The DØ experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DØ.

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The importance of weight and power estimates and methods for obtaining them are discussed. A method sufficiently accurate for system and launch vehicle planning is developed. It starts from operational requirements such as numbers of transponders, lifetime, eclipse service, radio frequency powers and certain general technology factors such as the performance of batteries and solar cells, and calculates the array power and the masses of the payload and primary power systems. Using these results, and differentiating between spinning and body stabilized satellites, the results of regression analyses on many communication satellites are then used to ascertain the weights of the other subsystems. Simple orbital mechanics are used to determine the weights of propellants, apogee motor, etc., to arrive at a final mass estimate. This estimate should be accurate to between 5 and 10 per cent if reliable input data are available.

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