Many sounding rocket payloads require rate or attitude control after separation from the rocket motors and commencement of the exoatmospheric flight and experiment phase.Rate control is normally used to remove any residual angular rates and consequently centrifugal accellerations from payloads containing microgravity experiments.
Attitude control provides accurate (~2 arc minutes) pointing of experiments at targets such as the Sun, Moon or stars. Large scan manoeuvres, angle of attack (alignment with the instantaneous flight direction), Earth pointing or active nutation damping may be required. Two axis (spinning control) or three axis stabilization may be provided.
Over the past three decades, the Mobile Rocket Base in cooperation with other DLR institutes, particulary the DFD, has developed a variety of sounding rocket rate and attitude control systems for national and international scientific and technical organizations. In addition, test assistance has also been provided to various organizations for the calibration, air bearing tests and launch support of rate and attitude control systems.
The sensors for rate control systems comprise gyroscopic or optical angular rate sensors, whereas attitude control systems use various combinations of gyroscopic devices and inertial platforms, optical Sun, star and Earth as well as magnetic sensors. A star tracker has been developed by the DLR for such control systems. Processing of the sensor signals into control torques is provided by specially developed analog, digital and hybrid processors. Control torques for the payload are generally provided by cold gas thrusters (solenoid valve thrusters using an inert gas) providing thrusts in the range of 0.1 to 30 Newtons. A feature of some of the systems is the incorporation of in-flight interactive control of manouvres and operational sequences using TM/TC. All systems are supported by comprehensive automatic checkout and quicklook systems and special purpose flight simulation computers.
Numerous custom designed Sun pointing, inertial scan and star pointing attitude control systems have been developed and successfully flown by the DLR for exoatmospheric research. Rate control systems have been developed and are currently supplied to the Swedish MASER and German and ESA Mini-TEXUS microgravity programs. The Mobile Rocket Base can provide a complete service for custom designed rate and attitude control systems for sounding rockets.