Close Range Photogrammetry: A Tool for Shape Measurement & Reflector Alignment
Carson Rooms 1 and 2, enter at Carson 1
C. Koteshwar Rao - Representing ISRO Satellite Centre
The integration of large and deployable reflectors onto communication satellites is one of the more difficult tasks undertaken at ISRO. Apart from CFRP/dual grid antennae, which vary from 2meters to 3meters in size, larger unfurllable antennae of about 6meters diameter are considered in the spacecraft configurations at ISACISRO. This requires a 3D measurement system that can be used at elevated heights for range testing (CATF) and thermo-vacuum environment areas to quantify gravity and temperature induced distortions. At the same time the system should be non-contact, reliable and highly accurate. Existing techniques such as ECDS, Laser Tracker & CMM fall short for some of these considerations.
A study has been undertaken by Mechanical Integration Division, ISAC, for evaluating Close Range Photogrammetry (CRP). The study involved a number of case studies on carefully selected test objects to the advantages of CRP over the existing measurement techniques currently being employed. After successful verifying the accuracy potential of CRP, it was successfully implemented for shape measurements and alignment activities of Ka-Band reflector of the Spacecraft, which is to be launched into geostationary orbit. This paper provides an overview of the various 3D measurement systems employed at ISRO and describes the comparison made among Laser Tracker, ECDS, CMM and CRP via a number of case studies. The paper further deals with the measurements of Ka-Band reflector of the Spacecraft, which is to be launched into geostationary orbit.
