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The ISO-satellite consists of a Service and a Payload Module, the latter being essentially made up of the Cryostat. The present paper describes the current status of this cryostat. The general structural and thermal layout, the He-flow schematic and safety system and the general cover layout are described together with an overview on the existing hardware. Some first test results are as well reported.

The ISO-satellite consists of a Service and a Payload Module (PLM), the latter being essentially made up of the Cryostat. The paper describes essentially the hardware status of the PLM-flight model as it is delivered for final satellite integration and acceptance testing before flight. The various test activities and essential results obtained during development, qualification and PLM-flight model acceptance up to delivery to ESTEC are summarized.

A novel orbital disconnect support (ODS) for cryogen tanks is described which makes use of the change of length of a “shape memory alloy (SMA)” element located at the warm end of a strap-type support. At room temperature the SMA-element is at its extended length with the support strap in disconnected condition. Upon heating the SMA-element to approximately 9O°C, it contracts such that it gets in contact with the support strap and provides the strap tensioning force. During testing of a breadboard ODS a ratio of up to 6,4 between the connected and disconnted heat flux via the ODS was demonstrated.

The Far Infrared and Submillimetre Space Telescope is one of ESA's cornerstone missions in the “horizon 2000” programme. One option to cool the scientific instruments of this satellite is a superfluid helium (He II) cryostat. A trade-off analysis was performed about different sizes and configurations of a cryostat such as to meet the operational lifetime requirement of 2 - 4 years on either a highly elliptical 24 hours orbit or on a far-away from earth orbit. The possible size alternatives for a cryostat using to a maximum extent existing ISO-technology are presented. Upon ESA-decision a final cryostat size for the 24 hours orbit which provides at least 3 years operational lifetime was selected. This cryostat is described and presented.