taipan fibre feed and spectrograph: engineering overview · taipan will conduct a stellar and...
TRANSCRIPT
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TAIPAN Fibre Feed and Spectrograph: Engineering Overview Nicholas F. Staszak*, Jon Lawrence, Ross Zhelem, Robert Content, Vladimir Churilov, Scott Case,
Rebecca Brown, Andrew M. Hopkins, Kyler Kuehn, Naveen Pai, Urs Klauser, Vijay Nichani, Lew Waller
Australian Astronomical Observatory, 105 Delhi Rd., North Ryde, NSW 2113, Australia.
ABSTRACT TAIPAN will conduct a stellar and galaxy survey of the Southern sky. The TAIPAN positioner is being developed as a prototype for the MANIFEST instrument on the GMT. The TAIPAN Spectrograph is an AAO designed all-refractive 2-arm design that delivers a spectral resolution of R>2000 over the wavelength range 370-870 nm. It is fed by a custom fibre cable from the TAIPAN Starbugs positioner. The design for TAIPAN incorporates 150 optical fibres (with an upgrade path to 300). Presented is an engineering overview of the UKST Fibre Cable design used to support Starbugs, the custom slit design, and the overall design and build plan for the TAIPAN Spectrograph. Keywords: spectrographs, Starbugs, MANIFEST, TAIPAN, UKST, GMT
1. INTRODUCTION TAIPAN, currently nearing completion, is a multi-object parallel-positioning fibre-optic spectrograph designed for the UK Schmidt Telescope at Siding Spring Observatory in northern New South Wales, Australia. The instrument will be used to perform galaxy and stellar surveys across the whole Southern hemisphere sky, over a 5 year period. An AAO designed fibre optic cable is used to transmit light from each of the 150 Starbug Robots (with an upgrade path to 300) to a custom designed slit as input to the TAIPAN Spectrograph. The TAIPAN Fibre cable is designed to minimize path length to the spectrograph for maximum throughput while incorporating the AAO’s best practices for minimizing focal ratio degradation within a fibre run. Presented is a discussion of the detailed design considerations of the fibre cable and slit design. The TAIPAN Spectrograph completely replaces the UKST 6DF spectrograph that was used for the RAVE survey and is part of the complete TAIPAN Instrument package being delivered to the UKST in 2016. The TAIPAN Spectrograph is an AAO designed all-refractive 2-arm design. It delivers a spectral resolution of R>2000 over the wavelength range of 370-870 nm. It contains completely custom optics and mechanical components starting with a 300 fibre slit assembly. The 300 fibre slit feeds a 5 element f/2.41 collimator assembly with one aspheric surface. The collimator optics reside within individual lens cells that provide tip, tilt, and x, y alignment adjustment. Alignment is accomplished on the AAO lens centering station. The beam from the collimator is split into two bands with the blue arm covering 370 to 592 nm and the red arm covering 580 to 870 nm. Two volume phase holographic (VPH) gratings are provided by Kaiser Optical Systems. The beam splitter and VPH grating assemblies reside in kinematically mounted holder assemblies for alignment and the ability to accurately remove and replace from the spectrograph. Custom camera barrels and lenses feed semi-custom Spectral Instruments 1100s Dewar Detectors. The red and blue cameras are F1.5, each a five element design with three aspheric surfaces. The optical subassemblies interface to a monolithic spectrograph structure. All optics in the TAIPAN Spectrograph have been manufactured by Optimax. An overview of the overall opto-mechanical design and assembly of the TAIPAN spectrograph will be presented. *[email protected]: phone 61-2-9372-4857: www.aao.gov.au
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, edited by Ramón Navarro, James H. Burge, Proc. of SPIE Vol. 9912, 991223
© 2016 SPIE · CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2233796
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The UK SchTAIPAN wilfield of viewEdinburgh. It
The telescopproduce photskies. It thenEpoch Sky S
The excelleninstalled but the spectra oconduct the Rtelescope to m
In addition tdome, shuttereplaced. Allmany years oand the Taipa
3The TAIPANobserved to asurvey will egalaxy survedataset will ebetween gas stellar and hafield by incor
2. UK hmidt Telescopll be commissiw. The telescot became part o
e was originaltographic atlasn undertook murvey in collab
nt optics and wno longer acti
of more than 1RAVE stellar smake way for t
o TAIPAN, ther, and windscrl major mechaof previous seran galaxy surv
. SCIENCEN instrument wa magnitude ofexplore the formey is to determenable studies
and stars, thealo mass functirporating data
SCHMIDTpe (UKST – sioned. The UKope was commof the AAO in
lly designed toses. The UKST
many other survboration with S
wide field of thive instrument00 objects in survey and thethe TAIPAN In
he UKST has ureen drive mo
anical drive gervice. The teleey with the TA
Figure 1. U
E GOALS Awill be used tof i < 17 with a mation history
mine the value of the bulk flo
e impact of enion), star formafrom radio sur
T TELESCOsee Figure 1) l
KST is a surveymissioned in 1
June 1988.
