FAAM CORE Particle Soot Absorption Photometer (Radiance Research)
The PSAP is used to measure in near real time the optical extinction coefficient for absorption which can in also be used to estimate concentrations of black carbon. The method is based on the same principle as the integrating plate, in which the change in optical transmission of a filter caused by a particles deposition is related to the optical absorption coefficient using Beer's Law. The instrument draws in air across a filter where particulate matter is deposited. The transmittence of a green (565 nm) LED light source through this medium is measured and compared to a reference cell, where the same light source is passed over the filter with no aerosol deposition. 






Below are the Radiance Research instrument manual, historic information (filter media, cable schedules etc) and TSSE. 


The data produced by FAAM in uncorrected, the document below discusses the correction techique from Bond et al (1999).  For corrections see   pdf PSAP_OBR_TN80_v1_0 (256.72 kB) (256 KB) . The flow and spot size calibrations can be seen below. This publication is an amendment to Tech Note 31. The instrument is now operated on the majority of flights, certain cloud flights are not included in the data set due to logistical issues. The flow is controlled using a low pressure Alicat flow controller and is stable at 3 SLPM up to 25 Kft.



Flow Calibrations
corrected PSAP flow = m*PSAP Flow + c
 Date  m  m error c  c error
 August 2011 1.084 0.009  0.030  0.032
 February 2013 1.071   0.007 0.060 0.021 
June 2013 1.094  0.010  0.072 0.029 
July 2015 1.088 0.011 0.079 0.034


Spot Size Calibrations 
These calibrations are done using a high resolution 1200 dpi scanned image, the pixel width is checked on each scan and Gimp software used to fit a circle marquee and the diameter in pixles counted and converted to mm. 
Project Mean Spot Diameter (mm)  Standard Deviation (mm)  
 SAMBBA  5.18  0.03
  Fennec  5.13 0.09
  ICE-D  5.31 0.03


Bond, T.C., Anderson, T.L. and Campbell, D., 1999: Calibration and intercomparison of filter-based measurements of visible light absorption by aerosols. Aerosol Sci. and Technol. 30, 582-600.

Additional information