Chapter II 



Observational and Experimental 

 Opportunities in Earth Orbit 



■ 



W. Berry, M. Duke and J. Tarter 



As a prelude to the discussion of scientific questions and the Earth-orbital 

 investigations that can be applied to answer them, it is appropriate to briefly 

 describe the Earth-orbital opportunities available to the exobiologist. These have 

 been limited to those projects which are already proposed and which have some 

 probability of going into operation before the end of this century. An excep- 

 tion, the lunar base, which may be operating in the first to second decade of the 

 21st century, has been included as it has particularly intriguing possibilities for 

 exobiological investigations. There are five classes of Earth-orbital flight oppor- 

 tunities: Space Shuttle (Space Transportation System (STS)) laboratories, 

 spacecraft deployed from the Shuttle, spacecraft deployed from expendable 

 launch vehicles (ELVs), the Space Station, and lunar bases. 



2.1 Free-Flying Spacecraft and the Space Shuttle 



The ELV* 3 program provides access to a variety of orbital inclinations and 

 altitudes. (Until the Shuttle is operational out of Vandenburg Air Force Base, 

 California, these vehicles offer the only means of reaching orbits of greater than 

 57° inclination, such as polar and sun-synchronous orbits.) Current U.S. civil 

 ELVs can insert from 200 kg into low Earth orbit with the Scout, to 2000 kg 

 into the higher-energy geostationary orbit with the Atlas-Centaur. NASA man- 

 ages payload launches with these ELVs and with the intermediate capability 

 Delta and Atlas-F systems. Commercial firms are also marketing launch services 

 with the expendable vehicles which supplement NASA's ELV capability. The 



A complete list of abbreviations is included in Appendix A. 



An Artist's concept of the Space Station in Earth orbit 



