The main objective of the project is the development of a balloon borne Lightweight In-situ Tracer Experiment in the Stratosphere (LITES) for simultaneous profile observations of ozone and the long-lived trace gases sulphur hexafluoride (SF6) and the chlorofluorocarbon CFC 12 (CF2Cl2) in the stratosphere. The LITES - package is designed to make measurements up to altitudes of about 30 km (< 10 hPa) if launched on small research balloons with volumes of 10000 m3 or less. The instruments are fully automated. Measurements of the mixing ratios of CFC-12 and SF6 will be made at least every 2 minutes. For data transmission a digital lightweight telemetry system will be developed that is based on standard ozonesonde components that are presently used for routine operations at various radiosonde and ozonesonde stations.
The chlorofluorocarbon CFC-12 is a long-lived trace gas, that represents the most abundant source gas of total reactive chlorine, Cly, in the stratosphere and is a good tracer for dynamic transport processes. SF6, is an inert tracer, that provides information about the age of the stratospheric air. In combination with the digital ozonesonde these instruments form a lightweight balloon payload to study the vertical distribution of total reactive chlorine in the stratosphere and quantitatively investigate the corresponding ozone depletion potential in the probed airmass.

Two lightweight automated in-situ gas-chromatographs will be developed for the measurement of the long-lived
trace gases CFC-12 and SF6 with a time resolution of 1 to 2 minutes onboard stratospheric research balloons.
Both instruments will use electron capture detectors (ECD) for identification of the measured species. The radio
transmitter of the standard Vaisala radiosonde will be modified for use as a telemetry system to transmit the data
provided by the gas chromatographs together with the ozone data that will be simultaneously measured by means
of commercially available ozone sondes, e.g. Science Pump ECC or EN-SCI ECC sensors. Two telemetry
channels will be used, one for the meteorological and ozone data (PTU and O3) and another one for the CFC
and SF6 concentration data plus related housekeeping information.
The following tangible results are expected from the project: -Two lightweight in-situ gas chromatographs for the measurement of SF6 and CFC-12, respectively, in
the lower and middle stratosphere with a time resolution of 1 - 2 minutes.
-An improved electrochemical ozonesonde with a two channel radio transmitter that is fully compatible
with the standard Vaisala radiosonde link (400 MHz).
-A new modulator that allows transmission of data provided by the serial interface of the internal control
computers of the digital gas chromatographs at a rate of 1200 baud employing one of the telemetry
channels of the new Vaisala transmitter.
-A set of vertical profile measurements of O3, SF6 and CFC-12 performed during a test flight of the
prototype instruments in Southern France.