KMOS is a multi-object near-infrared integral field spectrograph built by a consortium of UK and German institutes for
the ESO Paranal Observatory. We report on the on-sky performance verification of KMOS measured during three
commissioning runs on the ESO VLT in 2012/13 and some of the early science results.
KMOS is a multi-object near-infrared integral field spectrograph being built by a consortium of UK and German
institutes. We report on the final integration and test phases of KMOS, and its performance verification, prior to
commissioning on the ESO VLT later this year.
The pick-off arm is the part of the KMOS instrument which re-images a sub-field of the VLT focal plane to a position
outside of the main field where it can be used for integral field spectroscopy. In this paper we describe the optical
alignment and test procedure developed to meet the challenging alignment requirements of the instrument. It is important
to note that although the alignment is done at ambient temperature, the alignment of the optical components must be
maintained at the instruments cryogenic operational temperature. This paper describes the methods used to achieve the
absolute positioning accuracy and the test results obtained and discussed some of the practical difficulties that were
METIS: "Mid-infrared ELT Imager and Spectrograph" is the mid-infrared (3 - 14 microns) instrument for imaging and
spectroscopy for the European Extremely Large Telescope (E-ELT). To ensure high detection sensitivity the internal
radiation of the instrument needs to be eliminated (sufficiently reduced) and thus needs to be operated at cryogenic
The instrument is divided in a cold and warm system. The cold system, the actual heart of the system, is subdivided into
five main opto-mechanical modules located within a common cryostat (part of the warm system). The warm system
provides the crucial environment for the cold system, including the instrument control and maintenance equipment. The
end 2009 finished Phase-A study carried out within the framework of the ESO sponsored E-ELT instrumentation studies
has been performed by an international consortium with institutes from Netherlands (PI: Bernhard Brandl - NOVA),
Germany, France, United Kingdom and Belgium. During this conference various aspects of the METIS instrument
(design) are presented in several papers, including the instrument concept and science case, and the system engineering
and optical design.
This paper describes the design constraints and key issues regarding the packaging of this complex cryogenic instrument.
The design solutions to create a light, small and fully accessible instrument are discussed together with the specific
subdivision of the cold and warm system to ensure concurrent development at various different institutes around Europe.
In addition the paper addresses the design and development studies for the special, challenging units such as the large
optical image de-rotator, the (2D) chopper mechanism and the special cryogenic drives.
KMOS is a near-infrared multi-object integral-field spectrometer which is one of a suite of second-generation
instruments under construction for the VLT. The instrument is being built by a consortium of UK and German
institutes working in partnership with ESO and is now in the manufacture, integration and test phase. In this paper
we present an overview of recent progress with the design and build of KMOS and present the first results from the
subsystem test and integration.
This paper describes the mechanical design of the KMOS pick-off arms and the way in which the design is driven by
combinations of requirements. The use of a recirculating linear bearing in a cryogenic environment is novel and the
qualification of this component is described. Novel use is made of a single leadscrew with two leads to move optical
components at different speeds to maintain the optical path length. Cryogenic flexure, repeatability and torque tests are
KMOS is a near-infrared multi-object integral field spectrometer which has been selected as one of a suite of second-generation instruments to be constructed for the ESO VLT in Chile. The instrument will be built by a consortium of UK and German institutes working in partnership with ESO and is currently at the end of its preliminary design phase. We present the design status of KMOS and discuss the most novel technical aspects and the compliance with the technical specification.
Nowadays LZOS is carrying out work on the manufacturing of the M1 Mirror and M2 Mirror for the VISTA project (Visible and Infrared Survey Telescope for Astronomy) with the 4100mm diameter primary hyperbolic mirror with asphericity about 800 microns and the 1241mm diameter secondary hyperbolic mirror with asphericity about 350 microns. The current status of the work carried out is presented in the manuscript.
Nowadays LZOS is carrying out work on the manufacturing of the M1 Mirror and M2 Mirror for the VISTA project (Visible and Infrared Survey Telescope for Astronomy) with the 4100 mm diameter primary hyperbolic mirror with asphericity about 800 μmi and the 1241 mm diameter secondary hyperbolic mirror with asphericity about 350 μm. The current status of the work carried out is presented in the manuscript.
