Daily Image
10-12-2007
ASTRON’s ultimate responsibility to provide MIRI the best focus
| Submitter: | Ad Oudenhuysen |
| Description: | After intensive calibration of the silver-coloured optical test bench, and after first assembly of the gold-coloured SW box, the MIRI SMO Flight Model for the JWST is ready for optical inspection. Opto-mechanical technician Menno de Haan is spied on during adjustments for the focus measurements. One of the laser beams from the channel-1 slit simulator is illuminated (red glow). The five mirrors inside the Short Wave box and a grating substitution mirror will project the beam on a piece of ground glass that is positioned in the focal plane. The spot on the left side of the computer screen is the image seen via a microscope and a camera. Two slit images, for two spectrometer channels, each simulated by three laser spots, are going into the SW box and need to be coincidentally in focus on one Focal Plane Array. In Space (1.5 million km from Earth) there will be no arrangement to re-adjust focus, and most likely Menno will not be available there. So the MIRI crew at ASTRON has to make sure down here in the class-100 cabin of the clean room at Dwingeloo that the detector will be in the best possible focus up there. This is difficult enough, even without the complication that a correction is needed for the temperature change from the 300 K human environment to the eventual Space operating level of 7 K. In the coming days you might take the opportunity to peep inside the clean room from the backdoor window. Around Menno and the test setup you should not see more than 100 (dust) particles larger than 0.5 micrometer and no particles larger than 5 micrometer per cubic foot. This is a strange way to tell that Menno needs to be dressed like this and that we are now keeping the SMO in a high cleanliness environment during tests, measurements and transportation. We just want a good working instrument in space and no contamination spoiling all the efforts. |
| Copyright: | Ad Oudenhuysen |
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