o photograph 6T's initial task wvey projects inSpace Telescop
he telescope wt. 6DF was a ma single field
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undergone signtors and contrar boxes have scope is now i
AIPAN Instrum
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AND REQUo conduct the T
signal to noiseand evolution of H0 to ~1%
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OPE OVERlocated at Sidy telescope wit973 and, unti
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Redshift Survey
nificant infrastrols. The telesc
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UIREMENTTaipan galaxy e goal of 5-10 of galaxies to
%, though the dn the local univd mergers on correlated withwith radio teles
RVIEW ANDding Spring Obth an aperture il 1988, was o
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tructure upgradcope user interand dome bog
ondition to undnstrate the viab
g Spring Observa
TS OF THEsurvey, in whacross the entz < 0.3. The pr
dataset will beverse as an add
galaxy evoluth AGN activityscopes such as
Dbservatory is tof 1.2 metres
operated by th
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he near infrare
6-degree Field)trograph facilit
ommissioned incility is now be
des. The telescrface and guidgey rails have dertake the Funbility of the Sta
atory.
E TAIPAN Shich 0.5 − 1.5 tire southern herimary cosmol
e used for manditional cosmoltion, large scay as well as thes ASKAP.3
UPGRADE the telescope iand a very wi
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e Second
currently ld obtain s used to from the
ved new ave been hed after ar survey ogy.
s will be e Taipan e Taipan
oses. The nnection ncluding magnetic
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Figure 3. ormed to discussed From the s (Figure ube. The n internal e of fibre e 3.8mm ed steel, routed to quatorial
d beneath
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Figure 3, TA
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elescope operaton.
tion.
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11
4.1 Fibre CThe AAO fibsharing one tFrom previoushould be bepractice of infurcation tubratios, the uTAIPAN Fibused providin
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tubes are the inner ds of the ted at the ctor. The 3.8 mm the fibre t with an e against hould an
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9
4.3 Slit AsseThe fibre cabfibres and is slitlets (Figur(Figure 8). Ffibre spacingThe slit assegroove blockItem 5) beforlid, and gluethe slit body
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entering the V
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s bonded to thdy.
of all the from four ve blocks precision achieved. ed on V-igure 7 -
sed silica mbled to
abricated
V-groove
This aids
e Kevlar
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á
=1.
71 a O 129:0001-F
Il 10.1291-.
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The TAIPANconstruction shown succeThree lengthdegradation
t Assembly, delet. Four total fe Plate. Provid
erface Flange embly. Lens. Fibres aical Fibres – 2
N Optical Cabis to thorough
essful results ahs (30-32 met(FRD) of the
epicts the followfor the assembldes structural inLens Cell. Th
are coupled wit5 per branch.
5. Tle is construct
hly test fibre opcross the full tres) of opticafibre cable we
Figure 8. Fu
Figure
wing: ly giving 300 fnterface and prhe first lens c
th an index mat
TAIPAN FIBted with Ceramptical performavisible spectrual fibre were ere tested with
used Silica V-Gr
9. Slit Assembly
fibre input to threcision mountiell of the spe
tching gel to th
BRE PERFmoptec WF50/ance for its int
um where the tested under
h 2 collimated
Groove.
y.
he spectrographting for the slitlectrograph that
he uncoated su
ORMANCE/125A. The Atended applicaTAIPAN Spec
several condlight sources
h. lets. t also provide
urface of the sli
E AAO standard pation. Testing octrograph operditions. Throug(405nm and 6
es interface to
it lens.
process for fibof the optical frates from 370ghput and foc658nm), follow
o the slit
bre cable fibre has
0-870nm. cal ratio
wed by a
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405/658nm laser source
FC Cc
nglemode
200mm fl 1
mnectoI
rcu:111,ut
,_-_,..----
450 500 550
V
Variableiris
Detector
9 fibre over full
mm fl Fibreis I
600 650 7(
Vavelength (nm)
--. r.'ariable)erture
end on 3 -axis
)0 750 800
Fibre cable
cutback test source with a Throughput athe UKST TeFRD measurTAIPAN spthroughput amethod was u85% at 405nm
To determineinto the fibreand processeshow throughclear that the870nm, exclu
on one samplean integrating s
and FRD tests elescope. Tota
rements were cectrograph. Fi
at 658nm and 7used to determm.
e the throughpe, close to the ed with a specthput in the fibe fibre cable wuding Fresnel l
e to measure atsphere was per
(Figure 10) wal throughput mcarried out withigure 10 depi75% at 405nm
mine loss due so
F
ut of the fibre numerical apetrometer. Figu
bre due to absowill provide effilosses.
Figure 11. Fu
ttenuation fromrformed on a re
were performedmeasurements wh a 4.22mm apicts the setup
m, with a furtheolely to absorpt
Figure 10. FRD/
across the visierture. The outpure 11 shows thorption, with nficiency within
ull Spectrum Tra
m absorption. Aemaining samp
with a f/2.5 bwere performe
perture across tof these test
er 10% reductition; it was sho
/Throughput Op
ible spectrum put flux was inhe output of tho compensatiothe specificati
ansmission of Ce
A full-spectrumple.
eam injected ined with an openthe output, to sts. Throughpution due to FRDown that the fib
ptical Setup.
