The New Robotic Telescope (NRT) is an autonomous telescope that can operate multiple instruments at the Cassegrain focal station and the straight-through port. The optical beam is directed to the ports by a fold mirror subsystem in the focal station assembly. The fold mirror is elliptical in shape, manufactured by Instituto Nazionale di Astrofisica (INAF), and polished down to RMS surface deformation of λ/20. An optomechanical analysis is performed to simulate the effect of gravity over the mirror surface deformation and the results have been compared to the interferometry plots to optimize the Ion Beam Figuring (IBF) process to polish the mirror aperture. The mirror assembly is supported by a bipod flexure design to reduce surface deformation under gravity and thermal loads. There are three sets of bipod elements and a central support in the quasi-kinematic support structure. Using wire EDM, the bipods were manufactured precisely as one piece. Following careful preparation and the development of multiple glue jigs to ensure an even glue thickness, the bipods, and central pads are glued to the mirror, and multiple experimental tests have been performed to ensure the glue layer's strength and durability. Other components of the mirror assembly, such as the mirror cell, mirror stand, and moving platform, are being machined out of INVAR, assembled, and mounted on the linear stage and a rotary stage before being installed over the mechanism platform in the A&G box. The design and manufacturing of the mirror assembly, including the gluing process, will be summarised as part of this article.
The 4m class New Robotic Telescope (NRT) is an optical facility designed to revolutionize the rapid follow-up and classification of variable and transient objects. The project is at the stage where key systems are progressing through their detailed design phases, which presents a major engineering challenge for all project partners to manage design progress of the high-level interfacing systems while still ensuring the delivery of top-level science requirements. The freezing of key system architecture features at the preliminary design review in 2021 has allowed significant progress to be made towards a target of Engineering First Light (EFL) in 2027. The project critical path is currently driven by the optics and the enclosure. Both of these components are novel in design: the NRT will have an 18-segment primary mirror and a large, fully-opening clamshell enclosure. Particular progress has been made regarding enclosure design, software & control, science & operations software and the focal station and associated science support instrumentation. The Critical Design Review for the M3 (fold mirror) was completed Q4 2022 which enabled manufacturing of the first NRT glassware to begin and prototyping of the complete opto-mechanical, hardware and software subsystem for its control to take place. The NRT will join the 2m Liverpool Telescope on La Palma, and as such this existing facility has been exploited to prototype the new science operations user interface and the NRT wavefront sensor.
In an era characterized by the availability of affordable, powerful, and scalable cloud-based services, we delve into the strategic decision to design a cloud-based infrastructure for the New Robotic Telescope (NRT). We provide a comprehensive discussion on the design, implementation, and challenges encountered during this approach. Central to this infrastructure is the Software Operations Data Centre (SODC), serving as the public-facing web portal. The SODC leverages REDIS, modern RESTful APIs, web sockets, and cloud-based data pipelines allowing astronomers seamless access to their data while ensuring data availability when the observatory is offline due to unmanageable interruptions in data connections. These tools also grant us instant feedback from the facility, providing live system states of the observatory’s devices. In this paper, we specifically address the scalability and redundancies embedded in this cloud-based system, elucidating how they contribute to the robustness of the NRT’s operations. We also spotlight auxiliary tools in use to transmit this secure and public data. We aim to shed light on the strategic advantages of our cloud-based approach in astronomical observatories, emphasizing the role of the SODC in data accessibility, data security and observatory control interfaces with real world demonstrations.
The New Robotic Telescope (NRT) will be a 4-metre-class fully robotic telescope to be sited on La Palma. NRT will primarily be used in time-domain astrophysics, and, as such, there is a requirement for rapid response and high-efficiency observing and instrumentation. We have therefore developed a spectrograph concept for NRT with no moving parts. The primary design feature is a beamsplitter, where a small fraction of light will be reflected towards a dedicated acquisition detector. The rest of the light will pass through the system for spectroscopy with a second detector. We present initial calculations of the fraction of light required to be diverted from the science beam to minimize overall time spent per target. We also present the results of initial laboratory testing of a plane glass plate and a single-sided anti-reflection coated plate as beamsplitters. As expected these exhibit significant ghost images, and more sophisticated beamsplitter designs will be explored in the next phase of the project.
The 2-metre Liverpool Telescope will soon be assisted by the New Robotic Telescope (NRT), a 4-metre-class telescope, robotic and fully autonomous, at the Roque de los Muchachos Observatory (ORM) on La Palma, Canary Islands, Spain. The 4-metre primary mirror of the NRT will be comprised of 18 hexagonal segments of 1-meter diameter each. All the individual segments need to be sufficiently aligned to deliver images that can be successfully exploited by the telescope instrumentation. We therefore need an instrument to assist in the alignment of the different segments. To that end, we designed a wavefront sensor that would be not only reliable and robust (indispensable for a robotic telescope), but also economical, and therefore with as many on-the-shelf components as possible. We chose a Shack-Hartmann type of wavefront sensor, that rests on the use of a lenslet array. The assembly of segments can be mapped onto the array imaged at the image plane by the lenslet array. This will allow us not only to detect the misalignment of each segments with respect to the other segments, but also the misalignment of the primary mirror with respect to the secondary mirror. From these information, the position of the primary mirror segments and of the secondary mirror can be altered. A prototype Shack Hartmann wavefront sensor for the NRT has been tested in the laboratory and also on the 2-m Liverpool Telescope. We demonstrate that the basic functionality requirements are met. Detailed analysis of the images is currently underway.