The requirements for position, orientation and performance of the primary mirror active support system have been optimised through extensive FEA to minimise the wavefront slope error. The output of this optimisation has been a detailed performance specification which also takes into account telescope control and wind rejection requirements. The FE model has also been used to calculate the active force eigenmodes based on the static actuator patterns rather than approximations to the vibration modes. In addition significant development and prototyping has been undertaken in the actuator and definer design including control. Interesting aspects of this development include use of flexures in the mirror definers in order to meet the stiffness requirements and control of a pneumatic astatic system. This paper describes the process of requirement optimisation for mirror performance and also the development and design of the support system.
A 350GHz 4 × 4 element heterodyne focal plane array using SIS detectors is presently being constructed for the JCMT. The construction is being carried out by a collaborative group led by the MRAO, part of the Astrophysics Group, Cavendish Laboratory, in conjunction with the UK-Astronomy Technology Centre (UK-ATC), The Herzberg Institute of Astrophysics (HIA) and the Joint Astronomy Center (JAC). The Delft Institute of Microelectronics & Sub-micron Technology (DIMES) is fabricating junctions for the SIS mixers that have been designed at MRAO.
Working in conjunction with the 'ACSIS' correlator & imaging system, HARP-B will provide 3-dimensional imaging capability with high sensitivity at 325 to 375GHz. This will be the first sub-mm spectral imaging system on JCMT - complementing the continuum imaging capability of SCUBA - and affording significantly improved productivity in terms of speed of mapping. The core specification for the array is that the combination of the receiver noise temperature and beam efficiency, weighted optimally across the array will be <330K SSB for the central 20GHz of the tuning range.
In technological terms, HARP-B synthesizes a number of interesting and innovative features across all elements of the design. This paper presents both a technical and organizational overview of the HARP-B project and gives a description of all of the key design features of the instrument. 'First light' on the instrument is currently anticipated in spring 2004.
Systems Engineering has been used throughout the development of the Visible and Infrared Survey Telescope for Astronomy (VISTA). VISTA was originally conceived as being a classic 4m telescope with wide-field imaging capability. The UK Astronomy Technology Centre (UK ATC) radically changed this thinking by treating the whole design as one system, integrating the camera optics into the telescope design.
To maximise the performance, an f/1 primary mirror was adopted resulting in a very compact telescope and enclosure. Amongst other benefits, this reduced the overall mass of the telescope from 250 to 90 tonnes. During this optimisation process, the concept of a direct imaging K-short camera was developed. This development, in conjunction with an increase in IR field of view, produced a system with uniform image quality and throughput across a 350 mm diameter focal plane, 1.65 degree field.
While this has presented some major engineering challenges, the approach has produced a system which is both scientifically rewarding and achievable. The optimisation, design trade-offs and Technical Specification developed in the conceptual design phase were achieved through a systems analysis approach.
This paper describes some of the key systems engineering decisions and the tools employed to achieve them. Current systems engineering activities are described and future plans outlined.
The design of VISTA (Visible and Infrared Survey Telescope for Astronomy) requires close interaction between the science requirements, the optical and active mechanical design of the telescope and its instrumentation with the wavefront sensing. The optical design is based on an integrated approach of the telescope with tow separate cameras, one working in the IR waveband and the other working in the Visible waveband. The large field of view (2 degrees in the visible and 1.65 degrees in the IR), the seeing-limited resolution required (FWHM of 0.4 arcsec for the visible and 0.5 arcsec for the IR), the technological advance in active telescopes and large IR arrays and the f/1 quasi Ritchey-Chretien telescope design, makes this telescope a very powerful tool in performing high resolution and large astronomical surveys. A system analysis, modeling the various sources of errors such as optical aberrations, surface errors, control errors, environmental effects and detector effects is presented in this paper.
This paper describes an ambitious new wide field IR camera for the 3.8m UK IR Telescope (UKIRT), located on Mauna Kea, Hawaii. The camera, currently under design at the UK Astronomy Technology Center, will include 4 2048 by 2048 pixel focal plane array IR detectors operating over a wavelength range of 1-2.5 micrometers . The optics provide a 1 degree diameter corrected field of view and a pixel scale of 0.4 arcsec per pixel. A novel Schmnidt type optical design allows the large field to be imaged with excellent image quality. The optical design includes a cold stop to maximize rejection of background radiation and stray light. Precise microstepping will be used to improve sampling. Four parallel data acquisition and processing channels will be used to cope with the large data rates expected. It is envisaged that a substantial fraction of UKIRT time will be devoted to large area sky surveys once WFCAM is operational, resulting in a unique IR catalogue containing hundreds of millions of objects.
