Validation of a Strategy for Deformation Monitoring of the Herschel Spacecraft Under Ambient Conditions by Photogrammetry

Abstract

In the frame of the development of a videogrammetric system to be used in thermal/vacuum chambers at the ESA-ESTEC and other sites across Europe, the design of a network using micro-cameras was specified by ESA-ESTEC. The selected test set-up is the photogrammetric test of the Herschel Spacecraft Flight Model in the ESTEC Large Space Simulator. The videogrammetric system will be used to verify the Herschel Telescope alignment and Telescope positioning with respect to the Local Oscillator Unit inside the Large Space Simulator during thermal/vacuum/balance test phases. We designed a close-range photogrammetric network by heuristic simulation with a global accuracy of 1:100,000. A thermal/vacuum qualified videogrammetric system, which is able to work in vacuum and at cryo-temperatures in order to acquire images according to the designed network, was constructed by ESA-ESTEC Test Centre Division. In this paper we will present the videogrammetric system, the photogrammetric considerations, accuracy aspects, the result of photogrammetric network simulations, and real measurements. The results of real videogrammetric measurements of a dummy setup similar to the setup of Herschel spacecraft show a successful performance of the system in terms of functionality and accuracy.