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Title: Optical and NearInfrared Astronomical Instrumentation


1
Optical and Near-Infrared Astronomical
Instrumentation
  • Astronomy Instrumentation Postgraduate Course
  • Richard Myers r.m.myers_at_durham.ac.uk
  • Jürgen Schmoll jurgen.schmoll_at_durham.ac.uk
  • Tim Morris t.j.morris_at_durham.ac.uk
  • Tim Butterley timothy.butterley_at_durham.ac.uk
  • Ali Basden a.g.basden_at_durham.ac.uk
  • David Robertson d.j.robertson_at_durham.ac.uk

2
Course Overview
  • Introductory lectures (Shared with Astronomy PG
    course)
  • Lecture 1. Telescopes Facilities, Thu 13 Nov -
    Dr. Richard Myers
  • Lecture 2. Detectors, Tue 18 Nov (time to be
    re-arranged) - Dr. Alastair Basden
  • Lecture 3. Imagers, Thu 20 Nov - Dr. Juergen
    Schmoll
  • Lecture 4. Spectroscopy, Tue 25 Nov - Dr. Juergen
    Schmoll
  • Lecture 5. Introduction to Adaptive Optics, Thu
    27 Nov - Dr. Tim Morris
  • Advanced lectures (in Room 253)
  • Lecture 6. Advanced Spectrograph Systems, Tue 2
    Dec - Dr. Juergen Schmoll
  • Lecture 7. Interferometers, Thu 4 Dec (time to be
    re-arranged) - Dr. Alastair Basden
  • Lecture 8. Advanced adaptive Optics Systems, Tue
    9 Dec - Dr. Tim Butterley
  • Lecture 9. Space Optical/Near-IR Instrumentation,
    Thu 11 Dec - Dr. Juergen Schmoll
  • Lecture 10. Tour of NetPark Research Institute,
    Tue 16 Dec - Mr. David Robertson
  • (time and transport arrangements to be confirmed)

3
Books
4
Wavelength Ranges
5
Available Facilities
  • Funding most UK astronomical research is funded
    by STFC http//www.stfc.ac.uk/
  • Major Optical/Near-IR Facilities in which the UK
    has a part-share
  • AAO http//www.aao.gov.au/
  • ING http//www.ing.iac.es/
  • UKIRT http//www.jach.hawaii.edu/UKIRT/
  • Gemini http//www.gemini.edu/
  • ESO http//www.eso.org/
  • HST http//www.stsci.edu/hst/

6
Anglo-Australian Observatory
  • The Anglo-Australian Observatory at Siding Spring
    Mountain in Australia consists of two telescopes
  • The 3.9m diameter Anglo-Australian Telescope
    (AAT)
  • broad range of common-user instrumentation for
    observations in the optical and near infra-red
    wavebands.
  • STFC is an equal partner in the AAO with the
    Australian Research Council
  • The UK Schmidt Telescope (UKST) concentrates on
    high-resolution wide-area sky surveys, originally
    through the use of large photographic plates and
    films, but now through spectral surveys with
    fibre feed (6dF).

7
AAO instrumentation
  • AAOmega new AAT optical spectrograph
  • for 2 degree field 2df prime focus robotic fibre
    system and SPIRAL Cassegrain fibre integral field
    unit.
  • IRIS2 - IR imager spectrograph
  • 1024x1024 HgCdTe JHK imager / spectrograph
  • Uni. College London Coudé Echelle Spectrograph
    (UCLES)
  • Ultra High Resolution Facility (UHRF)
  • UKST 6dF - Galaxy survey multi-object
    spectrograph
  • ALSO OZPOZ for VLT, Echidna for Subaru

8
Isaac Newton Group
  • The ING is located at the Roque de Los Muchachos
    Observatory, La Palma, Spain, and it consists of
    two telescopes operating in the optical and
    near-infrared parts of the spectrum
  • William Herschel Telescope (WHT) (4.2 metre
    diameter)
  • Isaac Newton Telescope (INT) (2.5 metre diameter)
  • Jacobus Kapteyn Telescope (JKT) (1.0 metre
    diameter)
  • Operated on behalf of the Science and Technology
    Facilities Council (STFC) of the United Kingdom,
    the Nederlandse Organisatie voor Wetenschappelijk
    Onderzoek (NWO) of the Netherlands, and the
    Instituto de Astrofísica de Canarias (IAC) in
    Spain.

