Aerosols are the least studied components of the atmosphere that is resulting in uncertainty in the assessment of the impact of aerosols on the radiative balance of the Earth atmosphere. Moreover, information on the global distribution of anthropogenic aerosols is sparse, which makes it extremely difficult to test and improve aerosol transport patterns in the atmosphere and progress in understanding the human impact on climate and the environment.

     Following the unsuccessful launch of the Glory mission in 2011, there was a gap in the existence of up-to-date aerosol orbital instruments, because launches of similar types of devices were scheduled for 2019 and later. This is one of the reasons that we consider a scientific space project with ScanPol aerosol scanning polarimeter and a wide-angle multispectral imager-polarimeter (MSIP) on board the spacecraft as a timely mission that will produce the required microphysical and chemical parameters by defining the indicator refraction index of the natural and anthropogenic aerosols.

     The main purpose of the MSIP is to carry out polarimetric and photometric measurements of scattered solar radiation in order to have information on the characteristics of aerosols, as well as to determine the influence of clouds on measurements with the ScanPol polarimeter.

      We propose the concept of the MSIP optical layout, which is based on the principle of splitting the input image into four quasi-identical secondary images. This approach allows us to unify the optical layout of polarimeter channels, which allows, in own turn, to transform the polarization channel into a photometric channel with four subchannels with different spectral ranges. This transformation is performed by replacing the sector polarizer with a sector filter with four different wavelengths in each sector.

     The MSIP consists of five optical channels with a field of view 60x60°. The three channels are polarizing, each of which allows to perform polarimetric measurements of the three Stokes I, Q, U parameters at the central wavelengths of 410, 555, 865 nm with a spectral half-width of 20 nm FWHM. Two channels of MSIP are intended for photometric measurements in eight spectral bands with center wavelengths of 410, 443, 470, 490, 555, 670, 865, and 910 nm with spectral half-widths of 20 to 40 nm FWHM.

     The calculation and optimization of each of the optical layouts and the modeling of the mechanical construction of the polarimeter are performed. An experimental sample of one of the optical channels of the MSIP has been manufactured, compiled and verified. The preliminary results demonstrate the convergence of theoretical and experimental data. It should be noted that the studies were conducted without a polarizing element. The next steps will be related to the laboratory testing and calibration of the  MSIP polarization characteristics.