Below is a list of the projects the group is involved in.


  • APPs(Apodizing Phase Plates). High contrast imaging is important for detection and characterization of exo-planets. High contrast techniques are being developed and tested on the Adaptive Optics Testbed, to be used on E-ELT instruments. (Kenworthy, Otten)
  • Cryo-chopper More info here (Brandl, Molster)
  • CTA (Stuik)
  • dOTF Wavefront Sensing Sensing wavefront aberrations induced by Earth’s atmosphere is a pivotal part of adaptive optics systems. In this project, we simulate and build a prototype of a new type of wavefront sensor (WFS) using the differential Optical Transfer Function (dOTF) technique. The expected advantage of the dOTF WFS approach over other methods is its low cost and relative simplicity.
  • EPICS (ExoPlanet Imaging Camera and Spectrograph) is the E-ELT instrument that will enable direct detection and characterization of exoplanets. The EPICS polarimeter (EPOL)  will enable direct detections of rocky planets due to its small inner working angle at visible wavelengths, and its large contrast to to sensitive polarimetry. The polarimetry has the additional benefit of a direct distinction between a real planet and a background object. Spectropolarimetric observations at several phase angles allow for the unambiguous characterization of giant planets. (Keller, Snik, Rodenhuis, de Juan Ovelar, Korkiakoski)
  • ExPo The Extreme Polarimeter is a sensitive imaging polarimeter developed for high-contrast observations of circumstellar environments. ExPo suppresses unpolarized starlight while being very sensitive to the polarized light that has been reflected by circumstellar material. This allows the instrument to image structures that are otherwise very hard to observe, such as protoplanetary disks around young stars and dust envelopes of (post-)AGB stars. ExPo is an experimental instrument that is continuously being improved. It acts as a testbed for the future EPICS EPOL instrument but is also used for regular science observations at the William Herschel Telescope on La Palma. ExPo operates at visible wavelengths. (Rodenhuis, de Juan Ovelar, Snik, Keller, De Boer)
  • Immersed Gratings (Brandl)
  • iSPEX (Snik)
  • MASCARA (Multi-site All-Sky CAmeRA). Mascara is being developed to detect exo-planets around bright stars using off-the-shelf consumer cameras. (Snellen, Lesage, Spronck, Stuik, Otten, Kenworthy)
  • MATISSE (Multi-AperTure mid-Infrared SpectroScopic Experiment). MATISSE is a second-generation instrument for the interferometer mode of VLT, VLTI. It will measure closed phase relations, thus offering an efficient capability for image reconstruction at milli-arcsecond resolution. (Jaffe (co-PI), Bettonvil, Venema, Brandl)
  • METIS (Mid-infrared E-ELT Imager and Spectrograph). METIS is the mid-infrared instrument for the European Extremely Large Telescope, Europe's foremost optical/IR observatory for the next decade. Together with ASTRON, Leiden is the PI institute for the Phase A study for METIS, which was completed in December 2009. Current work includes follow-up on the Instrument Model, AO performance simulations and the development, characterization, testing and comparison of new methods for accurate background removal for METIS by modeling, prototyping and measuring. (Brandl (PI), Schmalzl, Molster, Heikamp, Stuik, Venema)
  • MICADO (Stuik)
  • MIRI (Brandl)
  • MUSE (Multi-Unit Spectroscopic Explorer) is a wide-field integral field spectrograph at optical wavelengths. A second generation instrument for the VLT Observatory Cerro Paranal, MUSE is currently undergoing commissioning at the telescope and will be offered to the scientific community in one of the next cycles (Stuik).
  • OmegaCAM (Kuijken) OmegaCAM is a 1 square degree wide field, optical, 16k X 16k camera for the VLT Survey Telescope (VST). OmegaCAM has been commissioned Summer 2011 and has started operations mid-Oct 2011. KIDS survey data is currently being taken at Paranal Observatory in Chile and processed by the Astro-WISE consortium in Europe.
  • Polarimetric IFU This is a technology R&D project to develop a prototype spectropolarimetric integral field unit for the future EPICS-EPOL imaging polarimeter. This E-ELT instrument will be able to detect and image rocky exoplanets. To also perform some rudimentary characterization of the detected planets, the wavelength resolution offered by an IFU will be crucial. The prototype IFU will be tested with the ExPo instrument. (Rodenhuis, Keller)
  • Polarimetry R&D. Leiden Observatory is a leading institute in the development of new polarimetric techniques:
    -The M&m's code for polarimetric error budgeting and performance prediction. (de Juan Ovelar, Snik, Keller)
    -The poly-polarimeter is a generic lab facility that will offer imaging and spectro-polarimetry, and ellipsometry at visible wavelengths. (Snik, de Juan Ovelar, van Harten)
    -A DoLP calibrator is under development. It will be used as a partially polarized calibration source. (Van Harten, Snik)
    -A mathematical formalism to fully describe polarized fringes has been implemented. (Keller, Van Harten, Snik).
    -Development of models of polarized diffraction effects. Studies the impact of, among others, segmentation and coronagraphy on polarization.(Keller, Snik, Debackere).
    -TreePol is a testbed for the remote detection of homochirality as a sign of life. Korte beschrijving: Measure the degree of circular polarization, as function of wavelength, of biological samples. We want to see if we can use the homochirality as a sign of life, for later use in remote sensing of exoplanets. (Visser)
  • Sorption Coolers More info here (Brandl, Molster)
  • Aquarius (Brandl, Heikamp) Aquarius detector testing, performance of various chopping patterns.
  • WEAVE (Stuik)
  • X-shooter polarimeter. After the successful construction and commissioning of the HARPS polarimeter, a full-Stokes polarimeter is now being designed for X-shooter. It consists of a novel "polychromatic" modulator that offers close-to-optimal polarimetric efficiencies over the full wavelength range of 300-2500 nm. (Snik, Van Harten)


