Space-Based Interferometers

Three different designs have been identified as possible candidates for a future Far Infrared space-based interferometer operating in the 25-400 jtm wavelength range. 

Tytler D. (1997) Cosmology with the Very Large Telescope Interferometer using a space-based astrometric reference frame. CERN Document Server astro-ph/9701197. 

In this Thesis an instrument simulator for a Far Infrared space interferometer is presented, as well as a test bed implementation of the technique intended to be used to achieve high spectral and spatial resolutions from space. In this Introduction the motivation for this system is given from a general view of the Far Infrared astronomy and the possible science cases, through the past and present Far Infrared instruments, to FIRI, the concept of a space based Far Infrared Interferometer. 

To achieve high angular resolution one needs to use interferometry, and to operate at the Far Infrared the best scenario is a space based system, where there is no attenuation from the atmosphere. With this requirements the Far Infrared Interferometer concept, FIRI, is defined. 

Recent developments for a balloon based experiment, BETTII (Rinehart et al. 2009 Rinehart 2010a,b, 2011 Rinehart and BETTII Team 2010 Leisawitz 2008), and space based spectral-spatial interferometers such as SPIRIT (Leisawitz et al. 2007, 2008 Leisawitz 2008), SPECS, FIRI have identified fhaf some technology needs to be developed and demonstrated, for example high sensitivity detectors (NEPs 10 ° W/Hz ), cooled apertures, beam combination and data processing algorithms. In all these proposals, the common point is the technique employed to perform observations, the Double Fourier Modulation. 

The Sub-arcsecond Space-Based FIR Interferometer 1.3.2.1 Double Fourier Modulation... 

The FIRI laboratory testbed is the the result of an effort by Cardiff University, the Rutherford Appleton Laboratory (RAL) and UCL to develop an instrument to demonstrate the feasibility of the Double-Fourier technique at Far Infrared (FIR) wavelengths, which in a long term basis is expected to be the precursor of the space-based Far Infrared Interferometer (Helmich and Ivison 2009). It is currently located at the Physics and Astronomy Department of Cardiff University. This system is in constant development, and here the current design and issues, the latest results and the future planned improvements are presented. 

The main problem of Far-Infrared ground based interferometers is the atmospheric attenuation at these frequencies. This effect can only be removed if the interferometer is space-based. However, water lines can be useful as a first instrument approach to calibrate the test-bed. Figure3.4 (left) shows the atmospheric attenuation and the Winston cone filtering in the 0-40 cm wavenumber range. 

The problem of ground based interferometry is that although the MV-coverage can be increased by making use of the Earth rotation, the fixed position of the antennas will always limit the performance capabilities of such a system. This will not be a problem for space based interferometry, because even if operating a boom-based interferometer one will have the freedom to move the full spacecraft and sample the MV-map according to the target requirements. 

R. Juanola-Parramon, P.A. Ade, W.F. Grainger, M. Griffin, E. Pascale, G. Savini, L. Spencer, B. Swinyard, A space-based far infrared interferometer (FIRI) instrument simulator and test-bed implementation, in SPIE Optical Systems Design (International Society for Optics and Photonics, 2012), pp. 85501Y-85501Y... 

This thesis describes the physics and the computational aspects of an end-to-end simulator aimed at predicting the performance of a space-based far-infrared interferometer, including the science capabilities and instrumental state of the art. It outlines the requirements involved in such a mission and describes this most promising technique to capture most of the astrophysical information by combining spectroscopy with spatial interferometry. 

Space-based laser interferometers provide the best method to observe in this frequency band. It is anticipated that... 

FIGURE 6 Strain noise sensitivity of the interferometric detectors. Top figure ground-based interferometers VIRGO (solid line), LIGO (dashed line), GE0600 (dotted line), and TAMA (dot-dash line). Bottom figure the space interferometer LISA. 

Spin-orbit(SO) coupling is an important mechanism that influences the electron spin state [1], In low-dimensional structures Rashba SO interaction comes into play by introducing a potential to destroy the symmetry of space inversion in an arbitrary spatial direction [2-6], Then, based on the properties of Rashba effect, one can realize the controlling and manipulation of the spin in mesoscopic systems by external fields. Recently, Rashba interaction has been applied to some QD systems [6-8]. With the application of Rashba SO coupling to multi-QD structures, some interesting spin-dependent electron transport phenomena arise [7]. In this work, we study the electron transport properties in a three-terminal Aharonov-Bohm (AB) interferometer where the Rashba interaction is taken into account locally to a QD. It is found that Rashba interaction changes the quantum interference in a substantial way. 

To achieve such angular resolution there are two options a very large aperture single dish telescope, or an array of telescopes, this is, an interferometer. It is possible for ground based systems to consist of very large apertures, but for space observatories there are launch requirements that limit both the size and the weight of the telescopes. In order to improve on the existing resolution in space, interferometry is therefore the most plausible solution. 

In the Introduction of this thesis the potential science cases that could be assessed by a Far-Infrared Spectro-Spatial Space Interferometer were introduced. This chapter focuses on one of these science cases, the Circumstellar Disks, because it is one of the major areas of focus in ground-based infrared interferometry observations. 

Chapter 3 focused in the spectro-spatial interferometer testbeds in which I have been involved dining my programme the FIRI laboratory testbed (based at Cardiff University) and WET, the Wide-fleld Imaging Interferometry Testbed (based at NASA s Goddard Space Flight Center). Both testbeds have demonstrated the theory of Double Fourier Spatio-Spectral Interferometry or the application of a Fourier... 

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