We present Mookodi (meaning “rainbow” in Sesotho), a multipurpose instrument with a low-resolution spectrograph mode and a multi-filter imaging mode for quick-reaction astronomical observations. The instrument, mounted on the 1-m Lesedi telescope at the South African Astronomical Observatory in Sutherland (South Africa), is based on the low-resolution spectrograph for the rapid acquisition of transients (SPRAT) instrument in operation on the 2-m Liverpool Telescope in La Palma (Canary Islands, Spain). Similar to SPRAT, Mookodi has a resolution R≈350 and an operating wavelength range in the visible (∼4000 to 8000 Å). The linear optical design, as in SPRAT, is made possible through the combination of a volume phase holographic transmission grating as the dispersive element and a prism pair (grism), which makes it possible to rapidly and seamlessly switch to an imaging mode by pneumatically removing the slit and grism from the beam and using the same detector as in spectrographic mode to image the sky. This imaging mode is used for auto-target acquisition, but the inclusion of filter slides in Mookodi’s design also provides the capability to perform imaging with a field-of-view ≈10′×10′ (∼0.6″/px) in the complete Sloan Digital Sky Survey filter set.
The New Robotic Telescope will be a fully autonomous, rapid reaction, primarily spectroscopic facility for the classification of astronomical transients. The 4.18m diameter primary mirror is to be composed of 18 hexagonal mirror segments, arranged with a secondary mirror that feeds the Cassegrain focal stations with an F/10.635 beam. The final telescope design does not follow an established prescription, although both primary and secondary remain hyperbolic. However, the tube length is retained from an earlier F/7.5 RC design and secondary mirror size reduced to minimise obscuration of the primary. The optimisation process involved considering the M2 / fold size trade-off while solving the surfaces for image quality, contrast and wavefront error after speeding up the primary mirror. The final effective focal ratio is then slower to allow for workable tolerances through manufacture, installation and operations. In this presentation the optimisation process, trade-offs, tolerances and final design will be summarised.
The Galway Liverpool imaging polarimeter (GLIP) has been designed to perform simultaneous linear and circular polarimetric measurements at sub-second cadence. The science goal of the instrument is to perform observations of fast evolving astronomical transients with leading robotic telescope facilities. GLIP builds on the legacy of polarimeter instruments developed by the Liverpool Telescope team of the Astrophysical Research Institute, Liverpool, with the RINGO & MOPTOP series, and the National University of Ireland Galway (NUIG) with the GASP polarimeter. The instrument works as a four-beam imaging polarimeter of a 2.3 arc-minute field-of-view onto one detector, allowing the determination of the full Stokes vector [I Q U V] across the image field once the characteristic matrix of the instrument is known. Optical design, characterisation of polarimetry and tolerance of the instrument optical components using computational, lab testing result & mathematical methods will be discussed.
The New Robotic Telescope (NRT), the 4-metre, next-generation Liverpool Telescope (LT), will be located on La Palma, Canary Islands. The design and development of the world’s largest robotic telescope, with a slew speed of approximately 10 degrees/second, poses challenges that have resulted in innovative design concepts, including the scheduling algorithms used for optimal science efficiency. We present the latest updates for the NRT project, focusing, in particular, on the status of the observing model which is being adapted from the existing LT model. The catalogue of LT data taken over the past 18 years is being used to model the observing behaviour of the facility and to act as input data for the future NRT scheduling algorithm. This algorithm will combine the existing LT observing model with a new facility Key Science Program, which will conduct rapid-response spectroscopic classifications of a variety of survey targets, transient alerts and variables.
The New Robotic Telescope (NRT) conceptual design has been developed to include an autonomous multi-instrument adaptor at the Cassegrain focal station. The focal station assembly is to consist of a field rotator to compensate the earth rotation, cable wrap, instrument adaptor, support structure, and a fold mirror mechanism to bring the telescope optical beam to the instruments. The design supports the use of multiple instruments around the Acquisition and Guidance box (A&G box) a single instrument port is located at the bottom of the box at the straight through port. The A&G box also includes an autoguider which will be mounted at the side of the box and fed a portion of the optical beam via a small pick off mirror. It will use a field outside that of usable the science field, and has been designed to comprise of off-the-shelf lenses, camera system and lens tubes to minimise cost. The field of view is large enough to conduct ‘blind autoguiding’ at an accuracy of 0.2” with the 4m class telescope. The entire assembly will then be mounted to the M1 cell, forming the bottom part of the telescope tube held between the telescope mount forks. The focal station assembly design will be summarised in this paper.
We present an update on the overall integration progress of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), now scheduled for first light in early-2021, with almost all components now arrived at the observatory. We also present a summary of the current planning behind the 5-year initial phase of survey operations, and some detailed end-to-end science simulations that have been implemented to evaluate the final on-sky performance after data processing. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 mini integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000.
The New Robotic Telescope is designed to conduct rapid target follow-up within 30 seconds of an ‘alert’ from survey facilities. To achieve this will require a quick settling time requirement for the mount structure and the mirrors. This means the structure shall be designed to be sufficiently rigid to achieve the mirror position within the ‘settle time’ after a quick slew operation. An optimization analysis using the finite element model is developed to conceptually design the mount structure that meets the mechanical and more importantly the NRT science requirements. The main objective of this study is to determine the required locked rotor resonance frequency (LRF) that provides enough rigidity for the telescope dynamic performance while minimizing the structural mass and cost.
The robotic 2-metre Liverpool Telescope (LT), located at Roque de los Muchachos, La Palma, has seen great success in its <15 year lifetime. In particular the facility thrives in time domain astronomy, responding rapidly to triggers from Swift and efficiently conducting a wide variety of science with its intelligent scheduler. The New Robotic Telescope (NRT) will be a 4-metre class, rapid response, autonomous telescope joining the Liverpool Telescope on La Palma in ~2025. The NRT will slew to targets and start observations within 30 seconds of receipt of a trigger, allowing us to observe faint and rapidly fading transient sources that no other optical facility can capture. The NRT will be the world’s largest optical robotic telescope. Its novel, first-generation instrumentation suite will be designed to conduct spectroscopic, polarimetric and photometric observations driven by user requirements.
