Visibility and clarity of remotely sensed images acquired by consumer grade DSLR cameras, mounted on an unmanned aerial vehicle or a manned aircraft, are critical factors in obtaining accurate and detailed information from any area of interest. The presence of substantial haze, fog or gaseous smoke particles; caused, for example, by an active bushfire at the time of data capture, will dramatically reduce image visibility and quality. Although most modern hyperspectral imaging sensors are capable of capturing a large number of narrow range bands of the shortwave and thermal infrared spectral range, which have the potential to penetrate smoke and haze, the resulting images do not contain sufficient spatial detail to enable locating important objects or assist search and rescue or similar applications which require high resolution information. We introduce a new method for penetrating gaseous smoke without compromising spatial resolution using a single modified DSLR camera in conjunction with image processing techniques which effectively improves the visibility of objects in the captured images. This is achieved by modifying a DSLR camera and adding a custom optical filter to enable it to capture wavelengths from 480-1200nm (R, G and Near Infrared) instead of the standard RGB bands (400-700nm). With this modified camera mounted on an aircraft, images were acquired over an area polluted by gaseous smoke from an active bushfire. Processed data using our proposed method shows significant visibility improvements compared with other existing solutions.
We perform correlation analysis between air temperature and surface brightness temperature over the Adelaide Central Business District and the surrounding parklands. The results indicate that three effective surface areas associated with three different mechanisms exist. They are the effective surface area with upward sensible heat transfer to heat up and maintain the air temperature, the effective surface area with downward sensible heat transfer to cool down the air, and the effective surface area related to very localized conditions (e.g., sky-view factors). The three mechanisms occur at different times of the day and result in different air temperature and surface temperature correlations. The first effective surface area exists in the daytime after the surface is heated up by solar radiation and can persist into the night, particularly in urban environments. The second effective area occurs in night-time when the surface has been cooled down sufficiently. The third effective area coexists with the second one and has a weaker correlation between the surface and air temperatures. It was also found that in an urban area, exclusion of roof pixels in the calculation of surface brightness temperature can increase the correlation between the surface and air temperatures in the middle of the night.
We present FLEX, an instrument to demonstrate the power of fibre Bragg grating OH suppression. This ground
breaking technology promises great gains in sensitivity for near infrared instrumentation and the time is now
right for a pioneer instrument to prove the effectiveness of the technique. Our proposal is for an adaptive optics
fed integral field unit for an 8 metre class telescope. We envisage a 61 element IFU with 0.22" sampling and a
2.2" field of view. J and H-band OH suppression units would cleanly suppress the atmospheric emission lines,
effectively lowering the sky background by 3 or 4 magnitudes respectively. The capabilities of FLEX will make
it ideal for deep Epoch of Reionisation studies, as well as studies of star formation at z~1-4. To enable rapid
and economical deployment FLEX would use an existing near infrared spectrograph with R ≈ 1000 and employ
facility adaptive optics.
We highlight the operational challenges and planned solutions faced by an optical observatory taking advantage of the
superior astronomical observing potential of the Antarctic plateau. Unique operational aspects of an Antarctic optical
observatory arise from its remoteness, the polar environment and the unusual observing cycle afforded by long
continuous periods of darkness and daylight. PILOT is planned to be run with remote observing via satellite
communications, and must overcome both limited physical access and data transfer. Commissioning and lifetime
operations must deal with extended logistics chains, continual wintertime darkness, extremely low temperatures and
frost accumulation amidst other challenging issues considered in the PILOT operational plan, and discussed in this presentation.
We present the concept design of a new fibre positioner and spectrograph system for the Anglo-Australian Telescope,
as a proposed enhancement to the Anglo-Australian Observatory's well-known 2dF facility. A four-fold multiplex
enhancement is accomplished by replacing the 400-fibre 2dF fibre positioning robot with a 1600-fibre Echidna unit,
feeding three clones of the AAOmega optical spectrograph. Such a facility has the capability of a redshift 1 survey of a
large fraction of the southern sky, collecting five to ten thousand spectra per night for a million-galaxy survey.
PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed Australian/European optical/infrared
telescope for Dome C on the Antarctic Plateau, with target first light in 2012. The proposed telescope is 2.4m diameter,
with overall focal ratio f/10, and a 1 degree field-of-view. In median seeing conditions, it delivers 0.3" FWHM wide-field
image quality, from 0.7-2.5 microns. In the best quartile of conditions, it delivers diffraction-limited imaging down
to 1 micron, or even less with lucky imaging. The areas where PILOT offers the greatest advantages are (a) very high
resolution optical imaging, (b) high resolution wide-field optical imaging, and (c) all wide-field thermal infrared
imaging. The proposed first generation instrumentation consists of (a) a fast, low-noise camera for diffraction-limited
optical lucky imaging; (b) a gigapixel optical camera for
seeing-limited imaging over a 1 degree field; (c) a 4K x 4K
near-infrared (1-5 micron) camera with both wide-field and diffraction-limited modes; and (d) a double-beamed midinfrared
(7-40 micron) camera.
PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed Australian/European optical/infrared
telescope for Dome C on the Antarctic Plateau, with target first light in 2012. The telescope is 2.4m diameter, with
overall focal ratio f/10, and a 1 degree field-of-view. It is mounted on a 30m tower to get above most of the turbulent
surface layer, and has a tip-tilt secondary for fast guiding. In median seeing conditions, it delivers 0.3" FWHM wide-field
image quality, from 0.7-2.5 microns. In the best quartile of conditions, it delivers diffraction-limited imaging down
to 1 micron, or even less with lucky imaging. The major challenges have been (a) preventing frost-laden external air
reaching the optics, (b) overcoming residual surface layer turbulence, (c) keeping mirror, telescope and dome seeing to
acceptable levels in the presence of large temperature variations with height and time, (d) designing optics that do
justice to the site conditions. The most novel feature of the design is active thermal and humidity control of the
enclosure, to closely match the temperature of external air while preventing its ingress.
FLEX is a concept for a fully OH suppressed near infrared integral field spectrograph, being developed at the AAO.
FLEX will be the first instrument to employ fibre Bragg gratings for OH suppression, a radical new technology which
cleanly suppresses the atmospheric OH emission lines at 30dB whilst maintaining a high overall throughout of ~90%. In
this paper we simulate the expected performance of FLEX, and discuss its impact on the science case. FLEX will
effectively make the near-infrared sky 4 mags fainter in the H band and 3 mags fainter in the J band, offering
unprecedentedly deep views of the near-infrared Universe. The FLEX concept is optimised for the identification of the
sources of first light in the Universe - high redshift galaxies or quasars identified through Lyman-alpha emission or a
Lyman break in the continuum spectrum. As such it will consist of a 2x2" integral field unit, composed of a 61 lenslet
hexagonal array, feeding an existing moderate spectral resolution spectrograph, via an OH-suppression unit. We have
simulated the performance of FLEX and show that it can provide robust identification of galaxies at the epoch of
reionisation. A FLEX-like instrument on an ELT could measure the ionisation and enrichment of the inter-galactic
medium beyond a redshift of 7 via metal absorption lines.
As part of the Starbug development, a range of actuator technologies have been prototyped and trialled in the quest to
develop this novel focal plane positioning system. The Starbug concept is a robotic positioning system that deploys
multiple payloads, such as pickoff optics, optical fibres and other possible devices to micron level accuracy over a flat or
curved focal plane. The development is aimed at addressing some of the limitations of other positioning systems to
provide a reliable, cost effective way of positioning multiple payloads in ambient and cryogenic environments. In this
paper we identify the specification and required characteristics of the micro-robotic actuators as applied to the MOMSI
instrument concept, present descriptions of some of the prototypes along with the results from characterisation and
performance tests. These tests were undertaken at various orientations and temperatures as well as using different
actuator concepts.
We explore the range of wide field multi-object instrument concepts taking advantage of the unique capabilities of the
Starbug focal plane positioning concept. Advances to familiar instrument concepts, such as fiber positioners and
deployable fiber-fed IFUs, are discussed along with image relays and deployable active sensors. We conceive
deployable payloads as components of systems more traditionally regarded as part of telescope systems rather than
instruments - such as adaptive optics and ADCs. Also presented are some of the opportunities offered by the truly
unique capabilities of Starbug, such as microtracking to apply intra-field distortion correction during the course of an
observation.
