| Abstract: | Based on the results of studies carried out by ESA several possibilities are discussed to achieve mission cost reductions for large Spacelab instrument facilities as compared to their flight on several 7-day duration Spacelab missions. As an example three scientific telescope facilities are selected (LIRTS, EXSPOS, GRIST) which are defined to a Phase A level.Three new mission modes are considered: • —Shuttle attached Spacelab mission mode with extended flight duration (up to 30 days) for which the application of planned capability extensions and new elements of the STS/Spacelab (e.g. Short Spacelab Pallets, Power Extension Package) are investigated. • —Shuttle deployed mission mode, for which the telescope, accommodated on a Spacelab pallet, is docked to the Power Module, a new element of the Space Transportation System under study by NASA. • —Free-flying mission mode, for which Shuttle launched dedicated missions of the facilities are considered, assuming varying degrees of autonomy with respect to supporting services of the Shuttle. Reduction of costs have been considered on the levels of single mission cost and total programme cost. Fundamentally the charges for the instrument can be reduced by constraining the mass/volume factors with respect to the Shuttle capability. However, the instrument as part of a payload is only viable if an acceptable resource sharing including observation time can be achieved. Any single instrument will require several mission opportunities or one mission which achieves a similar or longer total observation programme.Based on an identification of instrument modifications of the Phase A baseline designs to favour cost reductions and on a derivation of technical requirements, constraints and finally budgetary cost comparisons an attempt is made to assess the advantages and disadvantages of the different mission modes.The favoured option for GRIST is a 2–3 weeks sortie mission followed after refurbishment by a longer Power Module docked mission. For LIRTS and EXSPOS the free-flying pallet modes are very attractive in terms of the longer durations achieved and in terms of cost per unit operating time. |
