In order to measure simultaneously vertical profiles of ozone and further trace gases (e.g. NO2), which are relevant in stratospheric ozone chemistry, we have developed a new balloon-borne optical sonde. Its measuring principle is based on the detection of sunlight intensity with a miniature spectrometer over a wide wavelength range (200 850 nm) during the ascent.A control unit in the sonde evaluates and preprocesses the data already on-board. Every ten seconds parts of the measured spectrum, meteorological values, and GPS information are transmitted to the ground. Height-dependent column densities of the considered trace gases can be determined using radiative transfer calculations and their inversion leads to the vertical concentration profiles.The implementation of new light-weight components and innovative techniques results in an payload weight of 2 kg, thus reaching up to 40 km altitude with comparable small balloons. It can be operated by a two-men team and is suitable for field-work with limited logistic possibilities.The new sonde closes the gap between the electrochemical sonde ECC, the world-wide standard for routine ozone measurements, and sophisticated optical sensors used on large size stratospheric balloons. Due to the necessary logistics, these balloon experiments are very expensive and can only be carried out from special balloon launching facilities.During the first half of this year various test measurements will be performed to thoroughly check the overall technique and the analysis algorithm. We will present the detailed measurement concept, and show first results obtained during the measurements.