The PROBA-3 double-spacecraft formation flying mission of the European Space Agency (ESA) has been presented in recent papers with details about the mission profile, the operation objectives, and the implemented technologies. PROBA-3 will fly the externally occulted coronagraph ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), with the telescope on one satellite and the occulter on the other one, at 144m. The scientific objective is to realize an artificial total solar eclipse to observe the lower Sun corona. The high accuracy metrology control is the core of the mission and several sub-systems will be verified and validated to realize the coronagraphic formation. Between these, the Shadow Position Sensors (SPS), composed of eight photo-multipliers mounted around the ASPIICS entrance pupil monitoring the solar penumbra symmetry, will return the 3D positioning of the formation with the highest accuracy. The SPS on-ground calibration was completed in 2021 and one of the main aspects of the test has been the implementation of an illumination scheme to simulate the same conditions the SPS will experience in flight. This was realized using a suite of LED sources properly assembled in a testbed used to reproduce the expected observation configurations. This testbed is supported by a dedicated software able to simulate the different illumination conditions and to drive the control of the LEDs in order to feed each SPS sensor with the proper light flux. In this paper, we review the SPS metrology system, the calibration testbed setup, and we discuss the interface control software, the simulation tool, and the data acquisition procedure adopted to calibrate the LED sources. Additional presentation content can be accessed on the supplemental content page.
The Cherenkov Telescope Array Observatory (CTAO) consists of three types of telescopes: large-sized (LST), mediumsized (MST), and small-sized (SST), distributed in two observing sites (North and South). For the CTA South “Alpha Configuration” the construction and installation of 37 (+5) SST telescopes (a number that could increase up to 70 in future upgrades) are planned. The SSTs are developed by an international consortium of institutes that will provide them as an in-kind contribution to CTAO. The SSTs rely on a Schwarzschild-Couder-like dual-mirror polynomial optical design, with a primary mirror of 4 m diameter, and are equipped with a focal plane camera based on SiPM detectors covering a field of view of ~9°. The current SST concept was validated by developing the prototype dual-mirror ASTRI-Horn Cherenkov telescope and the CHEC-S SiPM focal plane camera. In this contribution, we will present an overview of the SST key technologies, the current status of the SST project, and the planned schedule.
The Coronal Magnetograph - CorMag - experiment aims at studying the magnetic field topology of the solar corona. The direction of the coronal magnetic field vector would be derived from narrow-wavelength bandpass observations of the linearly polarized FeXIV line-emission (530.3 nm), interpreted through the "saturated" Hanle effect. CorMag will be a medium-duration, high-altitude balloon payload of the European Union-funded HEMERA Program. CorMag is an internally-occulted coronagraph whose design was derived from the externally-occulted, formation-flying ASPIICS coronagraph of the PROBA-3 ESA solar mission. The configuration for this mission will be illustrated, together with the expected polarization sensitivity. This mission is a demonstrator for future space-based coronagraphs with the capability of visible-light and infrared polarization measurements for coronal magnetic field diagnostics.
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