(370 – 870nmntegrated overhe 30m fibre, on for Fresnel ions of at least
eramoptec WF50
m throughput t
nto the fibre, sn aperture on tsimulate the f/2
ut tests showeD. Following tbre has 92% ef
m), a uniform wr 50 seconds inacross the visreflection or Ft 70% for the w
0/125A.
test using a wh
simulating the the output of t2.37 input speed approximatethese tests, thefficiency at 65
white light was n an integratinible range. Th
FRD loss. Ovewavelength ran
hite light
speed of the fibre. ed of the ely 90%
e cutback 8nm and
injected ng sphere he results rall, it is nge 370-
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laser source
The LEMO cspring loadedas standard connection fcombination.(for standardtolerance for 6.1 InsertioConnectors w
The insertionconsists of thcompared to The two, 2 m(P3) is measureference meto be constareflection losP2/P1 and P3all measuremalignment slconnector, bawas .21 dB, o It is importatolerance of +in increased
6.
connectors used in the conneFC connector
from reflection. The LEMO s
d F2 contacts winstrument thr
n Loss Measu
were tested for
n loss is meashe ratio of the the power inje
meter, test lengured. The ratio
easurement inseant for all meass at the output3/P1 measuremments. The samleeve to mitigased on a sampor 5.1%.
ant to note tha+/- 2µm. This losses due to
LEMO CO
ed in TAIPAN ctor and alignes. Additional ns, defects at stated insertion
with standard mroughput a sam
urements
insertion loss u
sured by first power out of a
ected into the fi
gths are then co P3/P1 is the ertion loss is thasurements ant of both the re
ments. This meme connectionsgate loss due ple of 5, was .4
at these measuris a large tolercore misalign
ONNECTOR
utilize F2 typed using a cerathroughput lothe fibre inte
n loss (IL) for multimode fibremple of connect
using the setup
Figure 12
taking a refera bare fibre, w
fibre, P1. This i
connected via loss for the enhe insertion lo
nd the only uneference measuasurement is ths were measurto reflection
45dB, or 10.9%
rements were rance relative tnments. The c
R COUPLIN
e contacts. Thamic sleeve. T
osses will necerface, and mithese connecto
e). To ensure ttors was tested
p outlined in Fi
2. Connector IL
ence measuremwith terminated is leg 1 in Figu
the LEMO conntire assembly. ss of the conne
nknowns are turement and thehen repeated sered for IL agaiand surface im
%. When gel w
taken with Ceto standard teleonnectors rely
NG PERFO
he coupling conThis configuratessarily occur isalignment loors varies fromthat the couplind for insertion l
igure 12 below
test.
ment of input d and polished ure 12. This is c
nnector, as ab The differencection. This mthe transmissioe connector meeveral times win with the insmperfections.
was added to th
eramoptec Optecommunicatioy on the cladd
ORMANCE
nsists of two ction is essentia
in the instrumsses inherent
m 0-0.7dB for ng losses wherloss.
w:
power. The rferrules but wcalculated as a
bove, and the pce between this
method allows fon loss (negligeasurement wh
whilst keeping lsertion of indeThe average
he same connec
tran WF fibre ons multimodeding outer surf
ceramic ferruleally the same tement due to tin the connecmultimode co
re within an ac
reference measithout a conne
a loss in decibe
power exiting s insertion lossfor coupling cogible for 4m) hich is capturedleg 1 as the coex matching ginsertion loss
ctions, the aver
which has a e fibre which cface for moun
es axially echnique the fibre ctor/fibre onnectors cceptable
surement ector, P2, ls (dB).
the fibre s and the onditions
and the d in both nstant in el in the
s for the rage loss
cladding an result
nting and
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LEMO F2 contad
1Ceramic ferrule
Optran WF50 fibr
ri
therefore aliconnection. The index massembled geand reworkinaddition ther The reasonabpositioning d 6.2 Focal RThe contribuin Figure 13.angle of 11.3up to 6% loss
In this setup,This LED waeffectively cprojected oncontributes toFigure 14.
gnment. The
matching gel is el-free in the fng requires a ce is a risk som
ble performancdevice.
atio Degradat
ution of the LE. The FRD spe31° must produs for the consid
, the same test as placed 300mcollimated beamnto a CCD. Tho the broadeni
connectors are
not recommenfinal instrumenclean environme gel could be
ce of the LEM
tion Measurem
EMO connectorcification is w
uce an annulus dered telescope
lengths as meamm from the fibm to illumina
his annulus wing and thus in
e also keyed
nded by LEMOnt. There is no
ment that woulddeposited on th
MO fibre optic
ments
r to focal ratio ritten such thatwith a full-wi
e injection foca
Figure 13. FR
asured in the Ibre end and at
ate the fibre frill have a blurncreased FWHM
Figure
thus guarantee
O for use in tho guarantee thad be difficult whe field plate o
connection en
degradation wt a TAIPAN scidth half-maximal ratio and spe
RD Measuremen
L measuremenan angle of 11
from the LED.r due to mode M of the ring.
