Figure 6-1 shows the different technologies that will be important for the space IR interferometer. Dedicated flight demonstrations using simple experiments may be needed to validate key technologies and simplify integration and test of more complex instruments. The nanometer precision needed for a 75-m interferometer appears initially daunting. Fortunately, a series of nested structures tied together with laser metrology can span the range from meters to nanometers. Although the 75-m assembly needs to be no more precise than a few centimeters, exactly how this structure is to be achieved remains a matter for further study and development.
Inflatable structures offer advantages of reduced weight and packaging flexibility.
However, the structure would have to be rigidified for long-term, cryogenic operation. A significant amount of technology development is needed to bring this technology to the appropriate level. Assembly of the interferometer by astronauts at the Space Station has a number of attractive features, including a reduced risk of deployment failures and the opportunity for limited on-orbit testing before launching the system to its final orbit. Finally, there exists the option of having no metering structure at all. For some baseline greater than 75 m, it will become cheaper to operate each telescope as an independent spacecraft flying in precise formation to produce the desired array configuration.