ISO operations ran very smoothly from the start. They were well served by a superb spacecraft and by robust instruments which suffered only a few anomalies of relatively minor nature. The mission planning system produced schedules with an average efficiency of 92%. During the routine operations phase, some 50000 slews were executed in order to carry out over 30000 observations (including astronomical calibration observations). In total, over 27000 science observations were carried out successfully for nearly 600 observers corresponding to over 1000 different research programmes. About 400 hours of science observations were carried out per month with an average of 41 observations per day, but ranging from 6 to 238. The average observation duration was 24 minutes, ranging from 36seconds (a camera calibration) for the shortest measurements up to 7.6hours (on Titan) for the longest.
ISO was 1000 times more sensitive and had 100 times better
angular resolution than IRAS at 12
m. The wavelength
range was twice as large which enabled observations of the coldest
objects. The considerably higher spectral resolution allowed new
chemistry and kinematic studies. ISO also provided unique
polarisation capabilities. The results have impact on all
astronomical topics, from comets to cosmology.
All elements of the ground segment also performed excellently, leading to an overall availability of the system during Routine Phase of 98.3% of the time scheduled for science. Taking into account all possible reasons for failure, only 4% of observations were lost. Over 98% of the highest priority observations were successfully executed.