Package2a (Total Odd Nitrogen)

Instrument PI:     Norbert Houben, Forschungszentrum Jülich GmbH ( n.houbenNO SPAM -- FILTER@NO SPAM -- )

Package2a instrumentation (also denoted P2a) is designed for the autonomous measurement of total odd nitrogen (NOy). NOy is defined as the sum of nitrogen monoxide (NO) and its atmospheric oxidation products such as nitrogen dioxide (NO2), nitric acid (HNO3) and peroxyactetyl nitrate (PAN). The measurement principle is based on chemiluminescence, i.e., the photoelectric detection of the light (hν) produced in a chemical reaction (R1) between atmospheric NO and ozone (O3). Conversion of the oxidation products to NO is achieved by catalytic reduction with traces of hydrogen (H2) on a hot gold surface (R2). The specific set‐up of IAGOS P2a is very similar to the former MOZAIC NOy instrument which is described in detail by Volz‐Thomas et al., (2005) and Pätz et al., (2006).

R1                 NO +O3  =>  NO2 + O2 + hν (600 < λ < 3000 nm)
R2                 NOy + H2  =>  NO + H2O (T = 300°C)

The P2a instrumentation consists of the instrument unit and two pressure cylinders, which provide oxygen and synthetic air for operation and in-flight calibration. The instrument is connected with FEP tubing to the inlet (Rosemount TAT housing) at the fuselage. The front part of the tube is heated to 25°C. P2a is connected with Package1 via Ethernet for data transmission.

Time resolution:    4s (not all intervals contain data; 120 s (90% recovery) for HNO3)
Precision:              ±7%  or ±100 ppt (4s, 1 sigma)
Accuracy:              ±10%  or ±100 ppt (4s, 1 sigma)
Interferences:        HCN (100%)


The instrument is designed for autonomous deployment over periods of up to 6 months. The actual deployment can be shorter if, e.g., contamination or loss of sensitivity is encountered. The instrument operates fully automatically. It utilises the Weight on Wheels (WoW) signal of the aircraft to switch between standby (on ground) and normal operation (in air). In-flight calibration checks include determination of the sensitivity for NO and NO2 and of the instrument background. Before and after each deployment, the instrument is shipped to the laboratory for detailed quality assurance. Details of operating procedures, data analysis and quality assurance are described in the SOP.


P2a is flown (intermittently with P2b) on one aircraft (Lufthansa D-AIGT) under approval by Lufthansa Technik since 2011. EASA certification (STC) is in progress.


P2a was developed by Forschungszentrum Jülich GmbH in cooperation with enviscope GmbH and is manufactured by enviscope GmbH under licence agreement. Responsible Design Organisation (DO, EASA Part 21J):

  1. Lufthansa Technik for P/N IAGOS-PIIa-01, flown on Lufthansa D-AIGT
  2. Gomolzig Aircraft Services GmbH for P/N IAG0S-PIIa-02 (EASA STC pending).