Aerosols are small solid or liquid particles suspended in the air that affect climate directly through interaction with solar radiation. Aerosols affect climate indirectly by changing the micro- and macro-physical properties of clouds. According to the Intergovernmental Panel on Climate Change, aerosols are the largest source of error in quantifying the radiative forcing of climate change. SPEXone will enable measurements of optical and micro-physical properties of aerosols with unprecedented detail and accuracy.
SPEXone is being developed by a Dutch consortium consisting of SRON Netherlands Institute for Space Research and Airbus Defence and Space Netherlands, supported by optical expertise from TNO. SRON and Airbus DS NL are responsible for the design, manufacturing and testing of the instrument. The scientific lead is in the hands of SRON. SPEXone is a public-private initiative funded by the Netherlands Space Office (NSO), the Netherlands Organization of Scientific Research (NWO), SRON, and Airbus DS NL.
SPEXone will feature:
- A compact three-mirror segmented telescope assembly (patented by the consortium) to gather light from 0°, ±20° and ±50° (at satellite level) and direct the light towards a common entrance slit of a spectrometer.
- Polarization Modulation Optics (PMO) to encode the state of linear polarization in the intensity spectrum as a sinusoidal modulation.
- A compact and lightweight all-reflective imaging grating spectrometer.
Major steps in this development have been the development, characterization, and field-testing (ground-based) of a SPEX Prototype (originally designed for a Mars orbiter) and the "upgrade" of the SPEX prototype into a stand-alone instrument, SPEX airborne, for operating on the high-altitude (21 km or 13 mi) NASA ER-2 research aircraft.
The spectrometer of SPEXone is based on Dutch heritage with the Sentinel-5 precursor Tropomi instrument, its predecessor OMI, and the derived compact version Spectrolite.