9
WHT instrumentation
  • Spectroscopy
  • ISIS Medium-resolution (8 - 120 A/mm)
  • AF2/WYFFOS Multi-object spectrograph, fed by up
    to 120 2.7" fibres from AUTOFIB2 at prime focus
    (40' field).
  • INTEGRAL/WYFFOS Integral Field Unit
  • LIRIS near-IR spectrograph
  • Future HARPS North
  • Adaptive Optics
  • NAOMI
  • OASIS optical IFU spectrograph
  • OSCA coronograph
  • INGRID IR camera.
  • Rockwell 1k x 1k device.
  • GLAS - laser beacon.
  • Imaging
  • PFIP- Prime focus
  • Auxiliary port
  • Private instrumentsSauron, ULTRACAM, PNS, SCAM

10
INT instrumentation
  • INT 2.5m
  • Wide Field Prime Focus Camera
  • (4 EEV 2048x4100 CCDs)
  • IDS Cassegrain Intermediate Dispersion
    Spectrograph

11
UKIRT
  • The UK InfraRed Telescope (UKIRT) on the summit
    of Mauna Kea, Hawaii, is a 3.8 m diameter
    near-IR optimised telescope.
  • It supports a range of instruments providing
    spectrometric, photometric and imaging
    capabilities.
  • UKIRT is owned and operated by STFC through the
    Joint Astronomy Centre, Hawaii.

12
UKIRT Instrumentation
  • WFCAM Wide field 0.8-2.5 micron camera covering
    a 0.75 square degree tile in 4 pointings.
  • 4 x 2048x2048 HgCdTe Hawaii-II arrays

13
Telescope Parameters
  • D diameter of entrance pupil
  • determines light collecting power
  • also limits angular resolution to 1.2?/D
    (radians)
  • 1 arcsecond 1 1/206265 radians
  • For a 4.2m telescope at 500nm, resolution should
    be 0.03
  • in practice angular resolution on a good
    ground-based site is seldom better than 0.5 -
    mostly due to atmospheric turbulence.

14
Diffraction-limited imaging(only in space or
with Adaptive Optics)
J1(2m)/m J1(2m)2/m2
Intensity
m1.916,?1.22?/D
15
Telescope Parameters
  • f focal length
  • angular separation of 2 objects ? (radians)
    d/f
  • image scale, S (in mm/arcsec) f(mm)/206265
  • if f 10m, S 48?m/arcsec, typical for prime
    focus of modern 4m-class telescope.

16
Telescope Parameters
  • F-number or speed
  • F-Numberspeedfocal ratiof/D
  • Most telescopes have several foci with different
    focal ratios and re-imaging optics frequently
    change it within instruments
  • Field of view
  • angular area of sky which can be usefully imaged
    without excessive vignetting.

17
Telescope Types optical categories
  • Refractors use lens as main optical element
  • e.g., Yerkes 40inch, focal length 19.4m
  • larger lenses not practical
  • lenses sag under their own weight
  • difficult to keep refractive index constant over
    large piece of glass
  • Reflectors use a primary mirror
  • single mirrors up to 8m diameter have been built
    (e.g., Gemini)
  • segmented mirrors up to 10m (e.g., Keck)
  • modern primary mirrors can be fast ( f/3)
  • to reduce size of support structure and dome

18
Telescope mounts Equatorial
  • RA Right Ascension, Dec Declination
  • Advantages
  • Only RA must be driven at a constant rate to
    track
  • Star field does not rotate with time
  • Disadvantages
  • large, bulky, expensive

INT,La Palma
19
Telescope mountsAlt-azimuth
  • AltAltitude, AzAzimuth
  • Disadvantages field rotation, 3 axes require
    computer control, zenith blind spot.
  • Advantagessmaller, cheaper

WHT,La Palma
20
Telescope Constructionthe Serrurier truss
  • Preferred design for telescope tubes
  • Gravitational flexure of mirror cell and top-end
    end ring are parallel and equal for all
    orientations.
  • therefore optical alignment is maintained

