INTEGRAL project forges ahead despite problems
21 January 2001With 460 days before the launch set for April next year, members ofthe INTEGRAL Science Working Team have met to review all issues ofESA's gamma-ray mission. Integration of the spacecraft is proceedingat Alenia, construction of the Proton rocket has started in Russiaand the science teams with instruments still to deliver are doingtheir utmost to overcome development difficulties and meet theschedule.
Convened by Project Scientist Chris Winkler, some thirty people - principal investigators, mission scientists and project managers - attended the two-day meeting on 16/17 January at ESA's ESTEC Space Research and Technical Centre at Noordwijk in the Netherlands.
Several milestones in the programme have been reached since they had last gathered. In the clean rooms of prime contractor Alenia Spazio in Turin, the spacecraft itself is assuming its definitive appearance. The Optical Monitor Camera delivered in October has now been mounted, all the coded masks used by the mission's science instruments have been installed, and all of the spacecraft's onboard software has been frozen.
Construction of the Proton launcher has started in Russia and is to be finished by December. The mechanical qualification of the satellite adapter (the interface between INTEGRAL and the Proton) is due to be completed at the end of February. The Critical Design Review of the INTEGRAL specific launcher developments will take place in March-April 2001.
Regarding the mission's ground segment, the third System Verification Test (SVT-C) was completed in November and December, and the spacecraft has successfully been linked with INTEGRAL's Science Operations Centre (ISOC) at ESTEC, the Mission Operations Centre (IMOC) at ESOC in Darmstadt and the mission's Science Data Centre (ISDC) in Geneva. "Many similar tests and rehearsals still lie ahead but we are progressing well" said Ground Segment Manager Paolo Maldari.
Preparation of the remaining science instruments is proceeding. For various technical reasons, frequently encountered in the development of highly sophisticated equipment, the delivery dates for the IBIS, JEM-X and SPI instruments have been rescheduled to give the teams involved more time.
"To meet the April 2002 launch objective" said Peter Jensen, INTEGRAL System Engineering Manager, "we must recognise that this new schedule is still extremely tight and we cannot afford to have further delays. We are fighting to stay on track."
The teams supplying the science instruments are thus accentuating their efforts. Gilbert Vedrenne reported that the cryogenic cooler for the SPI gamma-ray spectrometer had been delivered in December. Electrical, mechanical and thermal vacuum tests, followed by more calibration tests, are now scheduled during the forthcoming weeks in order to deliver SPI to Alenia by the 3 May.
This is also the deadline set for the delivery of INTEGRAL's pair of JEM-X instruments. These X-ray cameras have encountered problems during tests on the qualification model. "We are investigating these dificulties and the two flight models are having to be assembled to incorporate the required changes" said JEM-X Principal Investigator Neils Lund.
As the IBIS Principal Investigator Pietro Ubertini, and his co-PI Frangois Lebrun reported, INTEGRAL's gamma-ray imager has encountered several issues which all highlight the importance of ensuring quality control throughout the development and manufacture of high-performance space science equipment. IBIS delivery is now scheduled 23 March.
"We are facing much work, but we are determined to find solutions in the present schedule" said Pietro Ubertini. As if to demonstrate this collective determination to succeed, Ubertini and his fellow investigators displayed some simulations of the performance of their instruments which will be bringing an unprecedented dimension to the field of gamma-ray astronomy.