  Spectropolarimetry is a powerful technique for remote sensing of the
environment. It enables the retrieval of particle shape and size distributions
in air and water to an extent that traditional spectroscopy cannot. SPEX is an
instrument concept for spectropolarimetry through spectral modulation,
providing snapshot, and hence accurate, hyperspectral intensity and degree and
angle of linear polarization. Successful SPEX instruments have included
groundSPEX and SPEX airborne, which both measure aerosol optical thickness with
high precision, and soon SPEXone, which will fly on PACE. Here, we present a
low-cost variant for consumer cameras, iSPEX 2, with universal smartphone
support. Smartphones enable citizen science measurements which are
significantly more scaleable, in space and time, than professional instruments.
Universal smartphone support is achieved through a modular hardware design and
SPECTACLE data processing. iSPEX 2 will be manufactured through injection
molding and 3D printing. A smartphone app for data acquisition and processing
is in active development. Production, calibration, and validation will commence
in the summer of 2020. Scientific applications will include citizen science
measurements of aerosol optical thickness and surface water reflectance, as
well as low-cost laboratory and portable spectroscopy.
