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Active Research Projects
Exoplanets and Observational Techniques
University of Cambridge
Institute of Astronomy
Unfolding Space Telescopes for Astronomy and Earth Observations
The power of space telescopes for astronomy has long been recognised. They are much more powerful than ground-based telescopes because the Earth's atmosphere blurs the images, blocks out many wavelengths and adds a bright background glow. Yet in the mainstream wavelength range of 0.3 to 5.0 microns there has only been one general purpose space observatory (the Hubble Space Telescope) and a handful of specialised, smaller telescopes. Furthermore, in the next 15 years there will only be two general purpose successors to Hubble - the James Webb Space Telescope and WFIRST. A major reason for this is of course the cost of putting a large telescope in space. I am therefore working on techniques to reduce costs by making them small and light-weight in their launch configuration but large (and therefore powerful) once in orbit. This will make 2-4m class telescopes far more affordable and enable huge telescopes in the 10-30m class to be possible.
On the other hand, for Earth Observation (EO) there are already hundreds of telescopes in orbit looking down at the ground, although most of these are relatively small. For EO, unfolding telescopes offer significant cost reduction enabling affordable high definition imaging and on-demand imaging. I am currently PI for an STFC-funded market research project into the commercial potential of unfolding telescopes.
The idea of unfolding space telescopes is of course not new and there are significant technical challenges. Firstly, we need an innovative and reliable unfolding scheme. Secondly, we need to put the deployed optics in to precise alignment and then continuously maintain that alignment. This requires a very precise metrology system, a set of high accuracy actuators and a sophisticated control system.
The research will procede in two stages.
The pictures on the left show that there is enough space inside a 12U cubesat to stow a 0.9m telescope which gives 30cm ground resolution for EO and 100 mas resolution for astronomy.
SUPER-SHARP: Space-based Unfolding Primary for Exoplanet Research via Spectroscopic High Angular Resolution Photography
The top picture on the left shows a concept for a 23.5m telescope that can fit into the 4.57m diameter fairing of an Ariane 6 rocket. To see how such a large telescope can fit into an Ariane 6 go to Youtube animation #1. Each of the 4 mirrors in the cross-shaped primary is 10m x 2.8m. The picture underneath shows another version of SUPERSHARP that fits in a Soyuz rocket fairing. The primary mirror for this is 24x3.3m (see Youtube animation #2). SUPER-SHARP will directly image exoplanets and its instrumentation includes active mirror control, a coronograph (to remove the light from the central star for exoplanet observations) and an integral field spectrograph (to give R=100 spectra for every pixel in the 2x2 arcsec FOV). The 23.5m mirror baseline gives an inner working angle (IWA) of 16 mas at 750nm with 8 mas spatial resolution and an IWA of just 2.7 mas at ultra-violet wavelengths.
The SUPER-SHARP design philosophy is to push extremely hard on spatial resolution and IWA while at the same time keeping within an affordable budget. SUPER-SHARP will therefore maximise primary mirror baseline, use the shortest possible operating wavelength and be pragmatic about everything else (number of instruments, field of view, thermal management, raw speckle contrast, etc.). Some mirror deployment strategies (i.e unfolding mechanisms) can achieve even greater baselines than 23m.
The mission's main science goals are:
Our latest paper on the white dwarf companion to HD114174 can be found here
MOONS description paper.
MOONS updated optical design paper.
This is the high resolution spectrograph for the European Extremely Large Telescope. Currently the project is in the conceptual design phase. There are numerous science drivers but the key ones are:
My HIRES collaborators in Cambridge are Roberto Maiolino, Didier Queloz, Martin Haehnelt, Max Pettini, Chris Haniff, David Buscher, Martin Fisher and David Sun.
Last updated on May 23rd 2017.