Noname manuscript No. (will be inserted by the editor) Helioseismology with Solar Orbiter

Abstract The Solar Orbiter mission, to be launched in July 2017, will carry a suite of re-mote sensing and in-situ instruments, including the Polarimetric and Helioseismic Imager (PHI). PHI will deliver high-cadence images of the Sun in intensity and Doppler velocity suitable for carrying out novel helioseismic studies. The orbit of the Solar Orbiter spacecraft will reach a solar latitude of up to 21 ◦ (up to 34 ◦ by the end of the extended mission) and thus will enable the first local helioseismology studies of the polar regions. Here we con-sider an array of science objectives to be addressed by helioseismology within the baseline telemetry allocation (51 Gbit per orbit, current baseline) and within the science observing windows (baseline 3×10 days per orbit). A particularly important objective is the measure-ment of large-scale flows at high latitudes (rotation and meridional flow), which are largely unknown but play an important role in flux transport dynamos. For both helioseismology and feature tracking methods convection is a source of noise in the measurement of longitu-dinally averaged large-scale flows, which decreases as T−1/2 where T is the total duration of the observations. Therefore, the detection of small amplitude signals (e.g., meridional circulation, flows in the deep solar interior) requires long observation times. As an example