Speaker
Description
Vigil is the first space weather mission in ESA’s Space Safety program to position a spacecraft at the Lagrangian L5 point of the Sun-Earth system. Vigil will peer behind the solar limb (as seen from Earth) and monitor solar activity in quasi real-time, 4-5 days before it becomes visible from ground.
A key instrument onboard Vigil is the Photospheric Magnetic-field Imager (PMI), a full-disc vector magnetograph and tachograph, that builds heavily on the heritage from the SO/PHI instrument, the Polarimetric and Helioseismic Imager on Solar Orbiter. Following the established design principles of SO/PHI, PMI relies on a reflecting off-axis telescope design and samples the photospheric Fe I absorption line at 617.3nm with a tuneable filter system based on a solid state LiNbO3 Fabry-Perot etalon. The polarisation of the incoming light is modulated by liquid crystal variable retarders and a linear polarizer, and subsequently recorded by a 2k x 2k CMOS detector, synchronously to the modulation. An image stabilisation system based on a limb-sensor provides the necessary stability to obtain difference images at a noise level of 0.001 of the continuum intensity, needed to detect line-of-sight magnetic fields as weak as 5-10 G.
The recorded spectropolarimetric data are converted into physical quantities of the solar atmosphere in near real-time, by numerically inverting the polarized radiative transfer equation onboard. PMI will provide full-disc maps of the photospheric continuum intensity, the three components of the magnetic field vector and the line-of-sight component of the photospheric flow velocity at a cadence of 30 min, with a spatial resolution of about 2” (1.6 Mm on the Sun), and with an on-board latency of about 20 min.
In addition to standard data products meant to improve forecasts, PMI will also provide observations of significant scientific value, as we are learning from the analysis of the data recorded by the SO/PHI instrument, especially when combining these data with those taken by resources in Earth orbit. Such observations will include Dopplergrams recorded at a 1 min cadence, making them useful for helioseismology.
| Do you plan to attend in-person or online? | In-person |
|---|
