Herschel Telescope Testing
18 February 2008The last two weeks have seen several testing activities around the Herschel telescope flight model in the cleanroom facilities at ESTEC. On 4 and 5 February the M1/M2 distance measurements of the telescope was performed. These M1/M2 measurements are to verify the optomechanical stability of the telescope under ambient conditions before launch. They are performed before and after significant mechanical and environmental testing, transport and handling activities of the telescope.
Last week's measurements were done after the transport of the telescope to ESTEC and were followed by a Post Test Review (PTR) performed on 6 February which proved the telescope to be in good condition.
The same measurements will also be performed after the telescope is integrated onto its support structure on the Herschel spacecraft. Later this year the telescope's optomechanical stability will be checked again after completion of the vibration and thermal vacuum testing of the satellite.
A set of three titanium bipods, each with a 49° optimal angle between its two legs, forms the telescope's isostatic mount function designed to enabe the telescope integration on the satellite cryostat vacuum vessel with negligible optical distortions.
The three bipods connect to three interface points beneath the telescope's large primary mirror. A close-up of one of the three bipods during the fit-check is seen here.
The Astrium team from France were fully successful in carrying out the reference plate fit-check of the telescope. All measured bipod displacements (radial and tangential) were within defined limits.