Ordinary Meeting, 2009 May 27

 

Pro/Am Collaboration with Schools using Robotic Telescopes

Mr Lewis began by explaining that the two Faulkes Telescopes formed a part of the Las Cumbres Observatory Global Telescope (LCOGT) Network, whose construction had been funded largely by the philanthropic generosity of Dr Martin C. (Dill) Faulkes, who had contributed £10 million to the project. This funding had been supplemented by a £1 million grant from the Particle Physics and Astronomy Research Council (PPARC; subsequently merged into the STFC in April 2007), and a £600k grant from the Department for Education and Skills (DfES; subsequently broken in multiple departments in June 2007).

At its inception, the Telescope Network had been envisaged as a part of the Millennium Dome project, providing a platform for bringing live astronomy into the Dome during the hours of UK daylight with the help of internet communications. In the end, that plan had not come to fruition and project's aim had shifted to providing a means of bringing data from remotely-controlled robotic telescopes into school classrooms. This remained the project's central aim, for which purpose it now owned and operated two purpose-built two-metre telescopes – the Faulkes Telescope North in Haleakala, Hawaii, and the Faulkes Telescope South in Siding Spring, Australia. The geographic placement of these telescopes in opposite hemispheres and at longitudes well-separated from that of the UK made it possible to make live observations of both the northern and southern celestial hemispheres throughout much of the UK school day; typically at least one of the two telescopes was online at any time between 6am and 7pm UK time.

Turning to give an overview of the telescopes themselves, the speaker explained that both were housed in unusual clam-shell domes which completely retracted when opened to give a full view of the sky. This aspect of the design was partially historic, dating back to early plans to link the two telescopes up with the similarly-sized Liverpool Telescope on the island of La Palma to form a network of telescopes, given the provisional name Robonet, for performing follow-up observations of Gamma Ray Bursters (GRBs) detected by the Swift satellite. Given the transient nature of GRBs, follow-up observations had to be made as rapidly as possible after their initial detection, and the lack of any dome around the Faulkes Telescopes eliminated any delay that a slowly-rotating dome might cause when slewing to such objects at speed. Had Robonet come to fruition, its three telescopes would have provided 24-hour coverage of the night side of the sky, but in practice the network had never been funded. Nonetheless, the Faulkes Telescopes were kept on standby to make GRB observations during those hours when they were online.

Mr Lewis added that there were plans to imminently expand the LCOGT network, both to increase the amount of observing time available to schools, and to increase the number of hours of the day when at least one of its observatory sites would be online. It was hoped that LCOGT would soon provide its own 24-hour facility for making follow-up observations of GRBs in the place of Robonet. Whilst these plans would not involve the building of any more two-metre telescopes of the same class as the existing pair of telescopes, a large number of much smaller 0.4-metre telescopes would be added to the network within the next 12 months. These would be arranged with between two and four alongside each of the current two telescopes, and, subject to planning negotiations, similar numbers at each of five further new observatory sites: Cerro Tololo in Chile, Mauna Loa in Hawaii, Sutherland in South Africa, Exmouth in Australia, and Tenerife in the Canary Islands.

Looking further ahead, there were more ambitious plans to add a similar number of one-metre telescopes to the network by 2012. It was currently hoped that as many as eighteen might be installed in total, arranged with three side-by-side on each of six sites, though such plans were not yet definite.

Mr Lewis then turned to outline the optics of the telescopes. The current pair of two-metre telescopes each had two-metre f/10 research-grade primary mirrors, which had been built at a cost of £250k each. Each had a field-of-view of 4.6 arcminutes – rather smaller than that of most amateur telescopes – and was fitted with a professional-grade 2048×2048 CCD camera. Given the large apertures and small fields-of-view of these telescopes, they were best suited for deep imaging of small patches of sky, rather than wide-angle photography. Typically, the seeing at each of the sites varied between 0"75 at best to 2" at worst. A wide range of different colour filters were available to observers, including the traditional BVR Bessel (similar to Johnson) filter set, the u'g'r'i' filter set of the Sloan Digital Sky Survey (SDSS), z' and y' filters to match those available on the Pan-STARRS telescopes, and narrowband filters including Hα, Hβ and OIII. Both of the Faulkes telescopes were fully robotic – to reduce costs, the observatory sites were completely unmanned – and were able to open and close in response to automatic weather alerts.

The forthcoming 0.4-metre telescopes would bear a much greater similarity to standard amateur telescopes. The optical tubes would be standard Meade parts, yielding a field-of-view of 30'×20' at a focal ratio of f/8. Nonetheless, professional-grade CCDs would be mounted on them, allowing 3-4 three-colour images to be taken in each of the 30-minute observing slots allocated to schools. A user-friendly pipelined interface would guide the schools through the process of taking three sequential exposures with different filters and then stacking them to produce colour images.

