Software development is an integral part of the science support we provide to our customers. During the past 15 years, scientific computing has evolved from entirely mainframe- based to today's configuration of distributed processing where a significant and growing portion of the work is done on workstations. These workstations either function alone or are connected by local networks with other workstations, individual systems forming clusters, and with supercomputers. This trend has accelerated as the computational power of workstations has advanced. At the same time, better-resolved modeling requires significantly greater computational resources and many modeling problems are extremely resource demanding on even the most powerful super computers.

The S/W challenge faced by SGT requires developing codes for two increasingly divergent environments, and also necessitates the need to avoid platform specificity. This trend mandates flexibility in design within the S/W development environment. There are also great opportunities for enhancements and advances in visualization that we are undertaking which are made possible by these developments. Furthermore, it has been necessary to identify and address issues regarding new trends, new computational environments, exploitation of multiple processor architectures, and most importantly, efficiency in coding and operations.

For example, the satellite geodesy software tools in use at GSFC have remained state-of-the-art for more than 30 years. Two programs relying on these tools, the GEODYN program, with its capability to compute precise orbits and generate the linear system of equations needed for model development, and the SOLVE program, which is used to manipulate, down-select parameters, and invert large linear systems of equations, have been at the center of this maintenance effort. SGT staff members have been engaged in the development and maintenance of these systems for three decades. With an expanding scope of interplanetary mission settings encompassing the Moon, Mars, Mercury, Europa and the asteroid EROS, sustained GEODYN developmental effort has been critical to meeting evolving orbital modeling and more stringent accuracy goals. In addition to changing central bodies for orbit determination, collateral changes have been seen in space sensors, tracking systems, and modeling goals. Coupled with today's rapidly changing computer environment, keeping GEODYN and SOLVE at the state-of-the-art in the multitude of new investigative settings and retaining accuracy, efficiency and flexibility, continues to be major challenge that we are undertaking.