Instrument Payload for the
NOAA -PMEL Manta:
The instrument payload
provides in situ measurements of aerosol chemical, physical, and
optical properties in order to tie changes in surface albedo to
pollution aerosol. The instruments consist of the following.
A chemical sampling
filter system with an 8 position sampling carousel. A pump pulls
sample air at 2.5 liters per minute through filters that can be
analyzed after the mission for chemical constituents. The filter
flow and be commanded from the ground station to start and stop.
Also, the sample flow can be switched to any filter in the sampling
carousel by command from the ground at any time during the flight.
A condensation nucleus
counter, CNC, that measures the total number concentration of
particles with sizes greater than about 10 nanometers in diameter.
This instrument uses butyl alcohol vapor to grow small particles to
a detectable range and provides data at a one second interval.
An aerosol absorption
photometer. This instrument passes a flow of sample air through a
small filter, which is illuminated is series with red, green and
blue (624, 525, and 450 nm) light from an LED light source. The
amount of light that passes through this filter decreases during the
flight as black carbon aerosol is collected on the filter. A
photodiode detector measures the transmission of light through the
filter and the rate at which the light transmission decays is
related to the concentration of absorbing aerosol in the atmosphere.
Although this instrument provided data at a one second rate, to
get useful measurements, 30 to 60 seconds averages of the data must
be used.
As part of the flow
control for all of the above instruments the payload also measures
the ambient pressure. The air temperature and humidity, RH, are
measured with a probe that extends below the main body of the
aircraft. Because the priority of the payload was to measure
aerosol properties, the sampling rate for the temperature and RH is
set to one reading per 10 seconds.
The data are stored at one
second intervals on a “micro SD” data card during the
flight. The data are also sent in real time to the ground station
through the RF and iridium satellite link.
|