14. Projected Ri
eing a consist
heir connectorsat the gel will when the instruor fibre face via
nabled the Sta
was also measucience fibre illumum (FWHM)ectrograph pup
nt setup
nt were illumin1.31° with resp. At the outpu mixing from An example o
ing
tent IL result
s, it was decidremain clear o
ument is installa the vacuum s
arbug to becom
ured using the uminated by a) of less than 2
pil stop.
nated by an LEpect to the ferruut of the connFRD related
of a projected r
for a single
ded that they shoptically and rled in the telessystem.
me a replaceab
setup illustratea collimated be2° at the output
ED centered onule axis. This anection the anphenomena. Tring is shown b
repeated
hould be replacing scope. In
ble robot
ed below eam at an t. This is
n 530nm. allows an nnulus is This blur below in
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Five separate connections were tested using this method to determine the broadening in this setup with an average result of 1.46°. These numbers are well within the tolerance of 2° and give a further 0.5° margin for the final completed science cable.
7. SPECTROGRAPH OPTICAL DESIGN The TAIPAN spectrograph is a 2 arm design with a 300 fibre input slit. The fibre near field is reimaged by the spectrograph optics onto the CCD detector, while the fibre far field forms the pupil which is projected by the spectrograph collimator onto the VPH gratings, dispersing the beam into the cameras. The design operates with two semi-custom Spectral Instrument Dewar detectors. The red and blue spectrograph cameras provide demagnification of the fibre slit and are therefore a more challenging design when compared to the collimator. Each camera images the spectra on a 2k x 2k E2V detector. The average resolution is approximately 2350. The wavelength range is from 370 nm to 870 nm with the dichroic cut-off at 590 nm and a common region to both cameras from 580 nm to 592 nm. The cut-off wavelength and the overlapping region were chosen based on science requirements and to minimize the overlap region. This in turn maximizes the resolution of the spectrograph for the same spectral length in each pixel. In order to produce quality spectra with a reduced number of optical elements, the TAIPAN spectrograph relies upon aspheric surfaces in both the collimator and camera. The fibre core size is 50 µm which corresponds to 3.3" on the sky. A design choice had to be made between two competing designs, one design using mirrors, the other a fully transmissive design. It was decided to use the latter based on specific advantages. Modern antireflection coatings are very efficient over a large wavelength range and different incident angles. While there are now better reflection coatings for mirrors than in the past, the large operational wavelength range starting at 370 nm remains a challenge. Also, the surface form error of a mirror creates far larger aberrations and scattered light than a lens surface of the same error. For a given root mean square (RMS) surface form error or surface roughness, the Optical Path Difference (OPD) RMS will be 2 RMS after reflection by a mirror. It will be (n-1) RMS after refraction by a lens surface with n the refractive index. The OPD is 0.43885 RMS for a CaF2 glass surface at the standard Nd wavelength of 587.6 nm. Light would have to pass 21 CaF2 surfaces to have about the same OPD RMS than after a single mirror reflection. A mirror is then equivalent to 21 CaF2 lens surfaces in that respect. Other advantages are that it avoids any diffractive and light blocking obstruction in the beam and the need for highly off-axis aspheres in the collimator, which would be required in a reflective design. Finally, the detector Dewar assembly can be made very small, when compared to the Dewar of a Schmidt camera design which would be required when using mirrors. The entire detector Dewar assembly can be decoupled from the rest of the spectrograph and placed in a mount for position adjustments and focus travel. An important disadvantage of transmissive systems is glass absorption at UV wavelengths. This was very significantly reduced in the present design by incorporating UV transmission as an important factor at every step of the design through choice of glasses. Total glass absorption from slit to detector starting at 370 nm is only 9%, reducing to 3.3% at 400 nm, and continuing to drop at longer wavelengths. The input of each fibre receives a beam with a focal ratio of about 2.5 from the UKST telescope, which is relatively fast. The collimator design had to be somewhat faster to accommodate focal ratio degradation in the fibres and tolerances due to fibre pointing error. Two designs were studied, the first with bare fibres as the spectrograph input slit, and a competing design in which a microlens array was added at the end of the fibres. The purpose of the microlens array was to increase the focal ratio of the beam entering the collimator. A microlens array would have permitted the collimator design to reduce to one lens (Figure 15). A disadvantage of this configuration is that the slit must be curved. The bare fibre slit input is geometrically straight and mated to a plano-concave, low cost, fused-silica lens. This is a relatively simple configuration. Another disadvantage of the microlens slit input is that microlens tolerances degrade the beam mostly through pupil defocus and angular errors in the beam direction. This is equivalent to a large FRD. The large tolerances are due to the fast telescope focal ratio. Using a microlens array with an Integral Field Unit (IFU) allows spectra to be packed very tightly thereby reconstituting a pseudo-slit without empty space between the images of each fibre. In Multi-Object Spectroscopy (MOS), where each fibre observes a different object, it is necessary to have gaps between spectra to avoid cross-contamination. The advantage of having more spectra with a microlens array is therefore not an option with the TAIPAN Spectrograph design. The final design choice was to use the bare fibre slit input with an additional four lenses in the collimator. The final collimator design is f/2.41 based on the combination of telescope focal
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001 (V1) Date: 00160.2857
2/01/2016
3D Layout
120.00 Millimeters
3D Layout
f I
70.00 Millimeters
ratio, FRD ofused silica laspheric surfadjustment.
