For over 40 years the Sounding Rocket Program has provided critical scientific, technical, and educational contributions to the nation's space program and is one of the most robust, versatile, and cost-effective flight programs at NASA.
Sounding rockets carry scientific instruments into space along parabolic trajectories, providing nearly vertical traversals along their upleg and downleg, while appearing to "hover" near their apogee location. Whereas the overall time in space is brief (typically 5-20 minutes), for a well-placed scientific experiment launched into a geophysical phenomena of interest, the short time and low vehicle speeds are more than adequate (in some cases they are ideal) to carry out a successful scientific experiment. Furthermore, there are some important regions of space that are too low to be sampled by satellites (i.e., the lower ionosphere/thermosphere and mesosphere below 120 km altitude) and thus sounding rockets provide the only platforms that can carry out direct in-situ measurements in these regions. Astronomy, solar, and planetary science missions include sophisticated telescopes with optional joy-stick operated, sub-arc-second pointing for >5 minute continuous observations of astronomical objects, including those too close to the sun for Hubble or EUVE observations. Microgravity missions are carried out on high altitude, free-fall parabolic trajectories which provide ideal microgravity environments without the vibrations frequently encountered on human-tendered platforms.
Because the science payload does not go into orbit, sounding rocket missions do not need expensive boosters or extended telemetry and tracking coverage. As a result, mission costs are substantially less than those required for orbiter missions. Furthermore, because the program is managed and the payloads are built in one central location (e.g., the NASA/Wallops Flight Facility), significant savings are realized through efficient, cost-savings operations that procures parts and rocket motors in large quantities and utilizes past designs of sub-systems for follow-on missions. In other words, the sounding rocket program takes advantage of a high degree of commonality and heritage of rockets, payloads, and sub-systems flown repeatedly. In many cases, only the experiment -- provided by the scientist -- is changed. Costs are also very low because of the acceptance of a higher degree of risk in the mission (compared to orbital missions), although safety is never compromised. In some cases (such as almost all astronomy, planetary, solar, and microgravity missions), the payloads are recovered which means the costs of the experiment and sub-systems are spread out over many missions.
Not only are sounding rocket missions carried out at very low cost, but also the payload can be developed in a very short time frame -- sometimes as quickly as 3 months! This rapid response enables scientists to react quickly to new phenomena (such as observing the Shoemaker-Levy comet impact to Jupiter) and to incorporate the latest, most up-to-date technology in their experiments.
The sounding rocket program continues to serve as a low-cost testbed for new scientific techniques, scientific instrumentation, and spacecraft technology, eventually flown on numerous satellite missions. For example, COBE, CGRO, EVUE, FAST, ASTRO-2, UARS, SOHO, TRACE, and numerous other recent NASA Satellite missions have been enabled by technology and techniques developed in the suborbital program. Furthermore, the low cost of sounding rocket access to space fosters innovation: instruments and/or technologies which are not sufficiently developed to warrant the investment of satellite-program scale funding are often "proto-typed" with initial space testing on sounding rockets.
In addition to science and technology, sounding rockets also provide invaluable tools for education and training. For example, a three-year sounding rocket mission at a university provides an excellent research opportunity for a Ph.D. dissertation, in which the student carries the project through all of its stages -- from conception to hardware design to flight to data analysis and, finally to the publication of the results. This "hands on" approach provides the student with invaluable experience of understanding the space flight mission as a whole. Indeed, over 350 Ph.D.'s have been awarded as part of NASA's sounding rocket program.