OMI Instrument Performance Plots

The plots below show the instrument performance (optical + detector) for the complete duration of the mission for the UV1, UV2 and VIS channels. Results are shown for the solar measurements via the quartz volume diffuser (measured once per day), the regular aluminium diffuser (measured once per week) and the backup aluminium diffuser (measured once per month). Data are also shown for the internal LED source and the White Light Source (WLS). The measurement data are divided by reference measurements from the beginning of the mission in order to examine the changes over the mission lifetime.
Note that for the orbit range 8632-10062 no solar, LED or WLS measurements were performed as a result of the FMM anomaly investigations.

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Performance Volume Diffusor





The peaks observed around orbit numbers 12266 (4 November 2006), 17576 (4 November 2007), 22910 (4 November 2008) and 28220 (4 November 2009) are caused by the fact that at these times the azimuth angle on the diffuser reaches its maximum (31.2 degrees for 4 November 2006, 31.0 degrees for 4 November 2007, 31.7 degrees for 4 November 2008, 31.8 for 4 November 2009) and the irradiance goniometry radiometric correction is slightly less accurate.
No peaks occur for orbit numbers 1641 (4 November 2004) and 6950 (4 November 2005), because the azimuth angles at those times were lower (30.6 degrees for 4 November 2004 and 30.2 for 4 November 2005).
For November 2008 (2009) the azimuth angle went beyond 31.2 degrees to 31.7 (31.8) degrees, causing the peak in the plot to appear differently than the peaks in 2006 and 2007.

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Performance Regular Diffusor




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Performance Backup Diffusor




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Performance Internal LED




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Performance Internal White Light Source (WLS)





For the orbit range 8632-10062 no White Light Source (WLS) measurements were performed as a result of the Folding Mirror Mechanism (FMM) anomaly investigations.
In this orbit range the WLS was operated twice for about 10-12 minutes as part of the FMM anomaly investigations. This longer burn time has resulted in increased WLS output, as can be seen from the plots. Between orbits 10062 and 19180 the WLS was used frequently (twice per week), but never longer than 1 minute each time. In orbits 19180 (22 February 2008) and 26315 (26 June 2009) the WLS was switched on for a duration of about 14 minutes. It can be observed that afterwards the WLS output has recovered to about the level observed in orbit 10062.

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