Mid-infrared observations are a vital tool for the study of a wide range of astrophysical phenomena. However, ground-based mid-infrared detectors must overcome the challenge of the overwhelming thermal background from sky and telescope emissions making them prohibitively costly for smaller (< 3 m) facilities. We describe the design and testing of a simple prototype, low-cost 10 µm imaging instrument built around an uncooled microbolometer camera. The instrument incorporates adjustable germanium re-imaging optics to rescale the image to an appropriate plate-scale for 1−2 m class telescopes and uses a gold coated chopping mirror to remove overwhelming sky background contributions. The instrument was tested with a programme of observations of bright mid-infrared sources on the 2 m Liverpool Telescope and the 1.52 m Carlos Sanchez Telescope. With these observations we confirm the instrument can be used for diffraction-limited imaging and has a photometric stability of ~10 %. We report an in-practice sensitivity limit of ~600 Jy, and a theoretical sensitivity limit of ∼ 450 Jy based on the noise equivalent differential temperature of the microbolometer system.
We present an update on the overall construction progress of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), now that all the major fabrication contracts are in place. We also present a summary of the current planning behind the 5-year initial phase of survey operations, and some detailed end-to-end science simulations that have been effected to evaluate the final on-sky performance after data processing. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project has experienced some delays in procurement and now has first light expected for the middle of 2019.
Astro-Ecology couples ‘off the shelf’ infrared imaging technology and astronomy instrumentation techniques for application in the field of conservation biology. Microbolometers are uncooled, infrared systems that image in the thermal-infrared range (8-15μm). These cameras are potentially ideal to use for the detection and monitoring of vulnerable species and are readily available as ’off the shelf’ systems. However to optimise the quality of the data for this purpose requires thorough detector calibration to account for the systematics that limit readout accuracy. In this paper we apply three analogous, standard astronomical instrumentation techniques to characterise the random and spatial noise present in a FLIR Tau 2 Core thermal-infrared camera. We use flat fielding, stacking and binning to determine that microbolometer FPAs are dominated by large structure noise and demonstrate how this can be corrected by subtracting median stacks of flat field exposures.
Weather monitoring has always been an element of observatory operations. For a robotic telescope there is the added complication that software needs to understand the ever changing atmospheric observing conditions in order to respond in real time, continuously balancing the schedule for both facility calibrations (i.e., standard stars) and targeted observations according to the TAC-assigned science priorities. For the Liverpool Telescope, in the past year we have been testing a new multi-threaded approach. We have long operated a single-element, integrated-all-sky, 10 m bolometer on site. To this we have added real-time photometric monitoring of field stars around the science target and analysis of publicly accessible weather satellite images. This gives us three estimates of any night's photometricity; two ground-based looking up through the cloud (optical and thermal IR) and one satellite-based looking down at the observatory. We present a comparison of the results from the different methods and share our experiences selecting between the complementary data sets to support real-time observing decisions.
The Liverpool Telescope group have been designing astronomical instruments for the LT and other 2-4m class telescopes for a number of years. This paper covers a variety of issues which need to be addressed in order to benefit from the unique advantages of 3D printing. In particular we discuss our experience of designing, building and testing a simple prototype structure that is analagous to a simple reflecting grating spectrograph.
The Liverpool Telescope has been in fully autonomous operation since 2004. The supporting data archive facility has largely been untouched. The data provision service has not been an issue although some modernisation of the system is desirable. This project is timely. Not only does it suit the upgrade of the current LT data archive, it is in line with the design phase of the New Robotic Telescope which will be online in the early-2020s; and with the development of a new data archive facility for a range of telescopes at the National Astronomical Research Institute of Thailand. The Newton Fund enabled us to collaborate in designing a new versatile generic system that serves all purposes. In the end, we conclude that a single system would not meet the needs of all parties and only adopt similar front-ends while the back-ends are bespoke to our respective systems and data-flows.
WEAVE is the new multi-object spectrograph for the William Herschel Telescope on La Palma. The culmination of prime focus, the large number of fibers and the wide resolution range has required a stringent optical design, which in turn demands a spectrograph with tight positional tolerances and large final focal plane. To capture this focal plane each of the two cryostats has two e2v 6k × 6k CCDs mounted as a mosaic. As well as being cooled to 150K via liquid nitrogen, the positional tolerances for the sensitive areas are flatness 60μm p-v over the entire image area, rotation around X and Y axis ±50 arcmin, translation in X, Y and Z ± 50 micron. We have used a Stil confocal measuring head mounted on two Thorlab translation stages to create a X,Y mount, controlled by a Raspberry Pi that is capable of recording measurements in Z to better than 1μm accuracy. This is used to measure the flatness and deformation of the image area under vacuum, and when cooled to 150K and the overall tip and tilt of the image plane to ensure they meet specification and are repeatable. In addition to this measuring system, we use a Thorlabs CMOS camera with a Navitar 50mm lens to ensure each CCDs image area is within specification with regards X and Y translation. In order to satisfy the above requirements, we designed the CCD mount to be adjustable (on initial setup), correctly constrained, isolated from liquid nitrogen boil-off vibration, and thermally insulating.
MOPTOP is a new polarimeter design for the Liverpool Telescope, which aims to provide a wide field of view with high temporal resolution and multi-colour capability using a combination of a half wave plate, a polarizing beamsplitter and multiple sCMOS cameras. Here we present the optical design of a single-band prototype. We use a combination of commercial achromat and photographic camera lenses to obtain an image quality (100% encircled energy) of < 1.5 arcsec across a 7x7 arcmin field of view and a wavelength range of 400-800nm.
The preferred programming languages and operating systems used in writing and running astrometric software have changed over time. The Python language is now well supported by the scientific community which provides open-source standard libraries for astronomical calculation including Astropy,1 SciPy2 and NumPy.3 We surveyed available open source astrometric libraries and compare ICRS coordinate to observation transforms using recent releases of C source code and Python wrappers from the IAU Standard of Fundamental Astronomy4 (SOFA), against those using the US Naval Observatory Vector Astrometry Software5 (NOVAS). The selection of an underlying operating system with long term support is also an important aspect of maintaining a working telescope control system. The installation and operation of the libraries under both Linux Ubuntu LTS (Long Term Support) and Windows 10 are explored.
