REFRACTION CONSIDERATIONS FOR PHOTOGRAMMETRIC MEASUREMENTS IN A THERMAL VACUUM CHAMBER

Photogrammetric measurements within environmental test chambers which incorporate viewing ports constitute an application of multi-media photogrammetry. Perturbations to the incident bundles of rays due to refraction must therefore be taken into account. In this paper, refraction compensation for the case of antenna measurements within thermal vacuum chambers is discussed. Correction models applicable to the camera invariant refracting surfaces of a glass window and vacuum chamber are reviewed, especially error compensation using the approach of analytical selfcalibration. Results of a sequence of measurements of a satellite antenna are then analysed to illustrate the high measurement accuracies which are afforded by the selfcalibration approach.