| 项目编号: | NE/L01243X/1
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| 项目名称: | Supra-terahertz technology for atmospheric and lower thermosphere and lower thermosphere |
| 作者: | Alexander Giles Davies
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| 承担单位: | University of Leeds
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| 批准年: | 2013
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| 开始日期: | 2014-01-03
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| 结束日期: | 2015-28-02
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| 资助金额: | GBP75979
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| 资助来源: | UK-NERC
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| 项目类别: | Research Grant
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| 国家: | UK
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| 语种: | 英语
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| 特色学科分类: | Atmospheric phys. & chemistry 
; (20%)
; Planetary science 
; (5%)
; Tools, technologies & methods 
; (75%)
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| 英文摘要: | Advances in satellite remote-sensing measurements of the constituents of the Earth's mesosphere and lower thermosphere (MLT) have increased our knowledge of atmospheric composition over the last decade. Nonetheless, global measurements of key atmospheric species have not been made directly by previous satellite missions and these species, particularly atomic oxygen and the hydroxyl radical (OH), are targets for a low Earth orbit mission operating in the multi-terahertz (THz) spectral range (3 - 5 THz). A LOw Cost Upper-Atmosphere sounder (LOCUS) has therefore been proposed to ESA, which would be able to detect a broad range of important species (O, O3, OH, NO, CO, H2O and HO2) between altitudes of 50 and 400 km.
Heterodyne radiometry provides a spectral resolution that is well suited to characterising emission signatures originating from the MLT. The technique has been demonstrated and proven at sub-terahertz frequencies through a number of space flight missions over the past two decades. However, operation above 3 THz (supra-terahertz) has never been attempted from a space environment, and measurements of a number of important atmospheric species that have potential impact on climate change and related space weather effects have therefore not been made. Even systems operated from an airborne platform are rare and require large instruments that are completely unsuitable for space flight. There is therefore a need to develop compact, high-sensitivity, supra-terahertz heterodyne systems capable of undertaking global atmospheric measurements from space. To achieve this goal, technical development of the heterodyne mixer detector and its local oscillator (LO) is required.
The preferred heterodyne mixing device for Earth observation is the Schottky barrier diode. Although a well-known semiconductor device, it has not been demonstrated in a planar form beyond ~3 THz and challenges related to fabrication and circuit embedding need to be solved to allow this technical evolution. Additionally, the provision of LO power and its coupling to the mixer diode, whilst already presenting a technical barrier at sub-terahertz frequencies, is a particularly difficult problem to resolve in the supra-terahertz range. Fortunately, the advent of the quantum cascade laser (QCL) semiconductor device provides the prospect of a miniaturized, low power, supra-terahertz LO source with sufficient output power to 'pump' the mixer diode as a part of the frequency down-conversion process. Additionally, electromagnetic simulation software now permits the analysis and optimisation of QCL and Schottky diode devices and their respective electrical embedding circuits, with new and advanced micro-fabrication techniques allowing corresponding manufacture. However, technical development is required before a supra-terahertz MLT remote sounding instrument can be realised. For instance, QCL and Schottky device performance optimisation, physical integration into a common (waveguide) package, and frequency stabilisation are necessary.
We therefore propose a proof-of-concept development programme with an objective of demonstrating key component technologies (QCL and Schottky diode) to a minimum technical readiness level of TRL 3. Within this programme we will significantly advance core heterodyne technologies through a stepwise development approach, and with a goal of integrating and testing a QCL and Schottky diode in a common waveguide mount. Consideration will also be given to the scientific application and future technical development towards TRL 4 and beyond.
ESA has accepted the LOCUS concept as one requiring further evaluation as a prelude to a future in-orbit demonstration. Technical advancement of a terahertz frequency spectrometer through this NERC Proof of Concept Programme would provide a step-change in the progress towards this important scientific objective, as well as positioning the UK ideally for future in-orbit programmes with ESA. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/102128
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| Appears in Collections: | 科学计划与规划
气候变化与战略
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作者单位: | University of Leeds
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| Recommended Citation: | |
Alexander Giles Davies. Supra-terahertz technology for atmospheric and lower thermosphere and lower thermosphere. 2013-01-01.
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