SPRAT1 is a low resolution (R ∼ 300) long-slit spectrograph operating in the optical range 400 – 800 nm. It employs a linear layout with deployable optics and can image a 7.5 × 1.8 arcmin field during target acquisition. SPRAT has successfully operated on the robotic 2-metre Liverpool Telescope (LT)2 on La Palma since late 2014, with >1000 calibration arc spectra and acquisition images taken since installation. Reliable autonomous acquisition without human intervention requires stricter stability criteria to reliably locate a target object in a long-slit spectrograph. We describe methods used to characterise the mechanical repeatability in deployment of the slit and optical components using calibration arcs and standard star spectra, together with acquisition field images. The effect of the instrument orientation and annual temperature variations on the accuracy in locating a target in the imaging plane is characterised together with longer term drifts. The characterisation is compared with the initial design goals of the instrument and used to calculate correction coefficients.
The limits to the angular resolution achievable with conventional ground-based telescopes are unchanged over 70 years. Atmospheric turbulence limits image quality to typically ~1 arcsec in practice. We have developed a new concept of ground-based imaging instrument called GravityCam capable of delivering significantly sharper images from the ground than is normally possible without adaptive optics. The acquisition of visible images at high speed without significant noise penalty has been made possible by advances in optical and near IR imaging technologies. Images are recorded at high speed and then aligned before combination and can yield a 3-5 fold improvement in image resolution. Very wide survey fields are possible with widefield telescope optics. We describe GravityCam and detail its application to accelerate greatly the rate of detection of Earth size planets by gravitational microlensing. GravityCam will also improve substantially the quality of weak shear studies of dark matter distribution in distant clusters of galaxies. The microlensing survey will also provide a vast dataset for asteroseismology studies. In addition, GravityCam promises to generate a unique data set that will help us understand of the population of the Kuiper belt and possibly the Oort cloud.
We present the design and science case for the Liverpool Telescope's fourth-generation polarimeter; MOPTOP: a Multicolour OPTimised Optical Polarimeter which is optimised for sensitivity and bi-colour observations. We introduce an optimised polarimeter which is as far as possible limited only by the photon counting efficiency of the detectors. Using a combination of CMOS cameras, a continuously rotating half-wave plate and a wire grid polarising beamsplitter, we predict we can accurately measure the polarisation of sources to ~ 1% at ~19th magnitude in 10 minutes on a 2 metre telescope. For brighter sources we anticipate much low systematics (⪅ 0.1%) than our current polarimeter. The design also gives the ability to measure polarization and photometric variability on timescales as short as a few seconds. Overall the instrument will allow accurate measurements of the intra-nightly variability of the polarisation of sources such as gamma-ray bursts and blazars (AGN orientated with the jet pointing toward the observer), allowing the constraint of magnetic field models revealing more information about the formation, ejection and collimation of jets.
The utility of a high-throughput, low resolution, optical long-slit spectrograph has been demonstrated with the recent deployment of the SPRAT and LOTUS spectrographs on the 2.0m Liverpool Telescope. In this paper we briefly explore some example science use cases for a more generic spectrograph. Our eventual aim is to a produce an adaptable and compact modular instrument design suitable for general deployment to other robotic or manual 1.5 - 3.0m class telescopes. We find that the wide variety of science goals mean that a single design may not be appropriate, however by developing a common optical/mechanical core to which standard optical elements are added we may be able to accommodate them.
We present the Final Design of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), together with a status update on the details of manufacturing, integration and the overall project schedule now that all the major fabrication contracts are in place. We also present a summary of the current planning behind the 5-year initial phase of survey operations. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project is now in the manufacturing and integration phase with first light expected for early of 2018.
Scientific-CMOS (sCMOS) cameras can combine low noise with high readout speeds and do not suffer the charge multiplication noise that effectively reduces the quantum efficiency of electron multiplying CCDs by a factor 2. As such they have strong potential in fast photometry and polarimetry instrumentation. In this paper we describe the results of laboratory experiments using a pair of commercial off the shelf sCMOS cameras based around a 4 transistor per pixel architecture. In particular using a both stable and a pulsed light sources we evaluate the timing precision that may be obtained when the cameras readouts are synchronized either in software or electronically. We find that software synchronization can introduce an error of ~ 200-msec. With electronic synchronization any error is below the limit (~ 50-msec) of our simple measurement technique.
The Liverpool Telescope is a fully robotic 2-metre telescope located at the Observatorio del Roque de los Muchachos on the Canary Island of La Palma. The telescope began routine science operations in 2004, and currently seven simultaneously mounted instruments support a broad science programme, with a focus on transient followup and other time domain topics well suited to the characteristics of robotic observing. Work has begun on a successor facility with the working title ‘Liverpool Telescope 2’. We are entering a new era of time domain astronomy with new discovery facilities across the electromagnetic spectrum, and the next generation of optical survey facilities such as LSST are set to revolutionise the field of transient science in particular. The fully robotic Liverpool Telescope 2 will have a 4-metre aperture and an improved response time, and will be designed to meet the challenges of this new era. Following a conceptual design phase, we are about to begin the detailed design which will lead towards the start of construction in 2018, for first light ∼2022. In this paper we provide an overview of the facility and an update on progress.
The Liverpool Telescope automated spectral data reduction pipelines perform both removal of instrumental signatures and provide wavelength calibrated data products promptly after observation. Unique science drivers for each of three instruments led to novel hardware solutions which required reassessment of some of the conventional CCD reduction recipes. For example, we describe the derivation of bias and dark corrections on detectors with neither overscan or shutter. In the context of spectroscopy we compare the quality of at fielding resulting from different algorithmic combinations of dispersed and non-dispersed sky and lamp flats in the case of spectra suffering from 2D spatial distortions.
