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Context. The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager on board the Solar Orbiter spacecraft (SO/PHI) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) both infer the photospheric magnetic field from polarised light images. SO/PHI is the first magnetograph to move out of the Sun–Earth line and will provide unprecedented access to the Sun’s poles. This provides excellent opportunities for new research wherein the magnetic field maps from both instruments are used simultaneously. Aims. We aim to compare the magnetic field maps from these two instruments and discuss any possible differences between them. Methods. We used data from both instruments obtained during Solar Orbiter’s inferior conjunction on 7 March 2022. The HRT data were additionally treated for geometric distortion and degraded to the same resolution as HMI. The HMI data were re-projected to correct for the 3° separation between the two observatories. Results. SO/PHI-HRT and HMI produce remarkably similar line-of-sight magnetograms, with a slope coefficient of 0.97, an offset below 1 G, and a Pearson correlation coefficient of 0.97. However, SO/PHI-HRT infers weaker line-of-sight fields for the strongest fields. As for the vector magnetic field, SO/PHI-HRT was compared to both the 720-second and 90-second HMI vector magnetic field: SO/PHI-HRT has a closer alignment with the 90-second HMI vector. In the weak signal regime (< 600 G), SO/PHI-HRT measures stronger and more horizontal fields than HMI, very likely due to the greater noise in the SO/PHI-HRT data. In the strong field regime (≳600 G), HRT infers lower field strengths but with similar inclinations (a slope of 0.92) and azimuths (a slope of 1.02). The slope values are from the comparison with the HMI 90-second vector. Possible reasons for the differences found between SO/PHI-HRT and HMI magnetic field parameters are discussed., BMWi - Bundesministerium für Wirtschaft und Energie (Alemania), AEI/MCIN/10.13039/501100011033, Ministerio de ciencia e innovación de España, Instituto Astrofísico de Andalucía (España), Agencia Estatal de Investigación (España), Fondo Europeo de Desarrollo Regional (Fondos FEDER), Centre national d'études spatiales (CNES) (Francia), CSIC (Centro Superior de Investigaciones Científicas) (España), Sección Deptal. de Óptica (Óptica), Fac. de Óptica y Optometría, TRUE, pub

Measuring magnetic fields in the inner corona, the interface between the solar chromosphere and outer corona, is of paramount importance if we aim to understand the energetic transformations taking place there, and because it is at the origin of processes that lead to coronal heating, solar wind acceleration, and of most of the phenomena relevant to space weather. However, these measurements are more difficult than mere imaging because polarimetry requires differential photometry. The coronal magnetograph mission (CMAG) has been designed to map the vector magnetic field, line-of-sight velocities, and plane-of-the-sky velocities of the inner corona with unprecedented spatial and temporal resolutions from space. This will be achieved through full vector spectropolarimetric observations using a coronal magnetograph as the sole instrument on board a spacecraft, combined with an external occulter installed on another spacecraft. The two spacecraft will maintain a formation flight distance of 430 m for coronagraphic observations, which requires a 2.5 m occulter disk radius. The mission will be preferentially located at the Lagrangian L5 point, offering a significant advantage for solar physics and space weather research. Existing ground-based instruments face limitations such as atmospheric turbulence, solar scattered light, and long integration times when performing coronal magnetic field measurements. CMAG overcomes these limitations by performing spectropolarimetric measurements from space with an external occulter and high-image stability maintained over time. It achieves the necessary sensitivity and offers a spatial resolution of 2.5″ and a temporal resolution of approximately one minute, in its nominal mode, covering the range from 1.02 solar radii to 2.5 radii. CMAG relies on proven European technologies and can be adapted to enhance any other solar mission, offering potential significant advancements in coronal physics and space weather modeling and monitor

