Like all fields of science, astronomy is developing rapidly. This also applies to the methods and techniques used in astronomical spectroscopy. It seems safe to predict that many of the instruments, methods, and procedures that have been discussed here will become obsolete during the next decades; and many techniques that are still experimental or unknown at present may become the standard tools of the future. Some new technical opportunities are expected to become available soon. Others will take longer. Some new methods, which are discussed at present, may never become practical. Nevertheless, when planning new scientific programs and future instruments, such new developments and opportunities must be taken into account.

Present-day major astronomical instrumentation projects typically take years or decades to complete. Some large projects are in progress at present, or in advanced planning stages. In these cases, the future scientific opportunities can be assessed with a fair amount of probability. There are other projects and new ideas whose chances of realization are less certain. Moreover, there may be different opinions concerning the potential of some of these ideas. Therefore, the following sections are necessarily more subjective than the earlier chapters of this book.

Scientific Drivers

Although astronomers do not always fully agree on priorities, a look into the recent relevant publications and reports (such as the 2010 Decadal Report of the U.S. National Academy of Sciences, the justification of NASA's Origins program, and the ASTRONET Science Vision document produced under the auspices of the European Commission) shows a surprising degree of agreement concerning the most important current research topics in astronomy.