IO:I is a new instrument that has recently been commissioned for the Liverpool Telescope, extending current imaging capabilities beyond the optical and into the near-infrared. Cost has been minimized by the use of a previously decommissioned instrument’s cryostat as the base for a prototype and retrofitting it with Teledyne’s 1.7-μm cutoff Hawaii-2RG HgCdTe detector, SIDECAR ASIC controller, and JADE2 interface card. The mechanical, electronic, and cryogenic aspects of the cryostat retrofitting process will be reviewed together with a description of the software/hardware setup. This is followed by a discussion of the results derived from characterization tests, including measurements of read noise, conversion gain, full well depth, and linearity. The paper closes with a brief overview of the autonomous data reduction process and the presentation of results from photometric testing conducted on on-sky, pipeline processed data.
Gaia, the 1 billion star, high precision, astrometric satellite will revolutionise our understanding in many areas of astronomy ranging from bodies in our Solar System to the formation and structure of our Galaxy. To fully achieve the ambitious goals of the mission, and to completely eliminate effects such as aberration, we must know the position and velocity vectors of the spacecraft as it orbits the Lagrange point to an accuracy greater than can be obtained by traditional radar techniques, leading to the decision to conduct astrometric observations of the Gaia satellite itself from the ground. Therefore the Ground Based Optical Tracking (GBOT) project was formed and a small worldwide network using 1-2 m telescopes established in order to obtain one measurement per day of a precision/accuracy of 20 mas. We will discuss all aspects of GBOT, setup, feasibility considerations, preliminary tests of observing methods, partner observatories, the pipeline/database (see also contribution by Bouquillon et al.1).
We describe the development of a low cost, low resolution (R ~ 350), high throughput, long slit spectrograph covering visible (4000-8000) wavelengths. The spectrograph has been developed for fully robotic operation with
the Liverpool Telescope (La Palma). The primary aim is to provide rapid spectral classification of faint (V ∼ 20)
transient objects detected by projects such as Gaia, iPTF (intermediate Palomar Transient Factory), LOFAR,
and a variety of high energy satellites. The design employs a volume phase holographic (VPH) transmission grating as the dispersive element combined with a prism pair (grism) in a linear optical path. One of two peak spectral sensitivities are selectable by rotating the grism. The VPH and prism combination and entrance slit are deployable, and when removed from the beam allow the collimator/camera pair to re-image the target field onto the detector. This mode of operation provides automatic acquisition of the target onto the slit prior to spectrographic observation through World Coordinate System fitting. The selection and characterisation of optical components to maximise photon throughput is described together with performance predictions.
WEAVE is the next-generation optical spectroscopy facility for the William Herschel Telescope and aims at
spectroscopic follow-up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE places in the re-fitted
prime focus either 1000 fibres, 20 fibre-coupled mini-IFUs or a single large 600 fibre IFU. A spectrograph on the
Nasmyth platform analyses the light and supports, in a single exposure, either R~5,000 observations over the full 366-
975 nm wavelength range or simultaneous R~20,000 observations over two out of three pre-specified bands within this
wavelength range. This paper describes the requirements, optical design and mechanical design of the WEAVE
spectrograph.
Some modern CCD designs provide a dummy readout amplifier that is designed to be operated with the same clock and bias signals as the true amplifier in order to provide a measurement of clock induced and other common-mode noise signals in the true amplifier readout. In general the dummy output signal is subtracted electronically from the true output signal in a differential input preamplifier before digitization. Here we report on an alternative approach where both signals are digitized and the subtraction done in software. We present the results of testing this method of operation using the ARC SDSU generation III CCD controllers and an e2v CCD231 device and find it works well, allowing a noise figure of ~ 2:2 electrons to be reached in the presence of significantly higher (~ 6 electrons) pickup noise. In addition we test the effectiveness of using unused (but still genuine) readout amplifiers on the detector to provide a pseudo-dummy output, which we also find effective in cancelling common mode noise. This provides the option of implementing noise reduction on CCDs that are not equipped with dummy outputs at the expense of overall readout speed.
The robotic 2m Liverpool Telescope, based on the Canary island of La Palma, has a diverse instrument suite and a strong track record in time domain science, with highlights including early time photometry and spectra of supernovae, measurements of the polarization of gamma-ray burst afterglows, and high cadence light curves of transiting extrasolar planets. In the next decade the time domain will become an increasingly prominent part of the astronomical agenda with new facilities such as LSST, SKA, CTA and Gaia, and promised detections of astrophysical gravitational wave and neutrino sources opening new windows on the transient universe. To capitalise on this exciting new era we intend to build Liverpool Telescope 2: a new robotic facility on La Palma dedicated to time domain science. The next generation of survey facilities will discover large numbers of new transient sources, but there will be a pressing need for follow-up observations for scientific exploitation, in particular spectroscopic follow-up. Liverpool Telescope 2 will have a 4-metre aperture, enabling optical/infrared spectroscopy of faint objects. Robotic telescopes are capable of rapid reaction to unpredictable phenomena, and for fast-fading transients like gamma-ray burst afterglows. This rapid reaction enables observations which would be impossible on less agile telescopes of much larger aperture. We intend Liverpool Telescope 2 to have a world-leading response time, with the aim that we will be taking data with a few tens of seconds of receipt of a trigger from a ground- or space-based transient detection facility. We outline here our scientific goals and present the results of our preliminary optical design studies.
The Small Telescopes Installed at the Liverpool Telescope (STILT) project has been in operation since March 2009, collecting data with three wide field unfiltered cameras: SkycamA, SkycamT and SkycamZ. To process the data, a pipeline was developed to automate source extraction, catalogue cross-matching, photometric calibration and database storage. In this paper, modifications and further developments to this pipeline will be discussed, including a complete refactor of the pipeline's codebase into Python, migration of the back-end database technology from MySQL to PostgreSQL, and changing the catalogue used for source cross-matching from USNO-B1 to APASS. In addition to this, details will be given relating to the development of a preliminary front-end to the source extracted database which will allow a user to perform common queries such as cone searches and light curve comparisons of catalogue and non-catalogue matched objects. Some next steps and future ideas for the project will also be presented.
