The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a tabletop workbench to study aspects of wavefront sensing and control for a segmented space telescope, including both commissioning and maintenance activities. JOST is complementary to existing optomechanical testbeds for JWST (e.g. the Ball Aerospace Testbed Telescope, TBT) given its compact scale and flexibility, ease of use, and colocation at the JWST Science & Operations Center. We have developed an optical design that reproduces the physics of JWST's three-mirror anastigmat using three aspheric lenses; it provides similar image quality as JWST (80% Strehl ratio) over a field equivalent to a NIRCam module, but at HeNe wavelength. A segmented deformable mirror stands in for the segmented primary mirror and allows control of the 18 segments in piston, tip, and tilt, while the secondary can be controlled in tip, tilt and x, y, z position. This will be sufficient to model many commissioning activities, to investigate field dependence and multiple field point sensing & control, to evaluate alternate sensing algorithms, and develop contingency plans. Testbed data will also be usable for cross-checking of the WFS&C Software Subsystem, and for staff training and development during JWST's five- to ten-year mission.
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8- to 16-m ultraviolet optical near infrared space observatory for launch in the 2025 to 2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including: Is there life elsewhere in the Galaxy? We present a range of science drivers and the resulting performance requirements for ATLAST (8- to 16-marcsec angular resolution, diffraction limited imaging at 0.5-μm wavelength, minimum collecting area of 45 m2, high sensitivity to light wavelengths from 0.1 to 2.4 μm, high stability in wavefront sensing and control). We also discuss the priorities for technology development needed to enable the construction of ATLAST for a cost that is comparable to that of current generation observatory-class space missions.
A starshade with the James Webb Space Telescope (JWST) is the only possible path forward in the next
decade to obtain images and spectra of a planet similar to the Earth, to study its habitability, and search for
signs of alien life. While JWST was not specifically designed to observe using a starshade, its near-infrared
instrumentation is in principle capable of doing so and could achieve major results in the study of terrestrialmass
exoplanets. However, because of technical reasons associated with broadband starlight suppression and
filter red-leak, NIRSpec would need a slight modification to one of its target acquisition filters to enable feasible
observations of Earth-like planets. This upgrade would 1) retire the high risk associated with the effects of the
current filter red leak which are difficult to model given the current state of knowledge on instrument stray light
and line spread function at large separation angles, 2) enable access to the oxygen band at 0.76 μm in addition
to the 1.26 μm band, 3) enable a smaller starshade by relaxing requirements on bandwidth and suppression 4)
reduce detector saturation and associated long recovery times. The new filter would not affect neither NIRSpecs
scientific performance nor its operations, but it would dramatically reduce the risk of adding a starshade to JWST
in the future and enhance the performance of any starshade that is built. In combination with a starshade, JWST
could be the most capable and cost effective of all the exoplanet hunting missions proposed for the next decade,
including purpose built observatories for medium-size missions.
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR
space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at
the forefront of modern astronphysics, including "Is there life elsewhere in the Galaxy?" We present a range of science
drivers that define the main performance requirements for ATLAST (8 to 16 milliarcsec angular resolution, diffraction
limited imaging at 0.5 μm wavelength, minimum collecting area of 45 square meters, high sensitivity to light
wavelengths from 0.1 μm to 2.4 μm, high stability in wavefront sensing and control). We will also discuss the synergy
between ATLAST and other anticipated future facilities (e.g., TMT, EELT, ALMA) and the priorities for technology
development that will enable the construction for a cost that is comparable to current generation observatory-class space
The scientific capabilities of the James Webb Space Telescope (JWST) fall into four themes. The End of the Dark Ages:
First Light and Reionization theme seeks to identify the first luminous sources to form and to determine the ionization
history of the universe. The Assembly of Galaxies theme seeks to determine how galaxies and the dark matter, gas,
stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the
present. The Birth of Stars and Protoplanetary Systems theme seeks to unravel the birth and early evolution of stars,
from infall onto dust-enshrouded protostars, to the genesis of planetary systems. Planetary Systems and the Origins of
Life theme seeks to determine the physical and chemical properties of planetary systems around nearby stars and of our
own, and investigate the potential for life in those systems. To enable these for science themes, JWST will be a large
(6.5m) cold (50K) telescope with four instruments, capable of imaging and spectroscopy from 0.6 to 29 microns wavelength.
