Space Research

The Actuator for the CAPS Instrument on NASA Spacecraft Cassini

The actuator for the 20 kg CAPS instrument onboard NASA's Cassini orbiter.

VTT has developed an actuator (ACT) under contract to the South-West Research Institute at San Antonio, Tx, USA. The ACT articulates the Cassini Plasma Spectrometer (CAPS) instrument ±100° in a windshield wiper fashion at a speed of 1 °/s. This is realized with a stepper motor and custom designed drive electronics with closed loop control. The ACT provides the mechanical platform for the instrument and an attachment ring for the spacecraft MLI. The ACT/CAPS is locked during launch by a Marman Clamp ring, which is released by a thermal wax actuator. The ACT also provides a flexible cable wrap for routing the CAPS electrical signals and a feedthrough for purge gas. The operational temperature range is -35...+45 °C. The design life is 500 000 cycles. The weight of the ACT is 3.8 kg and the power consumption is 2.5 W.

The Cassini orbiter was launched in 1997. Mission operations at Saturn take place during 2004 - 2008.