The ESA Gaia satellite mission will create a catalog of 1 billion stars with unprecedented astrometric precision. To achieve its aim in terms of astrometric precision, a ground based optical tracking campaign (GBOT) of the satellite itself is necessary during the five years of the mission. We present an overview of the GBOT project as a whole in another contribution1 (Altmann et al. in SPIE category "observatory operations"). The present paper will focus more specifically on the software solutions developed by the GBOT group.
We present an overview of and status report on the WEAVE next-generation spectroscopy facility for the William
Herschel Telescope (WHT). WEAVE principally targets optical ground-based follow up of upcoming ground-based
(LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree
prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object
(MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single
spectrograph, with a pair of 8k(spectral) x 6k (spatial) pixel cameras, located within the WHT GHRIL enclosure on the
telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single
exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project is now in the final
design and early procurement phase, with commissioning at the telescope expected in 2017.
IO:I is a new instrument in development for the Liverpool Telescope, extending current imaging capabilities beyond the optical and into the near infrared. Cost has been minimised by use of a previously decommissioned instrument’s dewar as the base for a prototype, and retrofitting it with a 1.7μm cutoff Hawaii-2RG HgCdTe detector, SIDECAR ASIC controller and JADE2 interface card. Development of this prototype is nearing completion and will be operational mid 2014. In this paper, the mechanical, electronic and cryogenic facets of the dewar retrofitting process will be discussed together with a description of the instrument control system software/hardware setup. Finally, a brief overview of some initial testing undertaken on the engineering grade array will be given, along with future commissioning plans for the instrument.
We present the preliminary design of the WEAVE next generation spectroscopy facility for the William Herschel
Telescope (WHT), principally targeting optical ground-based follow up of upcoming ground-based (LOFAR) and spacebased
(Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2 degree prime focus field of view
at the WHT, with a buffered pick and place positioner system hosting 1000 multi-object (MOS) fibres or up to 30
integral field units for each observation. The fibres are fed to a single spectrograph, with a pair of 8k(spectral) x 6k
(spatial) pixel cameras, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting
observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with
limited coverage in each arm at R~20000.
GRB jets contain rapidly moving electrons which will spiral around magnetic field lines. This causes them to
emit polarized synchrotron emission. We have built a series of polarimeters (RINGO and RINGO2) to investigate
this by measuring the polarization of optical light from GRBs at a certain single wavelength. The instruments
are mounted on the Liverpool Telescope, which is a fully robotic (i.e. unmanned) telescope on La Palma which
reacts to triggers from satellites such as the NASA SWIFT mission. This has had great success, with the first
ever detections of early time optical polarization being made. In addition, the first measurements of the change
in optical polarization from a GRB as the jet expands have recently been obtained.
In this paper we describe the design and construction of RINGO3. This will be a multi-colour instrument
that can observe simultaneously at three wavelengths. By doing so we will be able to unambiguously identify
where in the burst the polarized emission is coming from. This will allow us to distinguish between three
possibilities: (1) Magnetic instabilities generated in the shock front, (2) Line of sight effects and (3) Large-scale
magnetic fields present throughout the relativistic outflow. The instrument design combines a rapidly rotating
polaroid, specially designed polarization insensitive dichroic mirrors and three electron multiplying CCD cameras
to provide simultaneous wavelength coverage with a time resolution of 1 second.
The Liverpool Telescope has undergone a major revision of operations model, improving the facility's flexibility and
rapid response to targets of opportunity. We switched from a "full service" model where observers submitted requests to
the Support Astronomer for checking and uploading into the scheduler database to a direct access model where observers
personally load sequences directly into the database at any time, including during the night. A new data model describing
the observing specifications has been developed over two years for the back-end operations infrastructure and has been
invisible to users until early 2010 when the new graphical user interface was deployed to all observers. The development
project has been a success, defined as providing new flexible operating modes to users without incurring any downtime
at the change over or interruption to the ongoing monitoring projects in which the observatory specializes. Devolving
responsibility for data entry to users does not necessarily simplify the role of observatory staff. Ceding that absolute
hands-on control by experienced staff complicates the support task because staff no longer have advance personal
knowledge of everything the telescope is doing. In certain cases software utilities and controls can be developed to
simplify tasks for both observers and operations staff.
We describe the design and construction of a new novel optical polarimeter (RINGO2) for the Liverpool Telescope.
The instrument is designed for rapid (< 3 minute) followup observations of Gamma Ray Bursts in order to
measure the early time polarization and time evolution on timescales of ~ 1 - 10000 seconds. By using a fast
rotating Polaroid whose rotation is synchronized to control the readout of an electron multiplying CCD eight
times per revolution, we can rebin our data in the time domain after acquisition with little noise penalty, thereby
allowing us to explore the polarization evolution of these rapidly variable objects for the first time.
Presented in this paper are the designs of several algorithms which enable the identification and tracking of
various regions within a series of images using FPGA technology. Two example probLem domains in the areas
of plasma physics and observational astronomy have been expolored. In the plasma physics application, an
initial pixel extraction technique has been expanded to include spatial (related to the distance from a cathode)
and value measurements (based on intensity values), which are subsequently merged in order to identify different
intensity / emissivity regions within a plasma assisted deposition system. The optimum combination of these and
other techniques are discussed, together with their reasons for selection. The control signals, decoding method
and subsequent processing steps, associated with how a point within individual images is selected, will also be
presented. In the astronomical application, a variation of a scene change detection mechanism is shown and how
this system was adapted in order to track and chart the motion of Near-Earth Objects (NEOs).
This paper describes a modular component architecture for the construction of observation schedulers along with a simulation framework with which schedulers can be tested under a variety of environmental scenarios. We discuss a series of basic efficiency and quality metrics which can be used to measure the value of schedules. Results are presented from a series of simulations using this framework in which a set of observation scheduling paradigms ranging from on-demand despatching to a short-horizon look-ahead scheduler are tested under a series of increasingly challenging environmental conditions.
