The launch vehicle, an Ariane 44P rocket, placed ISO successfully into a highly elliptical geocentric orbit, completing one revolution around the Earth every 24 hours.

The primary mirror of its Ritchey-Chrétien telescope measured 60 cm in diameter and was cooled to 1.7 kelvins by means of superfluid helium.

A number of follow-up studies resulted in the selection of ISO as the next installment for the ESA Scientific Programme in 1983.

Like IRAS, ISO was composed of two major components: The payload module also held a conical sun shade, to prevent stray light from reaching the telescope, and two large star trackers.

The latter were part of the Attitude and Orbit Control Subsystem (AOCS) which provided three-axis stabilisation of ISO with a pointing accuracy of one arc second.

A complementary reaction control system (RCS), using hydrazine propellant, was responsible for orbital direction and finetuning shortly after launch.

The underside of the service module sported a load-bearing, ring shaped, physical interface for the launch vehicle.

The cryostat of the payload module surrounded the telescope and science instrument with a large dewar containing a toroidal tank loaded with 2268 litres of superfluid helium.

Very strict control over straylight, particularly that from bright infrared sources outside the telescope's field of view, was necessary to ensure the guaranteed sensitivity of the scientific instruments.

A combination of light-tight shields, baffles inside the telescope and the sunshade on top of the cryostat accomplished full protection against straylight.

Furthermore, ISO was constrained from observing too close to the Sun, Earth and Moon; all major sources of infrared radiation.

ESA's Space Operations Centre in Darmstadt in Germany had full control over ISO in the first four days of flight.

Cool-down of the cryostat proved to be more efficient than previously calculated, so the anticipated mission length was extended to 24 months.