Dr Fraser Clarke

Abstract:

As part of the Phase A study for the EPICS instrument, we investigate if there are any contrast limitations imposed by the choice of the integral field spectrograph (IFS) technology, and if so, to determine the contrast limits applicable to each technology. In this document we investigate (through simulations) the contrast limitations inherent in a slicer based IFS. Current results show the achievable contrast with the slicer to be promising when taking into consideration the fact that the central region of the apodized PSF has not been masked. Limiting the maximum intensity by a factor of 100-1000 using an obscuring focal plane mask should also reduce the intensity of the secondary speckles by an equivalent factor. Furthermore, the secondary speckles created in the slicer spectrograph only influence the few slices where the bright central core is imaged. By orienting these slices to lie along the spider arms of the E-ELT secondary, the fraction of the field of view affected can be minimized. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

The Oxford SWIFT spectrograph, an I & z band (6500-10500 A) integral field spectrograph, is designed to operate as a facility instrument at the 200 inch Hale Telescope on Palomar Mountain, in conjunction with the Palomar laser guide star adaptive optics system PALAO (and its upgrade to PALM3000). SWIFT provides spectra at R(≡λ/Δλ)∼4000 of a contiguous two-dimensional field, 44 x 89 spatial pixels (spaxels) in size, at spatial scales of 0.235″;, 0.16″, and 0.08″ per spaxel. It employs two 250μm thick, fully depleted, extremely red sensitive 4k X 2k CCD detector arrays (manufactured by LBNL) that provide excellent quantum efficiency out to 1000 nm. We describe the commissioning observations and present the measured values of a number of instrument parameters. We also present some first science results that give a taste of the range of science programs where SWIFT can have a substantial impact. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

HARMONI is a visible and near-infrared integral field spectrograph for the E-ELT. It needs to work at diffraction limited scales. This will be possible thanks to two adaptive optics systems, complementary to each other. Both systems will make use of the telescope's adaptive M4 and M5 mirrors. The first one is a simple but efficient Single Conjugate AO system (good performance, low sky coverage), fully integrated in HARMONI itself. The second one is a Laser Tomographic AO system (medium performance, very good sky coverage). We present the overall design of the SCAO system and discuss the complementary between SCAO and LTAO for HARMONI. © 2010 SPIE.

Abstract:

Our team is carrying out a multi-year observing program to directly image and characterize young extrasolar planets using the Near-Infrared Coronagraphic Imager (NICI) on the Gemini-South 8.1-meter telescope. NICI is the first instrument on a large telescope designed from the outset for high-contrast imaging, comprising a high-performance curvature adaptive optics (AO) system with a simultaneous dual-channel coronagraphic imager. Combined, with state-of-the-art AO observing methods and data processing, NICI typically achieves ≈2 magnitudes better contrast compared to previous ground-based or space-based planet-finding efforts, at separations inside of ≈2". In preparation for the Campaign, we carried out efforts to identify previously unrecognized, young stars as targets, to develop a rigorous quantitative method, for constructing our observing strategy, and to optimize the combination of angular differential imaging and spectral differential imaging. The Planet-Finding Campaign is in its second year, with first-epoch imaging of 174 stars already obtained out of a total sample of 300 stars. We describe the Campaign's goals, design, target selection, implementation, on-sky performance, and preliminary results. The NICI Planet-Finding Campaign represents the largest and most sensitive imaging survey to date for massive (≳1 MJup) planets around other stars. Upon completion, the Campaign will establish the best measurements to date on the properties of young gas-giant planets at ≳5-10 AU separations. Finally, Campaign discoveries will be well-suited to long-term orbital monitoring and detailed spectrophotometric followup with next-generation planet-finding instruments. © 2010 SPIE.