The scientific requirements of the James Webb Space Telescope fall into four themes. The End of the Dark Ages: First Light and Reionization seeks to identify the first luminous sources to form and to determine the ionization history of the Universe. The Assembly of Galaxies seeks to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present. The Birth of Stars and Protoplanetary Systems seeks to unravel the birth and early evolution of stars, from infall onto dust-enshrouded protostars, to the genesis of planetary systems. Planetary Systems and the Origins of Life seeks to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for life in those systems. These themes will guide the design and construction of the observatory.
"The Future of ELTs" is an intriguing as well as daunting title. But this is not about telescopes. After all, what could top visions of telescopes ranging from a "mere" 20 meters, to 100 meters, to plastic 30-meter telescopes in space, to new telescopes for the Moon and even a "hyper-telescope" designed to fill the volcanic crater on La Palma? Instead, this is about an equally interesting subject: Advanced Telescope Builders of the Early 21st Century, which reflects on the gathering of unique individuals that Arne Ardeberg and the University of Lund have so graciously brought together at this workshop.
Building instruments suitable for the new 8-10 m class of telescopes has been a major challenge, as specifications tighten, costs, scientific demands, and expectations grow, all while schedules remain demanding. This report provides a top level description of the status of various elements in the Gemini instrument program, and touches on some of the common problems the various teams building Gemini instruments are having. Despite these challenges, Gemini anticipates harvesting great scientific rewards from the combination of its Observatory facilities and exciting complement of scientific instruments.
The paper briefly reviews the scientific rational and scientific systems approach used by the Gemini 8M Telescopes Project in the design, construction and operations of the Gemini telescopes. We report on the progress of the telescopes on both Mauna Kea, Hawaii and Cerro Pachon Chile, give an updated schedule and describe some of the science operations concepts and planning that is going into the Gemini Observatory. In addition, at the end of this paper we give a full bibliography of Gemini papers presented at the numerous sessions of the 1998 SPIE meeting in Kona.
The following capabilities have been identified as high priority for future Gemini instrumentation. (1) A natural guide star/laser beacon adaptive optics (AO) system at Cerro Pachon, and laser beacon capability for the Mauna Kea AO system. (2) A near IR coronagraph/imager for Cerro Pachon. (3) 1-2.5 micrometers multi-object spectroscopic capability, including IFU and multi-slit capability for use with AO corrected images, and wide field multi-object capability over at least 5 arcmin field of view. (4) Polarization modulators for optical and IR wavelengths at both Mauna Kea and Cerro Pachon. (5) A high stability lab optical spectrometer for Cerro Pachon, with resolutions around 120K and >= 300K.
We review the Gemini Observatory science operations plan including the proposal submission, allocation and observation planning processes; the telescope operation model; and the scientific staffing plans and user support. Use of the telescope is shown via a sub-stellar companion search program to illustrate the planning tools and level of integration required between the observatory control, telescope control and data handling software systems.
The Gemini 8-M telescopes project is an international partnership of six countries to build and operate two 8-meter telescopes, one on Mauna Kea in Hawaii and one on Cerro Pachon in Chile. The construction phase of the project has demanding scientific requirements, a fixed budget that is tight, and an aggressive schedule. The work is distributed internationally between the Gemini Project Office in Tucson, Arizona, organizations in the partner countries, and industrial contractors. The project organization and management procedures used to cope with this challenging situation are described. Plans are now being formulated for management of Gemini in the operational phase. The organization proposed to operate Gemini in a cost effective manner is also described.
