(a) The ratio PREMOS-A:PREMOS-B during the overlap of observations at groups 1–6, as shown in (b) and linked by the blue, dashed lines. Exposure time is for PREMOS-A. Error bars represent the 95% confidence interval uncertainty on the mean from bootstrapping. (b) Raw PREMOS-A (grey) and PREMOS-B (black) TSI observations up to mission day 70 (b–i) and PREMOS-B for the full mission up to 1317 days (b–ii), or 27 July 2010 to 4 March 2014. The six periods of co-temporal measurements of A and B are highlighted blue with blue dashed vertical lines and numbered 1–6. Red groups 7–12 and red vertical dashed lines are when PREMOS-B had the same exposure as A at groups 1–6, respectively. (c) PREMOS-B data, as plotted in (b), but in terms of exposure time of PREMOS-B. The ratios labelled 1–6 in (a) are used to correct groups 7–12 here. For clarity, blue dashed lines between (a), (b) and (c) link the ratios/groups 1–6 from exposure-time in terms of PREMOS-A in (a) to mission time in (b) and exposure-time in terms of PREMOS-B in (c); red dashed lines link groups 7–12 in (b) and (c).