Telecommunication link performance, equipment characteristics and mission requirements determine the frequency bands that are preferred for deep-space research. This Report presents an analysis that leads to the selection of preferred frequency bands in the 1-120 GHz range. For information on general mission requirements and equipment considerations, see Recommendation ITU-R SA.1014; for information on required bandwidths, see Recommendation ITU-R SA.1015. The objective of identifying preferred frequency bands is to provide the technical basis for band allocations from which the designer can select operating frequencies best suited to mission requirements. Sections 2 and 3 of this Report give the technical basis for the selection of frequency bands in the 1-40 GHz and 40-120 GHz ranges.