The Imaging Magnetograph eXperiment Plus (IMaX+) is a brand-new solar magnetograph and tachograph, which is being developed by a consortium of five Spanish institutions for the third edition of the Sunrise stratospheric balloon mission.
IMaX builds upon the heritage of IMaX (Martínez Pillet et al. 2011, Solar Phys. 268, 57), an instrument built by the same institutions that flew in the first two editions of Sunrise in 2009 and 2013 (Solanki et al., 2010, ApJL 723, L127; Barthol et al., 2011, Sol. Phys. 268, 1; Solanki et al. 2017, ApJS 229, 2). Based on the successful IMaX technologies, IMaX+ includes new concepts and technologies. Among the concepts we can mention that IMaX+ is the first “line-tunable” imaging magnetograph, a larger FOV of 60” x 60” provided by the Sunrise ISLiD and permitted by the detector, and a signal oversampling with three pixels within the Airy disk in order to better recover the PSF of the instrument, hence improving the image quality and spectral integrity. Three spectral lines can alternatively be observed, namely, those of Fe I at 525.02 and 525.06 nm and that of Mg Ib2 at 517.3 nm; two of them are sampled in approximately one minute. Among the new technologies we can mention the two in-house-made, custom cameras, the relevant sub-system thermal enclosures, a new optical bench made out of CFRP skin and AluHoneycomb core, and the filter wheel mechanism that, besides the pre-filters, it includes the phase diversity plate and some image and polarization calibration optics.
The instrument consists of two main units, namely, the optical unit (O-Unit) and the electronic unit (E-Unit) linked by a harness. The O-Unit is located at the instrument platform, the so-called PFI, as a backpack of the telescope. The E-Unit is located at the electronic rack elsewhere in the gondola.