An active optics control layer based on piezo-electric layers incorporated into the mirror rear shell allowing control of the shape by internal stress rather than by reaction on a structure. We present in this paper the roadmap we have built to bring these three disruptive technologies to technology readiness level 3. We will achieve this goal through design and realization of representative elements: segments of mirrors for optical quality verification, active optics implemented on representative mirror stacks to characterize the shape correction capabilities, and mechanical models for validation of the deployment concept. Accompanying these developments, a strong system activity will ensure that the ultimate goal of having an integrated system can be met, especially in terms of (a) scalability toward a larger structure, and (b) verification philosophy.

Published
2016

30. On the performance of the Gaia auto-collimating flat mirror assembly: could it be even better?

Author

Bos, A., Witvoet, G., Pereboom, H.P., Steinbuch, M., MacEwen, Howard A., Fazio, Giovanni G., Lystrup, Makenzie, Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Electrical Engineering, and Control Systems Technology

Subjects
OM - Opto-Mechatronics, Computer science, Satellites, Millimeter waves, High Tech Systems & Materials, Space, Space telescopes, Collimated light, EMA, Aerospace ground support, Dynamic analysis, Accurate prediction, Design improvements, FEA, Simulation, Payload performance, TS - Technical Sciences, Ground support equipment, Industrial Innovation, Payload, Optical ground support equipment, Satellite ground stations, Flat mirror, Mirrors, FEA, EMA, Dynamic behaviours, Gaia mission, Nano Technology, Satellite, Electronics, Gaia satellite, Rotation (mathematics)
Abstract

The Auto-collimating Flat Mirror Assembly (AFMA) simulated the rotation of the Gaia satellite around its vertical axis. As such, it was one of the most important ground support equipment tools to test the payload performance of the Gaia mission. Although the performance of TNO's design during commissioning was excellent, one of the challenges of the AFMA design and realisation has proven to be the prediction of the dynamic behaviour of AFMA and the accurate prediction of its performance. Therefore, the dynamic behaviour of Gaia AFMA has recently been re-analysed. Dynamical points of attention are shown, and possible design improvements have been derived.

Published
2016

31. Mixture models for consumer credit risk

Author

Tong, Edward N.C.

Abstract

The three papers in this thesis comprise the development of three types of Basel models – a Probability of Default (PD), Loss Given Default (LGD) and Exposure at Default (EAD) model for consumer credit risk, using mixture model methods. Mixture models consider the underlying population as being composed of different sub-populations that are modelled separately. In the first paper (Chapter 2), mixture cure models are introduced to the area of PD/credit scoring. A large proportion of the dataset may not experience the event of interest during the loan term, i.e. default. A mixture cure model predicting (time to) default on a UK personal loan portfolio was developed and its performance compared to industry standard models. The mixture cure model's ability to distinguish between two subpopulations can offer additional insights by estimating the parameters that determine susceptibility to default in addition to parameters that influence time to default of a borrower. The second paper (Chapter 3) considers LGD modelling. One of the key problems in building regression models to estimate loan-level LGD in retail portfolios such as mortgage loans relates to the difficulty in modelling its distribution, which typically contains an extensive amount of zeroes. An alternative approach is proposed in which a mixed discrete-continuous model for the total loss amount incurred on a defaulted loan is developed. The model simultaneously accommodates the probability of zero loss and the loss amount given that loss occurs. This zero-adjusted gamma model is shown to present an alternative and competitive approach to LGD modelling. The third paper (Chapter 4) considers EAD models for revolving credit facilities with variable exposure. The credit conversion factor (CCF), the proportion of the current undrawn amount that will be drawn down at time of default, is used to calculate the EAD and poses modelling challenges with challenging bimodal distributions. We explore alternative EAD models which ignore the CCF formulation and target the EAD distribution directly. We propose a mixture model with the zero-adjusted gamma distribution and compare performance with CCF based models. We find the mixture model to be more accurate in calibration than the CCF models and that segmented approaches offer further performance improvements.