The Gemini-sponsored WFMOS Feasibility Study investigated a wide-field, prime focus installation for the Gemini telescopes. As constructed, the Gemini design allows for multiple, interchangeable telescope top-ends, although this capability has never been implemented. Constrained by a particularly challenging top-end mass budget, we proposed a new top end specific to WFMOS, employing a carbon fiber reinforced plastic structure. An innovative, out-of-autoclave manufacturing process using balanced pressure and liquid heating and cooling enables high-specification, large CFRP structures to be constructed suitable for incorporation as fundamental parts of telescope structures. Advantages include low weight, enhanced overall telescope stiffness, and cost-effective construction with on-site final assembly. We describe the manufacturing process and the proposed top-end structure, as well as highlighting the advantages of this type of structure and material for large and extremely large telescopes in general.
Photo-realistic computer graphics software provides a valuable visualisation tool in the development of astronomical instrumentation. The perceived realism can convey a valuable sense of feasibility or unfeasibility of a concept. We here look at POV-Ray, an open-source ray-tracing graphics package that has been in use for several years at the Anglo-Australian Observatory. AAO applications include development of both static images and short movies for detailed visualisations of conceived instruments, production of high-quality images for publication and publicity, rapid generation of illustrative figures and simple geometrical and optical studies.
An unsolved problem in astronomical instrumentation is an imaging integral field spectrograph where the user has the freedom to specify arbitrarily complex, contiguous or disjoint regions over the focal plane, rather than a contiguous rectangular field. We present a new concept to solve this problem. Our device allows the user to format the field of view with fibre bundles packed into arbitrary patterns. The field of view is segmented by a large N(N microlens array (e.g. N=1000). This element divides the wavefront into small beams which pass through a metal plate drilled with a grid of holes in the same format as the microlens array. On the reverse side of the grid, hexagonal blocks comprising 67 input fibres are plugged into position on the grid with a pair of sliding "croupier" sticks. The fibred blocks transport the light to the spectrograph. The blocks are held magnetically and the plugging ensures accurate and repeatable registration with respect to the microlens array. The grid plate is micromachined with baffled holes in order to ensure photometric uniformity over the field of view.
The Anglo-Australian Observatory has undertaken a design study for a ≈1000 fibre positioner for the prime focus of the Giant Segmented Mirror Telescope (GSMT) as part of the MOMFOS (Multi-Object Multi-Fibre Optical Spectrograph) instrument. To our knowledge this is the first design study funded for a prime focus instrument for an ELT. It offers a particularly elegant and efficient solution for wide-field multiobject spectroscopy on extremely large telescopes (>30m) for the acquisition of large scale high-redshift surveys (12), density coverage (≈2.5 million galaxies) and limiting magnitude (R≤26.5).
Closely based on the innovative Echidna positioner under construction for Subaru's FMOS system, the MOMFOS positioner uses piezoelectric microrobotic actuators able to position accurately all 1000 fibres simultaneously. The FMOS-Echidna design is extended to include a novel position feedback system offering radical benefits in cost and speed. We present positioning results for a design capable of a higher packing density than that developed for FMOS-Echidna, providing ≈1000 fibres across the 175 mm diameter field of view (20 arcmin).
The Anglo-Australian Observatory is currently designing a new fibre positioner for the UK Schmidt Telescope. The instrument will have 2250 fibres, positioned with sub-arcsecond accuracy across a six degree field of view, and will have a reconfiguration time of one minute. The instrument is to enable the RAVE survey of high precision abundances and velocities for up to 50 million stars. The design is largely adapted from the AAO's FMOS-Echidna fibre positioner for Subaru. New design challenges for Ukidna include the enormous number of fibres, the large focal surface, and the field curvature of the Schmidt telescope. These features are mostly shared with the expected needs of future prime-focus multi-fibre systems on 8-30m class telescopes. We present details and performance of the multi-actuator design.
We propose a new robotic system for positioning payloads such as pickoff mirrors, fibres or deployable IFUs on telescope focal planes. Based on a combination of concepts used in existing fibre positioning systems, the proposed system retains the advantages of each type of existing positioner, while eliminating many of the disadvantages. It employs micro-robotic actuators to independently and simultaneously position an arbitrary number of small payloads accurately on an arbitrarily large field plate and offers a cost-effective and multiply-redundant design for payload positioning systems suitable for use at Cassegrain or Nasmyth foci of large telescopes. Operation in cryogenic environments, positioning accuracies of a few microns, simultaneous movement of arbitrary numbers of positioners and the removal of many movement constraints are some of the advantages offered. We demonstrate a prototype positioner for the system.
