and atmospheric coverage at a rate of 12 times per day with a 1400 km swath requires 24 satellites, each with an 8-day repeat cycle (assuming the same sun-synchronous orbital parameters given above for land-observing satellites).
The technology available in the year 2000 (hypothetical IESIS deployment date) will, of course, dictate the actual satellite configuration employed. Still, the initial set of satellites should emphasize land observation with more sophisticated oceanic and atmospheric satellites phased in as the ability to model these systems develops. Figure 2.18 summarizes the basically land-observing system described earlier.
2.5 Time Phasing
? SUN SYNCHRONOUS
? 2-DAY PERIOD
? 6 SATELLITES-900 km, 99? INCLINATION
? 1 POLAR "SPARE"
? 2 GEOSYNCHRONOUS
? MODULAR
? SERVICEABLE
Figure 2.18. - Orbit characteristics: Possible initial IESIS satellite configuration.
The intelligent Earth-sensing information system proposed herein is an evolutionary system which considerably extends both planned and existing NASA missions. The time-phasing chart in figure 2.19 is oriented to development of the various components culminating in an operational system by the year 2000. Little attention was given to sensor development as this technology is driven by the various demands of other users and by general progress in this technical area (Breckenridge and Husson, 1979). Most attention was directed to software and artificial intelligence development as these lie at the heart of IESIS, although advanced hardware technology R&D also is required to achieve high packing densities, large wafers, fault-tolerant designs, advanced cooling techniques, advanced interconnections, more logic functions between array elements, advanced data output, and parallel input from sensors to buffer memory. Some of the major points are as follows:
- Research into automatic mapping and world model development should begin early. A world model for use onboard should be ground-demonstrated by mid- 1987 and a Shuttle demonstration of the world model/sensor operation completed by 1990 to meet the projected IESIS deployment date (2000 AD).
- Parallel processor development should be given high priority. The Massively Parallel Processor (a 128 X 128 array processor) will be operational in 1982. A 1000 X 1000 (or perhaps a 10,000 X 100) array for parallel processing should be developed by 1990 and should be flown on a Shuttle test satellite by 1995 to meet the 2000 AD deadline.
- Natural language user interfacing with the data system should be operational by 1990.
- Development of a model of the user population should begin immediately and be phased with natural language and world model development. The prospective ground demonstration of the world model using direct data from an advanced Landsat can be made available at some point to selected users on an experimental basis. The information on prospective selected users can form a preliminary user model.
- Signature analysis, data handling, and security will require continuing development and algorithm refinement. By 1995, software should be flown onboard both experimentally and as an initial phase-in on the autonomous satellites.
- A large world model encompassing terrestrial, oceano- graphic, and atmospheric components and a satellite system scheduler/controller should be ready by the year 2000.
- A gradual phase-out of Landsat D orbiters and phase-in of more autonomous "smart" satellites should begin. By the year 2000, fully autonomous satellites carrying world models should be available for long-term operation and initiation of the complete IESIS program.
