European Solar Telescope: Progress status

In this paper, the present status of the development of the design of the European Solar Telescope is described. The telescope is devised to have the best possible angular resolution and polarimetric performance, maximizing the throughput of the whole system. To that aim, adaptive optics and multi‐conjugate adaptive optics are integrated in the optical path. The system will have the possibility to correct for the diurnal variation of the distance to the turbulence layers, by using several deformable mirrors, conjugated at different heights. The present optical design of the telescope distributes the optical elements along the optical path in such a way that the instrumental polarization induced by the telescope is minimized and independent of the solar elevation and azimuth. This property represents a large advantage for polarimetric measurements. The ensemble of instruments that are planned is also presented (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

EST Adaptive optics performance estimations

We give a short overview of the Adaptive Optics (AO) and Multi‐conjugate Adaptive Optics (MCAO) system of the planned 4 m European Solar Telescope (EST). The optimization process of the AO / MCAO parameters is shown, including the parameters and layout of the Shack‐Hartmann wavefront sensor setup and the DMs. We show the expected performance of the AO and MCAO system (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Calibration measurements on the DEPFET Detectors for the MIXS instrument on BepiColombo

The Mercury Imaging X-ray Spectrometer (MIXS) will be launched on board of the 5th ESA cornerstone mission BepiColombo. The two channel instrument MIXS is dedicated to the exploration of the elemental composition of the mercurian surface by imaging x-ray spectroscopy of the elemental fluorescence lines. One of the main scientific goals of MIXS is to provide spatially resolved elemental abundance maps of key rock-forming elements. MIXS will be the successor of the XRS instrument, which is currently orbiting Mercury on board of NASAs satellite MESSENGER. MIXS will provide unprecedented spectral and spatial resolution due to its innovative detector and optics concepts. The MIXS target energy band ranges from 0.5 to 7 keV and allows to directly access the Fe-L line at 0.7 keV, which was not accessible to previous missions. In addition, the high spectroscopic resolution of FWHM ≤ 200 eV at the reference energy of 1 keV after one year in Mercury orbit, allows to separate the x-ray fluorescence emission lines of important elements like Mg (1.25 keV) and Al (1.49 keV) without the need for any filter. The detectors for the energy and spatially resolved detection of x-rays for both channels are identical DEPFET (DEpleted P-channel FET) active pixel detectors. We report on the calibration of the MIXS flight and flight spare detector modules at the PTB (Physikalisch-Technische Bundesanstalt) beamlines at the BESSY II synchrotron radiation facility. Each detector was calibrated at least at 10 discrete energies in the energy range from 0.5 to 10 keV. The excellent spectroscopic performance of all three detector modules was verified.     

The GREGOR polarimetric calibration unit

The new Solar telescope GREGOR is designed to observe small‐scale dynamic magnetic structures below a size of 70 km on the Sun with high spectral resolution and polarimetric accuracy. For this purpose, the polarimetric concept of GREGOR is based on a combination of post‐focus polarimeters with pre‐focus equipment for high precision calibration. The Leibniz‐Institute for Astrophysics Potsdam developed the GREGOR calibration unit which is an integral part of the telescope. We give an overview of the function and design of the calibration unit and present the results of extensive testing series done in the Solar Observatory “Einsteinturm” and at GREGOR (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Wave-Front Correction System for the Sunrise Balloon-Borne Solar Observatory

This paper describes the wave-front correction system developed for the Sunrise balloon telescope, and it provides information about its in-flight performance. For the correction of low-order aberrations, a Correlating Wave-Front Sensor (CWS) was used. It consisted of a six-element Shack??C?Hartmann wave-front sensor (WFS), a fast tip-tilt mirror for the compensation of image motion, and an active telescope secondary mirror for focus correction. The CWS delivered a stabilized image with a precision of 0.04?arcsec (rms), whenever the coarse pointing was better than ???45?arcsec peak-to-peak. The automatic focus adjustment maintained a focus stability of 0.01?waves in the focal plane of the CWS. During the 5.5?day flight, good image quality and stability were achieved during 33?hours, containing 45?sequences, which lasted between 10 and 45?min.     

A Fully Depleted pn-Junction CCD for Infrared-, UV- and X- ray detection

This paper describes the performance of the Fully Depleted pn-junction CCD (pn-CCD) system, developed for ESA's XMM-satellite mission for soft x-ray imaging and spectroscopy in the single photon counting mode in the 100 eV to 10 keV photon range. The 58 mm x 60 mm large pn-CCD array, designed and fabricated at the Semiconductor Lab (Halbleiterlabor) of the Max-Planck-Institut, uses pn-junctions for registers and as backside structure. This concept naturally enables full depletion of the detector volume independent of the silicon wafer's resistivity and thickness, and as such make it an efficient detector for the x-ray region and the infrared. For high detection efficiency in the soft x-ray region and UV, an ultrathin pn-CCD backside deadlayer has been realized. Each pn-CCD-channel is equipped with its own on-chip JFET amplifier which, in combination with the CAMEX-amplifier and multiplexing chip, facilitates parallel readout and fast data rate: the cooled pn-CCD system can be read out at a data rate up to 3 MHz with an electronic noise floor of ENC < 5 e-.     

An attempt to compare the differential rotation of the Ca+-network with that of the photospheric plasma

In this third paper of a series we report on results obtained from almost simultaneous observations of the differential rotation of the Ca⁺-chromosphere and the photospheric plasma. The observations (tracings of Ca⁺-mottles, Doppler-shift-measurements in a photospheric line) were performed at the Locarno station during two extended periods in 1976. Both data sets were used to search for a large scale circulation pattern. A regular long-lived pattern could not be detected, but a single cell with radial outflow (40 ms^-1) extending over more than 50° in longitude has been found. Statistically significant temporal changes of the differential rotation law of the Ca⁺-chromosphere correlated with changes of meridional motions and differences in the rotation of the two hemispheres were observed. The data of 1976 show no significant difference in the equatorial velocity of the Ca⁺-chromosphere and the photosphere. A comparison of temporal variations of the rotation velocity of the Ca⁺-mottles and the photospheric plasma yielded no significant correlation. Finally, we correlated the measurements of the photospheric rotation performed within the equatorial belts at Locarno with those obtained at Mt. Wilson by a different method during the same periods. The Locarno data show small temporal variations (±50 m^-1s) with no correlation between the two hemispheres, while from the Mt. Wilson data larger variations (±100 m s^-1) with a very high correlation between the two hemispheres have been found. A comparison of both sets of data yielded no correlation at all demonstrating the need for further coordinated observations and a drastic increase of internal accuracy.Mitteilung des Fraunhofer-Instituts Nr. 162.     

GREGOR ‐ optical design considerations

After many years of successful work the Gregory Coudé Telescope (GCT) is going to be replaced by GREGOR. This new 1.5 m telescope is the result of design considerations which to a wide extent are based on new technologies. Special aspects of the design are presented, including measures to compensate for optical aberrations caused by instrumental and atmospheric effects (Adaptive Optics). First light is expected for the end of 2004.     

The Filter Imager SuFI and the Image Stabilization and?Light Distribution System ISLiD of the Sunrise Balloon-Borne Observatory: Instrument Description

We describe the design of the Sunrise Filter Imager (SuFI) and the Image Stabilization and Light Distribution (ISLiD) unit onboard the Sunrise balloon borne solar observatory. This contribution provides the necessary information which is relevant to understand the instruments?? working principles, the relevant technical data, and the necessary information about calibration issues directly related to the science data.