Table Of ContentSpringer Theses
Recognizing Outstanding Ph.D. Research
Roser Juanola-Parramon
A Far-Infrared
Spectro-Spatial
Space
Interferometer
Instrument Simulator and Testbed
Implementation
Springer Theses
Recognizing Outstanding Ph.D. Research
Aims and Scope
The series “Springer Theses” brings together a selection of the very best Ph.D.
theses from around the world and across the physical sciences. Nominated and
endorsed by two recognized specialists, each published volume has been selected
foritsscientificexcellenceandthehighimpactofitscontentsforthepertinentfield
of research. For greater accessibility to non-specialists, the published versions
includeanextendedintroduction,aswell asaforewordbythestudent's supervisor
explainingthespecialrelevanceoftheworkforthefield.Asawhole,theserieswill
provide a valuable resource both for newcomers to the research fields described,
and for other scientists seeking detailed background information on special
questions. Finally, it provides an accredited documentation of the valuable
contributions made by today’s younger generation of scientists.
Theses are accepted into the series by invited nomination only
and must fulfill all of the following criteria
(cid:129) They must be written in good English.
(cid:129) ThetopicshouldfallwithintheconfinesofChemistry,Physics,EarthSciences,
Engineeringandrelatedinterdisciplinary fields such asMaterials,Nanoscience,
Chemical Engineering, Complex Systems and Biophysics.
(cid:129) The work reported in the thesis must represent a significant scientific advance.
(cid:129) Ifthethesisincludespreviouslypublishedmaterial,permissiontoreproducethis
must be gained from the respective copyright holder.
(cid:129) They must have been examined and passed during the 12 months prior to
nomination.
(cid:129) Each thesis should include a foreword by the supervisor outlining the signifi-
cance of its content.
(cid:129) The theses should have a clearly defined structure including an introduction
accessible to scientists not expert in that particular field.
More information about this series at http://www.springer.com/series/8790
Roser Juanola-Parramon
A Far-Infrared
Spectro-Spatial Space
Interferometer
Instrument Simulator and Testbed
Implementation
Doctoral Thesis accepted by
the University College London, UK
123
Author Supervisor
Dr. RoserJuanola-Parramon Dr. GiorgioSavini
University CollegeLondon University CollegeLondon
Department ofPhysics andAstronomy Department ofPhysics andAstronomy
London London
UK UK
ISSN 2190-5053 ISSN 2190-5061 (electronic)
SpringerTheses
ISBN978-3-319-29399-8 ISBN978-3-319-29400-1 (eBook)
DOI 10.1007/978-3-319-29400-1
LibraryofCongressControlNumber:2016936983
©SpringerInternationalPublishingSwitzerland2016
Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart
of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission
orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar
methodologynowknownorhereafterdeveloped.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this
publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom
therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse.
The publisher, the authors and the editors are safe to assume that the advice and information in this
book are believed to be true and accurate at the date of publication. Neither the publisher nor the
authorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinor
foranyerrorsoromissionsthatmayhavebeenmade.
Printedonacid-freepaper
ThisSpringerimprintispublishedbySpringerNature
TheregisteredcompanyisSpringerInternationalPublishingAGSwitzerland
To my family
’
Supervisor s Foreword
Aftertherecentsuccessesofthefar-IRmissionsIRAS,ISOandtheHerschelSpace
Observatory, the era of space interferometry beckons. Indeed interferometry is
indicatedasthewayforwardinmanyfieldsandatallwavelengthswithfar-infrared
having the possibility of leading the way, thanks to the reduced metrology
requirements. Interferometry in space is on the other hand extremely challenging
andmanyattemptstojump-startstudiesandmissionconceptshaveproveninmany
cases ahead of their time or in dire need of technology development to raise the
feasibility of the proposed concepts.
One technique which has been proposed as an optimal candidate for future
far-infrared interferometry is double-Fourier-modulated spectral-spatial interfer-
ometry, with preliminary concepts being studied in both the US and Europe and
testbed demonstrators explored at both the relevant wavelengths and the to-scale
optical wavelengths. This technique, unlike standard photometry or spectroscopy
that are mainstreamtechniques, has to conquer an additional challenge which isto
be understood and adopted by a larger community that is often sceptical of new
techniquesuntildataisproducedrobustlyandinareproduciblemanner.Toachieve
thelatter,anend-to-endphysicalsimulatorwascodedtoallowtheastronomerwho
is not familiar with this technique, as well as the instrumentation community to
visualize the potential of a mission concept adopting this technique, as well as the
implications of systematic effects introduced by given elements of such a payload
on the recovered data, in order to both plan the science capabilities and paramet-
rically test different configurations and observation modes.
Thisthesisdescribesthephysicsandthecomputationalaspectsofanend-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
promisingtechniquetocapturemostoftheastrophysicalinformationbycombining
spectroscopy with spatial interferometry.
