Short answers, pulled from the story.
The POLDER instrument is a passive optical imaging radiometer and polarimeter developed by the French space agency CNES. It measures the physical properties of light itself to deduce the nature of objects it observes, including solar radiation reflected by Earth's atmosphere, tropospheric aerosols, sea surface reflectance, and the Earth Radiation Budget.
The POLDER instrument was first launched as a passenger instrument aboard ADEOS I on the 17th of August 1996. The mission ended on the 30th of June 1997 when communication from the host satellite failed, cutting short the data collection period after ten months.
The POLDER instrument distinguishes between ocean color and vegetation by scanning between 443 and 910 nanometers full width at half maximum. The shorter wavelengths between 443 and 565 nanometers typically measure ocean color, while the longer wavelengths between 670 and 910 nanometers are used to study vegetation and water vapor content.
The POLDER 2 mission launched in December 2002 aboard ADEOS II ended prematurely after 10 months when the satellite's solar panel malfunctioned. This failure left the instrument in darkness and unable to power its systems, resulting in the loss of valuable data on long-term atmospheric changes.
The third generation POLDER instrument was permanently shut down on the 18th of December 2013. This decision was made to ensure the safety of the space environment and to prevent the creation of space debris, bringing an end to a mission that had spanned nearly two decades.