Published
2015

32. Mixture models for consumer credit risk

Author

Tong, Edward N.C.. and Tong, Edward N.C..

Abstract

The three papers in this thesis comprise the development of three types of Basel models – a Probability of Default (PD), Loss Given Default (LGD) and Exposure at Default (EAD) model for consumer credit risk, using mixture model methods. Mixture models consider the underlying population as being composed of different sub-populations that are modelled separately. In the first paper (Chapter 2), mixture cure models are introduced to the area of PD/credit scoring. A large proportion of the dataset may not experience the event of interest during the loan term, i.e. default. A mixture cure model predicting (time to) default on a UK personal loan portfolio was developed and its performance compared to industry standard models. The mixture cure model's ability to distinguish between two subpopulations can offer additional insights by estimating the parameters that determine susceptibility to default in addition to parameters that influence time to default of a borrower. The second paper (Chapter 3) considers LGD modelling. One of the key problems in building regression models to estimate loan-level LGD in retail portfolios such as mortgage loans relates to the difficulty in modelling its distribution, which typically contains an extensive amount of zeroes. An alternative approach is proposed in which a mixed discrete-continuous model for the total loss amount incurred on a defaulted loan is developed. The model simultaneously accommodates the probability of zero loss and the loss amount given that loss occurs. This zero-adjusted gamma model is shown to present an alternative and competitive approach to LGD modelling. The third paper (Chapter 4) considers EAD models for revolving credit facilities with variable exposure. The credit conversion factor (CCF), the proportion of the current undrawn amount that will be drawn down at time of default, is used to calculate the EAD and poses modelling challenges with challenging bimodal distributions. We explore alternative EAD models

Published
2015

33. Safety of Atrovent® CFC‐free inhaler: respiratory events reported from an observational cohort study in England.

Author

Tong, Edward, Osborne, Vicki, Layton, Deborah, Fogg, Carole, and Shakir, Saad A. W.

Abstract

Abstract: Objectives: The aim of the study was to identify any unexpected clinical events associated with starting the new CFC‐free formulation of Atrovent® MDI in general practice in England. Methods: An active surveillance cohort study was conducted with a focus on selected clinical events, including respiratory symptoms, in past users of Atrovent® CFC MDI (‘switchers’) and Atrovent® naïve users. Incidence density rate ratios (with 99% confidence intervals) for events occurring in the first 3 months of exposure (risk period‐ID1‐3) compared to 3 months prior to starting treatment (reference period‐IDR) were calculated. Results: The cohort consisted of 13 211 patients (median age 70 years, 50.1% female; 63.5% prior users of Atrovent® CFC MDI (‘switchers’)). Common respiratory events occurred at higher rates after starting treatment than before for switchers, for example lower respiratory tract infection (LRTI) [ID1/IDR = 1.45 (99% CI: 1.17, 1.81)] and worsening asthma [ID1/IDR = 1.58 (99% CI: 1.00, 2.51)]. Of these events only LRTI was significant for Atrovent® naïve patients [ID1/IDR = 1.42 (99% CI: 1.04, 1.95)]. Conclusions: The results of this study suggest effect modification of risk as a result of prior Atrovent® CFC MDI use. Overall, Atrovent® CFC‐free MDI appeared to be reasonably well tolerated in the immediate postmarketing period and the safety profile appeared similar to that of the CFC formulation. [ABSTRACT FROM AUTHOR]

Published
2018
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34. Observations in the 1.3 and 1.5 THz Atmospheric Windows with the Receiver Lab Telescope

Author

Marrone, Daniel P., Blundell, Raymond, Tong, Edward, Scott Paine, Loudkov, Denis, Kawamura, Jonathan H., Lühr, Daniel, and Barrientos, Claudio

