They follow parabolic trajectories, the duration of which is determined by the apogee reached by the rocket, and provide a valuable vibration-free microgravity environment for experiments into material properties and behaviour, biological phenomena and many other fields. For some experiments the micro-gravity timeframe afforded by the sounding rocket flight is sufficient to obtain self-standing results, in other cases the sounding rocket experiments are conducted as a precursor to longer-term research in space (aboard the ISS).
Astrium operates missions with sounding rockets on a commercial basis, acting as prime contractor to ESA or the German space agency (DLR). All sounding rockets for microgravity research are launched from Esrange in northern Sweden.
With TEXUS 17 and 18 (launched in May 1988) the TEXUS project was commercialised and Astrium Bremen has taken on overall responsibility.
The MAXUS long-duration sounding rocket programme is a joint venture between Astrium and the Swedish Space Corporation. This programme was initiated in 1990 to extend the microgravity time achievable with sounding rockets to 10–15 minutes. MAXUS is able to launch a gross payload of typically 800kg to an apogee of more than 700km. This corresponds to some 13 minutes of microgravity conditions.
The TEXUS rockets are launched with the new Brazilian VSB-30, a two-stage rocket motor which performed its maiden operational flight from Esrange in December 2005. With a typical gross payload weight of 400kg, an apogee of more than 250km is reached, and microgravity conditions are achieved for a period up to 390 seconds.