The ESA Space Science Department (now Research and Scientific Support Department) was responsible for the science operations, i.e. the in-flight operations of the scientific instruments. It developed the necessary software at ESTEC, part of it (RTA/QLA2.2, AOT2.3 logic, OLP2.4) in collaboration with the instrument teams. This software development was a difficult and challenging undertaking, mainly because of the high degree of automation required and the many constraints to be respected.
ESA's Space Operations Centre, ESOC in Darmstadt, Germany, was responsible for the overall ground segment and for operating the spacecraft. ESOC controled the satellite from its Operations Control Centre at Darmstadt during the Launch and Early Orbit Phase (LEOP), i.e. the first four days after launch. ESOC was also coordinating its operations with NASA-JPL, which provided the second ground station for ISO at Goldstone, and with ISAS in Japan, which provided support for ISO's flight operations.
After this critical phase of the flight, ISO and its scientific instruments were controlled from the Spacecraft Control Centre (SCC) at Villafranca, Spain (VILSPA), which was co-located with the ISO Science Operations Centre (SOC). The roles and responsibilities of the SCC and the SOC are detailed in Section 4.2. The co-location of so many experts close to each other was a major factor in successfully carrying out ISO's complex operations.
Following attainment of the operational orbit and successful checkout, validation and calibration of the spacecraft and instruments, routine operations started -- on schedule -- on February 4, 1996 and continued until exhaustion of the liquid helium coolant on April 8, 1998.