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Southern African Large Telescope (SALT)
ITT worked on a spectroscopic telescope nearly identical to Hobby-Eberly in South Africa — the Southern African Large Telescope (SALT).
In 2005, South Africa and its German, Polish, American and New Zealand partners completed building the largest single telescope in the southern hemisphere, with a hexagonal mirror array 11 metres across. ITT was a key supplier for the project and processed all 96 mirror segments required for the mirror array. Similar to the Hobby-Eberly Telescope (HET) in Texas, where ITT also successfully processed the mirror segments, the Southern African Large Telescope (SALT) has a redesigned optical system using more of the mirror array. SALT is able to record distant stars, galaxies and quasars a billion times too faint to be seen with the unaided eye — as faint as a candle flame at the distance of the moon.
ITT figured the optical surface of the low CTE, Astro-sitall mirror segments to a surface quality of 1/15 a wavelength of light, or 33nm RMS. This is equivalent to 1/3000 the thickness of a sheet of paper. All segments have radii matched to the nominal radius to within 0.5 mm. Testing for final optical figuring of the segments was performed by ITT, in our optical testing towers, at the average angle of 37° from the vertical, supported at nine points by a mirror mount identical to those in the telescope. Print-through of the nine support points is removed to the specified level during this operation.
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