A new 'specimen access device' (SPAD) to allow safe and fast access to spacecraft being tested in the Large Space Simulator chamber is now fully operational at ESA's Test Centre.
The SPAD is basically a customised crane, carrying a basket to move an operator inside the Large Space Simulator (LSS). The LSS is a huge chamber at ESA's European Space Research and Technology Centre (ESTEC) in the Netherlands, which can simulate the space environment. Its exceptional test volume makes it an excellent tool for testing large satellites and systems under conditions very close to those found in orbit.
The SPAD moves on parallel rails on the top floor of the LSS building. It has three main parts: the main bridge, the trolley that moves along the main bridge, and the 'telescopic' mast with the operator's 'basket' at the end.
Increasing safety and reducing manpower
It was completed in the last quarter of 2004 and will be used in future test campaigns, for example for the Automated Transfer Vehicle thermal test preparation, scheduled in the coming months.
Until now, it has been used for checking the yoke configuration of ADM-Aeolus, the new global atmospheric observing satellite, and for a 'videogrammetry' set-up in preparation of the thermal test of the Herschel far-infrared observatory (videogrammetry is a measurement technology in which the three-dimensional co-ordinates of points on an object are determined from video images taken from different angles).
The new system was designed mainly to the increase the safety for both the operator and the test items, and to reduce the time and manpower needed for different operations during test campaigns and test set-up procedures.
During previous test campaigns, if test engineers wanted to make checks or modifications to a spacecraft or system in the LSS, they were dangled on a special harness inside the chamber from an overhead crane, the so-called 'Flying Dutchman' operator.
Manoeuvres around the spacecraft being prepared for test were controlled visually by another engineer outside the chamber. However, this system posed safety problems, for example the operator could, due to a wrong manoeuvre, collide with equipment, damage test items, or worse, get injured. A new and drastically improved access system was needed.
For the new SPAD, an anti-collision system was built in by fitting ultrasonic and contact sensors to the basket. These prevent the basket from potentially damaging test items or other equipment positioned in the LSS, and assist the operator when manoeuvring in the limited workable volume of the LSS. Particular care was used to avoid any incompatibility with previously existing equipment located around the LSS chamber.
Improving the efficiency of future test campaigns
According to ESA test engineers Alessandro Cozzani and Rene Messing, relatively simple operations like routeing of thermocouples, installation of accelerometers on a test specimen, or pre- and post-test inspections could have not been easily performed without the help of the SPAD. "Tests can be interrupted now, for example, for minor checks or modifications to be made, without causing serious delays," they said.
The technical staff of ETS, the European Test Consortium, in charge of the maintenance and operation of the ESTEC Test Centre, confirmed the operational safety and ease of use of the SPAD, which will be a valuable tool to improve the efficiency of future test campaigns. The equipment has worked flawlessly so far, reducing overall time of a test set-up of a videogrammetry system by at least two days over a foreseen two weeks for installation.
The system was designed and manufactured under ESA contract by ADS International Lecco (Italy).
For more information, contact Francesco Ratti, ESA ESTEC Engineering Services Section, Noordwijk, the Netherlands.