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics
Abstract

The Receiver Lab Telescope (RLT) is a ground-based terahertz telescope; it is currently the only instrument producing astronomical data between 1 and 2 THz. The capabilities of the RLT have been expanding since observations began in late 2002. Initial observations were limited to the 850 GHz and 1.03 THz windows due to the availability of solid state local oscillators. In the last year we have begun observations with new local oscillators for the 1.3 and 1.5 THz atmospheric windows. These oscillators provide access to the 11-10 and 13-12 lines of CO at 1.267 and 1.497 THz, as well as the [N II] line at 1.461 THz. We report on our first measurements of these high CO transitions, which represent the highest-frequency detections ever made from the ground. We also present initial observations of [N II] and discuss the implications of this non-detection for the standard estimates of the strength of this line., 4 pages, 4 figures, IEEEtran.cls. To appear in the proceedings of the 16th International Symposium on Space Terahertz Technology

Published
2005

36. The Greenland Telescope (GLT): antenna status and future plans

Author

Raffin, Philippe, additional, Algaba-Marcosa, Juan Carlos, additional, Asada, Keiichi, additional, Blundell, Raymond, additional, Burgos, Roberto, additional, Chang, Chih-Cheng, additional, Chen, Ming-Tang, additional, Christensen, Robert, additional, Grimes, Paul K., additional, Han, C. C., additional, Ho, Paul T. P., additional, Huang, Yau-De, additional, Inoue, Makoto, additional, Koch, Patrick M., additional, Kubo, Derek, additional, Leiker, Steve, additional, Liu, Ching-Tang, additional, Martin-Cocher, Pierre, additional, Matsushita, Satoki, additional, Nakamura, Masanori, additional, Nishioka, Hiroaki, additional, Nystrom, George, additional, Paine, Scott N., additional, Patel, Nimesh A., additional, Pradel, Nicolas, additional, Pu, Hung-Yi, additional, Shen, H.-Y., additional, Snow, William, additional, Sridharan, Tirupati K., additional, Srinivasan, Ranjani, additional, Tong, Edward, additional, and Wang, Jackie, additional

Published
2014
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38. Heterodyn receiver for the Origins Space Telescope concept 2

Author

Lystrup, Makenzie, MacEwen, Howard A., Fazio, Giovanni G., Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Wiedner, M. C., Aalto, Susanne, Amatucci, Edward G., Baryshev, Andrey, Battersby, Cara, Belitsky, Victor, Bergin, Edwin A., Borgo, Bruno, Carter, Ruth C., Cooray, Asantha, Corsetti, James A., De Beck, Elvire, Delorme, Yan, Dipirro, Michael J., Desmaris, Vincent, Ellison, Brian, Gallego, Juan-Daniel, Di Giorgio, Anna Maria, Eggens, Martin, Gerin, Maryvonne, Goldsmith, Paul F., Goldstein, Christophe, Helmich, Frank, Herpin, Fabrice, Hills, Richard E., Hogerheijde, Michiel R., Huet, Jean-Michel, Hunt, Leslie K., Jellema, Willem, Keizer, Geert, Krieg, Jean-Michel, Kroes, Gabby, Laporte, Philippe, Laurens, André, Leisawitz, David T., Lis, Darek, Martins, Gregory E., Mehdi, Imran, Meixner, Margaret, Melnick, Gary, Milam, Stefanie N., Neufeld, David A., Nguyen Tuong, Napoléon, Plume, René, Pontoppidan, Klaus M., Quertier-Dagorn, Benjamin, Risacher, Christophe, Staguhn, Johannes G., Viti, Serena, and Wyrowski, Friedrich

Published
2018
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39. Origins Space Telescope: the far infrared imager and polarimeter FIP

Author

Lystrup, Makenzie, MacEwen, Howard A., Fazio, Giovanni G., Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Staguhn, Johannes, Amatucci, Edward, Armus, Lee, Bradley, Damon, Carter, Ruth, Chuss, David, Corsetti, James, Cooray, Asantha, Howard, Joseph, Leisawitz, David, Meixner, Margaret, Moseley, Samuel H., Pope, Alexandra, Vieira, Joaquin, and Wollack, Edward

