A Typical SR Mission
SRs fly missions so varied it is impossible to list them all. There are the purely scientific missions, some aimed at learning more about various aspects of the atmosphere, such as the ionosphere, the aurora, and even weather patterns. Then there are those that support some satellite operations, such as SOHO. These are flown to obtain additional data and even images to add to the data from the satellites.
Some missions are flown strictly in support of university educational programs. This is a significant part of NASA’s SR program—support of university research.
Whatever the mission, they follow a fairly typical mission profile, as illustrated below. The SR is launched at an angle slightly less than 90 degrees, depending on the altitude to be achieved. The fins on the lower stages impart a slow spin to the vehicle to provide stability. Once the final stage burn is complete, small rockets de-spin the upper stage and payload. The payload separates, and stabilization booms deploy to provide in-space stability.
As the payload coasts to apogee (the highest point above Earth) the Automatic Control System (ACS) locks onto a star or the Sun to keep the payload pointing toward the proper object. Previously, instrumentation doors have opened to expose the cameras, detectors or other instruments.
The payload coasts through apogee, continuing to make its measurements. Depending on altitude and launch angle, a payload package can stay at apogee for as much as 300 seconds.
As the payload begins to descend, the doors close and the stabilization booms retract or are ejected. After the package enters the atmosphere, a parachute deploys, to lower it safely to the surface so it can be reused.
So sounding rockets are a highly useful scientific tools, being relatively inexpensive, with, in most cases, reusable payloads, and unique capabilities.