New Astronomy Reviews 45 (2001) 41–43www.elsevier.nl / locate /newar

Instrumentation plans for the Anglo–Australian Observatorya , a b c*Jeremy Bailey , Keith Taylor , Gordon Robertson , Sam Barden

aAnglo Australian Observatory, P.O. Box 296, Epping, NSW 1710, AustraliabSchool of Physics, University of Sydney, Sydney, NSW 2006, Australia

cNational Optical Astronomy Observatories, 950 North Cherry Avenue, P.O. Box 26732, Tucson, AZ 85726, USA

Abstract

Plans for future instrumentation for the Anglo–Australian Telescope are described. Current projects for the AAT includethe IRIS-2 infrared camera and spectrometer, and a new controller system to be used with the IR detector and CCDs. The sixdegree field (6dF) fibre spectroscopy system is being developed for the Schmidt telescope, following on from the successfuldevelopment of 2dF for the AAT. A design study is now underway for a new advanced spectrograph (ATLAS) based on theuse of volume phase holographic (VPH) gratings. 2001 Elsevier Science B.V. All rights reserved.

Keywords: AAO; Telescopes; Instrumentation

1. Introduction our successful development of 2dF has led to AAOgetting the contract to develop a fibre positioner for

The main instrument projects for the AAO are the ESO/VLT.summarized in Table 1. It can be seen that theemphasis is on wide field instruments appropriate forsurvey-type observing. This is an appropriate role for 2. Fibre spectroscopythe AAT in the era of 8–10-m class telescopes.However, the AAO also aims in its instrumentation The two degree field (2dF) project has been theprogram to develop innovative ideas that may sub- main instrument project at the AAO until recently.sequently be used for larger telescopes. For example, 2dF is a multi-fibre spectrograph enabling observa-

tions of 400 objects over a two-degree field on theTable 1 sky. It mounts at the AAT prime focus. The instru-New AAO instrumentation

ment now meets all its major design goals, providingInstrument Field Range (mm) Resolution Date configuration of 400 fibres in under an hour, and2dF 28 0.35–0.9 600–5000 Now achieving a high level of reliability. The 2dF is beingIRIS-2 7.7 min 1–2.4 Broadband 7/00 used for a major galaxy redshift survey that will

1500–3000 eventually cover 250,000 galaxies (Colless,PFU/WFI 33 min 0.35–1.0 Broadband 12/99

1999a,b). By July 1999, redshifts of 49636 galaxies6dF 68 0.35–0.9 500–2000 09/00had been measured.ATLAS 24 min 0.37–1.1 1500–10000 ?

A new fibre spectroscopy system is now beingdeveloped to operate over a six degree field (6dF) onthe Schmidt telescope. 6dF will have 150 fibres*Corresponding author.

E-mail address: jab@aaoepp.aao.gov.au (J. Bailey). positioned by an r,u positioning robot. It will be used

1387-6473/01/$ – see front matter 2001 Elsevier Science B.V. All rights reserved.PI I : S1387-6473( 00 )00125-1

42 J. Bailey et al. / New Astronomy Reviews 45 (2001) 41 –43

for projects such as a redshift survey of galaxies dichromated gelatin mounted on a glass substrate.found by the DENIS and 2MASS infrared surveys. VPH gratings offer very high efficiencies (|90% at

peak compared with |60% for a conventional sur-face grating). Because of the significant thickness of

3. IRIS-2 the grating, the peak efficiency is obtained in direc-tions obeying the Bragg condition (effectively specu-

IRIS-2 is a near infrared imager and spectrograph lar reflection from the refractive index modulations).for the AAT based on a 102431024 Rockwell This has the consequence that the wavelength ofHgCdTe array. The optical system is a fully trans- peak efficiency of a grating can be changed by tiltingmitting collimator /camera which reimages the f /8 the grating, something that is not possible with afocus of the AAT onto the array at f /2.2, giving a surface grating that has a fixed blaze angle. How-7.7-min field with 0.45 arcsec pixels. The instrument ever, to take advantage of this capability, a spec-can also be used with the f /15 or f /36 secondaries to trograph must be designed with the ability to changeachieve smaller pixel sizes. Grisms can be placed in the angle between the collimator and the camera.the collimated beam to obtain spectroscopy with A VPH grating has recently been used successfullyresolution of |2000. A number of upgrade options on the AAT as part of an upgrade to the Loware possible, including a multi-object capability, Dispersion Survey Spectrograph (LDSS). Thepolarimetry, and an upgrade to a 204832048 array. LDSS11 upgrade replaced the standard grism with

In conjunction with the IRIS-2 project, the AAO is a VPH grism, uses an MIT Lincoln Labs deepdeveloping a new array controller which will be used depletion CCD with a very good red response, andinitially with the IR array, but also for CCD systems. introduces an observing mode in which telescopeThe new controller will provide high readout speeds nodding is synchronized with CCD charge shufflingand support for multiple readout devices. The data to provide excellent sky subtraction. These upgradesacquisition software will run on VxWorks and Solaris result in a very efficient red spectrograph which hassystems in the DRAMA environment and will allow been successfully used for projects such as a redshiftthe phasing out of our VAX/ADAM systems. survey in the Hubble deep field south.

The AAO has now begun a detailed design studyfor a new spectrograph based on VPH gratings to

4. Prime focus upgrade/wide field imager replace the existing RGO spectrograph as well asLDSS. The instrument is known as ATLAS (AAO

The upgrade of the prime focus imaging facility at Tunable Littrow Articulated Spectrograph) (Fig. 1).the AAT will provide automated filter changing and The ATLAS concept consists of transmittingshutter at the prime focus and is designed for use collimators and cameras with a 150 mm collimatedwith the wide field imager (WFI) being developed beam size. The instrument will cover a field of 24by the Research School of Astronomy and Astro- arcmin using an f /2.2 camera and a 4 K34 K CCD.physics at ANU. The WFI will use an 8 K38 K The camera is articulated so that it can accommodatemosaic array, using 8 CCDs made by MIT Lincoln collimator-grating-camera angles from 08 (straightLabs. On the AAT, this will give a 33-min field with though position for Taurus mode or direct imaging)0.248 arcsec pixels. The WFI will be shared between up to 908 or more for high dispersion gratings.the AAT and the ANU 1-m telescope on the Siding Resolutions from 1500 to 10,000 can be achievedSpring observatory site. using a 1.5 arcsec slit and possibly as high as 18,000

using an integral field unit. The instrument will be adual beam system using a dichroic to separate blue

5. VPH gratings and ATLAS and red arms, each of which will have its owncollimator /camera system. The wide field combined

Volume Phase Holographic (VPH) gratings (Bar- with high efficiency will allow ATLAS to be usedden et al., 1998) are constructed by introducing effectively as a multi-object spectrograph in a similarmodulations of refractive index into a layer of mode to that used with LDSS11.

J. Bailey et al. / New Astronomy Reviews 45 (2001) 41 –43 43

Fig. 1. Schematic showing the ATLAS design.

Colless, M.M., 1999b. Early Results from the 2dF GalaxyReferencesRedshift Survey. In: Colombi, S., Mellier, Y., Raban, B. (Eds.),Wide Field Surveys in Cosmology — 14th IAP Colloquium.

Barden, S.C., Arns, J.A., Colburn, W.S., 1998. SPIE Proc. 3355, Editions Frontieres, p. 77.866.

Colless, M.M., 1999a. First results from the 2dF Galaxy RedshiftSurvey. PTRSL 357, 105.