Designing a new astronomical instrument typically challenges the available cameras on the market. In many cases, no camera can fulfill the requirements of the instrument in terms of photon budget, speed, and even interfaces with the rest of the instrument. In this situation, the only options are to either downgrade the performance of the instrument or design new cameras from scratch, provided it is possible to identify a compliant detector. The latter is the case of the SPGCams, the cameras developed to be used with the Tunable Magnetograph (TuMag) and the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) for the Sunrise iii mission. SPGCams have been designed, developed, and built entirely in-house by the Solar Physics Group (SPG) at the Instituto de Astrofísica de Andalucía (IAA-CSIC). We report here on the scientific rationale and system engineering requirements set by the two instruments that drove the development, as well as on the technical details and trade-offs used to fulfill the specifications. The cameras were fully verified before the flight, and results from the assembly and verification campaign are presented as well. SPGCams share the design, although some parametric features differentiate the visible cameras (for TuMag) and the IR ones (for SCIP). Even though they were specifically developed for the Sunrise iii mission, the robust and careful design makes them suitable for different applications in other astronomical instruments. © 2023 Orozco Suárez, Álvarez García, López Jiménez, Balaguer Jiménez, Hernández Expósito, Labrousse, Bailén, Bustamante Díaz, Bailón Martínez, Aparicio del Moral, Morales Fernández, Sánchez Gómez, Tobaruela Abarca, Moreno Mantas, Ramos Más, Pérez Grande, Piqueras Carreño, Katsukawa, Kubo, Kawabata, Oba, Rodríguez Valido, Magdaleno Castelló and Del Toro Iniesta.

Aims. We use wavefront sensing to characterise the image quality of the High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (SO/PHI) data products during the second remote sensing window of the Solar Orbiter (SO) nominal mission phase. Our ultimate aims are to reconstruct the HRT data by deconvolving with the HRT point spread function (PSF) and to correct for the effects of optical aberrations on the data. Methods. We use a pair of focused–defocused images to compute the wavefront error and derive the PSF of HRT by means of a phase diversity (PD) analysis. Results. The wavefront error of HRT depends on the orbital distance of SO to the Sun. At distances > 0.5 au, the wavefront error is small, and stems dominantly from the inherent optical properties of HRT. At distances < 0.5 au, the thermo-optical effect of the Heat Rejection Entrance Window (HREW) becomes noticeable. We develop an interpolation scheme for the wavefront error that depends on the thermal variation of the HREW with the distance of SO to the Sun. We also introduce a new level of image reconstruction, termed ‘aberration correction’, which is designed to reduce the noise caused by image deconvolution while removing the aberrations caused by the HREW. Conclusions. The computed PSF via phase diversity significantly reduces the degradation caused by the HREW in the near-perihelion HRT data. In addition, the aberration correction increases the noise by a factor of only 1.45 compared to the factor of 3 increase that results from the usual PD reconstructions. © The Authors 2023.

The ESA/NASA Solar Orbiter space mission has been successfully launched in February 2020. Onboard is the Polarimetric and Helioseismic Imager (SO/PHI), which has two telescopes, a High Resolution Telescope (HRT) and the Full Disc Telescope (FDT). The instrument is designed to infer the photospheric magnetic field and line-of-sight velocity through differential imaging of the polarised light emitted by the Sun. It calculates the full Stokes vector at 6 wavelength positions at the Fe I 617.3 nm absorption line. Due to telemetry constraints, the instrument nominally processes these Stokes profiles onboard, however when telemetry is available, the raw images are downlinked and reduced on ground. Here the architecture of the on-ground pipeline for HRT is presented, which also offers additional corrections not currently available on board the instrument. The pipeline can reduce raw images to the full Stokes vector with a polarimetric sensitivity of 10−3⋅Ic or better., BMWi - Bundesministerium für Wirtschaft und Energie (Alemania), MPG - Max-Planck-Gesellschaft (Alemania), Ministerio de Ciencia e Innovación de España - MCIU, Instituto de Astrofísica de Andalucía - CSIC (España), CNES - Centre National d'études spatiales (Francia), Fondos FEDER, Agencia Estatal de Investigación - AEI (ESpaña), Sección Deptal. de Óptica (Óptica), Fac. de Óptica y Optometría, TRUE, pub

This work describes the successful education experience for five years of space engineering education at the Universidad Politécnica de Madrid (UPM), Madrid, Spain. The MSc. in Space Systems (MUSE, Máster Universitario en Sistemas Espaciales) is a 2-year and 120-ECTS (European Credit Transfer and Accumulation System) master program organized by the Microgravity Institute ‘Ignacio Da Riva’ (IDR/UPM), a research institute of UPM with extensive experience in the space sector. The teaching methodology is oriented to Project Based Learning (PBL), taking advantage of the IDR/UPM Institute experience. The main purposes are to share the IDR/UPM knowledge with the students and promote their collaboration with several space scientific institutions, both national and international. In the present work, the most relevant characteristics of this master program are described, highlighting the importance of the student’s participation in actual missions. In addition, to offer practical cases in all aspects of satellite development, the IDR/UPM decided to create its own satellite development program, the UPMSats. The latest, the UPMSat-2, is an educational, scientific, and in-orbit technological demonstration microsatellite (50 kg-class) that was launched in September 2020 on-board a Vega launcher (VV-16 flight). MUSE students have participated in all phases of the mission, from design to integration, calibration, and testing, and (at present) in-orbit operation. The construction of a microsatellite, although it exceeds in time the academic duration of the master, has proven to be a very interesting and versatile tool for PBL education, since it provides practical cases at all levels of development. Furthermore, the continuity of the project encourages graduated students to continue their education with a Ph.D. and the collaboration of master and doctoral students. These reasons have made MUSE one of the most successful academic programs in space systems engineering in Spain, with