  • Gaia is an ESA mission to measure the positions of an extremely large number of stars with unprecedented accuracy, allowing astronomers to study the 3D structure of our Galaxy, and thus learn about its origin and evolution. Gaia launched successfully and is currently undergoing performance verification. (Brown)
  • MIRI is the Mid-Infrared Instrument for the James Webb Space Telescope (JWST), NASA and ESA's next-generation space telescope set for launch in 2018. As part of a large international consortium, Leiden instrument scientists are involved in testing and calibration of MIRI's spectroscopy modes, as well as members of the MIRI European science team. (Brandl)
  • SPEX (Spectropolarimeter for Planetary EXploration) is a remote sensing concept for characterizing aerosols in planetary atmospheres from an orbiting, air-borne or ground-based platform. It is based on the spectral modulation polarimetric concept invented by Snik & Keller. A SPEX prototype has been constructed in collaboration with SRON and Dutch Industry, which performance exceeds expectations. SPEX instruments are being proposed on satellite missions to study Mars and Jupiter and its moons. A (wide-field) SPEX instrument for Earth observation from orbit is currently being designed. A prototype SPEX for ground-based observations from a meteorological station is being developed together with RIVM. (Van Harten, Snik, Keller)
  • LOUPE (Lunar Observatory for Unresolved Polarimetry of Earth) is an instrument concept for a lunar lander. The goal is to look back at Earth from the moon, and observe the Earth as if it were an exoplanet. LOUPE data will provide a crucial benchmark for future observations of Earth-like exoplanets. (Snik, Hoeijmakers)


  • NAOMi (Netherlands Adaptive Optics Microscope) aims to provide adaptive optics on commercial off-the-shelf multi-photon microscopes. In the microscopy case the aberrations are not caused by a turbulent atmosphere, but by inhomogeneous biological tissues instead. We will use adaptive optics to correct these and improve the resolution while at the same time reducing photo-toxicity (Van Werkhoven, Keller).