TOGA

Measurements Provided:
- TOGA provides atmospheric mixing ratios of an extensive list of compounds, nearly any organic species in the C2-C10 molecular structure range. The list includes alkanes, alkenes, alkynes, chlorofluorocarbons, halons, plus reactive oxygenated species such as alcohols, ketones, esters, and acids. Typically, a subset of some 40 different trace gases are measured, all at sensitivity to levels that occur in the atmosphere. The following table lists most, though not all, the compounds TOGA is capable of measuring:
Manufacturer or Builder of the Instrument: Eric Apel, ACD (Dan Riemer, subcontract, Univ. Miami)

Operational Status:
- requestable, ready for deployment
General Description:
- The instrument is a fast gas chromatograph combined with a mass spectrometer. Its main components are: Pump box, clean air generator/calibrator (CAG), electronics box, MS electronics/Flow controllers, MS chamber and high vacuum pumps, and LN2 dewar assembly. These are shown below in the rack schematic and photograph:
- TOGA is contained in a standard HIAPER rack, weighs less than 200 kg, and consumes ~1 kW of power.
- The inlet is a constant mass flow design to mitigate the intrusion of aerosols and allow for calibrations and system blanks through the inlet and associated tubing.
- A cryogenic preconcentrator, consisting of a custom-built dewar and a system of traps, is used for water removal, sample enrichment and cryofocusing of trace constituents. Flow switching between traps is done via a heated (50C) Valco 10-port valve. TOGA's flow system is diagrammed in the following figure:
- A quadrupole mass spectrometer operating in selected ion monitoring mode is used to quantify individual compounds. High speed electronics allow the simultaneous measurement of several peaks with ~ 1 second peak width.
- System calibrations and blanks are performed using a catalytic-clean air generator/dynamic dilution system with accurate (±1%) and precise (±1%) calibration gas delivery. The system operates continuously, allowing for frequent calibrations and zeros during flight.
Measurement Characteristics:
- Overall estimate of uncertainty: 15% or better.
- Response time: 40 s on a 2-minute cycle.
- Precision: 3% or less.
- Other measurement characteristics (comments on signal/noise, bias limits, etc):

Description of Software, Data Handling, and Data Flow:
- Software Components (data acquisition, display, processing, and analysis):
  - Instrument control and data acquisition are done with LabVIEW (National Instruments), providing comprehensive control of all TOGA functions. Gas flows, temperatures, pressures, logic states, and the aircraft serial stream constitute the parameter set which is displayed on the GUI and archived. The code performs the intricate time sequencing necessary for air sampling, preconcentration (water removal, organic compound pre-concentration, cryofocusing), GC injection and oven temperature programming.
- Data Processing Chain (from flight to archival): Data handling is independent of the aircraft data system. Some select gas concentrations can be merged into the standard netCDF archive files, but most of the results are archived as an independent dataset.
QA Procedures and Needs:

Lead Contacts

Lead Contact: Eric Apel, ACD; Mike Reeves

Documentation

Descriptive Publications
Documentation of the Processing Algorithm(s): See the Technical Note on Processing Algorithms at this URL (fix when available)
Operating Manual

Internal users: See http://wiki.eol.ucar.edu/rafscience/TOGA (last edited 2012-12-08)

Instrument Description

Identifying Information

Measurements Made and Methods Used

Lead Contacts

Documentation