The commercially-available Boltwood Cloud Sensor couples a sky-facing non-imaging thermopile operating in the 8-14
micron range with an ambient air thermometer, to determine the relative sky temperature, and thus indicate the presence
of cloud. A Boltwood sensor was installed on the Liverpool Telescope's weather mast on La Palma in the Canary
Islands in September 2006 in order to investigate its response to both thick and thin cloud at both low and high (cirrus)
levels. An additional aim was to investigate the detectability of calima (Saharan dust) that is occasionally blown over
the islands. In this paper we present the results of our investigations, presenting correlations between the observed
temperature differential and photometricity as determined from the observation of photometric standard stars, and give
some useful "rules-of-thumb" for others considering using such devices.
By the precise timing of the low amplitude (0.005 - 0.02 magnitude) transits of exoplanets around their parent
star it should be possible to infer the presence of other planetary bodies in the system down to Earth-like
masses. We describe the design and construction of RISE, a fast-readout frame transfer camera for the Liverpool
Telescope designed to carry out this experiment. The results of our commissioning tests are described as well as
the data reduction procedure necessary. We present light curves of two objects, showing that the desired timing
and photometric accuracy can be obtained providing that autoguiding is used to keep the target on the same
detector pixel for the entire (typically 4 hour) observing run.
In the last few years the ubiquitous availability of high bandwidth networks has changed the way both robotic and non-robotic telescopes operate, with single isolated telescopes being integrated into expanding "smart" telescope networks that can span continents and respond to transient events in seconds. The Heterogeneous Telescope Networks (HTN)* Consortium represents a number of major research groups in the field of robotic telescopes, and together we are proposing a standards based approach to providing interoperability between the existing proprietary telescope networks. We further propose standards for interoperability, and integration with, the emerging Virtual Observatory.
We present the results of the first interoperability meeting held last year and discuss the protocol and transport standards agreed at the meeting, which deals with the complex issue of how to optimally schedule observations on geographically distributed resources. We discuss a free market approach to this scheduling problem, which must initially be based on ad-hoc agreements between the participants in the network, but which may eventually expand into a electronic market for the exchange of telescope time.
KEYWORDS: Telescopes, Web services, Java, Signal to noise ratio, Standards development, Astronomy, Robotics, Astronomical telescopes, Information security, Sun
Distributed, heterogenous networks of telescopes will require a very different approach to scheduling than classically operated single site instruments. We have previously discussed the advantages of an economic (free market) approach to this problem. In this paper we describe a test implementation of the technologies using a generic
toolkit designed to make negotiable and chargeable web services.
We describe the design and construction of a novel optical ring-polarimeter (RINGO) for the Liverpool Telescope. The instrument is designed for rapid (< 5 minutes) followup observations of Gamma Ray Bursts in order to measure the early time polarization and its evolution for the first time. Sensitivity calculations and data reduction procedures are described, and the results of on-sky commissioning presented. The instrument is now on the telescope and in routine use during GRB followup.
Linking ground based telescopes with astronomical satellites, and using the emerging field of intelligent agent architectures to provide crucial autonomous decision making in software, we have combined data archives and research class robotic telescopes along with distributed computing nodes to build an ad-hoc peer-to-peer heterogeneous network of resources. The eSTAR Project* uses intelligent agent technologies to carry out resource discovery, submit observation requests and analyze the reduced data returned from a meta-network of robotic telescopes. We present the current operations paradigm of the eSTAR network and describe the direction of in which the project intends to develop over the next several years. We also discuss the challenges facing the project, including the very real sociological one of user acceptance.
In this paper we discuss the requirements for producing instrumentation suitable for robotic use, on a fully automated telescope. The design compromises and simplifications needed to produce instruments that can be left unattended for long periods of operation are investigated. We describe how we structure the control system to provide fail-safe operation of the instruments.
The Liverpool Telescope is a 2.0 metre robotic telescope that is operating unattended at the Observatorio del Roque de Los Muchachos, Spain. This paper gives an overview of the design and implementation of the telescope and its instrumentation and presents a snapshot of the current performance during the commissioning process. Science observations are under way, and we give brief highlights from a number of programmes that have been enabled by the robotic nature of the telescope.
The Liverpool Telescope (LT) is a fully robotic 2m telescope located on La Palma in the Canary Islands. It has been in operation since July 2003 and has just started (April 2004) initial robotic operations. In this paper we describe the implementation of the heuristic dispatch scheduler, its interaction with the Robotic Control System (RCS), details of performance metrics we intend to use and present some initial results.
As distributed systems are becoming more and more diverse in application there is a growing need for more intelligent resource scheduling. eSTAR Is a geographically distributed network of Grid-enabled telescopes, using grid middleware to provide telescope users with an authentication and authorisation method, allowing secure, remote access to such resources. The eSTAR paradigm is based upon this secure, single sign-on, giving astronomers or their agent proxies direct access to these telescopes. This concept, however, involves the complex issue of how to schedule observations stored within physically distributed media, on geographically distributed resources. This matter is complicated further by the varying degrees of constraints placed upon observations such as timeliness, atmospheric and meteorological conditions, and sky brightness to name a few.
This paper discusses a free market approach to this scheduling problem, where astronomers are given credit, instead of time, from their respective TAGs to spend on telescopes as they see fit. This approach will ultimately provide a community-driven schedule, genuine indicators of the worth of specific telescope time and promote a more efficient use of that time, as well as demonstrating a 'survival of the fittest' type selection.
The eSTAR Project uses intelligent agent technologies to carry out resource discovery, submit observation requests and analyze the reduced data returned from a network of robotic telescopes in an observational grid. The agents are capable of data mining and cross-correlation tasks using on-line catalogues and databases and, if necessary, requesting additional data and follow-up observations from the telescopes on the network. We discuss how the maturing agent technologies can be used both to provide rapid followup to time critical events, and for long term monitoring of known sources, utilising the available resources in an intelligent manner.
