Recent instruments and algorithms for passive shortwave remote sensing

Passive remote sensing of aerosol using the shortwave spectrum draws on a long heritage of experience that began with three main techniques described in Chapter 7: occultation methods, dark target approaches, and spectral ultra-violet (UV) algorithms. Beginning in the 1970s, these techniques have been applied to instruments flown on a series of different satellite platforms and have produced important time series of aerosol parameters that span decades. This heritage is especially valuable given the fact that the early downward-viewing sensors used for aerosol retrieval – the Advanced Very High Resolution Radiometer (AVHRR), the Total Ozone Mapping Spectrometer (TOMS) and even the Geostationary Operational Environmental satellites (GOES) – were designed for purposes other than retrieving aerosol. However, the success of using these instruments for aerosol characterization motivated the development of sensors designed with aerosol retrievals in mind. Improved spatial resolution, narrower spectral channels, increased spectral range and density, enhanced capability in terms of multiple angular views of the same scene and polarization are some of the specific improvements designed into the sensors flying during the 2000s that were intended to provide better aerosol retrievals than AVHRR and TOMS.