The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is an instrument for the third flight of the Sunrise balloon-borne solar observatory planned for 2022. To verify the high spatial and spectral resolutions required in the balloon flight, the SCIP optical unit was subjected to a thermal-vacuum test in which the SCIP optical unit was installed in a vacuum chamber and was exposed to the thermal vacuum environment expected in the balloon flight. We verified the heater control performance and the temperature distribution in the SCIP optical unit in hot and cold conditions created by the shrouds in the vacuum chamber. We confirmed the optical performance, such as spatial and spectral resolution, and an air-to-vacuum difference of the optics by injecting the laser and white lights through a vacuum window.

Este trabajo analiza el comportamiento térmico de un CubeSat 3U, después de seleccionar los acabados exteriores de las superficies del mismo, a fin de evaluar la fiabilidad del satélite a pesar de la variación de las condiciones exteriores. El diseño térmico de un satélite se basa en establecer las conexiones y parámetros térmicos necesarios, para lograr un intervalo de temperaturas adecuado en todas las zonas del vehículo. El trabajo expuesto se centrará esencialmente en el control térmico pasivo, pero sin descartar que en momentos puntuales sea necesario usar elementos activos como medida correctora. Inicialmente se hará una serie de estudios en Matlab para lograr una aproximación tanto de las condiciones térmicas exteriores, como del comportamiento del propio satélite. Esto se realizará mediante un conjunto de análisis estacionarios simplificando el vehículo a un único nodo, y a través de un estudio del intercambio radiativo de calor en el interior del satélite. Logrando de esta forma una aproximación de las temperaturas de la estructura. Posteriormente, con la intención de lograr la evolución detallada de las temperaturas, se hará un estudio en ESATAN introduciendo los materiales y uniones utilizadas en el diseño del satélite, y seleccionando los recubrimientos y acabados superficiales conforme a los resultados obtenidos del análisis en Matlab. Una vez construido el modelo completo, se simulará el satélite en su entorno durante 15 órbitas y para todos sus distintos modos. Por último, en virtud de los resultados obtenidos, se describirán las correcciones necesarias, y las posibles futuras acciones a realizar que permitirían una optimización del modelo.

Access to space in the 1950s opened an unprecedented door for science. On one side, it allowed to observe the solar system as well as the cosmos, from outside the Earth atmosphere, and capture ultraviolet radiation or x-rays, which did not reach the Earth’s surface. In addition, the possibility of approaching the subject matter (the Sun, planets and their satellites, comets, etc.) through space probes has translated into a better understanding of the Solar System and its origins. On the other side, the ability of observing our planet from the outside has provided countless data which have led to a myriad of day-to-day applications. Furthermore, it has allowed us to investigate in a greater extent our planet and how it evolves. This article outlines the main scientific activities that have been made from space since the begining of the space race, especially those developed in Europe., El acceso al espacio en los años 50 del siglo pasado abrió una puerta sin precedentes para la actividad científica. Por una parte, permitió observar tanto el sistema solar como el cosmos desde fuera de la atmósfera terrestre, pudiendo captar de este modo la radiación ultravioleta o los rayos X, no accesibles desde la superficie terrestre. Además, la posibilidad de acercarse mediante sondas espaciales al objeto de estudio (al Sol, a los planetas y sus satélites, cometas, etc.) ha permitido conocer mejor el sistema solar y sus orígenes. Por otra parte, el poder observar nuestro planeta desde fuera, además de permitirnos conocer mejor cómo es y cómo evoluciona, ha proporcionado una infinidad de datos que han desembocado en numerosas aplicaciones utilizadas en nuestro día a día. En este artículo se repasan las principales actividades científicas realizadas desde el espacio desde el comienzo de la carrera espacial, principalmente aquellas desarrolladas en Europa.