Infrared interferometer

If was nof until fhe developmenf of Fourier fransform infrared (FTIR) specfromefers (see Section 3.3.3.2) fhaf fhe possibilify of using an infrared laser routinely was opened up. The intensify advanfage of an infrared interferometer, wifh which a single specfrum can be obfained very rapidly and fhen many specfra co-added, coupled wifh fhe developmenf of more sensitive Ge and InGaAs semiconductor infrared defectors, more fhan compensate for fhe loss of scatfering intensify in fhe infrared region. 

Figure 9.3. Emission spectra from the infrared interferometer spectrometer on board the Nimbus 3 satellite for the tropical Pacific Ocean under clear-day conditions. The dashed lines represent outgoing long-wave, blackbody radiation at the temperature indicated. CO2 absorbs in the spectral window of 13-17 pm, O3 between 9-10 pm, and H2O in the entire spectral domain. Emission is measured in arbitrary units. (After Ramanathan, 1988.)...

I am particularly grateful to Professor Ben van der Veken (University of Antwerp) who has obtained new spectra, with an infrared interferometer, which are shown in Figures 6.8, 6.27, 6.28 and 6.34, and to Dr Andrew Orr-Ewing (University of Bristol), who provided original copies of the cavity ring-down spectra in Figures 9.38 and 9.39. 

Figure 7.13 (a) Infrared interferometer Fourier transform instrument (b) GC infrared lightpipe sample cell (c) HPLC infrared mieroliquid sample cell. 

The spectrometer was a commercial (Mattson Instruments) Fourier Transform Infrared Interferometer (FTIR) equipped with both a liquid nitrogen-cooled mercury-cadmium-telluride detector and an inium antimonide detector. The instrument was modified into an emission FTIR by the removal of the source and relocating mirrors as shown in Fig. 9. 

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. 

Two instruments have been extensively studied and proposed so far regarding space interferometry the Space Infrared Interferometric Telescope (Leisawitz et al. 2007) (SPIRIT), as a practical step towards the more ambitious Submillimeter Probe of the Evolution of Cosmic Structure (Harwit et al. 2007) (SPECS), and the Far Infrared Interferometer (FIRI). 

RE. Dewdney, P.J. HaU, R.T. Schilizzi, T.J.L.W. Lazio, The square kilometre array. Proc. IEEE 97(8), 1482-1496 (2009). ISSN 0018-9219. doi 10.1109/JPROC.2009.2021005 H. Dole, G. Lagache, J.-L. Puget, K.I. Caputi, N. Femandez-Conde, E. Le Floc h, C. Papovich, P.G. P6rez-Gonzalez, G.H. Rieke, M. Blaylock, The cosmic infrared background resolved by Spitzer. Astron. Astrophys. 451(2), 417-429 (2006). doi 10.1051/0004-6361 20054446 ESA Concurrent Design Facility. Far Infrared Interferometer—CDF Study Report. CDF-49(A) 1-294, (2006). http //sci.esa.int/future-missions-office/40738-firi-cdf-study-report/... 

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 Far-infrared Interferometer Instrument Simulator, FllnS, is an instrument simulator for a Far-infrared Spectro-Spatial Interferometer. The main goal is to simulate both the input and the output of such a system, and compare the input sky map with the synthesised one after data processing algorithms have been applied. With a modular design, intermediate outputs are also available. In this chapter the different modules created to build FllnS are described, from the sky map generator to the raw data on the detectors module. In Chap. 5 the data processing algorithms are presented and the simulator is verified via the Cardiff-UCL FIRI testbed described in Chap. 3. 

For the ideal instrument, the capabilities of a Far Infrared Interferometer from space to extract the spatial and spectral contents of a circumstellar disk have been proved. Due to the extended nature of the source, the importance of the selection of the baseline configuration and range has been shown, as it defines the interferometric dirty beam which is then convolved with the sky map. 

The second and third year have focused in the development and testing of the Far Infrared Interferometer Instrument Simulator FllnS, and preliminary results have been presented at international Conferences (Juanola-Parramon et al. 2012 Juanola-Parramon and Savini 2013). 

This work presented here provides, for the first time, an end to end simulator of a Double Fourier Modulation Far Infrared Interferometer. It is intended to be a tool for the astronomical community to explore the limits of a space interferometer, as well as to test the performance and technical limits of such a system. 

ESA concurrent design facility. Far infrared interferometer—CDF study report. CDF-49(A), 1—294 (2006). http //sci.esa.int/future-missions-office/40738-firi-cdf-study-report/... 

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... 

R. Juanola-Parramon, G. Savini, FllnS The far-infrared interferometer instrument simulator, in Fourier Transform Spectroscopy (Optical Society of America, 2013)... 

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. 

---