WHT,La Palma
21
Telescope Foci Prime Focus
AutoFib-2 Prime Focus Fibre Robot. Built
Durham AIG WHT,La Palma
  • Focus formed by primary mirror alone
  • Used for direct imaging and wide-field
    multi-object spectroscopy
  • angular field of view can be up to 2 degrees
    diameter
  • Image is only aberration-free for a parabola and
    only on-axis
  • need a prime focus corrector to get a usable
    large field

22
Telescope Foci Cassegrain Focus
  • Classical Cassegrain
  • paraboloidal primary and convex hyperboloidal
    secondary. WHT f/11
  • mainly used for spectroscopy and polarimetry
  • modest field of view (10-20 arcminutes)

23
Telescope foci Coudé focus
  • A stationary focus for equatorial telescopes
  • Used for very high resolution (Echelle)
    spectrographs bulky, heavy instruments
  • The beam must be folded through the declination
    and RA axes.
  • This needs several flat mirrors and a very slow
    beam ( f/50).
  • Field of view 1-2

24
Telescope foci Nasmyth focus
  • Gravity-stable focus on an alt-azimuth telescope
  • rotates with azimuth
  • a flat tertiary mirror folds light away from
    Cassegrain and through the altitude axis.
  • used for heavy spectrographs
  • also used for sensitive instruments
  • adaptive optics

WHT f/11 Cass/Nasmyth
Tertiary flat
Nasmyth platform
Nasmyth platform
25
Ritchey-Chrétien Telescopes
  • Both primary and secondary mirrors are
    hyperboloids
  • corrects spherical aberration and coma
  • introduces large field curvature
  • more easily corrected so fields are in fact large

Gemini-North, May 27, 1998
26
Schmidt Telescopes
  • Spherical mirror with aspheric corrector
  • excellent field of view (gt 6 degrees)
  • survey work
  • curved focal plane
  • UK Schmidt 1.2m aperture.

27
Current/new generation of large telescopes
  • 3 primary mirror technologies
  • segmented
  • lightweighted borosilicate honeycomb
  • meniscus with active support
  • Keck 2 telescopes, 10m segmented primary
  • one working
  • ESO VLT 4x 8m meniscus primaries
  • LBT 2x 8.4m honeycomb primaries in binocular
    configuration with with 14.4m centre-centre
    spacing
  • MMT 6.5m honeycomb primary
  • Magellan 2x 6.5m honeycomb primary
  • Hobby-Eberly 11m spherical segmented
  • Subaru 8.3m meniscus
  • Gemini 2x 8.1m meniscus (Hawaii and Chile)

28
Gemini
  • 2x8m
  • US176M, funded by Argentina/Australia/Brazil/Ca
    nada/Chile/UK/USA
  • Scientific requirements
  • image quality lt0.1 arcsec
  • Emissivity lt4 (2 goal)
  • 8.1m ULE meniscus primary
  • lightweight secondary with fast tip-tilt
  • f/16 Cassegrain focus
  • Active mirror support actuators
  • 120 axial, 72 lateral
  • Raised Alt-Az mount
  • thermal control
  • mirror 0.2,-0.6 ambient

Gemini-NorthMauna Kea, Hawaii 1999
Gemini-SouthCerro-Pachon, Chile 2000
29
Gemini Instrumentation
  • Gemini South
  • T-ReCS (mid-IR imager/spectrograph)
  • GMOS (optical multi-object spectrometer and
    imager)
  • Phoenix (near-IR spectrograph)
  • NICI near-IR coronograph
  • Flamingos 2 near IR MOS
  • GSAO-I near IR imager
  • MCAO/Canopus !!!
  • GPI (Gemini Planet Imager)
  • Gemini North
  • NIRI (near-IR imager)
  • Michelle (mid-IR imager/spectrometer)
  • GMOS (optical multi-object spectrograph and
    imager)
  • NIFS (near-IR IFU, destroyed by bush fire
    18/01/03) rebuilt!)
  • Altair/LGS laser guide star
  • GNIRS near-IR spectrograph
  • Partially destroyed by overheating 2007 under
    rebuild!

