We report a laboratory experiment to assess the performance and limitations of the four-quadrant phase mask coronagraph we proposed 2 years ago. A total flux rejection factor of 4400 was reached using off-the-shelf optical components. The peak intensity of the Airy pattern is correspondingly reduced by a factor of 44,000 with a stability of a few hours. In this paper, we discuss implications of this excellent result regarding the next generation of instruments for extrasolar planet detection.

/pdf/the-four-quadrant-phase-mask-coronagraph-iii-laboratory-3sio95xiz1.pdf

The Four-Quadrant Phase Mask Coronagraph. III. Laboratory Performance

The James Webb Space Telescope (formerly the Next Generation Space Telescope) will be capable of unprecedented science, owing to its large diameter, its low background, and its dedicated IR instruments. One of these instruments is a mid‐IR facility called MIRI (Mid‐IR Instrument), which is being studied through a collaboration of US and European teams. Our group at Observatoire de Meudon has developed a coronagraphic device for the MIRI camera. Taking advantage of the reduced star‐planet contrast in this spectral range, the prime goal of this coronagraph is the direct detection of extrasolar planets. Differential imaging in several well‐chosen spectral windows is foreseen. In this paper, we evaluate the manufacturing process of the coronagraphic masks and compare the intrinsic performance, as measured in the laboratory, with the scientific requirements.

https://www.jstor.org/stable/10.1086/503124

Feasibility of the Four‐Quadrant Phase Mask in the Mid‐Infrared on the James Webb Space Telescope

ArTeMiS is a wide-field submillimeter camera operating at three wavelengths simultaneously (200, 350 and 450 microns). A preliminary version of the instrument equipped with the 350 microns focal plane, has been successfully installed and tested on APEX telescope in Chile during the 2013 and 2014 austral winters. This instrument is developed by CEA (Saclay and Grenoble, France), IAS (France) and University of Manchester (UK) in collaboration with ESO. We introduce the mechanical and optical design, as well as the cryogenics and electronics of the ArTeMiS camera. ArTeMiS detectors are similar to the ones developed for the Herschel PACS photometer but they are adapted to the high optical load encountered at APEX site. Ultimately, ArTeMiS will contain 4 sub-arrays at 200 microns and 2x8 sub-arrays at 350 and 450 microns. We show preliminary lab measurements like the responsivity of the instrument to hot and cold loads illumination and NEP calculation. Details on the on-sky commissioning runs made in 2013 and 2014 at APEX are shown. We used planets (Mars, Saturn, Uranus) to determine the flat-field and to get the flux calibration. A pointing model was established in the first days of the runs. The average relative pointing accuracy is 3 arcsec. The beam at 350 microns has been estimated to be 8.5 arcsec, which is in good agreement with the beam of the 12 m APEX dish. Several observing modes have been tested, like On-The-Fly for beam-maps or large maps, spirals or raster of spirals for compact sources. With this preliminary version of ArTeMiS, we concluded that the mapping speed is already more than 5 times better than the previous 350 microns instrument at APEX. The median NEFD at 350 microns is 600 mJy.s1/2, with best values at 300 mJy.s1/2. The complete instrument with 5760 pixels and optimized settings will be installed during the first half of 2015.

The ArT\'eMiS wide-field submillimeter camera: preliminary on-sky performances at 350 microns

ArTeMiS is a wide-field submillimeter camera operating at three wavelengths simultaneously (200, 350 and 450 μm). A preliminary version of the instrument equipped with the 350 μm focal plane, has been successfully installed and tested on APEX telescope in Chile during the 2013 and 2014 austral winters. This instrument is developed by CEA (Saclay and Grenoble, France), IAS (France) and University of Manchester (UK) in collaboration with ESO. We introduce the mechanical and optical design, as well as the cryogenics and electronics of the ArTeMiS camera. ArTeMiS detectors consist in Si:P:B bolometers arranged in 16×18 sub-arrays operating at 300 mK. These detectors are similar to the ones developed for the Herschel PACS photometer but they are adapted to the high optical load encountered at APEX site. Ultimately, ArTeMiS will contain 4 sub-arrays at 200 μm and 2×8 sub-arrays at 350 and 450 μm. We show preliminary lab measurements like the responsivity of the instrument to hot and cold loads illumination and NEP calculation. Details on the on-sky commissioning runs made in 2013 and 2014 at APEX are shown. We used planets (Mars, Saturn, Uranus) to determine the flat-field and to get the flux calibration. A pointing model was established in the first days of the runs. The average relative pointing accuracy is 3 arcsec. The beam at 350 μm has been estimated to be 8.5 arcsec, which is in good agreement with the beam of the 12 m APEX dish. Several observing modes have been tested, like “On- The-Fly” for beam-maps or large maps, spirals or raster of spirals for compact sources. With this preliminary version of ArTeMiS, we concluded that the mapping speed is already more than 5 times better than the previous 350 μm instrument at APEX. The median NEFD at 350 μm is 600 mJy.s1/2, with best values at 300 mJy.s 1/2 . The complete instrument with 5760 pixels and optimized settings will be installed during the first half of 2015.

The ArTÈMiS wide-field sub-millimeter camera: preliminary on-sky performance at 350 microns

Recent advances in the design of all reflective integral field units have led engineers to look for new techniques to manufacture monolithic mirror arrays for use in such instruments. One such design is being developed at the UKATC for use on the Mid-Infrared Instrument (MIRI) on the James Webb Space telescope. The MIRI instrument will contain four integral field units with image slicer and re-imaging mirror arrays manufactured at Cranfield University. The mirror arrays have been designed with particular attention to the requirements of precision machining and subsequent metrology. The philosophy of "design for manufacture" has led to the production of mirror arrays with unrivalled levels of accuracy. Initially, this paper will describe the opto-mechanical design of the mirror arrays. The paper will then discuss the diamond turning manufacturing technique specially developed to machine these complex components. The paper will also describe the precision metrology capability developed specifically for the MIRI project that is used to accurately measure mirror locations and surface form errors. Finally, the paper will present the results obtained so far for the mirror arrays being prepared for the IFU verification model and prototype.

Development of diamond machined mirror arrays for integral field spectroscopy

MIRI is the mid infrared instrument planned for the NGST. Working in the 5-28 μm band, it includes 3 units: a spectrograph, an imager and a calibration facility. We describe here the optical design of the MIRI imager channel as it is at teh end of the phase A study. The MIRI imager provides 3 observing modes: an imaging mode with a field of view of 1.3 arcmin x 1.7 arcmin and a Pixel Field of View of 0.1 arcsec/pixel, a coronagraphic mode and a low resolution spectroscopic mode for point sources, between 5 μm and 10 μm, with a spectral resolution R = λ/Δλ around 100.

Optical design for the 5-28μm NGST infrared imager MIRI

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Optical design for the 5-28μm NGST infrared imager MIRI