August 17, 2016

Experiments life cycle on board the ISS

Selection of the experiments

Regularly, ISS partner agencies issue a joint call for tenders solliciting scientific experiments for instruments developed for the ISS. An international committee evaluates the answers sent by scientists or teams. The evaluation is based on the relevance, originality, and quality of the proposition as well as the skills of the proposing teams. Then, an international team of engineers from space agencies evaluates the technical feasibility of the proposition, taking into account the constraints implied by an inhabited spaceflight.

Preparation of the experiments

When experiments are selected, national space agencies finance the special equipment development needed for their conduct. In the case of EXPOSE, CNES the financed PROCESS and AMINO experiments. Concerning the European propositions, ESA supplies the launch vehicle (shuttle, ATV, Soyuz, Progress, etc.), the resources for the in-flight experiment, and its duplications on ground if needed. The preparation and the tests can last from 2 to 5 years depending on the complexity of the experiment scenario. ESA's User Support Operation Centres (USOC) such as CADMOS located at CNES (Toulouse), MUSC in Germany, or MARS in Italy, help this preparation and mostly the preparation phases required to send the experiment in orbit and operate it. When the experiment is ready, what remains is to find the launch opportunity on one of the spacecraft going to the station.

Once on board, the experiment is switched on by astronauts and controlled by USOC which is then responsible for it. The scientists regularly monitor its course, adjusting parameters if needed. In experiments such as Expose, there is no real scientific data collected during the flight. Only environment data (lighting, temperature) are carefully measured in flight, then downloaded to the ground. The arrival in orbit is not the end, it is quite the opposite. The scientists wait for the return of the exposed samples to analyze them. Some room must then be found on one of the spacecraft bringing the astronauts back to Earth.

In the case of experiments using samples, the true scientific work begins when they are back on Earth, in good conditions, in the laboratory. They have value provided the control experiments conducted on the ground have succeeded in reproducing exactly the main environmental conditions that the space samples have encountered. Once stored, preserved, identified, and analyzed, the samples are ready to reveal all their secrets. Scientists interpret the results, compare them between themselves and to theoretical models, and publish them (with their interpretation of them) in a scientific journal. The experiment is considered successful once the paper is published. From the very start to the ultimate phase, 5, 6, or even 10 years may have gone by!