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TIM Observations of 2006 Mercury Transit The TIM viewed the Sun for the three SORCE orbits during which the 8 Nov. 2006 Mercury transit occurred. During this latest transit, Mercury decreased the sunlight at the Earth by up to 30 ppm (0.003%), indicated by the modeled light curve (in faint red) that accounts for solar limb darkening and the SORCE position. Even with the TIM's low noise, this transit is not independently detectable in TSI because of the underlying continual solar variations, which have much greater amplitude. High cadence TIM measurements are shown in red with orbital averages and their standard deviations in blue. The spacecraft was in the Earth's shadow for both ingress and egress. 
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TIM Observations of 2003 Mercury Transit The TIM also measured during the 7 May 2003 Mercury transit, which had a slightly larger effect than the 2006 transit. As the modeled light curve (in faint red) indicates, Mercury decreased the sunlight at the Earth by 40 ppm (0.004%) at the peak of this transit. As with the 2006 observations, this transit is not readily apparent in TSI measurements alone because of the underlying solar variations. Again during this transit, the SORCE spacecraft was in the Earth's shadow for both ingress and egress. High cadence TIM measurements are shown in red with orbital averages and their standard deviations in blue. (Published in Kopp, G., Lawrence, G., and Rottman, G., The Total Irradiance Monitor (TIM): Science Results, Solar Physics, 230, 1, Aug. 2005, pp. 129-140.) 
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TIM Observations of 2004 Venus Transit The TIM measured a decrease in the TSI reaching the Earth as Venus transited the Sun on 8 June 2004 (red dots). In agreement with predictions (faint red curve) accounting for limb darkening and the SORCE position, the incident sunlight dropped slightly less than 0.1% during the transit. The gaps in the plotted data are from times when the SORCE spacecraft was in the Earth's shadow and could not view the Sun. Both 1st and 2nd Contacts, as Venus began its transit, were observed directly, although egress (3rd and 4th Contacts) occurred when the spacecraft was occulted by the Earth. The increases in brightness near ingress and egress are due to solar limb darkening. The small fluctuations in brightness on short time scales are from normal solar oscillations and can be seen both before and after the transit. (Published in Kopp, G., Lawrence, G., and Rottman, G., The Total Irradiance Monitor (TIM): Science Results, Solar Physics, 230, 1, Aug. 2005, pp. 129-140.) 
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Largest Short-Term Decrease in TSI The passage of two large sunspot groups in late October 2003 caused a decrease in TSI larger than any short-term decrease in the 25-year TSI composite. 
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The First Solar Flare Observed in TSI The TIM is the first TSI instrument with the sensitivity and low noise to detect a solar flare in TSI. While flares are readily detectable at short wavelengths, where the Sun generally has relatively low signal, their contribution to the entire energy output from the Sun is almost negligibly small, making them extremely difficult to detect in TSI. Nevertheless, TSI observations provide a direct means of measuring the total radiant energy output from a flare, as these measurements integrate solar energy over all wavelengths. NOAA/GOES reported peak X-ray (0.1-0.8 nm) values from the X17 flare at 11:10 UT on 28 Oct. 2003. The TIM measured a significant and sudden increase in TSI slightly prior to this, putting the TSI peak nearly in phase with the hard X-rays (as indicated by the derivative of the softer GOES X-rays). The abruptness of this increase and the following gradual decrease are typical of flares observed at EUV and X-ray wavelengths. (Kopp et al., AAS 2004; Woods et al., 2005) 
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TIM Flare Measurements Provide Total Flare Energy The TSI measurements of a flare provide the total, spectrally-integrated flare energy, which we estimate at 5e32 ergs for the 28 Oct. 2003 X17 flare. (Kopp et al., AAS 2004; Woods et al., 2005) 
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