The tremendous growth in the building of large 8 m and 10 m telescopes, which give substantial gains in sensitivity over the current 4 m telescopes, presents a significant challenge to the builder of a future 21st Centrum groundbased telescope. To try and explore the possible scientific motivations that may drive a future groundbased facility, I have chosen a current observational project whose completion is beyond the capabilities of our new generation of telescopes. By examining what is required of a groundbased facility to undertake spectroscopy on the majority of the objects in the Hubble deep field (HDF), it becomes apparent this project will need a very large imaging infrared array (VLIA) or a 50 m telescope. The main conclusion of this comparison is that any groundbased facility capable of undertaking this project is likely to cost at least one billion dollars. The choice between the two differing approaches should therefore be driven by the scientific aspirations of the 21st century community of astronomers. Superficially, the 'scientific edge' probably belongs to the VLIA facility, with its ability to probe structures at infrared wavelengths down to the milli-arcsecond scale. The more profound issue is whether it is time for groundbased astronomers to begin looking to space for the placement of their next 21st Century telescope.
Construction of the Gemini Telescopes is underway. The first mirror blank has been completed, concrete piers on both Mauna Kea and Cerro Pachon have been poured, fabrication of the telescope structures has started and the erection of the first enclosures have begun. In this paper, we give a progress report on the Gemini 8-M Telescopes Project. In addition, we highlight some of the unique scientific characteristics of the Gemini Telescopes including our approach to image quality performance, the use infrared wavefront sensors, the development of silver coatings and our 'adaptable observing' system. The scientific performance of these telescopes will be heavily dependent on atmospheric conditions, Gemini will be allocating at least 50% of its observing time to 'queue scheduled observing.' The implications of adopting this novel observing mode on the design of the control system and on the telescope operations model are briefly discussed.
The Gemini Telescopes are being built to exploit the unique infrared sites of Mauna Kea in Hawaii and Cerro Pachon in Chile. Both telescopes are being designed to deliver 0.1 arcsec images at the focal plane at 2.2 micrometers which will include all tracking and enclosure affects. Beyond 2 micrometers , using fast tip/tilt secondaries these 8 m telescopes will be essentially diffraction limited. In addition the use of protected silver coatings for both the primary and secondary mirrors and efficient in-situ mirror cleaning means the Mauna Kea telescope should be capable of delivering focal plane emissivities of approximately 2%. The baseline design for the Mauna Kea telescope also includes an adaptive optics system capable of feeding a 1 - 2 arcminute corrected field to near infrared instruments mounted at the f/16 Cassegrain focus. Fully exploiting the superb characteristics of the Gemini Telescopes will require a new generation of instruments which will challenge both instrument designers and infrared array technologies. The baseline complement of infrared instruments includes a 1 - 5 micrometers imager, a 1 - 5 micrometers spectrometer, and a mid-infrared (8 - 25 micrometers ) imager. Several optical instruments will also be built under the baseline instrumentation plan.
In this paper we describe the impact that instrument design can have on the overall performance of the Gemini Telescopes. We discuss the interaction between the instruments and some of the other telescope facilities such as A&G and Adaptive Optics. We also briefly describe the instruments that have been proposed for delivery during the construction phase of the project and list some of their features.
We present data on the image quality achieved with the near IR array spectrometer cooled grating spectrometer 4 (CGS4) on the UK IR telescope (UKIRT) on Mauna Kea. A design spot size of 30 micrometers was specified for CGS4, to maintain acceptable image quality with both the 58 by 62 pixel array with which it is currently equipped and the 256 by 256 array which CGS4 was also designed to accommodate. Details are given of the design, construction and alignment method which allow linear tolerances of 50 micrometers and angular tolerances of 25 mrad to be met and maintained at cryogenic temperatures. The instrumental flexure is also discussed. Both laboratory spectra and those taken at the telescope illustrate that design spot sizes of 30 micrometers have been achieved in the near IR. It will be demonstrated that the theoretical resolution of the instrument is attained for resolving powers from approximately 200 to 20,000.
