Main Objective: Perform coordinated observations with the Solar Orbiter PHI (SO/PHI) instrument and the Hinode spectropolarimeter (Hinode/SP) during the first Remote Sensing Window (RSW1) of the SO nominal mission phase that will take place between March 2 and March 12, 2022. The main goal of this HOP is to provide support to one of the Solar Orbiter Observing Plans (Coronal-He-Abundance program) and to acquire co-sapatial and co-temporal SO/PHI and Hinode/SP data to perform a detailed calibration of the SO/PHI instrument, including both telescopes, the full disk telescope (FDT) and the high resolution telescope (HRT). These observations will help us achieve some of the scientific objectives of the mission sand bring the full capabilities of the SO instruments for science as well as to acquire additional calibration data.
Scientific Justification: Solar Orbiter (SO) was successfully launched on Feb.10, 2020. All its onboard instruments were commissioned during the early phase of the mission and additional tests and scientific observations have been carried out during the cruise phase. SO is now entering its nominal mission phase and detailed scientific observations will be acquired during the so-called remote sensing windows (RSWs). Among the science programs, called SOOPs (Solar Orbiter Observing Plan - the analogue of a Hinode HOP), the Coronal-He-Abundance SOOP aims at determining the helium abundances in the corona / inner solar wind through He+ emission and neutral hydrogen measurements. The main two instruments involved in these observations are the EUI/FSI 30.4 nm and Metis (Ly¿ - 121.6 nm). Metis will provide maps of the near-surface elemental abundances which will help setting a reference for determining the abundance variations in the solar wind.
SO/PHI will provide maps of the vector magnetic field and line-of-sight velocities with the High Resolution Telescope (HRT) which will allow performing local coronal magnetic field extrapolations. In order to fully test the capabilities of SO/PHI and make it science ready, it is important to complement these observations with the Hinode/SP. These observations will be carried out while SO is crossing the Sun-Earth line so SO/PHI will see the Sun from the same angle as Hinode and at a distance of about 0.5 A.U.
This gives us the chance to make a full characterization of the imaging and polarimetric properties of the SO/PHI HRT. Notice that the next opportunity will be in March 2023 and then SO will leave the ecliptic. Hence this is almost the last chance to get real co-aligned observations from Earth.
This SOOP will also make use of synoptic FDT observations carried out before and after the observation window for a full modeling of the solar corona magnetic status. As for the HRT, we need to acquire Hinode/SP observations together with the FDT. Since the FDT resolution is lesser than the HRT and Hinode/SP, we would like Hinode to point at Active Regions, if possible, and to strong network/plage areas in case no activity is present. Contrary to what we are going to do with the HRT, these FDT observations will be taken on March 8, 2022 between 7-7:30 UT. These data will help fine-tune the polarimetric observations of both telescopes and make much more reliable field extrapolations in subsequent observations with SO/PHI.
Details about this specific science SOOP are public and can be found in:
*It is important to mention that the HERSCHEL/SCORE sounding rocket is scheduled to be launched during that time slot: the observations of this SOOP are also meant to support that launch (in case that happens on time).