Polder
The POLDER instrument weighed approximately 100 kilograms. It consumed 77 watts of power during imaging mode operations. A mean consumption of 29 watts occurred when the device was not actively scanning. This physical mass required a robust mounting system on its host satellites. Engineers designed the unit to fit within strict launch vehicle constraints. The optical system used a telecentric lens paired with a charge-coupled device matrix. That matrix held a resolution of 242 by 548 pixels. The focal length remained unspecified in available records, but the focal ratio measured 4.6. Field of view angles ranged from plus or minus 43 degrees to plus or minus 57 degrees depending on tracking methods.
Scientists utilized specific wavelength ranges between 443 and 910 nanometers for distinct measurements. Shorter wavelengths spanning 443 to 565 nanimeters typically measured ocean color properties. These values helped researchers analyze sea surface reflectance characteristics. Longer wavelengths covering 670 to 910 nanimeters studied vegetation health instead. Those same longer bands also tracked water vapor content in the atmosphere. The device scanned these spectral regions using a push broom scanner architecture. Data transmission occurred at 465.9875 MHz during uplink operations. Downlink reception happened at 401.65 MHz with a slower data rate. The main data transfer speed reached 880 kilobits per second at 12-bit quantization levels.
POLDER first launched as a passenger instrument aboard ADEOS I on the 17th of August 1996. This mission aimed to observe solar radiation reflected by Earth's atmosphere. Researchers planned to study tropospheric aerosols and bidirectional reflectance distribution functions of land surfaces. Communication from the host satellite failed abruptly on the 30th of June 1997. That failure ended the mission prematurely after less than one year of operation. The French space agency CNES developed this passive optical imaging radiometer for such missions. Scientists hoped to gather data on the Earth Radiation Budget through these observations. The sudden loss of contact left many atmospheric studies incomplete.
A second generation instrument named POLDER 2 launched in December 2002 aboard ADEOS II. This deployment followed the earlier success of the initial flight. The mission ended prematurely after only 10 months of operation. A malfunction involving the satellite's solar panel caused the shutdown. Engineers could not restore power to the system once the panel failed. The device had been designed to measure ocean color and vegetation properties again. No further data transmission occurred after the solar array issue arose. This event highlighted the vulnerability of long-duration orbital missions to hardware failures.
A third generation instrument flew on board the French PARASOL microsatellite. The satellite maneuvered out of the A-train formation on the 2nd of December 2009. Operators permanently shut down the system on the 18th of December 2013. This final phase documented the instrument's role until its permanent end. Researchers used the device to observe solar radiation reflected by Earth's atmosphere throughout this period. Studies included tropospheric aerosols and sea surface reflectance measurements. The mission concluded a multi-decade effort to map Earth's reflectances using polarization techniques. The final shutdown marked the end of active POLDER operations for over two decades.
Common questions
What were the physical specifications of the POLDER instrument?
The POLDER instrument weighed approximately 100 kilograms and consumed 77 watts during imaging mode operations. It utilized a telecentric lens paired with a charge-coupled device matrix holding a resolution of 242 by 548 pixels.
When did the first generation POLDER instrument launch on ADEOS I?
POLDER first launched as a passenger instrument aboard ADEOS I on the 17th of August 1996. The mission ended prematurely after less than one year of operation following communication failure on the 30th of June 1997.
How long did the second generation POLDER 2 operate before shutting down?
A second generation instrument named POLDER 2 launched in December 2002 aboard ADEOS II but operated for only 10 months. Engineers could not restore power to the system once the satellite's solar panel malfunctioned.
On what date was the final POLDER system permanently shut down?
Operators permanently shut down the third generation instrument on board the French PARASOL microsatellite on the 18th of December 2013. This event marked the end of active POLDER operations for over two decades.
What wavelength ranges does the POLDER instrument use for measurements?
Scientists utilized specific wavelength ranges between 443 and 910 nanometers for distinct measurements. Shorter wavelengths spanning 443 to 565 nanometers measured ocean color properties while longer wavelengths covering 670 to 910 nanometers studied vegetation health.