The upgraded 3.8 m UK Infrared Telescope is now provided with: (1) tip-tilt image stabilization by a light-weighted secondary mirror on piezo-electric actuators, controlled by a fast guider sampling at >= 40 Hz on guide stars V <EQ 18.<SUP>m</SUP>6; (2) active primary mirror figure and secondary mirror alignment control, via a regularly-maintained look-up table; (3) active focus measurements and correction by the fast guider, supplementing a focus maintenance model which corrects for elastic and thermal changes; (4) ventilation of the 2600 m<SUP>3</SUP> dome by 16 apertures totalling 50 m<SUP>2</SUP>; (5) insulation of the underside of the concrete dome floor; and (6) internal air circulation during the day, to reduce heating of the upper telescope steelwork.
The 3.8 m UK Infrared Telescope has been the focus of a program of upgrades intended to deliver images which are as close as possible to the diffraction limit at (lambda) equals 2.2 micrometers (FWHM equals 0.'12). This program is almost complete and many benefits are being seen. A high-bandwidth tip-tilt secondary mirror driven by a Fast Guider sampling at <EQ 100 Hz effectively eliminates image movement as long as a guide star with R < 16.<SUP>m</SUP>5 is available within +/- 3.'5 of the target. Low-order active control of the primary mirror and precision positioning of the secondary, using simple lookup tables, provide telescope optics which are already almost diffraction limited at (lambda) equals 2 micrometers . To reduce facility seeing the dome has been equipped with sixteen closable apertures to permit natural wind flushing, assisted in low winds by the building ventilation system. The primary mirror will soon be actively cooled and the concrete dome floor may be thermally insulated against daytime heating if fire safety concerns can be resolved. Delivered images in the K band now have FWHM which is usually <EQ 0.'8, frequently <EQ 0.'6 and quite often approximately 0.'3. Examples of the latter are shown: these approximate the resolution achieved by NICMOS on the HST. We estimate that the productivity of the telescope has approximately doubled, while its oversubscription factor has increased to > 4.
The 3.8 m United Kingdom Infrared Telescope (UKIRT) has recently installed active control of the primary mirror figure, taking advantage of aspects of the original mirror design, which permits the correction of low order aberrations. In this paper, we present results from a campaign of all-sky wavefront sensing carried out UKIRT. As a result of the campaign, a lookup table is being used to correct for attitude dependent astigmatism, while fixed corrections are applied to trefoil and spherical aberrations. Coma is removed by secondary mirror alignment. A continuous, model based, correction of focus for thermal and elastic effects is also applied. Accurate focus is now maintained throughout an observing night.
An imaging spectrometer is being designed to take advantage of recent improvements in the image quality achieved at the UK Infrared Telescope. The realization of near-diffraction limited imaging at two microns brings with it the possibility of significant improvements in sensitivity to IR observations. UIST will provide a versatile facility for high spatial resolution imaging and spectroscopy in the 1-5 micrometers wavelength range. We will present the opto-mechanical design of this new instrument, highlighting the innovative features. These include provision of multiple pixel scales within the camera and polarimetry via a Wollaston prism. One of the most challenging areas of the design is the inclusion of a cryogenic integral field unit for area spectroscopy over a 5 inch field. The spectroscopic modes include cross- dispersed spectroscopy over the complete 1-2.5 micrometers wavelength ranges and moderate resolution long slit or area spectroscopy over the complete 1-5 micrometers range. A higher resolution mode will also the included. This will allow USTI to take advantage of the very low backgrounds to be found between OH sky lines. The instruments will incorporate a 1024 X 1024 Indium Antimonide array from SBRC. The development of the IR array controller for UIST will also be discussed.
As the only two optical instruments appearing in its first fleet of instrumentation, the GEMINI MultiObject Spectrograph (GMOS) are indeed being developed as workhorse instruments. One GMOS will be located at each of the GEMINI telescopes to perform: (1) exquisite direct imaging, (2) 5.5 arcminute longslit spectroscopy, (3) up to 600 object multislit spectroscopy, and (4) about 2000 element integral field spectroscopy. The GMOSs are the only GEMINI instrumentation duplicated at both telescopes. The UK and Canadian GMOS team successfully completed their critical design review in February 1997. They are now well into the fabrication phase, and will soon approach integration of the first instrument. The first GMOS is scheduled to be delivered to Mauna Kea in the fall of '99 and the second to Cerro Pachon one year later. In this paper, we will look at how a few of the more interesting details of the final GMOS design help meet its demanding scientific requirements. These include its transmissive optical design and mask handling mechanisms. We will also discuss our plans for the mask handling process in GEMINI's queue scheduled environment, from the taking of direct images through to the use of masks on the telescope. Finally, we present the status of fabrication and integration work to date.
