ARISTO-2016 instruments

Detailed experiment descriptions and related flight objectives are below the overview table.

Only one 2D-C will be flown due to the limitations of the wing installation locations.

Right wing pod: LAMS, 3V-CPI; Left wing pod: 2D-S, PHIPS, 2D-C; Left wing tip: CDP (possibly RAF UHSAS)

ARISTO instruments and science

2D-S and BCPD:

The 2DS captures two-dimensional images of particles passing through the sample volume where laser beams overlap. Two 128-photodiode linear arrays work independently as high-speed and high-resolution optical imaging probes. The region where the beams overlap uniquely defines the depth-of-field (and thus the sample volume) for small particles. The 2DS measures particles from 10 to 1280 microns at a 10 micron resolution.  The Backscatter Cloud Probe with Polarization Detection (BCPD) measures cloud droplet size distributions in the 2 to 50 micron range. Particles passing through the laser beam scatter light in all directions. Some of this light transmits within a cone with subtending angles between 143° and 169° (156° ± 13°). These photons are directed onto a photodetector that converts their pulses into electrical pulses, which are then transmitted to a signal processor that amplifies and digitizes them. Mie theory is used to determine the particle’s size from the peak amplitude of the scattering signal. At programmable intervals, the BCPD sends out a particle size distribution. This information is then used to determine particle number concentration. The BCPD’s polarization feature allows the instrument to discriminate between ice and water particles.

Instrument testing needs:  The instruments measure cloud particles that are found in cumulus, stratus and cirrus. These clouds form at various altitudes. The preference would be to sample mixed phase clouds or ice clouds, so altitudes above the freezing level are preferred. The typical flight would consist of constant level flight legs at various temperatures in clouds. There is no airspeed requirement although cruise speed is preferred. The RAF 3V-CPI and RAF SID would be desired for instrument comparison.

Meteorological or target needs for testing:  The target conditions would be those conducive to the formation of mixed phase clouds or ice clouds (e.g. moisture advection at 500 mb and higher, low level moisture combined with cooling at 500 mb).


Continuous flow diffusion chamber - version 1H (CFDC-1H)

The CSU CFDC instruments measure number of ice nucleating particles (INPs) per volume of air sampled through any inlet. The principle of setting steady T and supersaturation for processing uses a thermal gradient diffusion chamber with particle free sheath air directing the minor sample flow between cylindrical ice-coated plates held at two temperatures. INP detection is via optical measurement of the growth of nucleated ice particles. Processing time is several seconds. Sample volume is 1-2 liters per minute, but possible to enhance this using upstream particle concentrators.

Instrument testing needs:  Our primary goals for ARISTO are: 1) To complete re-certification of the instrument for readiness for flight in SOCRATES or any future study on the G-V; 2) To add filter sampling canisters to the CFDC-1H rack and test automated control of sampling with these during flight periods. The filters will feed a different ice nucleation instrument, the CSU Ice Spectrometer (IS), for processing samples offline; 3) To test selected new automated software-based controls (of temperature and filters) for the CFDC-1H.  Special maneuvers that would be useful are level flight periods of 10 minutes minimum, or an accumulation of time spent at one altitude or in one air mass of a minimum of 20 minutes.

Meteorological or target needs for testing:  Target sampling conditions of interest due to other funded work underway are: 1) Sampling at lower altitude over agricultural regions 2) Sampling of forest fire smoke plumes 3) Sampling of urban air  Clouds are not a necessary target, but if so, sampling of sub-cloud aerosols of cloud targets would be desirable.


Extractive Electrospray Ionization High Resolution Time of Flight Mass Spectrometer (EESI-HR-TOF)

