Synonyms: 
Acetone
Propan-2-one
Propanone
C3H6O

Proton-Transfer-Reaction Mass Spectrometer

PTR-MS is a state-of-the-art chemical ionization mass spectrometry technique that allows for fast (seconds) and highly sensitive (detection limits in the tens of pptv range) of volatile organic compounds (VOCs). A detailed description of the measurement principle and the instrument can be found at: http://en.wikipedia.org/wiki/Proton-transfer-reaction_mass_spectrometry

The technique was developed in the mid-1990s at the University of Innsbruck in Austria and has since then become a routine and integral part of most tropospheric chemistry field campaigns including INDOEX 1999, SOS 1999, TEXAQS 2000, AOE 2001, BEWA 2002, ECHO 2003, ARCTAS-2008, DISCOVER-AQ 2011 – just to name a few of the campaigns in which the University of Innsbruck measurement team has been involved. An interactive presentation of the airborne PTR-MS instrument can be found at: http://discover-aq.larc.nasa.gov/instruments.php (click on interactive viewer and on PTR-MS)

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PAN and Trace Hydrohalocarbon ExpeRiment

PANTHER uses Electron Capture Detection and Gas Chromatography (ECD-GC) and Mass Selective Detection and Gas Chromatography (MSD-GC) to measure numerous trace gases, including Methyl halides, HCFCs, PAN, N20, SF6, CFC-12, CFC-11, Halon-1211, methyl chloroform, carbon tetrachloride.

3 ECD (electron capture detectors), packed columns (OV-101, Porpak-Q, molecular sieve).

1 ECD with a TE (thermal electric) cooled RTX-200 capillary column.

2-channel MSD (mass selective detector). The MSD analyses two independent samples concentrated onto TE cooled Haysep traps, then passed through two temperature programmed RTX-624 capillary columns.

With the exception of PAN, all channels of chromatography are normalized to a stable in-flight calibration gas references to NOAA scales. The PAN data is normalized to an in-flight PAN source of ≈ 100 ppt with ±5 % reproducibility. This source is generated by efficient photolytic conversion of NO in the presence of acetone. Detector non-linearity is taken out by lab calibrations for all molecules.

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PeroxyAcetylNitrate, Aldehydes and Ketones

The Ames PANAK instrument is a computerized 3- channel Capillary Gas Chromatographic system designed for the collection and analysis of low ppt (10-12 v/v) levels of peroxyacyl nitrates (PANs), alkyl nitrates, and tertrachloroethene in Channels 1 and 2; and C2-C3 aldehydes, C1-C2 alcohols, C3-C4 ketones, and C1-C2 nitriles in channel 3. Channels 1 and 2 use ECD detectors and have a sampling frequency of 2.5 minutes. Channel 3 uses a Photo Ionization detector placed in series with a Reduction Gas detector and has a sampling frequency of 5 minutes. The main manifold draws 5 SL/min of ambient air through a heated Teflon lined probe from which each of the three instrument channels draws a 200 ml aliquot of sample air. This aliquot is dried by passing it through a –35 °C cold trap, cooled to -140 °C for constituent pre concentration, and then heat desorbed into the gas chromatographic columns. All calibrations are performed in-flight by using an installed dilution system and in a manner that mimics ambient air sampling. Primary standards are generally referred to a series of permeation tubes. In addition high concentration standards are also carried on board. Sensitivities under typical conditions are: 1-3 ppt PANs, 1-5 ppt alkyl nitrates, 5-20 ppt OVOC, and 20-30 ppt nitriles.

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Airborne Scanning Microwave Limb Sounder

The National Research Council decadal survey for earth science identified the need for a Global Atmospheric Composition Mission (GACM) to address crucial issues on how changes in atmospheric composition affect the quality and well-being of life on earth. The baseline GACM instrument suite comprises UV/Vis and IR/SWIR spectrometers and an advanced microwave limb sounder working together to retrieve atmospheric composition worldwide with high spatial resolution. The Scanning Microwave Limb Sounder (SMLS) is designed to meet the measurement requirements of GACM by providing complete orbit-to-orbit retrieval of O3, N2O, temperature, water vapor, CO, HNO3, ClO, and volcanic SO2 in the upper troposphere and lower stratosphere. Unlike previous MLS instruments that only scanned the limb vertically leaving large orbit to orbit gaps, SMLS will simultaneously scan both in azimuth and elevation providing complete global coverage with 6 or more repeat measurements per day. SMLS will employ extremely sensitive, broadband, sideband-separating, SIS receivers centered at 230 and 640 GHz that provide the same precision as those on Aura MLS with a 100 fold reduction in integration time. SMLS will use a novel antenna design that provides high vertical resolution and enables rapid horizontal scanning of the field of view.

Since the late summer 2008, the development of the SMLS instrument technology has been underway within NASA Earth Science Technology Office’s Instrument Incubator Program. The objective of this development is to advance the core signal path technologies required for a microwave limb sounder with the capability to map the composition of the upper troposphere and stratosphere with 50x50x1 km spatial sampling and six times daily mid-latitude repeat coverage. The specific goals of this effort include:

* the mitigation of the optics and calibration risks of the SMLS flight sensor design by constructing and testing an airborne prototype of the SMLS sensor and calibration system - A-SMLS - using prototype sideband-separating mixers, line sources, and advanced spectrometers and calibration targets;

* the mitigation of the development risks of the cryogenics system by developing a flight-like cryostat and demonstrating an end-to-end prototype of the SMLS signal path from the antenna interface through the back-end electronics, and quantifying its stability, calibration accuracy, linearity, and sensitivity; and

* the demonstration of the potential science measurement capability of SMLS through the A-SMLS science flights.

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