Space Technology 7's (ST7) Disturbance Reduction System (DRS) consists of clusters of micronewton thrusters and control software residing on a dedicated computer.
The micronewton thrusters, along with the spacecraft electrical interface and other electronics, sit outside of and around the thermal-shielded instrument box. The thrusters are mounted in clusters at two points on the host spacecraft perimeter. They will continuously and smoothly counteract both external and internal pressures on the test masses within the LTP and control the spacecraft position.
In the LISA Pathfinder Spacecraft, ST7 DRS Clusters of Colloidal Thrusters in relationship to LISA Technology Package Inertial Sensor.
Both the European Space Agency's LTP Inertial Sensor and NASA's New Millennium Program ST7 thruster technologies are essential for DRS performance. The LTP test masses are used as reference for spacecraft-position control and as high-precision accelerometers to validate the performance characteristics of the microthrusters. The micronewton thrusters provide spacecraft-position control, keeping noise forces on the freely floating test masses small enough to meet acceleration-noise performance goals. These technologies:
- use freely falling masses to measure femtonewton forces in space (a newton is a unit of force that is equal to the weight of about 100 grams (four ounces). A femto equals 10-15, a very minute part of a newton)
- demonstrate disturbance-free orbits
- demonstrate ultra-low accelerations in space
Once validated, these enhanced position measurement and control technologies will be applied to follow-on missions well into the 21st century. The capability of following a trajectory determined by purely gravitational forces will enable tests of general relativity, determination of planetary gravity fields, and detection of gravitational waves. The capability of controlling spacecraft position to a fraction of a wavelength of light will enable new types of separated-spacecraft interferometer missions.