Turning to outline the scientific research for which the telescopes were being used, Mr Lewis explained that research projects had been developed with the aim not only that they should produce genuinely useful and interesting science, but also that schools should be able to contribute to them with a wide range of different levels of commitment. Furthermore, it was hoped that each project would provide as much interaction as possible between the schools and the professional researchers who were guiding the research to make new discoveries, whilst at the same time being accessible to schools which could not be expected to come to the project with much background expertise. The speaker thus explained that in the design of each project, considerable effort had gone into preparing training material for teachers so that they could get involved without needing to have any prior specialist knowledge; the detailed work of planning worthwhile observing campaigns was largely done for them. The speaker went on to remark that the two Faulkes telescopes were not well suited for observing many of the most obvious stereotypical astronomical objects – for example, the Moon and planets – because they had such large apertures and small fields-of-view. He explained that this was in many ways a deliberate choice: it provided a useful way of driving schools into participating in a more diverse and challenging set of scientific projects – with the end reward that genuine new discoveries could be made – than they might otherwise have devised themselves.

The speaker then outlined one particularly successful project which schools had been involved with, in which they had taken time-lapse images of asteroids. He explained that on the most basic level, a school which took a single image of an asteroid discovered the impossibility of distinguishing asteroids from stars in such images: both appeared as unresolved point sources. On the next level, when a few time-lapse images had been taken and made into a movie or otherwise animated, the motion of the asteroid relative to background stars became very apparent. The most committed schools could then go on to perform photometry and estimate the asteroid's brightness, and over time construct a light-curve for it. Eventually, it might be possible to measure the asteroid's rotation period.

In reality, this project had proven such a success, and some schools had been so committed to it, that a particularly notable first had been achieved. The speaker explained that for some time, professional astronomers had been hoping to detect a theoretically-predicted phenomenon called the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) Effect, that the spin rate of non-spherical asteroids should change over time as a result of the pressure exerted on them by the sunlight falling on their surfaces. Einstein's theory of special relativity predicted that even though photons of light had no mass, they still exerted a force – a very tiny force – when they collided with things; this was termed radiation pressure. Applying this theory to a non-spherical asteroid which might have, for example, a knobbly mountain sticking out of one side, it was possible that the mountain would present a disproportionately large surface area for sunlight to push against on one side of the asteroid, and by this means act as a lever with which sunlight could spin up the asteroid.

In practice, the effect was very small because sunlight only exerted very tiny forces, and hence it had never been successfully detected. However, observations of a small near-Earth asteroid by the name of (54509) 2000 PH5 by the Faulkes Telescope North, when combined with data from various other professional instruments, had revealed the rotation period of the asteroid to be decreasing by around a millisecond each year, in agreement with theoretical predictions of the magnitude of the YORP Effect for this object.1,2

The speaker moved on to discuss some of the science which had been made possible during the brief window in 2007 when Uranus' ring and moon system had passed through its edge-on orientation as seen from Earth. The speaker explained that this event had been analogous to the more readily observable ring-plane crossing which Saturn would shortly be undergoing in 2009 August. Just as Saturn's system of moons was presented in an edge-on orientation during its current 2009 apparition, and amateurs had been able to observe mutual occultations of its moons over the past few months, so the Faulkes Telescope had been able to image and obtain accurate timings for mutual occultations of Uranus' moons in mid-2007. For example, on 2007 May 5, an occultation of Umbriel (IV; 1,500-km across) by Oberon (II; 1,200-km across) had been observed by the Faulkes Telescope South. Interestingly, however, the event had occurred 10 minutes later than had been predicted by the best models of Uranus' moon system. This highlighted the surprising fact that our knowledge of the orbits of the moons of the outer planets often remained quite sketchy, and were often based on small numbers of observations.

Other projects with which schools were involved included making follow-up observations of candidate extrasolar planets as they were reported by the SuperWASP robotised search programme. These typically involved making photometric measurements of the parent star to build up a lightcurve over a moderately long period in the hope of finding any short and well-defined dips which might be attributed to the transit of a planet across the star's disk. On a similar theme, lightcurves could be constructed for a variety of variable star systems, including variable X-ray sources. All of these photometric projects required the collation of data collected over a period of days, and so encouraged collaboration between schools, each taking photometry for half an hour before passing on to the next.

The speaker closed by addressing the question of whether amateur astronomical societies could use the Faulkes Telescopes. He remarked that the enthusiasm of amateurs for the work of the telescopes was very pleasing to see, and that amateurs were very welcome to sign up with the project and make use of the data collected by the two telescopes. However, he explained that the principal audience for the project were young people who would not otherwise have access to telescopes, whereas most amateur societies had their own observing facilities. Thus, astronomical societies were generally not permitted to schedule their own observations unless there was a clear educational purpose to their work.

Following the applause, the President introduced the evening's second speaker, Dr David Walker, head of the Optical Science Laboratory at University College London (UCL) and technical director of a private optical engineering company, Zeeko Ltd.

Fairfield

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