Description: | The pump failed on the single-wavelength nephelometer line. The vacuum gauge also failed,
giving vacuum readings that made it appear that the pump was still working. Technicians
reported that the pump was still working during this period, although the vacuum gauge
read slightly lower than expected. The nephelometer was measuring aerosol scattering
inside the scattering volume, which over time showed consistently low scattering values.
This problem was difficult to diagnose given the faulty vacuum gauge and the fact that the
site experienced relatively low ambient aerosol scattering values during this period. The
repair was made just prior to the AOS annual maintenance visit in April 1998. The only
field in the AOS data files that was affected was Field 29, "Bscat530nm". |