Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://www.stsci.edu/ftp/instrument_news/GHRS/Ghrs_isr/ghrs_isr073/ghrs_isr073_3.html
Дата изменения: Thu May 30 21:47:59 1996 Дата индексирования: Sun Dec 23 21:07:24 2007 Кодировка: |
The observations obtained are detailed in Table 1
. As a first look at the data, Gilliland plotted the total counts in each spectrum as a function of time, to see if stellar variability was present. What was revealed instead was a regular decline of the observed counts of roughly 10% over the course of each orbit (Figure 1). A plot of counts in the wavecals showed a decline of about the same percentage (Figure 1). Similar declines have been seen previously in stellar spectra obtained with the GHRS Small Science Aperture (SSA) and have been attributed to motions of the star in the aperture that reduce the throughput. In this case that explanation could not account for declines in both the star and wavecal simultaneously. Dr. Gilliland brought this to our attention, and here we provide additional information and a likely explanation.