A wide range of positioning technologies has been exploited to flexibly configure fiber ends on the focal surfaces of telescopes. The earliest instruments used manual plugging, or glued buttons on the focal plane. Later instruments have used robotic fisherman-round-the-pond probes and articulated armsto position fibres, each probe or arm operated by its own motors, or buttons on fiber ends moved by pick-and-place robotic positioners. A positioner using fiber spines incorporating individual actuators operating over limited patrol areas is currently being manufactured and a derivative proposed for future large telescopes. Other techniques, using independent agents carrying the fiber ends about the focal plane have been prototyped. We describe these various fiber positioning techniques and compare them, listing the issues associated with their implementation, and consider the factors which make each of them suitable for a given situation. Factors considered include: robot geometries; costs; inherent limits to the number of fibers; clustering of targets; serial and parallel positioning and reconfiguration times; adaptability to curved focal surfaces; the virtues of on-telescope versus off-telescope configuration of the field, and suitability for the various telescope foci. The design issues include selection of actuators and encoding systems, counterbalancing, configuration of fiber buttons and their associated grippers, interchanging field plates, and the need for fiber retractors. Finally we consider the competing technologies: fiber and reflective image slicer IFUs, multislit masks and reconfigurable slits.
KEYWORDS: Telescopes, Space telescopes, Mirrors, Adaptive optics, Optical instrument design, Stars, James Webb Space Telescope, Reflector telescopes, Near infrared, Sensors
We present a design concept for a 16 metre, wide-field, fixed-axis, all-reflective, segmented f/4 Schmidt telescope to take advantage of the unique possibilities of Antarctica for both optical and near infrared astronomy. The design allows observation of all RA/dec's accessible from Antarctica, with tracking times of several hours.
Prime and Cassegrain foci are provided, giving plate scales 300-3000microns/", over fields of view 1.5'-0.5°. Diffraction limited, natural guide-star AO-corrected Kdark images are possible over
arc-minute sized fields, over 70% of the sky. The sensitivity, resolution, field of view and cost all compare favourably with current or proposed space or ground-based telescopes.
The science case for wide fields on ELTs is well developed and justifies the implementation of 20 arc-minute and larger fields-of-view with seeing-limited performance on a 20 to 30-meter telescope. However, the practical implementation of a wide field can prove to be challenging with classical telescope design when low-thermal emissivity performance is also being optimized. Segmented mirrors assemblies need not be full aperture, axially symmetric structures. Space for secondary, tertiary, and quaternary mirror support structures that do not cross the optical path can be achieved with off-axis mirror assemblies. Barden, Harmer, Claver, and Dey described a 4-mirror, 1-degree FOV 30-meter telescope. We take that concept further with an off-axis approach. Three conic mirrors are required to produce excellent image quality in the 1-degree FOV (diffraction limited across the central few arc-minutes, better than 0.3" imaging performance at the edge of the field). A flat quaternary mirror is utilized both as a beam steering mirror to different instrument ports on the lower side of the telescope and as an adaptive mirror for wind-buffeting and possible ground layer AO correction. The final f/2.2 focal ratio allows the use of an echidna-style fiber positioner for very dense target field acquisition. Extreme AO and Ground Layer AO ports can both be implemented as well. Diffraction characteristics may possibly be improved given the lack of a spider mount for the secondary mirror but will be elliptical rather than circular.
Given the physical size of the GSMT prime focus field is approximately equivalent to that of the Subaru telescope it is possible to directly apply current technology developed for the Fiber Multi-Object Spectrograph instrument (FMOS, to be commissioned in 2005) and substantially reduce the risk associated with developing a new solution for wide-field multi-object spectroscopy on an ELT. The Anglo-Australian Observatory has recently completed a design study for an ~1000 fiber, Echidna-style positioner for the prime focus of the Giant Segmented Mirror Telescope (GSMT). The positioner forms part of the wide-field Multi-Object Multi-Fiber Optical Spectrograph (MOMFOS), an ELT prime focus instrument offering a minimum of 800 fibers patrolling the corrected 20 arcmin field. The design study identified 2 components of an equivalent MOMFOS positioner design that required prototyping. Firstly, a higher spine packing density is required to satisfy the proposed scientific program. Secondly, the fiber position measurement system adopted for FMOS cannot be simply scaled and applied to MOMFOS given space constraints in the top end unit. As such a new and, if possible, simpler system was required. Prototyping results for both components are presented.
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