Functional Area Problems. Opportunities, and Constraints 41 



The movement of space platforms from Shuttle altitude 

 to geosynchronous orbit will require transfer vehicles 

 having greater lifting capabilities than those of the Inertial 

 Upper Stage and the Spinning Solid Upper Stages of the 

 Space Transportation System currently being developed 

 in coordination with NASA by the U.S. Air Force and 

 industry, respectively. NASA is considering development 

 of orbit transfer vehicles to meet those needs when they 

 arise. The vehicles would also have the capability to place 

 satellites in orbits that depart from the vicinity of Earth, 

 and possibly to retrieve satellites both near to and remote 

 from the Shuttle, The likely near-term (1990s) need is for 

 an advanced propulsion system to serve as an upper stage 

 for planetary missions in the space science program 

 (SPACE). 



Future advances in long-term manned space systems 

 raise additional questions on how the human body func- 

 tions in space. Neither the short-term nor the long-term 

 effects of spaceflight on physiological functions are as yet 

 adequately understood. Methods for mitigating potential 

 adverse effects as well as advanced subsystems to provide 

 life support for human operators are needed. Further- 

 more, optimal patterns of work, exercise, nutrition, and 

 sleep must be worked out. and new procedures for main- 

 taining health and treating illnesses in space will require 

 development (SPACE). Thus, although the Space Trans- 

 portation System opens a myriad of possibilities for the 

 exploration of the potential of space, optimal use of the 

 system will require many additional contributions from 

 the science and technology enterprise. 



REMOTE SENSING, COMMUNICATIONS. AND 

 DATA MANAGEMENT 



Sensing Earth and its environment from space provides 

 information that can be obtained by no other known 

 means. Thus, remote sensing is a singular resource which 

 can contribute significantly to the acquisition of knowl- 

 edge. Likewise, satellites in geosynchronous orbit have 

 the unique capability of being in the direct line of sight of 

 appreciable sections of the Earth's surface. They therefore 

 offer unparalleled facility for receiving, processing, and 

 transmitting information. 



THE USES AND POTENTIALS OE REMOTE SENSING 



Remote sensing from space can provide accurate and 

 continuously updated information on Earth's resources 

 and environment vital to the effectiveness of public policy 

 decisions (SPACE; NR). as well as information useful in 

 protecting our national security. Some remote sensing 

 programs are already in operation, while others are in 

 planning or development stages. Since 1972, the United 

 States has conducted civil remote sensing for natural 

 resources management and environmental monitoring 



through Landsat satellites. Those satellites provide infor- 

 mation about both renewable and nonrenewable natural 

 resources throughout the world, and their information is 

 used by many other countries. The acquisition of those 

 data has implications for the search for additional sources 

 of such materials as scarce minerals and energy resources 

 iASTR-III). 



Monitoring urban and suburban residential patterns is 

 also possible through remote sensing. Another potentially 

 useful application is in forecasting the production of all 

 major crops (AGR; SPACE). Descriptions of additional 

 applications appear in the Source Volumes (AGR\ NS; NR; 

 SPACE; NRC-9). 



COMMUNICATIONS 



The phenomenal growth in international and domestic 

 communications satellite networks during the 1970s sur- 

 passed all projections and created a need for communica- 

 tions satellites with greatly enhanced capabilities 

 (SPACE). That growth rate is expected to continue, par- 

 ticularly as some of the middle-tier countries implement 

 their own systems and as other experimental applications, 

 such as emergency and disaster communications and 

 land-module voice communications, become operational 

 (SPACE; lA). It should be noted that the development and 

 use of communications satellites is one aspect of the 

 national space effort where the private sector has been and 

 will continue to be heavily involved. 



The Tracking and Data Relay Satellite System currently 

 under development is expected to become operational in 

 1984. It is designed to be able to handle increasingly 

 higher rates of data transmission from Earth-orbiting sat- 

 ellites. However, no existing or planned system is ex- 

 pected to be able to handle the large data loads expected in 

 the 1990s. For this reason, NASA is presently focusing 

 research on developing, within a decade, a communica- 

 tions capacity that is several times as large as the current 

 capacity and is based on a highly flexible wide-band data 

 communications network. Aspects of this research and 

 development program include opening up a new frequen- 

 cy band for satellite communications applications and 

 developing advanced multibeam antennas and onboard 

 switching systems to increase the capacity of presently 

 used and planned frequency bands (SPACE). 



DATA MANAGEMENT 



Remote sensing and communications satellite capabilities 

 are placing considerable stress on the ability to process 

 and use data both effectively and cheaply. Thus, the field 

 of data processing has emerged as a very important ele- 

 ment in translating the potential of space into actual bene- 

 fits. As a result of past technological developments, the 

 end-to-end cost of processing satellite data has decreased 

 substantially — from about $100 per processed megabit (in 



