LARS is an Absolute Reference Spectrograph designed for ultra-precise solar observations. The high-resolution echelle spectrograph of the Vacuum Tower Telescope is supported by a state-of-the-art laser frequency comb to calibrate the solar spectrum on an absolute wavelength scale. In this article, we describe the scientific instrument and focus on the upgrades in the last two years to turn the prototype into a turn-key system. The pursued goal was to improve the short-term and long-term stability of the systems, and enable a user-friendly and more versatile operation of the instrument. The first upgrade involved the modernization of the frequency comb. The Fabry-Perot cavities were adjusted to filter to a repetition frequency of 8GHz. A technologically matured photonic crystal fiber was implemented for spectral broadening. The second, quite recent upgrade was performed on the optics feeding the sunlight into a single-mode fiber connected to the spectrograph. A motorized translation stage was deployed to allow the automated selection of three different fields-of-view with diameters of 1", 3", and 10" for the analysis of the solar spectrum. The successful upgrades allow for long-term observations of up to several hours per day with a stable spectral accuracy of 1 m/s limited by the spectrograph. Stable, user-friendly operation of the instrument is supported. The selection of the pre-aligned fiber to change the field of view can now be done within seconds. LARS offers the possibility to observe absolute wavelength positions of spectral lines and Doppler velocities in the solar atmosphere. First results demonstrate the capabilities of the instrument for solar science. The accurate measurement of the solar convection, p-modes, and atmospheric waves will enhance our knowledge of the solar atmosphere and its physical conditions to improve current atmospheric models.
Thermal and Optical Characterization of Near-Earth Objects: Science Commissioning of the Recently Upgraded Mid-Infrared Camera MIRSI on the NASA Infrared Telescope Facility
Commissioning and on-sky performance of FiberPol: a fiber-fed spectropolarimetric system for the SAAO 1.9 m telescope
South African Astronomical Observatory（南非天文台）；Sub-department of Astrophysics, University of Oxford（牛津大学天体物理子系）；Department of Astronomy, University of Cape Town（开普敦大学天文学系）；Space Science and Engineering Initiative, College of Engineering, University of Hawaii at Manoa（夏威夷大学马诺阿分校工程学院空间科学与工程倡议）；Centre for Space Research, North-West University（西北大学空间研究中心）；University of Wisconsin–Madison（威斯康星大学麦迪逊分校）
The Sunrise Chromospheric Infrared Spectro-Polarimeter SCIP: an instrument for SUNRISE III
National Astronomical Observatory of Japan（日本国立天文台）；The Graduate University for Advanced Studies, SOKENDAI（高等研究院 (SOKENDAI)）；Department of Astronomy, Graduate School of Science, The University of Tokyo（东京大学大学院理学研究系天文学专攻）
