588 research outputs found
Testing the Ariel exoplanet space observatory
Get PDFAriel is an ESA mission that will use the transit spectroscopy method to observe the atmospheres’ of ~1000 exoplanets. Ariel is a 1 m class cryogenic space telescope that will be placed in a halo orbit around the Earth-Sun L2 point. To detect atmospheric molecular absorption features, Ariel will produce medium-resolution spectra (R ≥ 15) using three spectroscopic channels covering 1.1 – 7.9 µm as well as having photometric channels covering 0.5 – 1.1 µm. The technical driver for Ariel, though, is the photometric stability. This is to enable the detection of atmospheric spectral features that are a signal of tens of ppm relative to the host star. Ariel, therefore, aims to have tens of ppm stability over long (10 hr) timescales.
To achieve Ariel’s science goals, the payload requires detailed calibration and performance verification. The testing of the integrated Ariel payload will be the subject of this work. The ground calibration of the Ariel payload will take place in 2026 in the 5m vacuum chamber at the Rutherford Appleton Laboratory’s space instruments test facility. The payload will be enclosed in a Cryogenic Test Rig (CTR), to provide a space-like (35 K) thermal environment. During the cryogenic vacuum testing, the payload will be illuminated by the Optical Ground Support Equipment (OGSE). The OGSE used to calibrate the payload is being developed by a team led by Oxford University and the University of Lisbon.
The author joined the project just before mission adoption. The thesis was submitted just after the completion of the payload Preliminary Design Review (pPDR). The work completed in this thesis focused, therefore, on performance simulation, requirement derivation and design of the OGSE system. In this thesis, many of the key performance parameters will be derived. It will be shown how these parameters have shaped the OGSE system from an architectural level down to the detailed design.
To define the performance parameters of the OGSE, the calibration observation modes must be defined. Methods were, therefore, defined to show how the OGSE can be used to perform the payload-level calibration of Ariel. End-to-end radiometric simulations were also provided to simulate the focal plane signal when the payload is illuminated in the various calibration modes of the OGSE.
The photometric stability and dark current tests were identified as particular drivers for the OGSE design. The need for dark testing of the payload was used to derive the thermal requirements for the system. Finite Element Analysis (FEA) was then used to assess the thermal performance of the OGSE system, and thus enable low-background testing of the payload (<1 e-pix-1s-1 ). The other performance driver identified was the photometric stability test. End-to-end time-domain simulations of this test were performed to derive the required performance of OGSE flux monitoring systems. OGSE monitoring detector candidates were then assessed to demonstrate these could be used to verify the stability of the payload.
Alignment during ground testing was discovered to be a critical technical risk to the OGSE system. It will be shown how monitoring alignment from ambient to cryogenic temperatures led to a major redesign of the OGSE architecture. Moreover, Ariel’s tiny field of view (~30’’) leads to extreme (arcsecond) alignment maintenance requirements. An alignment monitoring system will be presented, built and verified, to enable the closed-loop monitoring required to keep the OGSE spot within the payloads’ spectrometer slits
The cost and performance of paid agricultural extension services : the case of agricultural technology transfer in Nicaragua
Get PDFBudgets for extension services have been reduced in many countries. One response to these reductions in public services in some countries has been to privatize extension services - with extension services provided for a fee, by either public agencies or private companies. Under the new approach, producers become clients instead of beneficiaries. The authors examine ways to measure the cost of providing paid-extension services and its performance and apply these indicators to data on Nicaragua, where paid extension has existed for several years. Data were insufficient to compare the quality of privately and publicly provided extension services, but available data suggest that the costs of extension have declined over time. Results suggest that paid extension is feasible and has a positive impact, even in a relatively poor country such as Nicaragua. The national system for agricultural technology-transfer services was redesigned to include three main modules: mass media and free demonstrations; cofinanced extension services; and private extension services. The relatively high cost recovery rates in Nicaragua and the economic performance of the two paid programs show that even poor farmers are willing to pay for a service that improves their economic efficiency and ability to earn a living. To the surprise of everyone involved, Nicaragua's producer clients understood that without cost-sharing, the system would not endure.ICT Policy and Strategies,Agricultural Knowledge&Information Systems,Environmental Economics&Policies,Enterprise Development&Reform,Montreal Protocol,Agricultural Knowledge&Information Systems,ICT Policy and Strategies,Environmental Economics&Policies,Governance Indicators,General Technology
High-precision photometry with Ariel
Get PDFThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.In this paper we describe the photometry instruments of Ariel, consisting of the VISPhot, FGS1 and FGS2 photometers in the visual and mid-IR wavelength. These photometers have their own cadence, which can be independent from each other and the cadence of the spectral instruments. Ariel will be capable to do high cadence and high precision photometry in independent bands. There is also a possibility for synthetic Jsynth, Hsynth, and wide-band thermal infrared photometry from spectroscopic data. Although the cadence of the synthetic bands will be identical to that of the spectrographs, the precision of synthetic photometry in the suggested synthetic bands will be at least as precise as the optical data. We present the accuracy of these instruments. We also review selected fields of new science which will be opened up by the possibility of high cadence multiband space photometry, including stellar rotation, spin-orbit misalignment, orbital precession, planetary rotation and oblateness, tidal distortions, rings, and moons. © 2021, The Author(s).This work has been supported by the Hungarian National Research, Development and Innovation Office (NKFI) grants K-119517, K-115709, and GINOP-2.3.2-15-2016-00003, the Lendület Program of the Hungarian Academy of Sciences, project No. LP2018-7/2020, and the City of Szombathely under agreement No. S-11-1027. L.V.M. and E.P. was supported by the ASI grant n. 2018.22.HH.O. ZG and TP acknowledge support from the VEGA grant of the Slovak Academy of Sciences No. 2/0031/18 and by the grant of the Slovak Research and Development Agency number APVV-15-0458. LBo acknowledges the funding support from Italian Space Agency (ASI) regulated by “Accordo ASI-INAF n. 2013-016-R.0 del 9 luglio 2013 e integrazione del 9 luglio 2015 CHEOPS Fasi A/B/C”.With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.Peer reviewe