KEYWORDS: Telescopes, Space telescopes, Network security, Local area networks, Internet, Computing systems, Robotics, Computer security, Network architectures, Control systems
Since the Faulkes Telescopes are to be used by a wide variety of audiences, both powerful engineering level and simple graphical interfaces exist giving complete remote and robotic control of the telescope over the internet. Security is extremely important to protect the health of both humans and equipment. Data integrity must also be carefully guarded for images being delivered directly into the classroom. The adopted network architecture is described along with the variety of security and intrusion detection software. We use a combination of SSL, proxies, IPSec, and both Linux iptables and Cisco IOS firewalls to ensure only authenticated and safe commands are sent to the telescopes. With an eye to a possible future global network of robotic telescopes, the system implemented is capable of scaling linearly to any moderate (of order ten) number of telescopes.
KEYWORDS: Telescopes, Java, Control systems, Data transmission, Optical instrument design, Control systems design, Human-machine interfaces, Robotics, Computer programming, Stars
This paper describes the design and implementation of the Next Generation Telescope Control System (NGTCS). It outlines the requirements of a generic telescope control system and presents an architectural solution to the requirements problem, and an implementation in Java. The modular design of the NGTCS enables a TCS application to be developed for virtually any telescope using the NGTCS core system, and developing Java classes for system-specific functionality. The Liverpool Telescope will use a TCS built with the NGTCS software.
In the traditional, manned observatory, an astronomer must continually be weighing together many factors during the course of an observing run in order to make an appropriate decision on the course of action at that time. Weather conditions may force suspension of the observing program to protect the telescope, later to be resumed when conditions improve. Power outages may force controlled shutdown of computers and other hardware. Changes in sky condition may require on-the-fly changes to the scheduled program. For the Liverpool Telescope (LT), the Robotic Control System (RCS) is designed to act as a replacement for the duty astronomer. The system is required to be robust, reliable and adaptable e.g. to future instrument configurations and varying operational objectives. Consequently, object-oriented techniques which promote modularity and code re-use have been employed throughout the design of this system to facilitate maintainance and future upgrading. This paper describes the task management architecture (TMA) - a configurable, pattern based object model defining the cognitive functionality of the RCS, the environment monitoring architecture (EMA) - a configurable, rule-based decision making paradigm and the use of our proprietary Java message system (JMS) communications architecture to control the telescope and associated instrumentation.
KEYWORDS: Telescopes, Astronomy, Robotics, Databases, Astronomical telescopes, Space telescopes, Astrophysics, Prototyping, Control systems, Data archive systems
The e-STAR (e-Science Telescopes for Astronomical Research) project uses GRID techniques to develop the software infrastructure for a global network of robotic telescopes. The basic architecture is based around Intelligent Agents which request data from Discovery Nodes that may be telescopes or databases. Communication is based on a development of the XML RTML language secured using the Globus I/O library, with status serving provided via LDAP. We describe the system architecture and protocols devised to give a distributed approach to telescope scheduling, as well as giving details of the implementation of prototype Intelligent Agent and Discovery Node systems.
The cost effectiveness of modern telescope operations depends upon appropriate telescope system design. We explore telescope operating models and define the efficiency of telescope usage, using recent operational data. We investigate the efficiency of telescope use with respect to several generic types of operational programme. We derive a model of telescope operating efficiency and explore the operational implications of several telescope design factors and configurations.
Five per-cent of the observing time on the Liverpool Telescope (a 2-m robotic telescope sited in La Palma) will be set aside for public understanding of science. Schools access will be via, a queue scheduling mechanism, and public access via live Planetarium shows. We describe the development and performance of a generic Java message passing system to allow communication between the processes implementing the robotic control of the telescope and the remote processes that will be run at the Planetarium. We also describe an adaptive data compression algorithm to allow transfer of data back from the telescope in near real time and our software for Planetarium access which allows staff at the Planetarium to implement their own control system and display software. Finally we describe our hierarchical web-based system for schools to input observation requests and the image processing software we have developed to allow them to make quantitative measurements of the resulting data.
The Liverpool telescope on La Palma will provide live images for planetarium shows in the Liverpool Museum in the UK. Data transfer will be achieved using the Internet. We implemented an automatic program of hourly ftp file transfers from La Palma to the UK throughout 1998 and 1999 to monitor the transfer rates achievable. We find that both the mean and minimum (on 9 out of 10 nights) transfer rates are a function of time of day on weekdays. In addition we find that the minimum transfer rate in early evening has increased from approximately 5 Kbytes/sec in 1998 to approximately 25 Kbytes/sec in 1999. This implies that a compression ratio of around 30:1 must be achieved to allow live display of 2048 X 2048 pixel CCD images in the UK within 10 seconds of the data being taken.
KEYWORDS: Telescopes, Databases, Java, Observatories, Control systems, Data modeling, Robotics, Computer programming, Optical tracking, Commercial off the shelf technology
The Liverpool Telescope will be a fully robotic 2m telescope situated in La Palma and managed from Liverpool John Moores University. The telescope observatory control system is responsible for operating the telescope in a fully automated fashion, with observations selected from a database. After a brief introduction to object-oriented techniques this paper presents a class model for observatory control system database and discusses the choice of programming language and database management system. Finally, we present a brief description of the automatic code generation tool we have developed to allow fast and reliable implementation of the object model and discuss our overall experience of using object-oriented techniques to implement an observatory control system.
The Liverpool Telescope will be a fully robotic 2 m telescope situated in La Palma and managed from Liverpool John Moores University. The data flows between the robotic components of the telescope are discussed and the functionality of those components described. We pay particular attention to the design of the telescope scheduler. Using simulations we show that a relatively simple dispatch scheduler may be tuned to produce a schedule that has acceptable trade-offs between conflicting scheduling criteria.
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