01 Sep 2008 09:43

The LISA Pathfinder science and propulsion modules in the acoustic chamber. Credit: ESA/Astrium

For these acoustic tests a spare flight model of the science module has been equipped with representative models of the micro-propulsion thrusters, the flight model of the solar array and a number of dummy masses (which take the place of many of the standard system units).

A model of the LISA Pathfinder Technology Package (LTP), comprising the structural model of the inertial sensor and several dummy electronic boxes, has been installed in the science module. The sensor has previously been used during mechanical stand-alone tests. The forthcoming acoustic tests will provide a representative measure of the acoustic input effects in a number of locations inside the sensor.

A number of measurement devices (accelerometers and strain gauges) have been attached to both the science and propulsion modules, and to the LTP, to record the loads during the test sequences. The red and blue cables attaching these devices are clearly visible in many of the photographs displayed on this page.

Two European micro-propulsion (FEEP) technologies (needle indium thrusters and slit caesium thrusters) are currently being developed for LISA Pathfinder. Both types have been mounted on the science module for this series of tests.

A needle indium thruster unit installed on the science module. Credit: ESA/Astrium	A slit caesium thruster unit attached to the science module. Credit: ESA/Astrium

The flight model of the solar array, weighing 21 kg, was secured to the science module at eight points, using eight bolts and bars, to maintain a separation of 8 cm between the surface of the science module and the solar array.

The science module is prepared for the integration of the solar array. Credit: ESA/Astrium	The LISA Pathfinder solar array. Credit: ESA/Astrium

	The solar array is lowered onto the science module (left) and finally, secured to the science module (above). Credit: ESA/Astrium

In parallel to the science module preparations the propulsion module was also readied for the tests with the attachment of measuring devices and four dummy mass propulsion tanks.

The Propulsion Module (right) in the cleanroom at ESTEC. (The science module can be seen in the background.)  Credit: ESA/Astrium	NTO-MMH dummy tanks for the Propulsion Module. Credit: ESA/Astrium
The Propulsion Module at ESTEC before (left) and after (right) installation of the dummy mass propulsion tanks. Credit: ESA/Astrium

The final step in the preparation sequence was to mate the science and propulsion modules and transfer the assembled unit to the acoustic chamber of the LEAF.