nasa identifies what hobbled hubble. - precision laser measuring tools

NASA found out why Hubble made two mistakes. -
A man, a machine-
To weaken the primary mirror of the Hubble Space Telescope, NASA-
The panel was announced last month.
But compared to the human goof-upside-
Insert the precision measuring tool down into the optical system that guides the mirror grinding--
Panel member and telescope Roger Angel said that the defective structure of the surveyor alone may cause defects in the main mirror
Mirror designer at the University of Arizona in Tucson.
Mirror manufacturers of the Hubble telescope use laser and precision measuring tools-
Called measuring rod--
In order to determine the spacing between the two parts of the grinding guide rail, a device called a reflective zero-correction device (SN: 7/21/90, p. 39).
Measuring the distance in this way should provide greater accuracy than using a millimetre.
However, this technique requires the laser beam to pass through a small hole in the non-reflective sleeve that covers one end of the precision Metering rod, so that the beam bounces off the rod, not from the sleeve.
When cutting mm
There was a hole of the size on that sleeve, and the technician accidentally cut off the non-reflective coating of the hat.
This caused the laser beam to bounce incorrectly from the sleeve and Rod.
The extra signal returned from the sleeve confused the scientists, inadvertently causing them to misposition the components of the zero correctors.
The panel notes that the spacing error appears to be confused by human error.
Accidentally reversed the measuring rod before the cover--
Therefore, the sleeve is loosely covered at the end of the relative, poorly processed-
Causes scientists to put the test lens and small mirror in the zero calibration device 1.
Angel said the distance was 3mm more than expected.
The panel says these errors have led to today's poor ball that makes the Hubble mirror actually useless ---
No corrective lens-
Used to distinguish weak, distant objects in the universe.
As the NASA team prepares a final report due next month, it will look at how measurement errors escaped detection.
Angel told Science News that some clues that were rejected or ignored suggested that some might be wrong.
The examples he cited included a test of the reflective zero calibration device, which found what appeared to be an error in its components, and the measurements made with the second zero calibration device showed that the main mirror did deform.