Each of the two Gemini telescopes will be instrumented with the Gemini Multi-Object Spectrograph (GMOS), a general purpose optical spectrograph mounted at one of the Cassegrain foci. Two GMOS are currently being designed and built by a team of scientists and engineers in Canada and in the UK. A stringent flexure specification is imposed on these instruments by the scientific requirement to measure velocity to high precision, 2 km/s at R equals 5,000 with 0.5 arcsec slits. This implies a basic stability specification of 3.125 micrometer/hour at the detector focal plane. The GMOS design has met this specification by using a combination of stiff structure (where flexure is minimized); Serrurier trusses (where the flexure is controlled); precision mechanisms (where mechanical hysteresis and error are minimized) and, finally, an open-loop active correction system at the detector focal plane (where the CCD is translated to counteract any residual flexure). Once the GMOS design was conceptualized and its component groups were identified, the design team divided the basic stability specification into allowable contribution from each group. The final division was weighted according to the degree of design difficulty, based on inputs from the engineers. An error budget was developed and maintained to ensure that GMOS would meet its overall flexure specification by controlling the contribution from each component. The error budget approach will be described and discussed in the paper. We will also look at examples from the GMOS design with reference to calculations, analyses, FEA and actual measurements from prototype components.
Reliable calibration of astronomical data from large telescopes is an essential factor in obtaining high sensitivity observations for both the astronomer at the telescope and the archive researcher. A dedicated calibration unit provides an efficient and predictable method of observing calibration frames. Such a facility is being designed for the Gemini telescopes. It is required to calibrate instruments with wavelengths from the UV to the infrared, covering a broad range of both spectral and spatial resolution. We present the design of this calibration unit and the predicted performance with the 'first-light' Gemini instruments.
The 3.8 m UK infrared telescope (UKIRT) is currently the focus of an upgrades program to improve its imaging performance, ideally to approach its diffraction limit in the near-IR at 2.2 micrometer, with FWHM approximately 0.'12. This program is now in its late stages. All the new systems have been designed, most have been manufacture and many have been installed. A new top end carries an adaptive tip-tilt secondary mirror with active precision alignment, which, with low-order active control of the primary mirror, should provide the desired intrinsic optical performance. The adaptive tip- tilt system will correct image motion from telescope vibrations and drive errors and from atmospheric wavefront tilt; delivered images are expected regularly to be less than 0.'5 over wide fields, and within a factor 2 or so of the diffraction limit, at least inside an isoplanatic patch of order an arcmin radius. To reduce facility seeing the primary mirror has been equipped with a ventilation system and will receive a 5 kW cooling system; the dome is being equipped with sixteen closable apertures to permit natural wind flushing, which can be assisted by the building air handling system in low winds. It is hoped that facility seeing -- excluding boundary layer effects -- will be imperceptible during approximately 85% of observable time. The upgraded UKIRT should be well capable of exploiting fully the very best conditions on Mauna Kea.
In the 1970s the pioneering thin-mirror 3.8 m United Kingdom Infrared Telescope (UKIRT) of the UK Science and Engineering Research Council (SERC) was conceived as a low-cost `light bucket', with an 80% encircled-energy diameter <EQ 3'. However the delivered primary mirror had an 80 encircled- energy diameter of approximately 1' and the telescope has regularly delivered sub-arc-second images. To exploit this quality and to keep UKIRT competitive in a 21st century of 8-meter telescopes, in 1991 the SERC initiated an ambitious Upgrades Program, with the goal of routinely providing near- diffraction limited images at 2.2 microns. The major elements of the program are an adaptive tip-tilt secondary system, an active five-axis secondary collimation system, an upgraded primary mirror support system providing active control of the main optical aberrations, and modifications to the telescope and its enclosure to reduce or eliminate dome and mirror seeing, so as to take advantage of the excellent natural seeing on Mauna Kea. This paper outlines the overall project goals, the proposed strategies for upgrading the telescope and the progress to date.