Fig
The TAIPANThe overall croom. Overarequirement optical table
Spe Coll Bea VPH 5 Ax Bac
obtained from ens glued to thfaces. The last
gure 15. TAIPAN
Figur
N Spectrographconstruction ofll temperature that is not ovebut a post mou
ctrograph struclimator Barrel
am splitter asseH grating assemxis mounts wh
ck Illumination
fibre testing, ahe slit (Figure 1t lens is also
N Spectrograph
e 16. Final spect
8. SPECTh mechanical df the TAIPAN stability of the
erly strenuousunt design has b
cture which supAssembly.
embly. mblies. hich support the Assembly.
and the fibre p16). One collimthe window o
conceptual desig
trograph design
TROGRAPdesign followedSpectrograph ie room must b. The TAIPANbeen avoided.
pports the colli
e Spectral Instr
pointing error.mator surface iof the detector
gn with microlen
with bare fibres
PH MECHAd a strategy ofis out of alumie controlled to
N SpectrographThe mechanic
imator, beam s
ruments Dewar
. The collimatois an asphere. Er cryostat whic
ns array slit inpu
as slit input to t
ANICAL DEf creating simpinum since it wo +/- 1.5 degreh size was sucal design is bro
splitter, and VP
r detector assem
or has 4 lenseEach camera hch is on a mo
ut and a single le
the spectrograph
ESIGN ple to machine,will reside in a ees for the specch that it couldoken up to 6 m
PHs.
mblies.
es plus a planohas 5 lenses incount for tilt an
ens collimator.
h.
, modular comtemperature co
ctrograph to ped fit complete
major componen
o-convex cluding 3 nd focus
mponents. ontrolled erform, a ly on an nts.
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" r
.
The TAIPANplate. The usground surfafor the build angles for thoptical axis oshims under equipped witpractices on t
N Spectrographse of this mate
aces from the mand alignmen
he collimator aof the system. each of the camth pockets thatthe spectrograp
h structure (Figerial has two amill, allowing t of the instrum
and cameras. TNominal angl
meras allow tipt hold kinematph structure ali
F
Figure
Figure 19
gure 17, Figureadvantages, stafor minimal sument. The struThe collimator les and positiop tilt adjustmentic mounts forignment needs
Figure 17. Taipa
18. Taipan Spec
9. TAIPAN Spec
e 18, Figure 19ability by beinurface machinicture base platmounting pla
ons of the red nt if required b
r the beam spliare nearly irre
an Spectrograph
ctrograph Assem
ctrograph Assem
9) is constructeng in a full streing. The spectrte has a profile
ate includes a pand blue camebut this is highitter and two g
elevant allowin
Assembly.
mbly Section Vie
mbly during a tes
ed of Alcoa MIess relieved corograph structue machined in precision boreeras is set throhly unlikely. Thgratings. Throu
ng for a fast int
ew.
st fit.
IC-6 aluminumondition, and pure sets the fouto set the posi
e which establiough machininhe box like strugh normal megration.
m cast jig precision undation ition and ishes the
ng. Three ructure is
machining
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SLIT / Light
The beam spof 416 Stainldesigned to athe optic. Eaposition of eaThe kinematalignment, an
The collimatAAO lens ce8]. Each lensfirst run out are then rotatsurfaces, as olens cell. An To complete the next lensby observingthe two lenseusing this mcollimator an
The semi-cuThe 5 axes shimming buadjustment, t
litter mount anless and platedathermalize theach optic sits kach sphere cantic mounting nd in general a
F
tor and cameraentering stations is mounted inon the precisioted on the air bobserved by thRTV bond is aa lens assemb cell assembly
g the runout of es are coaxial,
method results nd cameras are
stom, Spectralof adjustment
ut will not be ntheir rotational
nd VPH gratingd with blackenee assembly. Eakinematically in be adjusted tharrangement a
a valuable desig
Figure 20. Beam
a assemblies (Fn (LCS) with an an individualon AB Tech aibearing stage whe PSM, is minapplied to the pbly a bonded ley placed on top
the return beam, the lens cellsin an extreme+/- 15 m dec
Figure 2
l Instrument, Dare tip-tilt, ro
necessary. The l center aligned
g mounts (Figued electroless nach mount contin the spectroghrough shimmiallows highly gn feature.
