Description
In the absence of other qualified sources, it is the intent of the Meteorological Chemistry Group of the National Oceanic and Atmospheric Administration's Aeronomy Laboratory (NOAA/AL) to acquire a Black Carbon Aerosol Measurement System from Droplet Measurement Technologies, Inc. (DMT) in Boulder, Colorado. A. BACKGROUND: NOAA/AL has committed to measure the abundance of black-carbon-containing aerosols (commonly known as soot) in the upper troposphere and lower stratosphere. Measurements of the number, size, and mass of aerosols containing black carbon are essential for properly characterizing the radiative balance of the atmosphere. Soot is produced primarily in the burning of fossil fuels and biomass. Changes in Earth's radiative balance from human activities and natural processes may lead to climate change. NOAA/AL proposes to measure individual black carbon and other aerosol particles in internally- and externally-mixed states in the atmosphere. In order to accomplish this goal a modified Single Particle Soot Photometer is required that can measure scattered light from individual particles in a laser beam and emitted light from single, incandescing particles that are heated by absorption of the same laser light. By measuring incandescence at two wavelengths, particles containing black carbon can be distinguished from other absorbing and non-absorbing particles. Sizes in the 0.1 to 2 micron diameter range will be analyzed. B. SCOPE: This procurement is for a Single Particle Soot Photometer Measurement System and Instrument Technical Support. C. PERIOD OF PERFORMANCE: The measurement system will be delivered by November 1, 2003. After receipt of the system the Contractor shall provide up to 120 hours of instrument related technical support during the following twelve-month period. D. SOLE SOURCE: NOAA has determined that only Droplet Measurement Technologies, Inc. (DMT, Inc.) of Boulder, Colorado has a Single Particle Soot Photometer that can meet the following required performance and delivery specifications for a black-carbon aerosol instrument: 1) DETECTION OF SINGLE PARTICLES CONTAINING ELEMENTAL BLACK (GRAPHITE AND AMORPHOUS) CARBON WITH SIZES BETWEEN 0.1 and 2 MICRON DIAMETER AND AT NUMBER CONCENTRATIONS IN AN AMBIENT SAMPLE UP TO 5000 PER CUBIC CENTIMETER. Carbon-containing particles must be distinguished in an ambient air sample from other particles containing other chemical components such as ammonium sulfate, sodium chloride and organics. Detection occurs in a jet of ambient air containing the particles. The Single Particle Soot Photometer (SP-2) from DMT, Inc. can detect single particles containing elemental black (graphite and amorphous) carbon with sizes between 0.1 and 2 micron diameter and at number concentrations in an ambient sample up to 5000 per cubic centimeter. Ground-based tests with atmospheric samples have been conducted in urban settings to show the basic performance of the system. The detector, called a laser-induced incandescence photometer for atmospheric black carbon, uses the principle that light-absorbing particles will heat to incandescence when illuminated with high-intensity light (US Patent # 5920388 (July 6, 1999)). The incandescence temperature, as determined by two- or three-wavelength pyrometry, identifies carbon when it is a principal component of the particle. The photometer utilizes a diode-pumped Nd:YAG laser (1.06 µm wavelength) for particle heating and four optical detectors with filter elements arrayed around an aerosol jet for monitoring particle light scattering and incandescence. The time-resolved signals from each of the detectors are digitized and stored for analysis for individual particles. The detectors are selected for broadband and narrowband incandescence and infrared scattered laser light. The scattered light signal in the SP-2 nominally provides particle size information. When a particle is heated to incandescence, the scattered light no longer provides accurate particle size information. The signal from the broadband detector can instead be used to size the particle. For black carbon particles sampled in a laboratory instrument, the signal positively correlates with the particle size. The ratio of the two incandescence sensor signals can be used to determine the temperature of the particle and the temperature can be used to determine the composition of the particle. The number of particle types that incandesce in a laser cavity depends strongly on laser power and wavelength. Extensive tests have been performed at DMT to categorize the types of particles that can incandesce in the SP-2 configuration. Only a few metal particles aside from black carbon have been found to incandesce in the instrument. 2) COMPLETE DATA PROCESSING AND STORAGE OF SINGLE-PARTICLE AVENTS USING SELECTED SIGNAL-PROCESSING HARDWARE AND CUSTOMIZED SOFTWARE. The full response from each detector must be recorded for later analysis for each particle event up to a few hundred-particle events per second. The software must also handle acquisition of instrument status data and provide some real-time analysis of the acquired data. The SP-2 software consists of three programs: the data acquisition program, which has three components, and two post-acquisition analysis and review tools. The main data acquisition module acquires particle spectra at rates up to 5000 events/second with a 28% duty cycle, and is able to achieve a 100% duty cycle for particle rates below a few hundred per second. Since the four digitizer channels each sample at 5 MS/sec, a 100% duty cycle corresponds to continuously streaming 40MBytes/sec of data, scanning it for randomly-occurring events, and saving the events to disk. The two other data acquisition modules handle acquisition of housekeeping/instrument health data and provide real-time analysis of the acquired data. The post-acquisition analysis tools extract numerous parameters from the spectra and categorize each spectra into particle size and type bins. The SP-2 software has been highly tuned and customized for this application and has been thoroughly tested. There is currently no other software available that can operate the SP-2 instrument at the same performance level. 3) DEMONSTRATED SUITABILITY OF THE PARTICLE DETECTION AND DATA ACQUISITION SYSTEMS FOR OPERATION ON AN AIRCRAFT PLATFORM. The instrument systems must be able to function in the variable temperature, pressure, and vibration environment of an operating aircraft. The basic detection system must be able to connect to an external inlet to acquire particles from outside the aircraft. Maximum weight of the particle detection instrument must be less than 40 kg, excluding the sample pump and data system. The SP-2 was demonstrated on board the NASA DC-8 aircraft during a 6-week mission in early 2003 involving measurements in the Arctic troposphere and lower stratosphere. The SP-2 prototype instrument successfully detected particles on several of the mission flights. The weight of the SP-2 was less than 40 kg, excluding the sample pump and data system. 4) PROVIDE DELIVERY OF A COMPLETE BLACK-CARBON AEROSOL MEASUREMENT SYSTEM AND SUPPORT COMPONENTS. The aerosol measurement system is being developed to participate in an airborne mission in mid-2004. The time required for preparation of the system for flight and integration of the instrument on board the aircraft require that the basic instrument be received by November 1, 2003. DMT, Inc. can meet this schedule. E. Conclusion: DMT, Inc. is therefore uniquely qualified to carry out this effort. This notice may represent the only notice. See note 22.