|
Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://www.apo.nmsu.edu/Telescopes/SDSS/mirror_report/node1.html
Дата изменения: Thu Nov 25 00:45:46 1999 Дата индексирования: Sun Apr 10 00:20:24 2016 Кодировка: Поисковые слова: enceladus |
On the afternoon of 19 October 1999, it was discovered by John Briggs that
the secondary mirror in the 2.5m SDSS telescope had developed a series of
circular cracks around its axis of symmetry. As the telescope had not been
in use since the early morning of 16 October 1999, there was a great deal of
concern and consternation as to what caused these fractures in the glass.
As there had been a dramatic drop in temperature over the weekend, a drop
of some 15
C during a snow storm over the weekend of 16 October 1999, it
seemed plausable that
the temperature drop was the immediate cause for the fracture. However,
what needed to be understood was why the mirror was under enough stress
to expose it to the possibility of cracking in the first place. It was
decided by the APO Site Manager that the SDSS Observers should undertake an
analysis of all available forensic data on hand, as they are the people best
equipped for such an analysis: they have intimate day-to-day knowledge of
the telescope; are responsible for the overall health and safety of the
telescope (on a daily basis); and were responsible for the operation of the
telescope up until the morning of 16 October 1999. Also, as the dark run
was close in time to the event, there may have been misunderstood and poorly
documented behaviour, which in hindsight, might point to important clues
about the behaviour and state of the secondary before the fractures appeared.