splitter and VPH
Figure 21) are ca Z stage mounl cell, with the ir bearing stagwhile the lens inimized, thus bperimeter of thens cell assembp. The optical am, through thes are potted anely high level center and +/- 2
21. Cross Sectio
Dewar detectorotation, lateraldetector assemd with the surf
ure 20) follow tnickel. The opttains three sphgraph structureing, allowing m
accurate rem
H grating mounts
constructed of nted point souroptical surface
ge to form the ois tilted on the bringing the op
he lens cell andbly is again plaxis of the secoe PSM, while snd then screwe
of accuracy.20 arc seconds
on of Collimator
rs are assemblel decenter, and
mblies are face face of the det
the same desigtics are bonded
heres whose cee, its Z space pminute adjustm
moval and repl
s. Covers not ye
f aluminum. Thrce microscope resting on a topto-mechanictangential sea
ptical axis of td an axial retentlaced in the LCond lens assemsimultaneouslyed into place. Typical alignmtilt.
and Blue Came
ed in a commod focus. A hemounted to a
tector. A rotati
gn principle. Thd into each moenter is coincidposition set th
ments in tip/tilt,lacement of th
et blackened.
hey are designee (PSM) and atangential cell cal axis of the at. The return bthe lens to the tion ring is thr
CS, optical aximbly is made coy adjusting in thSerial progresment accuracy
era.
on 5 axis moueight adjustmestructural ring
ion adjustment
hey are construount with RTVdent with the suhrough machin and roll for thhe optic, used
ed to be alignean air bearing surface. Lens cell. The lens
beam runout ofestablished axeaded into placs established, oincident withhe x, and y, axsion of lens aly requirements
unt design (Fignt is possible . Flexures allot is built intern
ucted out , the gap urface of
ning. The he VPHs. d during
ed on the stage [7, cells are and cell
f the lens xis of the ce. and then
h the first xis. Once lignment s for the
gure 22). through
w tip tilt nal to the
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I
tilt flexure thoccurs throuplacement ofdimension anadjusters. Thconfigured w
The TAIPANStarbug sciecharacterizatcamera. Sincposition of thThe back illuthin profile athe 5 axis mUltimate pos
hrough cylindrugh linear bearf the camera and then replache focus travelwith an integral
N spectrographnce fibres in ion of their po
ce positioning the science fibreumination assemallows it to fit bmount for desig
ition accuracy
rical mating srings. The 5 aassembly. If laced. All axes ol, and tip-tilt w drive spindle,
F
h is configuredthe TAIPAN sition relative the Starbugs ree the back illummbly positionsbetween the lasgn commonaliis not a requir
urfaces, adjustaxis mount is ateral adjustmeof travel, excewill be motor 29:1 gear head
Figure 22. Five A
d with a back ilfibre positionto their three melies on only vmination unit ws a 24V MetaBst collimator lety but fitted inement.
Figure 23. Bac
ted by precisikeyed to the
ent of the camept lateral mov
driven in the d, and 500 cou
Axis Dewar Dete
llumination unner. The benefmetrology fibreviewing the mewas deemed a uright Thin Bac
ens and the beanstead with a
ck Illumination A
on adjuster scspectrograph
mera is requiredvement, can befinal configur
unt per turn enc
ector mount.
nit (Figure 23) fit of back illues can occur utetrology fibresuseful facility ck Light unit inam splitter. It is
machine screw
Assembly.
crews and thenstructure. Thid the key stoce actuated throration through coder.
with the purpouminating the tilizing the fibrs and referringfor periodic ch
n front of the cs driven by thew for the addi
n locked. Focuis allows for pck is simply grough manual puse of Maxon
ose of illuminascience fibre
re positioner mg it to the charahecking of the collimator asseme same Maxon mitional require
us travel precision round to precision n motors
ating the s is that
metrology acterized Starbug. mbly. Its motor as
ed travel.
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Specirop
Eu
CA
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led Tip Motor
led Tilt Motor
clue Focus Motor
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lack Illuminationce
Integration wtransported tointo three maassembly. Treplacement aligned and tverification i 8.1 SpectroThe spectrogincludes an inIn order to fathe CANopecomponents. light sensor sroom and spusing a solid The servo mThe Copley cback illumina
The AAO coelements of b0.185 mm. AThe device pfull map of th
will occur at o Siding Sprinajor componenhe kinematic for shipping.
tested, allows fis expected onc
graph Electro
graph control nput/output (I/acilitate remoteen devices. TThe I/O modu
switch, and 4 cectrograph temstate relay.
motor control uncontrollers drivation actuation
9. SPECT
ontracted Optimboth the blue aAsphericity of produces the inhe optical surf
the AAO Sydg Observatory
nts, the two Demounting of The keyed De
for easy disassce the spectrog
onic Control
system (see F/O) module ande operation, theThe spectrograule reads inpuchannels of themperatures. Th
nit is implemeve 7 motors on
n.
