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N° 25–1996: Ariane-5 and Cluster update

27 June 1996

At its meeting on 25 and 26 June 1996, the ESA Council was informed in detail of the measures taken after the Ariane 501 failure and of the proposed approach to revive the scientific objectives of the Cluster mission. Council noted that following the Ariane 501 flight failure on 4 June, the ESA Director General, Jean-Marie Luton, and the CNES Chairman, Alain Bensoussan, set up an Enquiry Board to determine the causes, investigate whether the qualification and acceptance tests were appropriate and recommend corrective action to eliminate the causes of the anomaly and other possible weaknesses in the system(s) found to be at fault. At the same time, they decided to strengthen the investigative powers of the Launcher Qualification Review, in particular by setting up specialised audits (see ESA/CNES joint press releases N s. 21 and 22 of 10 and 14 June).

The Enquiry Board started work on 13 June and will report by mid-July. The Launch Qualification Committee resumed its activities on 14 June. The ESA Director General and the CNES Chairman will have to rule on the Enquiry Board's recommendations and the Launch Qualification Committee's requirements. The ESA Executive will then be able to determine - with CNES - the technical and programmatic implications for the Ariane-5 development programme. The Enquiry Board's findings and recommendations and their implications will be made known to the press soon afterwards.

The Ariane Launcher Programme Board (the ESA delegate body that supervises the programme) will meet on 12 August, when the ESA Executive will present the programmatic implications. On the payload side, the Cluster Science Working Team (SWT) met on 17 and 18 June to assess the situation after the loss of the Cluster mission and to explore ways in which its scientific objectives could be revived.

The SWT proposed the following approach: a. integration of the Cluster structural model with flight spare subsystems (the Phoenix project) together with a rebuild of three spacecraft identical to the originals. This scenario offers alternative options:

a1. integration and testing of the Cluster spare (Phoenix), storage and launch at a later date together with the three rebuilt satellites, and a2. integration and reflight of Phoenix as soon as possible and production and launch of the three rebuilt satellites at a later date.

The SWT stressed that the case for an early launch of Phoenix was largely dependent on whether the follow-on programme was also approved.

A further option would call for:

b. use of the Cluster spare (Phoenix) as outlined above, augmented by three new "mini" satellites funded and produced by ESA Member States that would carry subsets of the Cluster instrumentation. This mission would thus fly one main spacecraft and three "companion" spacecraft, as described in an early proposal for Cluster.

On 21 June the Space Science Advisory Committee (SSAC, the highest scientists' advisory body reporting to both the ESA Director General and the Science Programme Committee) discussed the Cluster situation and recommended that as an initial step the Cluster spare model be made ready for flight, aiming for a launch in spring or summer 1997, and then that the various options for recovery of the Cluster science be evaluated by the full science advisory structure of the Science Programme in the immediate future.

Also on 21 June the Science Programme Committee (SPC, ESA's delegate body that defines the scientific policy of the Agency) met to discuss the recovery options and in particular the feasibility of proceeding with preparation of the Cluster spare model as recommended by the SSAC. It also discussed the potential consequences for the Horizon 2000 programme.

The final decision on whether to proceed with the Phoenix project is expected at the next SPC meeting, scheduled for 2-3 July in London.

Iterations on how best to achieve the scientific aims of the Cluster mission will continue during the summer for further discussion in the forthcoming months. A final decision on the full mission recovery plan is expected to be taken by the SPC meeting on 6-7 November.


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