Future European Ground Segment

lhe existing European ground infrastructure is capable to support earth observation satellites, the present ARIANE program and scientific manned spaceflight missions as demonstrated during the first German Spacelab D 1 mission flown as payload onboard NSTS in October 85. Future European space program like EURECA, COLUMBUS, HERMES, ARIANE 5, DRS and scientifi~ satellites will require a ground based end-to-end o~eration and verification infrastructure (GEOVI) of a new order of magnitude. Individual program needs and required user support ground segments exceed the very tight budgetary frame available for the European space com~unity (agencies and i ndust.ry) . Investments are\u27 necessary for i ndust ri a 1 development faci- 1 iti es to ~upport the AIV phase, support facilities for development and operation, launch and landing facilities operation~ facilities for mission and payload control and payload data facilities for data dissemination, archiving, retrieval etc

Interference through quantum dots

We discuss the effect of quantum interference on transport through a quantum dot system. We introduce an indirect coherent coupling parameter alpha, which provides constructive/destructive interference in the transport current depending on its phase and the magnetic flux. We estimate the current through the quantum dot system using the non-equilibrium Green's function method as well as the master equation method in the sequential tunneling regime. The visibility of the Aharonov-Bohm oscillation is evaluated. For a large inter-dot Coulomb interaction, the current is strongly suppressed by the quantum interference effect, while the current is restored by applying an oscillating resonance field with the frequency of twice the inter-dot tunneling energy.Comment: 10 pages, 3 figure