The GIS Status Report (September 2006)

Paul Kuin, the ex - GIS instrument scientist, MSSL
npmk@mssl.ucl.ac.uk
+44-(0)-1483-204-295

1. Introduction

The GIS calibration will from now on be maintained through the SOHO project at RAL. The MSSL no longer has a dedicated person to provide this support, but of course assistance will be provided as much as is possible when the answer depends solely on our expertise. The last work done on the GIS was a study of the GIS performance based on ten years of quiet sun data, nearly a whole solar cycle by Kuin and Del Zanna. We have written up the results of that study and it has been submitted for consideration for publication. This direct manner of deriving the GIS performance, essentially treating all the detailed processes that affect the sensitivity as a 'black box', is complementary to the previous studies of the GIS sensitivity based on detailed modelling of the LTGD. We find that overall, the GIS has performed very well. For most spectral regions the changes in sensitivity are small. This supports the use of the radiometric calibration of Del Zanna (2001) with some corrections for the long term trends on a line-by-line basis. Detailed plots will be published as time permits here .

2. Status of the detectors and the implications

The status of the detectors is good since May 2006.

3. Existing and possible new programs

The GIS is works fine now that new gsets have been installed in April-May 2006. The pointing offset from NIS has been well-established by Kuin and Del Zanna (see the new CDS report 57). The radiometric sensitivity changes have been found to be fairly small for most lines, except in detector 1, while the changes can be modelled well. The ghosting is limited to a limited number of lines, many of which can be reconstituted because the ghost does not blend with an existing line. Some lines that were thought to be affected by ghosting due to sensitivity changes in the past (particularly in detector 3) were affected instead by drifts in sensitivity which may be due to instrumental changes like in the pre-amplifiers. After 2000, these have been nearly absent. Now that we have a the hindsight of a long-term record, we can seperate the long-term changes to short-term changes, and make a correction on a line-by-line basis.

4. GIS Support

If you need GIS support, contact Peter Young at RAL.

Links

GIS Website: http://www.mssl.ucl.ac.uk/www_solar/gis/

GIS Publications: http://www.mssl.ucl.ac.uk/www_solar/gis/gis_publications.html

GIS Pointing (CDS Software Note #57: http://solar.bnsc.rl.ac.uk/software/notes.shtml

Lapingdon & Foley: http://www.mssl.ucl.ac.uk/www_solar/gis/2004GIS.report.Lapington.Foley.pdf

GIS calibration images: http://www.mssl.ucl.ac.uk/www_solar/gis/images

The in-flight performance of the SOHO Grazing Incidence Spectrometer: http://www.mssl.ucl.ac.uk/~npmk/draft.pdf