TROGRAPH
max Systems toand red camerathis magnitud
nterferograms oface. Additiona
dney laboratorfor installation
ewar detector athe beam spl
ewar detector embly in Sydnraph is deliver
Figure 24) used servo drive ae electronics coaph CANopen
uts from the opermocouple inpe I/O module p
ented using 7 Cn the spectrogr
Figure 24. El
H COMPON
o manufacture a assemblies h
de can be verifof multiple oveal test optics fo
ries in North n in the UK Scassemblies in tlitter and VPHassembly allo
ney and re-assered.
es a CANopenamplifiers. Theontrol uses an n I/O moduleptical bench airputs. The thermprovides one o
Copley Controraph, tip/tilt fo
lectronic control
NENT MAN
the complete save the most a
fied using an ierlapping sub-aor each aspheri
Ryde and aftchmidt telescoptheir mounts, p
H gratings allows simple repembly at site w
n (Controller e system is scalEthernet to CA
e is implemenr pressure swi
mocouple chanoutput to contr
ols CANopen mocus actuation
l system
NUFACTU
set of optics foraspheric surfacindustry standaapertures, whicic surface are n
ter testing the pe. The assembplus the main low for easy placement. Th
with essentially
Area Networklable for futureAN adapter, whnted with Beitch, spectrogrannels are used trol the back ill
motor controlleon the Dewar
RING AND
r the TAIPANces, with maximard aperture stch are averagenot necessary,
spectrograph bly easily disasspectrograph removal and e overall desig no re-alignme
k) architecturee changes, if nehich provides aeckhoff Bus Taph door switcto monitor the lumination ligh
er digital servodetectors and
D TEST
N spectrograph. mum depth remtitching interfeed and integrateas is the case w
will be ssembles structure accurate gn, once ent. Only
e, which ecessary. access to Terminal ch, room ambient
ht power
o drives. the fibre
The last moval of erometer. ed into a with null
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1
0.9
0.8
0.7
0.6
it asto.
0.4r°1-
0.3
0.2
0.1
0350 40(
,z..-_
-
PH grating2 wv RMS 0.022 wv
tter Dichroic mirrorwv RMS 0.012 wv
Red VPH grating
PV 0.21 wv RMS
eamsplitter in transV 0.16 wv RMS 0.02
.037 wv
The TAIPANof equal thickof the gratinghas shown thprocessing coand the AR cuncoated VPsmall size ofsent for the A
Figure 26. T When applyiTypically thedeposition teAR coatingsgratings haveOptical for th The TAIPAN590 nm. A mrequired in thsubstrate for coating was dwas applied t
Figure
N VPH gratingkness. The blugs uncoated an
hat the delivereonstraints of thcoatings have b
PH gratings andf the TAIPAN AR coating.
TAIPAN VPH g
ing an AR coate surface beingemperature to 1 are becominge been succeshe blue and red
N dichroic beammultilayer coatihis case, are cothe TAIPAN
deposited firstto the opposite
27. The reflecte
gs measure 110ue and red gratind then followed wavefront ohe VPH, distorbeen already dd verified the dgratings, the s
gratings tested in
ting to a VPH g coated is heat120°C, and preg more commosfully coated w
d bandwidths.
m splitter refleing was requireomposed of a ldichroic beam
, to verify coate side of the sub
ed wavefront off
0 x 110 x 28 mings were fabri
wing internal inf an assembledrtion can occureposited, they diffraction effisubstrates did n
n transmission in
grating strict tted to create beeferably 100°Con on bonded with a 0.5% r
cts the blue waed to separate blarge amount o
m splitter is 14ting performanbstrate. Both co
f the dichroic (bl
mm with the dificated by Kaise
nspection applyd grating may nr on thin substwould have tociency (Figurenot acquire sig
n zero order. P to
temperature limetter adhesion. for safety marassemblies wieflectance, low
avelength rangboth spectral cof thin films, w40 mm in diamnce and wavefroatings were m
lue arm) and tran
ffractive gelatiner Optical Systy the AR coatinot be sufficientrates. If post po be removed ae 25) and wavegnificant distor
o V and RMS wa
mits in the depThe grating ge
rgin, as they arith a variety ow-temperature
ge and transmitchannels efficiewhich may exemeter, and has ront quality (Fimanufactured b
nsmitted wavefro
ne layer enclostems. The AAOings to each sunt for a particupolishing of thand reapplied. efront quality (rtion. Subseque
avefront is show
osition processelatine and adhre sensitive to of thin film m
AR coating, d
ts the red with ently. Complexert bending strean aspect rati
igure 27). Afteby Cascade Opt
ont (red arm) in
sed between twO chose to takurface. Past exular applicationhe grating is neThe AAO rece(Figure 26). Duently the gratin
wn in waves at 63
sing must be ohesive limit theheat. Low-tem
materials. The Tdeveloped by
the split wavex coatings, whess on a substrio of 1:7. The erward, the ARtical.
waves at 632 nm
wo plates ke receipt xperience n. Due to ecessary, eived the ue to the ngs were
32 nm.
observed. e coating
mperature TAIPAN Cascade
length at hich were rate. The dichroic
R coating
m.