We propose to fly a recently developed extractive electrospray ionization (EESI) system coupled to a HR-TOF platform to measure a suite of particle phase organic compounds, including oligomers, at high time resolution (1Hz). We propose exchanging the inlet and chemical ionization assembly with an online extractive electrospray based aerosol ionization system, recently developed at PSI, which allows soft ionization of a wide range of aerosol organics without any thermal desorption. Thermal desorption of aerosol components for analysis is typical in most online aerosol sampling instruments (e.g. AMS, ATOFMS, SPLAT, PALMS) and even most ground-based instruments (e.g. TAG, SV-TAG, FIGAERO, Ziemann). Thermal desorption often results in thermal fragmentation and loss of key molecular information, which is critical for mechanism development and source apportionment. While there are other established techniques to measure aerosol in real time they suffer from two general pitfalls. Most single ingle particle instruments utilize simultaneous laser desorption/ionization, which is not quantitative due to matrix effects . Other approaches like the AMS operate under conditions that are quantitative but result in extensive thermal decomposition and/or fragmentation due to the high temperatures and hard ionization techniques used. While recent developments in semi-continuous measurements coupled to GC or soft ionization techniques like CIMS have provided very useful molecular analysis on the ground and chambers, even the fastest systems require collection and analysis timescales with timescales of ~30-60 min and this fact alone precludes their use for aircraft measurements. Therefore there is a fundamental need in the atmospheric chemistry community for online, rapid response chemical characterization of atmospheric aerosol without artifacts from thermal decomposition. To fill this gap in the measurement capabilities of the atmospheric chemistry community PSI has recently developed an inlet for fast molecular analysis of organic aerosol without fragmentation. We propose to deploy a prototype of the EESI coupled to a proven mass spectrometric technique utilizing a high-resolution mass spectrometer.   Briefly, the extractive electrospray instrument operating principle involves the collision of atmospheric aerosol with charged electrospray droplets. The soluble components are extracted into the electrospray droplet, and as the solvent from the electrospray evaporates, ion ejection by the coulomb explosion mechanism results in gas phase ions formed from the extracted aerosol. Therefore aerosol are ionized rapidly, and transferred into the gas phase without any need for heating.  We have recently tested many different designs, geometries and configurations of the EESI in the laboratory at PSI and now have reached a version which provides rapid response (1Hz) measurements of highly oxidized organic species and oligomers with individual compound detection limits as low as 10 ng m-3 in 5 seconds.  The coupling of the EESI inlet to the aircraft proven HR-TOF-MS allows for the simultaneous retrieval of molecular compositions for hundreds of compounds that comprise organic aerosol at high time resolution, which is ideal for aircraft applications.

Instrument testing needs:  We would like to sample downwind of forested and urban regions to characterize the performance of the EESI instrument when sampling both biogenic and anthropogenic sources. Vertical profiles nearby these types of regions would allow testing of the stability of the technique during profiling potentially measure long-range transport from other regional sources.

Meteorological or target needs for testing:  We would prefer to fly in polluted air within the boundary layer, but then free tropospheric excursions for brief periods. The Denver urban plume and aloft would be sufficient, but it would also be useful to measure a region impacted by biogenic emissions (e.g. pine forests such as near Manitou).


Scanning Mobility Particle Sizer (SMPS)

Measure particle size distributions by bringing them in with air through one of the inlets, charging the particles, separating them out by mobility diameter using a DMA (differential mobility sizer) and then finally counting the particles in each size bin using a condensation particle counter (CPC).

Instrument testing needs:  I'm mostly looking for boundary layer conditions with reasonable particle number concentrations to test the performance of two different sizers (nano DMA and regular long-column DMA).  And also different inlets.  So constant altitude legs through nearly uniform urban and rural areas.  Perhaps some race tracks to sample the same air more than once.    The main objectives here are to test different inlets (SMAI, diffuser, and/or HIML) for the instrument as well as test the differences between operating using a long-column DMA vs. the standard DMA.  We're looking for any biases introduced in particle size or transmission efficiency between inlets.  We're also looking to see how the particle size distribututions match up with the CN counter or UHSAS (if available).  Some higher altitude legs would be useful to determine how large of a particle size we can sample (as this requires a high voltage subject to breakdown in the DMA at low pressure).  For future missions, it would be useful to have some historical data for people to choose the best set up of inlet, DMA and operating conditions to best capture the particle size distributions in the various size ranges.  On all size distributions and inlets, we'd like to be able to compare integrated number counts with the stand-alone CN counter that is usually part of the EOL package.  

Meteorological or target needs for testing:  Want combination of rural background air with low particle counts as well as polluted air with higher concentrations and also different size range.  Denver metro area as well as any location(s) in NE Colorado will suffice.


Microwave Temperature and Humidity Profiler (MTHP)

Microwave radiometer that measures two frequency bands at 55 GHz and 183 GHz for temperature and water vapor sensing respectively. The MTHP scans forward of flight to perform atmospheric profiling above and below the aircraft.

Instrument testing needs:  We would like to have access to aircraft data (roll, pitch, yaw) and any other in situ measurements, if available. Validation with dropsondes would be beneficial. Otherwise no specific requirements or limitations.

Meteorological or target needs for testing:  Would like to probe regions of elevated water vapor, investigating the instruments ability to sense these conditions.


