The GREGOR infrared spectrograph ( GRIS, Collados et al. 2012, AN 333, 872) provides high resolution spectropolarimetric data of features on the sun. Data older than one year is open for anyone to use. Current public data include more than 500 data sets recorded from 2014 onward. Most observations are single-raster scans recorded in spectropolarimetric mode in the 1.08µm and 1.56µm wavelength bands. Some of them are measurements in spectroscopic mode, time sequences capturing the evolution of solar features, or observations in other wavelength bands such as 2.2µm. We further provide overview maps; context data for each calibrated data are science-ready and can be downloaded directly from the archive. Further information on the GREGOR Telescope (GREGOR, Schmidt et al. 2012, AN 333, 796S) and GRIS can be found on our website or in the respective publications.

LARS, the Laser Absolute Reference Spectrograph of the Institute for Solar Physics, is a scientific instrument for the ultramodern observation of the Sun at the Vacuum Tower Telescope (VTT) at the Observatorio del Teide on Tenerife. LARS allows for the measurement of the solar spectrum of a selected field of view with the high-resolution Echelle spectrograph of the VTT. Additionally, the emission spectrum of the newly installed Laser Frequency Comb is superimposed with the solar spectrum. Since each emission peak of the comb spectrum represents one well-defined frequency, the solar spectrum can be calibrated on an absolute wavelength scale. Figuratively, the comb serves as a ruler for the spectral lines. The accuracy is of the order of m/s or below and is therefore a multiple better than former devices. After the invention of the Laser Frequency Comb, awarded in 2005 with the Nobel Prize in Physics, the first astrophysical Frequency Comb was realised in 2008 at the VTT. The successful upgrade of the system in May 2016 by MenloSystems enables the continuous operation of this worldwide unique spectroscopic observation of the Sun. Since then, we have performed several successful observing campaigns focused on the convective blueshift in the solar atmosphere and on motions in sunspot umbrae. The results were published in a series of papers (see below).

ChroTel is a 10 cm aperture telescope to observe the chromosphere of the Sun. It was developed at the Institute for Solar Physics (KIS) Freiburg together with the High Altitude Observatory (HAO) in Boulder, USA. With a spatial resolution of about 2 arcsec it observes the solar chromosphere in its most prominent lines in the near UV, the red and the infrared (Ca II K, Hα and He I) using a 2048x2048 pixel CCD. ChroTel uses a two mirror system ("turret") next to the VTT building that relays a stabilised image of the solar disc into a laboratory within the VTT building. The heart of the optical lab is a filter system consisting of three narrow-band Lyot filters, one of which is tunable. The He I filter is tunable and observations are taken at seven wavelength positions fully covering the whole spectral line, giving full-disk chromospheric Doppler maps. Images in all channels (and the seven He I bands) can be taken with a cadence of below one minute. The operation of ChroTel is automatic, to the extent possible. ChroTel also serves live images for VTT and Gregor. The scientific data of ChroTel are freely available for scientific and educational use. Observing campaigns together with the Tenerife Infrared Polarimeter (TIP) at the VTT enable us to calibrate the Doppler shift maps derived from the seven filtergrams of ChroTel in the Helium I channel. The main goals of the science operations of ChroTel are to study the dynamic response of the chromosphere to photospheric driving especially in the chromospheric network, large-scale structures and their disturbance such as flares and CMEs and the chromospheric source of the fast solar wind. An overview of the available data products and the header structure of the individual fits files can be found here.