Brief History

December 1997 Installation
April 1998 Warmed up for SHARP run
December 1998 Images taken with the small field objective of SOFI suffers from image distortion near the lower and upper edges of the field of view. These regions are unsuitable for PSF fitting routines. An alternative to the SOFI small field is the large field in combination with the focal elongator in the grism wheel. Thes gives a pixel scale similar to that of the small field objective, a more stable PSF across the field of view, but a slightly lower throughput.
Warmed up to repair grism wheel and to install HR grism
Feb 18, 1999 A new grism, with a resolving power of one to two thousand was installed and commissioned during the new year. The grism is used in orders 3 to 8 with the broad band filters acting as order sorting filters. The resolving power and the spectral coverage of each order are listed on the main SOFI page. This grism complements the two low resolution grisms, simply known as the red and blue grisms, which have been used since the beginning.
Before using this grism, one should consider the following points carefully:
- The spectral coverage of orders 3 and 4 are defined by the order sorting filters, which are respectively Ks and H.
- The spectral coverage of orders 5, 6, 7 and 8 are defined by order overlap within the order sorting filters, which are Z and J.
- The line profile steadily degrades from red wavelengths, where the full resolution with the 0.6" slit is achievable, to blue wavelengths, where the resolution is not much better than the blue grism. Furthermore, the lines in the blue have a very broad component.
- The throughput of the grism in the red is similar to the red grism, but, in the blue, the throughput is significantly less than that of the blue grism.
Thus, we expect this grism to be most useful in orders 3 and 4. If you would like to use the higher orders, please contact the team for further technical advice.
July 1999 Warmed up for CCC maintenance
October 1999 Warmed up to repair grism wheel
March 2000 Upgrade of IRACE
April 2000 Warmed up to replace grism wheel
May-June 2001 Warmed up twice to fix the aperture wheel
March 2002 Warmed up for maintenance
June 2003
 Warmed up because the cycle cooling system died (open twice because evaporation during the heating)
August 2003
 Warmed up for important maintenance (fix the switch wheels problem
and improve the image quality of the large field mode)
October 2003
 The filter wheel number 2 (with the narrow band filters) is broken.
November 2003
 Warmed up to replace the filter wheel #2, and take opportunity to replace the filter wheel #1 and the slit/mask wheel too.
The instrument was  back to life the 4th !
All the parameters seem ok.
Large Field image quality improved.
August 2004 Warmed up to fix severe image quality problem with the Small Field and the Focal Elongator - they were taken out of the instrument for alignment.
January-February 2005 Warm up to fix a problem with the grism wheel; it losses position and for the last two months the instrument was used entirely in imaging mode; the SF and FE wereput back in place and the image quality improved tremendously. However, a week after the intervention the problem resurfaced.
November 2005 SofI underwent an intervention during the first half of Nov 2005 to fix the Slit/Mask wheel which has showed erratic behaviour recently. The intervention was sucesful, the S/M wheel improived but it is sitll not completely reliable and it requires slit/grism re-alignment after every spectroscopic acquisition. The S/M wheel init switch was also restored. Bottom line: SofI is operational with 1-2 min of extra overheads.