Air-Force-managed Titan 34D (which can insert 5000 kg into geostationary 

 orbit), the French-managed Ariane, and the U.S.S.R. Proton ELVs are also 

 potential launch vehicles. 



The Space Shuttle can reach an altitude of 600 km with a payload the mass 

 of the Space Telescope (11,600 kg) and will be able to reach more than twice 

 this altitude if plans go forward to add additional Orbital Maneuvering System 

 kits. The Shuttle will be able to carry 30,000 kg to a 400-km orbit and half this 

 into a polar orbit when the western launch site (Vandenburg) begins supporting 

 launches. A variety of payloads can be carried and either retained aboard the 

 Shuttle during the mission or deployed into space or into Earth orbit. If 

 retained, the payload will be functional only during the 7-day period typical of 

 orbital operations. Small payloads may be flown as payloads of opportunity in 

 the Shuttle cargo bay as "getaway specials" (GAS) or as part of the Hitchhiker 

 program on the orbiter mid-deck, provided that they have minimal resource 

 needs. More complex and/or larger payloads fly in the 60- by 15-foot Shuttle 

 cargo bay as part of a Spacelab manifest, either inside Spacelab or exposed to 

 space on a pallet. Either configuration has access to the extensive services 

 provided by Spacelab, such as communications, fluid loops, and control panels. 

 More complex, and likely more costly, independent payloads using a portion or 

 all of the bay can also be considered; these could be extended beyond the bay 

 once orbit is attained. 



Spacecraft deployed from the Shuttle provide long exposures, flexibility in 

 orbit selection, and the possibility for retrieval. These payloads can be visited 

 periodically by the Shuttle for servicing, retrieval and replacement of experiment 

 packages, and recovery for return to Earth. Another option would be to share a 

 spacecraft performing another primary task; this option relies on an already 

 approved mission which would not be compromised by the addition of an exo- 

 biology experiment. Drawbacks to this approach are that the orbit, altitude, 

 resource availability, etc., are dictated by the host. 



Greater flexibility is provided by sharing accommodations on a spacecraft 

 designed to support multiple tasks, in that the accepted payloads are roughly 

 equal in priority; such spacecraft will be available in the near term. In order of 

 increasing capability they include NASA's Long Duration Exposure Facility 

 (LDEF), Spartan, and the European Retrievable Carrier (EURECA). LDEF 

 will be flown in a series of missions providing exposure to space for a number of 

 self-contained experiments; i.e., the spacecraft does not provide power, propul- 

 sion, communication, or pointing. (LDEF I was deployed in April 1984 and 

 because of the Challenger accident has yet to be retrieved.) After exposure to 

 the space environment for a period of up to several years, LDEF is retrieved by 

 the Shuttle and returned to the ground for experiment evaluation. NASA's 

 Spartan is an autonomous package intended for short, dedicated, space astron- 

 omy missions, but can be used for other types of experiments. It is deployed 

 from the Shuttle and then retrieved after approximately 100 hours in space. 



