The flight of SALACIA

SALACIA (Saline Liquids and Conductivity in the Atmosphere) was finally launched on board the 21 REXUS rocket from Esrange after one day delay with respect to schedule due to the weather conditions. Everything went according to plan and, after the recovery of the rocket, it could be verified that all the systems in the instrument functioned properly and the sensors took the expected measurements. This success gives place to the last but not least stage of the project: the scientific exploitation of the obtained data; the definitive task whose results will give a sense to all the earlier work.
The rocket took off from Esrange Space Center’s launching platform at 11:43 (local time), reaching an acceleration of 20 g to soar up to a maximum height of 85,6 km, scratching the limit of the Mesosphere (the third atmospheric layer from the ground). During the flight the sensors included in SALACIA worked as expected, gathering data of temperature (both that inside the vessels and the ambient one within the module containing the instrument), relative humidity and pressure. All these measurements will provide the appropriate environmental framework to analyse the hydration process of the salts within the vessels, which was the main objective of the experiment since it was initially aimed to be a prospective test of HABIT performance. The conductivity sensors, whose measurements will provide information about the course of the mentioned hydration state of the salts throughout the traverse of the rocket, showed also an optimal functioning.

REXUS 21 assembly. Credit: Álvaro Soria Salinas

Besides, a camera was mounted above each vessel containing salts (4 out of the 5 the instrument has), to record images of their behaviour at a pace of some 16 frames per second. From them, it will be possible to obtain a video which will serve as a useful reference information when analysing the hydration data and also to get interesting clues of their mechanical behaviour under the strains of a launch.
The project, therefore, can be considered as a remarkable success. Regarding the main objective of the REXUS programme, the educational one, the team members have had the invaluable chance of completing a space project, from the mere conception of the initial idea to its final successful realization, working by the way in every aspect it entails.
However, the ultimate reason of any scientific project is to go into depth on the studied subject from the results yielded by the correspondent experiment, and this work is still pending. Now, the data gathered have to be adequately evaluated to reach scientific conclusions, which in this case are meant to provide preliminary insights into the very basic idea of HABIT instrument performance. The thorough and well-aimed exploitation of the data is the way to achieve it, a work which started right after the recovery of the module with the retrieval of the data. The first task in this sense is to match the data recorded by SALACIA’s sensors and cameras with those from the rocket itself, which define accurately the course of the flight. This way, it will be obtained a proper timing of the data sets, which will allow to determine when and under what precise conditions every single step of the monitored hydration process happened. It is very important, for instance, to know the parameters of the electric current from the general power supply unit, since SALACIA measures conductivity, and their measurements are influenced by the mentioned current. Hence, they have to be calibrated according to that current variations.

REXUS rocket launch. Credit: DLR

As for the images, some frames are missing due to minor failures of the cameras (caused for different reasons), so each of those available has to be placed in its precise instant, filling the resulting gaps afterwards in order to obtain the correspondent video, in which the whole process can be visualized.
At last, a paper (the final product of every scientific investigation) will be hopefully written, and its content will provide the definitive value of the work developed throughout the whole project.
Fortunately, SALACIA returned in one piece and in running order, so maybe it can be useful further on to carry out some other studies supporting different aspects of HABIT development in the near future. It will be worth being attentive to this possibility.

Watch the video of the salts vessels during the flight of the rocket