No abstract

The results obtained during the total Solar Eclipse on July 2, 2019, in Chile are presented together with the Eclipse K-corona Polarimeter (EKPol). The EKPol is equipped with an electro-optically modulating Liquid Crystal Variable Retarder (LCVR) for the polarimetric observation of the solar corona. The use of this technology has been an important ground-based test for the application of this technology in space-based observatories. The usage of LCVRs in a polarization rotator configuration, allows the replacement of mechanically rotating retarders avoiding moving parts and reducing noise, failure probability, and mass. Indeed, EKPol was developed as a technology demonstrator for the Metis coronagraph on-board Solar Orbiter. The results, from the composition of the image to the electron density map evaluation, are compared and are consistent with what is obtained by other ground-based and space-based instruments, and with past EKPol campaigns.

BORGUET Benoit (2) , ARTS Mathijs (3) , TOMUTA Dana (3) , GEORGES Marc (4) , VANDENRIJT Jean-François (4).

Abstract-The Global Ozone Monitoring Experiment-2[1](GOME-2) represents one of the European instruments carried on board the MetOp satellite within the ESA's "Living Planet Program". Consisting of three flight models (FM's) it is intended to provide long-term monitoring of atmospheric ozone and other trace gases over a time frame of 15-20 years, thus contributing valuable input towards climate and atmospheric research and providing near real-time data for use in air quality forecasting.The ambition to achieve highly accurate scientific results requires a thorough calibration and characterization of the instrument prior to launch. These calibration campaigns were performed by TNO in Delft in the Netherlands, in the "Thermal Vacuum Calibration Facility" of the institute.Due to refurbishment and / or storage of the instruments over a period of a few years, several re-calibration campaigns were necessary. These re-calibrations provided the unique opportunity to study the effects of long term storage and build up statistics on the instrument as well as the calibration methods used.During the re-calibration of the second flight model a difference was found in the radiometric calibration output, which was not understood initially. In order to understand the anomalies on the radiometry, a deep investigation was performed using numerous variations of the setup and different sources. The major contributor was identified to be a systematic error in the alignment, for which a correction was applied. Apart from this, it was found that the geometry of the sources influenced the results. Based on the calibration results combined with a theoretical geometrical hypothesis inferred that the on-ground calibration should mimic as close as possible the in-orbit geometry.

In space Earth Observation related projects, Sun Simulators are regular used for on-ground calibrations of the flight instruments. Instrument radiometric calibration is established by illuminating the on-board diffuser(s) via the Sun port in irradiance configuration and an external OGSE calibrated diffuser for the radiance configuration via the Earth Port. Usually, Sun Simulator designs are complex containing multiple coated mirrors, and its implementation requires large volume and mass. The paper will present an elegant and innovative concept of building such a Sun Simulator using minimum elements. The new concept consists of three major units: the illumination unit, the diffuser unit and the collimator unit. All units have been purchased, mounted on an optical table and aligned. Finally, preliminary performance tests of the Sun Simulator Breadboard are presented. The Breadboard proves the concept and also allows scaling to different instrument needs.