The Gemini Project is an international partnership of Canada, the U.K., the U.S., Chile, Argentina, and Brazil, to build two 8-meter telescopes, one on Mauna Kea, Hawaii, and one on Cerro Pachon, Chile. The telescopes are to achieve an unprecedented combination of light-gathering power and image quality over the infrared, optical, and ultraviolet spectral regions observable from the ground. The key scientific requirement for the telescopes is that images at 2.2 microns delivered to the focal plane are not degraded more than 0.1 arcseconds over an hour's integration. In addition, these telescopes, in particular the Mauna Kea telescope, should be capable of reaching infrared emissivities of between 2 - 4% in operation. These requirements present special challenges for large telescope builders. To address these challenges, the Gemini project regards the entire observatory as a system. All aspects which may limit performance are tracked through the use of a systems error budget that includes the enclosure, telescope structure, both mirrors, control system and the instrumentation. This paper will highlight the meniscus mirror support system, the control philosophy to reduced wind buffeting and strategies to reduce thermal effects such as mirror and dome seeing.
This paper summarizes adaptive optics performance estimates obtained for the Gemini 8-m telescopes, with an emphasis on relatively low order systems employing Shack-Hartmann wavefront sensors, continuous facesheet deformable mirrors with zonal actuators, and either a natural guide star or a laser guide star in the mesospheric sodium layer. Adaptive optics performance is characterized in terms of the fractional encircled energy within a 0.1 arc sec detector at 2.2 microns under average seeing conditions at Mauna Kea. The increased sky coverage achieved using laser guide stars according to this definition of performance is significant, even for a relatively low order adaptive optics system designed for turbulence compensation at 2.2 microns at a good astronomical site.
First light with the advanced cooled grating spectrometer (CGS4) was achieved at the United Kingdom Infrared Telescope on February 4, 1991 following successful delivery of the instrument from the Royal Observatory, Edinburgh. We discuss the performance of CGS4 and summarize our experience in maintaining optimum array sensitivity. CGS4 is unique in that both the data acquisition and reduction can be almost completely automated, and the key elements of the software and their impact on observing are described. We discuss how various aspects of CGS4 such as the reproducibility of flat fields relate to the ability to provide users with flat-fielded, sky-subtracted spectra almost in real-time. We also discuss the problems of the variability of OH line emission and atmospheric transmission and describe the sky subtraction techniques which we have been using both at the telescope and in post observing analysis.
The optical and the cryogenic designs for IR imagers and spectrographs of the 8-m UK Large Telescope (UKLT) are described. Performance figures for astronomical observations are presented showing that the basic designs can be matched to the range of optical configurations of 3.5 to 10 m telescopes. A diagram of the cryogenic spectrometer for the UKLT showing the layout of optical elements is presented together with schematics of the f/7 imager.
The main features of the Cooled Grating Spectrometer (CGS4), for the United Kingdom Infrared Telescope (UKIRT), are described. The CGS4 for use at 1 to 5 microns is designed to fully utilize foreseeable arrays and to take maximum advantage of the solid imaging detectors. The spectrometer can use low dispersion first order grating in a back-to-back configuration with a high dispersion echelle, giving wavelength resolutions from approximately 1,000 to 24,000.
This paper describes an implementation of a recently developed charge amplifier, called Integration Amplifier, in the UKIRT 7 channel spectrometer (CGS2), resulting in the conversion of the CGS2 from the traditional transimpedance amplifier to a commercial charge integration scheme. Also described is a new data acquisition system; the news system allowed the implementation of a noise reduction algorithm which is a mojor factor in the improved sensitivity of CGS2. The noise reduction algorithm is presented together with a system diagram of CGS2.