Ruy Mauro Marini: An unavoidable in the Latin American debate
Get PDFEl militante y académico brasileño Ruy Mauro Marini es habitualmente reconocido como uno de los principales referentes dentro de lo que se ha dado a conocer como la vertiente marxista de la Teoría de la Dependencia, de gran relevancia en el debate político y social latinoamericano durante las décadas de 1960 y 1970. En este artículo, nuestra intención es revisitar algunos de sus principales aportes al pensamiento crítico de nuestra región, pero -más allá de situarlos históricamente- afirmaremos que se trata de un autor con plena vigencia para la compresión de la legalidad específica de las leyes del capitalismo en economías dependientes, el debate sobre la inserción internacional de la región y el rol de los movimientos sociales en el siglo XXI. Además de algunas ineludibles referencias a su trayectoria de vida personal, nos abocaremos fundamentalmente a analizar cómo entiende Marini el Ciclo Dependiente, lo cual es indisoluble de los conceptos de Subimperialismo, de Superexplotación de la fuerza de trabajo y de Cooperación antagónicaThe militant and Brazilian academic, Ruy Mauro Marini, is generally recognized as one of the main references in what has become known as the Marxist perspective of "dependency theory", of great importance in the political and social debate in Latin America during the 1960s and 1970s. In this article we intend to revisit some of its major contributions to critical thinking in our region. Regardless of place them historically, we affirm that it is an author with full force for compression of specific legality of the laws of capitalism in dependent economies, the debate on the international insertion of the region and the role of social movements in the XXI Century. In addition to some unavoidable references to his personal life path, we will focus primarily to how Marini analyze the Dependency Cycle, which is inseparable from the concepts of Sub-imperialism, Super-exploitation of the labor force and Antagonic CooperationFil: Slipak, Ariel M.. Universidad de Buenos Aires; Universidad Nacional de Moreno; CONICET
The Ariel 0.6 - 7.8 μm stellar limb-darkening coefficients
No full textWe provide here tables of stellar limb-darkening coefficients (LDCs) for the Ariel ESA M4 space mission. These tables include LDCs corresponding to different wavelength bins and white bands for the NIRSpec, AIRS-Ch0 and AIRS-Ch1 spectrographs, and those corresponding to the VISPhot, FGS1 and FGS2 photometers. The LDCs are calculated with the open-source software ExoTETHyS for three complete grids of stellar atmosphere models obtained with the ATLAS9 and PHOENIX codes. The three model grids are complementary, as the PHOENIX code adopts more modern input physics and spherical geometry, while the models calculated with ATLAS9 cover wider ranges of stellar parameters. The LDCs obtained from corresponding models in the ATLAS9 and PHOENIX grids are compared in the main text. All together the models cover the following ranges in effective temperature (1500K ≤ Teff ≤ 50000K), surface gravity (0.0 dex ≤ log g≤ 6.0 dex), and metallicity (− 5.0 ≤ [M/H] ≤ 1.0). © The Author(s), under exclusive licence to Springer Nature B.V. 2021.G.M. was supported by the LabEx P2IO, the French ANR contract 05-BLANNT09-573739. S.S. was supported by United Kingdom Space Agency (UKSA) grant: ST/S002456/1.With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.Peer reviewe
A more comprehensive and commanding delineation: Mary Shelley's narrative strategy in Frankenstein
Get PDFThis thesis argues that the first edition of Frankenstein challenges conventional reading by employing what Simpson in Irony and Authority in Romantic Poetry calls Romantic irony, where the absence of a stable 'metacomment' precludes an authoritative reading. The novel hints at such readings but prevents them. The insights offered by Tropp's Mary Shelley's Monster, Baldick's In Frankenstein's Shadow, Poovey's The Proper Lady and the woman writer and Swingle's, 'Frankenstein's Monster and its Relatives: Problems of Knowledge in English Romanticism' are considered, but none recognises the full implications of the instability deriving from multiple first- person narratives. Clemit's The Godwinian Navel acknowledges the novel's indeterminacy, but reads a specific ideological purpose in it. Paradise Last provides a language to describe the relationship between the monster and Frankenstein, but proves too unstable to fix identity or establish moral value. Similarly, Necessity ultimately fails to provide a stable explanation in terms of cause and effect. The status of nature shifts between foreground and background, never allowing final definition. These uncertainties destabilise knowledge which is compromised by its provisional nature: no authoritative reading is possible, yet the novel has narrative coherence. The reader is encouraged to try to develop a reading the structure prevents. The radical nature of the first edition is highlighted by comparison with the 1831 edition, which removes much of the ambivalence and gives the novel a clearer morality. The novel challenges conventional methods of deriving authority by disturbing the reader's orthodox orientation in the world around him' (Simpson) in order to afford 'a point of view to the imagination for the delineation of human passions more comprehensive and commanding than any which the ordinary relations of existing events can yield' (Mary Shelley)
Obras de teatro sobre el cultivo de la especie humana ...
No full textAutograph letter from author inserted in v. 1.Vol. 4-5, 2d ed. Avila, M. Díaz, 1922; v. 1-3, undated.Mode of access: Internet
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