Purpose of the flight and payload description
The chemiluminescent technique is based on detecting the intensity of the radiation emitted from the chemical reaction of the NO interacting with ozone and oxigen when an excess of O3 is added to a flow of air containing NO.
The instrument used to exploit this technique in a balloon-borne platform works as follows: ambient air is drawn through a 2.4-m length of 7.6-cm-ID black-anodized aluminum pipe. After being heated to near 27º C and mixed with O3 in the reaction vessel it is exhausted through 10-cm-diameter tubing at least 2.4 m in length attached upward to the payload support cables. An excess of O3 is added either directly to the reaction region for measurement of ambient NO or sufficiently far upstream to remove all the NO from the sampled air for the true background photomultiplier reading. Provision is made for 'onboard' calibration by addition of small known flows of NO to the sampled air.
In addition to the photomultiplier signals, measurements were also recorded of the flow rate, temperature, pressure, O3 content of the gases flowing through the reactor, and the flow of the calibrating gas. The data were recorded on board by a digital cassette tape recorder and also telemetered to the ground. The detection limit of the instrument was >0.02 ppb by volume above 18 km.
Details of the balloon flight