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Interferomete
Interferome
Collimator
dlimator R
-rVeturn flat
uvera (Blue/Red
Corrector lens
9.1 Optical The testing operformance individually corrected by 28) over thecollimator ascameras.
The full systor VPH gratiwindow. Thein the cryostaoptically. Thplane as show
The alignmendesign the cprecision maexpectation t The first stepstructure, a preference to wangles are veand VPH gracryostats arecamera at apflattener is sltest spectrumwith a calibrathe spectral r
testing and ve
of the TAIPANrequirements
by means of a each camera. A
e full aperture.ssembly. A sim
em test will being are not incle slit lens is intat. In the absenhe residual errown inFigure 29
nt strategy of tcollimator andachining of ththat they will c
p in the alignmpiloted referencwhich all anguerified throughatings are moune co-aligned wpproximately 1lightly decente
m from a calibration lamp for resolution will
erification
N spectrograph have been mdouble pass in
A null lens is n. A meniscus milar double p
Figure 28.
e performed, inluded. The colltegrated with t
nce of the slit leor of this setup9. The return be
Figure 29
the spectrograpd cameras are he spectrograpo-aligned to le
ment process ice target, and
ular and transla an additional nted and adjustith the rest of degree and 0red. The cross ation lamp. Ththe alignment be evaluated fo
encompasses aet. The collimnterferometric necessary for elens, with zer
pass arrangeme
Optical test setu
n double pass,limator and camthe optical cabens and the fiep is compensaeam is formed
9. Setup for testi
ph is based upbuilt as suba
ph structure aless than 2 arc m
is to establish alignment scop
ational degrees reference targeted in tip and ti
f the system. T.5 degrees for talk between a
he slit is installof the spectro
for compliance
a series of verimator and both
test. The collimeach subsystemro power, corrent will be us
up for TAIPAN
with the collimmera assemblile, whereas the
eld flattener, thated by a paralafter a reflecti
ing collimator-ca
pon by the modssemblies as llow assembly
minutes upon at
the optical axpe. The opticaof freedom of et and goniomilt using their k
The spectrograpthe blue and r
all the degrees led into the spegraph to be cowith requirem
ification and alh cameras are mator is design
m. The collimatrects for the rsed to verify th
collimator assem
mator and the ces do not inclue field flattenee collimator-callel plate of apion from a Cali
amera performan
dular design ofdescribed in t
y of the collimttachment.
xis of the systal axis, now def the remaining
meter. Followingkinematic mouph focal surfacred units, respof freedom is
ectrograph andomplete. The im
ments.
lignment setupseparate subs
ned to producetor assembly isresidual wavefhe performanc
mbly.
camera co-aligude the slit lenser lens serves aamera assemblppropriate thiciballTM.
nce.
f its subsystemthe mechanicamator and cam
tem using the efined by the a
g optical elemeng camera assem
unting arrangemce is tilted to
pectively. At thbest determine
d the optical fibmage quality o
ps to ensure thasystems to be e an output thas tested on-axisfront aberratioce of the blue
gned. The beams and the field as the detector ly is not fully cckness before t
ms. In this all real design sectimera barrels w
collimator boralignment scopnts are set. Thembly, the beamment. In the finthe optical ax
he same time, ed using the imbre cable is illuf the test spect
at system certified
at is fully s (Figure n of the and red
m splitter flattener window
corrected the focal
efractive ion. The with the
re of the pe, is the e camera m splitter nal stage, is of the the field
mage of a uminated trum and
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10. SUMMARY TAIPAN is a spectroscopic instrument that incorporates a fibre positioning system, an optical spectrograph, and a fibre cable linking the positioner with the spectrograph slit. This paper has described the spectrograph, which is a novel all-refractive 2-arm design delivering a spectral resolution of R>2000 over the wavelength range 370-870 nm, and the fibre cable, which has been designed to maximize throughput and minimize focal degradation. All three aspects of the TAIPAN instrument will be installed at the UKST towards the end of 2016 and will commence science observations in 2017.
REFERENCES
[1] ‘The UK Schmidt Telescope’, (accessed 24 May 2016). [2] Kyler Kuehn, Jon Lawrence, David M. Brown, Scott Case, Matthew Colless, Robert Content, Luke Gers, James
Gilbert, Michael Goodwin, Andrew M. Hopkins, Michael Ireland, Nuria P. F. Lorente, Rolf Muller, Vijay Nichani, Azizi Rakman, Samuel N. Richards, Will Saunders, Nick F. Staszak, Julia Tims, Lewis G. Waller. “TAIPAN: Optical Spectroscopy with Starbugs,” Proc. SPIE 9147, 914710, (2014).
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[4] Ricker, G.,“Transiting Exoplanet Survey Satellite (TESS),” Proc. SPIE 9143, 914320 (2014). [5] Nicholas F. Staszak, Jon Lawrence, David M. Brown, Rebecca Brown, Ross Zhelem, Michael Goodwin, Kyler
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