- Adaptive Optics (AO) instrumentation
30
ESO VLT
  • The Paranal Observatory comprises four 8 meter
    Unit Telescopes, working separately
  • or at a combined interferometric focus with
    three 1.8m. diameter "outriggers" for improved
    interferometry.
  • Also a 2.5 meter diameter telescope, the VST,
    will provide the OmegaCAM wide-field optical
    imaging capability.
  • Also the UK 4 m diameter VISTA telescope will
    bring a very large IR-Optical wide-field
    facility.

31
ESO VLT
32
VLT instrumentation
33
VLT instruments
  • CRIRES cryogenic high-resolution IR spectrograph
  • Resolution gt 100,000
  • 1 5 microns
  • 0.2 arcsec slit
  • Adaptive optics

34
VLT instruments
  • ISAAC IR spectrometer/ camera.
  • 1-2.5 µm imaging over a 2.5 arcmin x 2.5 arcmin
    field.
  • 1-2.5 µm imaging polarimetry over 2.5 x 2.5
    arcmin
  • 1-2.5 µm long slit low (Rs 500) and medium
    resolution (Rs 3000) spectroscopy
  • 2.5-5 µm imaging over a 1.25 x 1.25 arcmin field.
  • 2.5-5 µm long slit low (Rs 500) and medium
    resolution (Rs 3000) spectroscopy

35
VLT Instruments
  • FLAMES Fibre Large Array Multi Element
    Spectrograph
  • 130 objects with sky on Giraffe Optical
    Spectrograph
  • 8 object feed to UVES
  • IFU

36
VLT instrumentation
  • FORS FOcal Reducer/low dispersion Spectrograph
  • FORS1 imaging and long-slit / multi-object
    spectroscopy and spectopolarimetry
  • FORS2 as above plus Echelle and high
    time-resolution modes

37
VLT instrumentation
  • VISIR mid infrared imager spectrograph
  • diffraction limited imaging with variable
    magnification utilizing broad and narrow-band
    filters up to a maximum field of 80x80 arcsec ²
    between 8 - 13 µm and 16.5 - 24.0µm
  • long-slit spectroscopy between 7.9 - 14 µm with R
    250 and R gt 30,000

38
VLT Instrumentation
  • VIMOS VIsible MultiObject Spectrograph
  • Field of view 4 x 7' x 8' with 0.205"/pixel
    sampling
  • Wavelength range 0.37 - 1.0 µm
  • Spectral resolution for 1 arcsec slit 200
    (LR), 600 (MR), and 2000 (HR)
  • 150 slits _at_ R 2000, 750 slits _at_ R 200
  • Integral field Unit providing up to 54" x 54"
    field of view

39
VLT instrumentation
  • SINFONI - SINgle Far Object Near-ir Investigation
  • integral field spectroscopy with 32 x 32 spatial
    pixels
  • multiplied by 1024 spectral pixels
  • spatial sampling variable from 0.25 arcsec to
    0.025 arcsec.
  • 1.0 - 2.5 µm range
  • spectral resolution from 1000 to 4,500
  • Adaptive Optics sodium laser guide star

40
VLT instrumentation
  • UVES UV-Visual Echelle Spectrograph
  • two-arm cross-dispersed echelle spectrograph
    covering the wavelength range 300 - 500 nm (blue)
    and 420 - 1100 nm (red)
  • with the possibility to use dichroics.
  • The spectral resolution for a 1 arcsec slit is
    about 40,000.
  • The maximum resolution that can be attained with
    still adequate sampling, using a narrow slit, is
    about 110,000 in the red and 80,000 in the blue.

41
VLT instrumentation
  • CONICA Near-Infrared Camera
  • 1-2.5 µm
  • image scales13.25, 27.0, 54.3 mas/pixel
  • NAOS Nasmyth Adaptive Optics System
  • Near-IR AO system with visible or near-IR Natural
    Guide Stars

42
VISTA
  • NEW Visible Infrared Survey Telescope for
    Astronomy
  • 75 of time on long-term targeted surveys
  • 4m telescope
  • IR camera 1 square degree field of view,
  • zJHK, 0.34 arcsec pixels
  • Paranal (VLT site)
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