velop and validate complex models complete in their inclusion of aerial chemistry, distribution of minor constituents, radiation fields, and large-scale dynamics as a three-dimensional time-dependent problem. When the upper atmosphere is sufficiently understood, appropriate parameters to be monitored and modeled can be determined. Useful techniques for verifying models will involve checking model predictions with the observed distribution and concentration of chemically active species (some of which may also be useful as tracers of atmospheric motions). Current planning for the versatile microwave limbsounders seems to be moving in a direction compatible with Earth and planetary sensing requirements. The radiometers will be modularly constructed so that they can be easily exchanged as measurement priorities change and technology advances. Limb-sounder instruments will probably be capable of accommodating several radiometers for simultaneous measurements. Instruments in different spectral ranges will be employed for complementary measurements. The antenna, scanning, data handling, and power supplies should be common to any complement of radiometers used in the system. The Earth atmospheric modeling technology requirements are: • Definition of lower and upper atmosphere niches (spatial location or characteristic properties) • Adaptive modeling of weather complex pattern recognition algorithms weather expert system • Sensors for measuring lower atmospheric properties • Determination of set of properties in an atmospheric niche which give consistent boundaries • An understanding of the atmosphere sufficient to know what parameters need to be monitored development of high resolution satellite microwave techniques for ineasurement of minor constituents • Use of microwave limb-sounding techniques for continuous global coverage • Development of an optimum sensor set for monitormg the upper atmosphere.
6. 1.3. Planetary Modeling For a relatively unknown body, surface and atmospheric modeling must ewlve in greater detail during the course of the mission as more information on important planetary characteristics is obtained. A systematic methodology is required for understanding and exploring a new envirtmment using high sensor technology. This methodology must determine what questions should be asked, and in what order, to efficiently and unambiguously model an uncharted atmosphere and planetary surface. A decision must be made early in the planetary mission whether to place emphasis on elaborate remote sensing from orbit, which may ensure survivability but will not allow all of the scientific objectives to be met, or to physically probe the atmosphere, thus exposing a mission component to increased danger but allowing more precise determination of useful atmospheric properties. The planetary probe must be capable of orbiting, investigating, and landing during a single mission. This is a difficult task to accomplish in one fixed design because of the uncertainties in the nature of the unknown planetary environment. The resulting planetary modeling requirements are: • Systematic methodology for exploring an initially unknown environment • Decision ability in the face of lethal dangers • Modeling ability to establish norms of a planetary surface which allow recognition of interesting sites • Autonomous creation and updating of planetary models using a variety of complementary sensors • Adaptive programming of atmospheric modeling to establish atmospheric parameters • Complex modeling or organic chemistry processes • Expert systems for spectral line identification of complex and ambiguous species • Develop general spacecraft capable of adaptation under uncertain atmospheric and surface conditions and which possesses a broad set of sensors • Exchangeable radiometers, each capable of simultaneous measurements, and with wide spectral range and setlZtuning ability • Mass spectrometers and radio spectrometers based on range of organic compounds considered important or highly probable • Instruments with interchangeable and reconfigurable basic elements • Development of space qualified subsystems, instruments with hmg life times • Development of smart probe sensors and high speed image processors able to operate in the short period of time available during descent • Use of sensors which record only significant variations in incoming data • Simple redundancy so spacecraft will not be overloaded with back-up instrumentation • Automated failure analysis systems, self-repairing techniques.