ThesimulationofsuchasystemisextremelycomplexrequiringmultipleFourier
transforms each of which is subject to instrument non-idealities and appropriate
vii
viii Supervisor’sForeword
optimization techniques. As a conclusion, the thesis provides an example of the
basicperformanceachievablewithsuchaninstrumentwhentargetingayoungstar
formationregionbyrunningthesimulatorwithapreviouslygenerateddatacubeand
recovering the astrophysical scene.
London Dr. Giorgio Savini
February 2016
Preface
A large and growing number of astronomers recognize the importance of high
spatial and spectral resolution observations in the far-infrared. Half of the energy
emittedbystarsandaccretingobjectscomestousinthefar-infraredwavebandand
has yet to be explored in detail. On the one side, to study the far-infrared wave-
length range there is a need for space observatories due to one main reason: the
Earth's atmosphere. On the other side, to achieve high angular resolution there are
two options: a very large aperture single dish telescope, or an array of smaller
telescopes, that 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. Hence, to
satisfy the community's sensitivity requirements in the far-infrared and in order to
improve the existing resolution in space, a space-based interferometer is the most
practical solution.
Far-infrared interferometer (FIRI) is a concept for a spatial and spectral space
interferometer with an operating wavelength range 25–400 µm and sub-arcsecond
angularresolution,andisbasedonthecombinationoftwowell-knowntechniques,
stellar interferometry and Fourier transform spectroscopy, to achieve high spectral
and spatial resolution in the far infrared. The resulting technique is called Double
Fourier Spatio-Spectral Interferometry (Mariotti and Ridgway 1988) or Double
FourierModulation.Withanincreasedspatialandspectralresolution,anumberof
interesting science cases such as the formation and the evolution of active galactic
nuclei and the characterization of gas, ice and dust in disks undergoing planetary
formation, among others, can be investigated.
InChap.1Igiveanintroductiontofar-infraredastronomyandthesciencecases
thatcouldbestudiedwithadoubleFourierinterferometerfromspace.Anoverview
of past, current and future instruments is given and the scope of this thesis is pre-
sented.InChap.2thetheoreticalbackgroundneededtounderstandtheprinciplesof
Double Fourier Modulation is presented. Starting with the basics of Fourier trans-
formspectroscopy,wherethegenerationandsamplingofinterferogramsisshown,
and stellar interferometry, with an emphasis on the uv-map generation, the link is
ix
x Preface
made to explain analytically Double Fourier Modulation. The state-of-the-art data
synthesistechniquesarealsosummarized.
Inthis thesisI present two approachesto study thefeasibility of aFIRIsystem:
(a) An experimental approach via the Cardiff University-UCL FIRI testbed, a
laboratory prototype spectral-spatial interferometer to demonstrate the feasibility
ofthedoubleFouriertechniqueatthefar-infraredregime,includingtheWide-Filed
Imaging Interferometry Testbed at the Optical and Near-infrared regime located at
NASA’s Goddard Space Flight Center, both presented in Chap.3. My contribution
hasbeentothecharacterizationofthesystem,dataanalysisandforwardmodelling
for the Cardiff–UCL FIRI testbed, and in the data analysis and verification for the
WIIT. Both systems are operational and ongoing, and the current issues and next
steps are shown.
(b) The Far-Infrared Interferometer Instrument Simulator (FIInS) to assess the
performanceofaspace-basedsystem.Themaingoalofthissoftwareistosimulate
boththeinputandtheoutputofsuchasystem,whichisthecoreofmyresearchand
is described in Chap.4. With a modular design, the different components of the
software are explained, from the sky generator to the interferograms readout. The
moduleswillallowfutureinstrumentartifactstobeaddedtothesimulator.Itisalso
capable of simulating different instrument configurations, i.e. boom-based or for-
mation flying interferometers.
In Chap.5 the interferograms generated by FIInS are processed and synthesized
toobtainthesourceinformationandtocomparewiththeinputskymap.Inorderto
verify the performance of FIInS, the parameters are tuned to simulate the Cardiff-
UCL FIRI testbed and the results obtained are shown.
FIInS is intended to be a tool available to the scientific community to test the
performance of such an instrument for the different science cases. In Chap.6 a
description and simulation of a selected science case, a circumstellar disk, is pre-
sented for both an ideal instrument (noise-free) and a more realistic instrument.
Finally, in Chap.7 a summary of the conclusions of the work in this thesis is
presented, as well as future work possibilities regarding the Cardiff-UCL FIRI
testbed and the possible extensions of the instrument simulator FIInS.
TheworkdescribedhereistheresultofmyPh.D.research,whichwasstartedin
October2010,defendedin2014.Dr.GiorgioSavinithensuggestedthenomination
of this thesis for publication in the Springer Theses series, and thanks to the
endorsement of Dr. David Leisawitz (NASA Goddard Space Flight Center) it was
accepted by Springer in July 2015. I would like to thank both of them for their
encouragement and support.
Washington, D.C. Dr. Roser Juanola-Parramon
February 2016
