Package2b (Nitrogen Oxides)

Instrument PI:     Norbert Houben, Forschungszentrum Jülich GmbH (

Package2b (also denoted P2b) is designed for the autonomous measurement of nitrogen oxides (NOx). NOx is defined as the sum of nitrogen monoxide (NO) and nitrogen dioxide (NO2). 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 NO2 to NO is achieved by photolytic conversion (R2) using the light of 4 UV-LEDs. The set‐up of IAGOS P2b is similar to P2a, except for the converter.

R1                 NO +O3   =>  NO2 + O2 + hν   (600 < λ < 3000 nm)
R2                 NO2 + hν + O2 =>  NO + O3     (λ = 390 nm)

The instrument measures NO and NOx sequentially, by switching the LEDs of the converter off and on.

The P2b 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 PFA tubing to the inlet (Rosemount TAT housing) at the fuselage. P2b is connected with Package1 via Ethernet for data transmission.

Time resolution:    4s (not all intervals contain data; 120 s (90% recovery) for HNO3)
Precision:              NO: ±5%  or ±25 ppt (4s, 1 sigma);  NOx: ±5%  or ±35 ppt (4s, 1 sigma)
Accuracy:              NO: ±7%  or ±25 ppt (1 sigma);  NOx: ±15%  or ±40 ppt (1 sigma)
Interferences:        HONO (8%); potentially HNO4 and PAN


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 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.


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


P2b 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-PIIb-01, flown on Lufthansa D-AIGT
  2. Gomolzig Aircraft Services GmbH for P/N IAG0S-PIIb-02 (EASA STC pending).