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Laboratory for Atmospheric and Space Physics

SOLSTICE Version 15

October 1, 2015

By Marty Snow – LASP, University of Colorado

The latest version of SOLSTICE data has just been released. It includes several important corrections that improve the data quality.

SOLSTICE V15 Oct 2015

Sample time series showing the difference between versions 14 and 15 for SORCE SOLSTICE. The previous version is shown in black, while the new version is shown in red. (SOLSTICE V15 Oct 2015)

We have made two changes related to the January 2006 slit anomaly with the following effects: the discontinuity in the time series has been removed at most wavelengths, and the degradation correction is now fit separately before and after this event. We will continue to analyze the data from the first few years of the mission to improve our understanding of the instrument degradation during the decline of SC 23.

Another correction is that we have discovered the cause of the annual oscillation in the SOLSTICE data. Although we make a correction for the Sun-Earth distance (1/r2), we had not made a correction for the geometrical illumination of the optics due to the change in apparent size of the Sun. Using our weekly “haystack” measurements, we calculated a change in the average responsivity over the year. This second order correction has been a great success in removing the periodic artifact from the data.

Finally, we have corrected for responsivity changes seen after the two extended safe-holds (six weeks in 2011 and six months in 2013). Without stellar measurements to track absolute responsivity, we have had to use comparisons to proxy models to estimate short term changes in the instrument. We have applied offsets to the responsivity using the SATIRE-S model. These offsets do not influence long term trends in the data, and we have added to the irradiance uncertainty. Version 14 applied such a correction to only the 2014+ data and only in the MUV. Version 15 also corrects data in 2012-2013 time frame and both FUV and MUV channels.


Solar cycle variability for the new version of SOLSTICE data compared to the previous version and the NRLSSI-1 model for the decline of cycle 23 and the rise of cycle 24.

The solar cycle trends in the current version of SOLSTICE data are very similar to previous versions. The following plot shows the old version (black and gray), the new version (red and salmon), and the NRLSSI-1 model (blue and dodger blue) solar cycle variability for both the decline of cycle 23 and the rise of cycle 24. As before, SOLSTICE data is similar to model predictions for cycle 24, and still shows larger than expected variability in cycle 23.

We will continue to analyze the early-mission calibration data to derive the best degradation correction. In the past month, we have begun to take new calibration measurements to correct for the solar-stellar field-of-view, and we are working with the mission operations team to investigate the possibility of resuming some stellar measurements! The future for SOLSTICE is very bright…almost as bright as the Sun!

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