{"id":43,"date":"2014-11-24T13:01:11","date_gmt":"2014-11-24T13:01:11","guid":{"rendered":"https:\/\/gregor.aip.de\/cms\/?page_id=43"},"modified":"2022-06-02T11:14:36","modified_gmt":"2022-06-02T11:14:36","slug":"instruments","status":"publish","type":"page","link":"https:\/\/gregor.aip.de\/cms\/instruments\/","title":{"rendered":"Instruments"},"content":{"rendered":"

Data Policy<\/a><\/h3>\n

Bibliography<\/a><\/h3>\n

GREGOR Fabry-P\u00e9rot Interferometer (GFPI)<\/h3>\n

\"\"<\/a>Fast processes on the Sun require instruments capable of acquiring data in a time span comparable to the evolution time-scale of solar features, which is on the order of minutes and sometimes even on the order of seconds. Imaging spectropolarimetry with the GFPI (Puschmann et al.<\/em> 2012<\/a>, 2013<\/a>) is ideally suited for this type of application. The instrument comprises two tunable etalons in collimated mounting, which provide a spectral resolution of\u00a0\u211c\u2009\u2248\u2009250.000. Scanning a spectral line takes a few tens of seconds to from a few minutes depending on the sampling, the number of images acquired per wavelength position, and the observing mode (spectroscopy vs. polarimetry). Two cameras with 1376\u2009\u00d7\u20091024 pixel acquire images strictly simultaneously in the narrow- and broad-band channels to facilitate post-facto image restoration including simple destretching, speckle masking imaging and deconvolution, and multi-object mult-frame blind deconvolution (MOMFBD). The field-of-view (FOV) is 50\u2033\u2009\u00d7\u200938\u2033 in the spectroscopic observing mode and about half the size for polarimetric observations. Small sunspots and substantial portions of active regions can thus be observed. The coatings of the etalons are optimized for the wavelength range 530\u2013860\u2009nm, while the polarimeter limits the spectral observing window to 580\u2013660\u2009nm. Many interesting photospheric and chromospheric spectral lines are accessible, and two of them can be observed sequentially.<\/p>\n

All GFPI data (i.e., raw data and high-level data products) are stored in the GREGOR archive at AIP, where they can be accessed and queried on this website after registration<\/a>. New data is embargoed for one year or two years in case of PhD theses.<\/p>\n

PI Institute:<\/strong> Leibniz Institute for Astrophysics Potsdam (AIP<\/a>)
\nContact:<\/strong> Carsten Denker<\/a><\/p>\n

Blue Imaging Channel (BIC)<\/h3>\n

High-cadence imagi\"BIC<\/a>ng provides important context information for the\u00a0 GFPI observations. Small-scale magnetic features are more more easily detected in particular wavelength regions, e.g., the Fraunhofer G-band. Furthermore, the broad Calcium H and K lines offer chromospheric diagnostics.\u00a0 Two CCD cameras (pco.4000 and pco.sensicam) were used in the BIC of the GFPI depending on the availability of the GREGOR\/VTT facility cameras until the end of 2015. Three interference filters (Ca\u2009II<\/small>\u2009H \u03bb396.8\u2009nm, G-band \u03bb430.7\u2009nm, and blue continuum \u03bb450.8\u2009nm) are available. Recently, MPS contributed a 0.1-nanometer-wide Ca\u2009II<\/small>\u2009H \u03bb396.8\u2009nm interference filter of the Sunrise mission. The maximum FOV of the pco.4000 CCD cameras is limited to 75\u2033\u2009\u00d7\u200993\u2033 (2160\u2009\u00d7\u20092672 pixel) because of dichroic pentaprism splitting the light between GFPI and BIC. The FOV of the pco.sensicam CCD camera is much smaller 34\u2033\u2009\u00d7\u200926\u2033 (1376\u2009\u00d7\u20091040 pixel) but the data acquisition rate is much higher (eight vs. three frames per second). However, in both cases post-facto image restoration is feasible (Knox-Thompson, speckle masking imaging, and multi-frame blind deconvolution).<\/p>\n

All BIC data (i.e., raw data and high-level data products) are stored in the GREGOR archive at AIP, where they can be accessed and queried on this website after registration<\/a>. New data is embargoed for one year or two years in case of PhD theses.<\/p>\n

PI Institute:<\/strong> Leibniz Institute for Astrophysics Potsdam (AIP<\/a>)
\nContact:<\/strong> Carsten Denker<\/a><\/p>\n

High-Resolution Fast Imager (HiFI)<\/h3>\n

\"\"<\/a>In early 2016, we installed HiFI at the GREGOR solar telescope,\u00a0 where it resides in the blue imaging channel of the GFPI , which is fed by a dichroic beamsplitter with a cut-off at \u03bb530 nm. Two Imager sCMOS cameras from LaVision replaced older PCO.4000 and PCO.sensicam facility cameras. The new sCMOS detectors are synchronized by a programmable timing unit and record time-series suitable for image restoration either separately for each channel or making use of both channels at the same time. The exposure time is usually a few milliseconds. Different count rates in both channels are balanced by choosing suitable neutral density filters. Short exposure times are essential to freeze the wavefront aberrations in a single exposure. The\u00a0 2560\u00d72160-pixel images with a FOV of 64.8\u2033 \u00d7 54.6\u2033 are digitized as 16-bit integers and recorded with a data acquisition rate of almost 50 Hz. Thus, the image scale is about 0.025\u2033 pixel-1<\/sup> or about 20 km on the solar surface at the disk center. The diffraction-limited resolution of the GREGOR telescope with a diameter D<\/em> = 1.5 m at a wavelength \u03bb\u00a0= 400 nm is\u00a0\u03b1 = \u03bb \/ D = 0.055\u2033. According to the Nyquist sampling theorem, HiFI images are critically sampled at the shortest wavelength of the standard interference filters. A solar feature moving at 1 km s-1<\/sup> traverses a pixel in little over 20 s. In the standard observing mode, sets of 2 \u00d7 500 images are continuously written to a RAID-0 array of SSDs at a cadence below 20 s. The imaging system has achieved a sustained write speed of up to 660 MB s-1<\/sup>. To limit the final data storage requirements, only the best 2 \u00d7 100 images of a set are kept for image restoration and further data analysis.<\/p>\n

All HiFI data (i.e., raw data and high-level data products) are stored in the GREGOR archive at AIP, where they can be accessed and queried on this website after registration<\/a>. New data is embargoed for one year or two years in case of PhD theses.<\/p>\n

PI Institute:<\/strong> Leibniz Institute for Astrophysics Potsdam (AIP<\/a>)
\nContact:<\/strong> Carsten Denker<\/a><\/p>\n

<\/h3>\n

Improved High-Resolution Fast Imager (HiFI+)<\/h3>\n

\"HiFIplus\"<\/a>The upgraded High-resolution Fast Imager (HiFI+) consists of three camera control computers with two synchronized sCMOS (16-bit digitization) or CMOS (12-bit digitization) cameras each. Starting in the 2022 observing season, HiFI+ will offer near-diffraction limited imaging at high cadence in six spectral windows:<\/p>\n