## 1 Introduction  
Water vapor (H\({}_{2}\)O), methane (CH\({}_{4}\)) and carbon dioxide (CO\({}_{2}\)) are major greenhouse gases (GHGs) with a strong impact on the climate. CO\({}_{2}\) is one of the main boosters of GHGs since the beginning of the industrialization era due to anthropogenic activities, and it is considered as the main cause of global warming [1]. Anthropogenic activities such as fossil fuels, ruminant emissions, and biomass burning constitute the major sources of carbon dioxide and methane. The increase of H\({}_{2}\)O concentration [2] in the stratosphere could cause a cooling of this atmospheric region, impacting the recovery of the ozone layer [3]. Therefore, having information and data about the vertical distribution of H\({}_{2}\)O, CO\({}_{2}\) and CH\({}_{4}\) is very useful to improve our knowledge of the future of our climate. It has been widely recognized, with virtually unanimous agreement from scientists, that the Earth's atmosphere is growing warmer due to greenhouse gas emissions generated by human activity. The aim of the Paris Conference ([[http://www.cop21.gouv.fr/](http://www.cop21.gouv.fr/)]([http://www.cop21.gouv.fr/](http://www.cop21.gouv.fr/))) held in December 2015 was to come up with a response to this problem. According to the evidence of climate change and that the radiative effects in Earth's climate system is related to the atmospheric composition in the upper troposphere and the lower stratosphere [4; 5], one should improve the knowledge/estimation of the regional anthropogenic greenhouse natural sinks and emission sources for a better quantification. This goal becomes possible: (1) by enhancing the atmospheric chemistry-transport models that are used to connect sources and sinks to atmospheric concentration; and (2) by increasing the atmospheric observations (satellite, aircrafts, balloons,... ) in addition to ground measurements such as the Integrated Carbon Observation System (ICOS, [[https://www.icos-ri.eu/](https://www.icos-ri.eu/)]([https://www.icos-ri.eu/](https://www.icos-ri.eu/))). Moreover, an increase of in situ measurements which are complementary to satellite-measured data (for accurate and precise concentration scaling) is highly required. A vertical concentration distribution up to a few tenths of a kilometer can nowadays be obtained by techniques such as remote sensing (lidars, radiometers) or through in situ measurements such as aircraft, drones, open stratospheric balloons (BSO) and meteorological balloons. Each technique has specific advantages and disadvantages. Balloon systems, for example, can reach higher altitudes at lower speed than aircraft, which is essential for higher spatial-resolution measurements, while their random trajectories are not well defined, in contrast to aircraft. On the other hand, the lighter the weight of the instrument, the easier the logistic preparation and authorization for flights under smaller balloons [6]. Moreover, the average price of a meteorological balloon flight is much cheaper than that of BSO balloons and aircraft flight. Therefore, small balloons are considered as a good option to help understand greenhouse gas emission processes. Since an increase in the atmospheric greenhouse gas distribution is crucial, we report in this paper the development of a lightweight instrument that complies with the requirements for a flight from weather balloons. This instrument is dedicated to in situ measurements of carbon dioxide up to 10 km altitude in order to study and understand the Atmospheric Boundary Layer (ABL) levels. This instrument could further be useful to study the coupling process between the upper troposphere and the lower stratosphere. Hence, [PERSON] and [PERSON] have reported in situ CO\({}_{2}\) data obtained with a balloon-borne cryogenic sampler [7]. These measurements have revealed a deficiency of a few tenths of ppm between the upper troposphere and the lower stratosphere that could be related to the transport and mixing processes coupling those two altitudes.