Particle Habit Imager and Polar Nephelometer (PHIPS)

The Particle Habit Imager and Polar Nephelometer (PHIPS) is first of its kind to simultaneously image a cloud particle and measure its angular scattering phase function. The instrument consists of an imaging part that produces two images of the particle with two cameras. The viewing angles of the two cameras are 120° apart, so that the orientation of the particle can be defined. The optical resolution of the images is about 2.5 micrometers. The polar nephelometer part measures the scattering phase functions of single particles in the angular range 1-170°. These scattering phase functions can be related to the microscopic images for studying the single scattering properties of individual cloud particles. The PHIPS is certified for the operation on-board the German research GV aircraft HALO (High Altitude and LOng Range).

Instrument testing needs:  We need flights in liquid, mixed-phase and ice clouds. The flight legs in clouds should be straight, avoiding unnecessary curves. We would also like to have varying airspeeds in the clouds to test the influence of airspeed to instrument performance.

Meteorological or target needs for testing:  Flights in clouds of different phase. Priority is for ice clouds, but we need also some time in liquid clouds.


Multifunction Airborne Raman Lidar (MARLi)

MARLi is a NSF funded MRI development. MARLi integrates laser, telescope and receiving optics with a long optical table to provide simultaneous water vapor, aerosol,  and temperature measurements below aircraft. MARLi transmits  355 and /or 266 nm laser, and receive signals at 10 wavelengths.

Instrument testing needs:  Testing needs: legs at different levels; spiral descending or ascending legs to collect calibration data.

Meteorological or target needs for testing:  Any condition is fine, but like to have a case with large spatial water vapor and temperature gradient.


Broadband radiometer stabilized platform

Upward and downward oriented platforms that compensate for aircraft pitch and roll to keep radiometers level.

Instrument testing needs:  Pitch/roll maneuvers Heading specifications into/away from sun Low solar angle

Meteorological or target needs for testing:  Clear air


Picarro G1301-f Carbon Dioxide and Methane Analyzer (Pic CO2/CH4)

The Picarro ringdown spectroscopic CO2 and methane measurements have a known humidity interference (Rella, 2010; Karion, 2012).  We propose to characterize the time- and instrument-dependence of correction factor.  During NOMADSS 2013 we had the opportunity to intercompare two models of Picarro instruments, one having an internal water vapor sensor (3-channel) and internal  humidity correction, and our own 2-channel model, which has no internal water measurement.  In comparing the data from the two parallel measurements, we learned that the Rella et al. published correction factors, applied to data from our 2-channel model, did not produce accurate CO2 mixing ratios.  Data from intercomparison with CO2 measurements on the NOAA P3 agreed best with the data from the 3-channel borrowed Picarro.  This result was further confirmed by personal communication from Colm Sweeney (2015) that in his experience that Picarro interference correction factors tend to be instrument specific.  During ARISTO 2016, we propose to fly the same two Picarro instruments in parallel to update the most accurate humidity correction factors for our 2-channel instrument. We are also developing and bench testing ambient drying methods to by-pass the need for an internal water vapor measurement.  We would like to take the opportunity during ARISTO 2016 to flight test the impacts on precision and accuracy of a new cryogenic drying approach.

Instrument testing needs:  Two sets of 4 level, 10 minute transects under the a range of humidity and altitude conditions. 

Meteorological or target needs for testing:  Conduct 2 each of 10-minute level transects under the following 4 altitude/RH conditions:  low alt, low RH (e.g. CO or other SW US PBL) high alt, low RH (max alt, clear sky) low alt, high RH (middle US rainy/humid PBL; MBL also works)  high alt, high RH (>= 20 kft, in-cloud)


Solar Occultation Flux (SOF)

The mobile SOF instrument consists of an imaging solar tracker with an INS that has access to the Euler angles of the sun, and which has been optimized for deployments from mobile platforms. This fast digital solar tracker is coupled to an infrared spectrometer to measure total columns of numerous trace gases in the mid-infrared spectral region.

Instrument testing needs:  Needs for testing include:  (1) Instrument specific tests, such as (a) tracking of the solar disk via an IR transmittive view port in the top of the aircraft fuselage; (b) mounting of the instrument from the ceiling of the aircraft fuselage; (c) instrument remote control via the Remote Instrument Control software (RIC) for future deployments. The instrument needs to be tested for ascends/ descends and spirals.  (2) solar tracking and spectral retrievals under conditions with pollution influences (e.g., oil and natural gas; urban pollution; biomass burning plumes). The effect of plume opacity on the (d) CCD imaging loop of the tracker, (e) ability to record and analyze interferograms needs to be tested. This includes low altitude flights surrounding pollution sources, and transects below, above and through biomass burning pollution plumes. 

Meteorological or target needs for testing:  Polluted and unpolluted air; targets are biomass burning plumes; oil and natural gas emissions; urban pollution; agricultural sources (e.g., biofuel production)