Since the last issue of ISO INFO, the integration of the ISO Flight Model at ESTEC has been completed and a wide range of environmental tests successfully carried out. The cover photo shows ISO as it was in November 1994. The satellite is being used to perform operational interface tests with the ground segment in January/February and again at the end of April. Thereafter, the satellite will be shipped to Kourou for its planned launch on 19 September.
All the major system-level environmental tests - electromagnetic cleanliness, mechanical vibration, acoustic, thermal vacuum and balance - were completed successfully. The infrared background inside the cryostat is higher than was expected due to ``warm'' spots on the inner parts of the cover that closes the cryostat on the ground. An intensive investigation has concluded that the problem is confined to the cryo-cover, which will be ejected in orbit. During the thermal-vacuum test, a few functions - including a column of pixels in ISOCAM and a detector element in ISOPHOT - showed intermittent behaviour. This is still under investigation.
Concerning the overall ground segment of ISO, the first end-to-end test of the instruments, satellite, Spacecraft Control Centre and Science Operations Centre has just come to a very successful conclusion. The second such test is planned for the end of April.
Good progress is being made with NASA concerning the co-operation on ISO. All interfaces with the second ground station are agreed and NASA is well advanced in the upgrading and refurbishment of the antenna station for ISO. Compatibility tests between the NASA station and ESOC are planned for April. Following signature of the ESA-ISAS Memorandum of Understanding on ISO, details of the support to be provided by Japan are under elaboration.