The definition and development of new analytical instruments to be flown on flyby, orbital, and landed spacecraft must be a high pnonty. In situ imaging and measurements of physical and chemical properties are the justification for NEO spacecraft missions that do not return samples, and the severe mass and power limitations imposed by smaller spacecraft will demand a new generation of instruments. However, in the case of some NEOs, it may be easier to collect and return samples than to do adequate in situ analyses. Nonchemical propulsion concepts hold particular promise for NEO missions. Sampling missions would be most effective if focused on collecting samples from well-charactenzed geologic units or the subsurface of NEOs and from an object exhibiting cometary behavior.
Sample return involves many complex manipulations that pose engineering challenges.
Study technical requirements for human expeditions to NEOs. Human exploration of NEOs would provide considerable improvement in understanding because of the ability to make intensive geologic observations and take carefully chosen samples. The technical requirements for human expeditions to NEOs, although undefined, are intermediate between those for lunar and martian missions. A particularly attractive aspect is that human spaceflight beyond the Moon will probably require incremental steps, and an expedition to a NEO would be of considerably shorter duration and risk and lower in cost than one to Mars.