Our pre-phase A study of NGST science instrumentation had two goals: 1) to explore specific trade issues in sufficient depth both to support development of our ISIM concept and to bring them to the attention of the NGST project and, 2) to develop a comprehensive integrated science instrument module from an independent viewpoint to allow comparison with the GSFC (Goddard) yardstick (Greenhouse 1999). We have investigated how detectors, cooling options, multi-object spec troscopy concerns, and the effects of telescope design affect scientific performance of the ISIM. Our proposed ISIM concept provides 1) imaging from 0.4-35 mu m plus very wide field imaging over 0.4-5 mu m, 2) multi-object spectroscopy from 1-35 mu m (R less than or equal to 3000 to 5 mu m, R less than or equal to 1000 to 35 mu m), and 3) crossdispersed R = 3000 single object spectroscopy over the 5-35 mu m region. The instrument package is composed of multiple, simple modules. To the greatest extent possible, we have limited the number of observing modes and capabilities of each module to optimize scientific performance, and at the same time, minimize complexity and risk. We discuss advantages of modularity graceful descopes, and the readiness of key technical items in the design. We provide a comparison with the GSFC Yardstick and estimate our ISIM cost. The full study report can be found at http://www.ngst.nasa.gov/cgi-bin/doc?Id=501.
