Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/~cima/bad_fits_2.txt Дата изменения: Thu Mar 1 19:02:29 2012 Дата индексирования: Mon Oct 1 21:45:05 2012 Кодировка: Поисковые слова: asteroid

INACCURATE POSITIONS RECORDED IN ARECIBO FITS-HEADERS
Data affected between 2004-Sep-16 to 2004-Nov-30
=====================================================

The software writing the WAPP FITS-files was changed on 30 November to correct
a bug affecting the positional information (and all the keywords listed in
earlier emails regarding problems with the interpolations of telescope
positions).

Phil has discovered a bug consisting of an error in the sign of the tracking
error offset used. The FITS-writer has up until now calculated the actual
telescope position by taking the commanded position and adding the tracking
error. Unfortunately, the tracking error is defined in the opposite sense -
the correct way to get the actual position is thus to SUBTRACT the tracking
error from the commanded position.

This problem has now been corrected.

All spectral-line FITS-files taken up until 30 November are affected by this
bug. However, since tracking errors typically are <1-2", the effects are
rather small.

The only time you will see large errors in the positional information is if
you were taking data while the telescope still were slewing towards your
source.


Mikael Lerner

Arecibo, 30 November 2004