It was decided that the observatory should be made available to a wide community, rather than be restricted to instrument developers, as had been the case for all previous ESA (ESRO) scientific programmes.

In July 1981 ESA released the first Announcement of Opportunity (AO) for participation in the Exosat observation programme to the scientific community of its Member States.

To provide the data handling subsystem with an exceptional flexibility of operation, the OBC and Central Terminal Unit were in-flight reprogrammable.

Once in orbit the flaps which cover the entrances to the ME and LEIT were swung open to act as thermal and stray-light shields for the telescopes and star trackers, respectively.

[4] There was no need for any onboard data storage as Exosat was visible from the ground station at Villafranca, Spain for practically the entire time the scientific instruments were operated.