Published
2018
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41. HabEx Lite: a starshade-only habitable exoplanet imager alternative

Author

Lystrup, Makenzie, MacEwen, Howard A., Fazio, Giovanni G., Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Redding, David, Coste, Keith, Polanco, Otto, Pineda, Claudia, Hurd, Kevin, Tseng, Howard, Quezada, Jose, Martin, Stefan, Nissen, Joel, Schulz, Kevin, Tesch, Jonathan, Cady, Eric, Rodgers, Michael, East, Matthew, Mooney, James, and Stark, Chris

Published
2018
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45. HabEx space telescope exoplanet instruments

Author

Lystrup, Makenzie, MacEwen, Howard A., Fazio, Giovanni G., Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Martin, Stefan, Rud, Mayer, Mawet, Dimitri, Nissen, Joel, Shaklan, Stuart, and Marchen, Luis

Published
2018
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48. The Habitable Exoplanet Observatory (HabEx)

Author

Lystrup, Makenzie, MacEwen, Howard A., Fazio, Giovanni G., Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Gaudi, B. Scott, Mennesson, Bertrand, Seager, Sara, Cahoy, Kerri, Clarke, John, Domagal-Goldman, Shawn, Feinberg, Lee, Guyon, Olivier, Kasdin, Jeremy, Marois, Christian, Mawet, Dimitri, Tamura, Motohide, Mouillet, David, Prusti, Timo, Quirrenbach, Andreas, Robinson, Tyler, Rogers, Leslie, Scowen, Paul, Somerville, Rachel, Stapelfeldt, Karl, Stark, Christopher, Stern, Daniel, Still, Martin, Turnbull, Margaret, Booth, Jeffrey, Kiessling, Alina, Kuan, Gary, and Warfield, Keith

Published
2018
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49. The large UV/optical/infrared surveyor (LUVOIR): decadal mission study update

Author

Lystrup, Makenzie, MacEwen, Howard A., Fazio, Giovanni G., Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Bolcar, Matthew R., Crooke, Julie, Hylan, Jason E., Bronke, Ginger, Collins, Christine, Corsetti, James, Generie, Joe, Gong, Qian, Groff, Tyler, Hayden, William, Jones, Andrew, Matonak, Bryan, Park, Sang, Sacks, Lia, West, Garrett, Yang, Kan, and Zimmerman, Neil

Published
2018
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50. Overview of the Origins Space telescope: science drivers to observatory requirements

Author

Lystrup, Makenzie, MacEwen, Howard A., Fazio, Giovanni G., Batalha, Natalie, Siegler, Nicholas, Tong, Edward C., Meixner, Margaret, Armus, Lee, Battersby, Cara, Bauer, James, Bergin, Edwin, Cooray, Asantha, Fortney, Jonathan J., Kataria, Tiffany, Leisawitz, David T., Milam, Stefanie N., Pontoppidan, Klaus, Pope, Alexandra, Sandstrom, Karin, Staguhn, Johannes G., Stevenson, Kevin B., Su, Kate Y., Bradford, Charles Matt, Benford, Dominic, Burgarella, Denis, Carey, Sean, Carter, Ruth C., De Beck, Elvire, Dipirro, Michael J., Ennico-Smith, Kimberly, Gerin, Maryvonne, Helmich, Frank P., Kaltenegger, Lisa, Mamajek, Eric. E., Melnick, Gary, Moseley, Samuel Harvey, Narayanan, Desika, Neff, Susan G., Padgett, Deborah, Roellig, Thomas L., Sakon, Itsuki, Scott, Douglas, Sheth, Kartik, Vieira, Joaquin, Wiedner, Martina, Wright, Edward, and Zmuidzinas, Jonas

Published
2018
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