TIM Status and Contributions to the Total Solar Irradiance Record

Transcription

1 TIM Status and Contributions to the Total Solar Irradiance Record Greg Kopp Laboratory for Atmospheric and Space Physics University of Colorado 1234 Innovation Dr., Boulder, CO 80303, USA TIM Status Greg Kopp, Page 1

2 Basis of TSI Proxies Is Recent Measurements Sunspot and cosmogenic isotope records give longterm TSI proxies to compare with climate. TSI proxies are extrapolations from recent observations. TSI is compared to sunspot record for last 27 years. Sunspot record is compared to cosmogenic isotopes for last 400 yrs. Ilya Usoskin, Physical Review Letters, (Groveman and Landsburg; 1979) (Lean et al.; 1995). Courtesy of J. Lean, NRL. TSI measurements need to be accurate and well-connected to existing 27-year record. TIM Status Greg Kopp, Page 2

3 TIM TSI Record TIM Status Greg Kopp, Page 3

4 TSI Record updated regularly at TIM Status Greg Kopp, Page 4

5 TSI Accuracy Workshop Held at NIST, Gaithersburg in July 2005 Representatives of 7 of the space-borne TSI instruments: ACRIM I, II, and III; ERBE; VIRGO/PMO; VIRGO/DIARAD, SOLCON, SOVA; TIM 3-day agenda Review the absolute accuracies of each space-borne TSI instrument Review degradation corrections and the ability to track long-term solar variability Discuss possible future improvements to calibration accuracy TIM Status Greg Kopp, Page 5

6 Agreement Between TIM Cones Remains ~270 ppm TIM cone agreement ~270 ppm 1- standard deviation Variations likely caused by uncertainty in applying linearity corrections from ground TIMs to each cone of flight unit TIM Status Greg Kopp, Page 6

7 Comparison to Trapped Diode Compare TIM to transfer standard 6- element BoulderMetrics trapped diode Power comparison (not irradiance) Optical setup Power levels 1-10 mw Intended TIM power 68 mw Laser stability 10-3 Spatial filter improves uniformity Expanded (~6 mm diam) beam gives appropriate cone illumination Still have small calibration details to include for the TIM Witness Unit Will be doing similar test at NIST for all current TSI instruments (ACRIM, VIRGO/PMO, VIRGO/DIARAD, TIM) Setup: David Harber, Karl Heuerman TIM Status Greg Kopp, Page 7

8 Space-Borne TSI Record Relies on Continuity Glory TIM Status Greg Kopp, Page 8

9 10 ppm/yr Stability Facilitates Trend Detection? TIM s 4 duty-cycled cavities and photodiodes monitor degradation. SORCE/TIM has measured degradation of <50 ppm/yr. Corrected with an uncertainty <10 ppm/yr TIM Status Greg Kopp, Page 9

10 Cone Intercomparisons Show <100 ppm Degradation in Primary Cone (B) after First Two Years in Orbit Weekly simultaneous solar observations with Primary Cone (B) and Secondary Cone (A) track changes in Primary Cone Photodiodes monitoring reflectance from each cone show similar changes Degradation is very small and is corrected in data processing TIM Status Greg Kopp, Page 10

11 Cumulative Exposure of Backup Cones Is Low At current exposure rates, Secondary Cone will not start to degrade significantly during 5-year SORCE mission x20 x50 x50 TIM Status Greg Kopp, Page 11

12 Low Noise Detects Dynamic Solar Effects 2003 Drives instrument requirements on thermal stability thermistor noise shutter cycle period amplifier & AtoD noise SORCE/TIM was the first TSI instrument with sufficient sensitivity to detect a solar flare. TIM Status Greg Kopp, Page 12

13 TSI Flare Observations Measure Total Flare Energy See presentation by T. Woods on flares TIM Status Greg Kopp, Page 13

14 Data Processing Has TSI Data Available In 1 Week TIM TSI measurements from 1 March 2003 to the present are available via Daily data updates follow data acquisition by roughly 7 days Evaluating making processed data available within a day of telemetry of raw data for quicker comparisons with other solar activity indicators TIM Status Greg Kopp, Page 14

15 TIM Will Next Be Flying on Glory... S/C TSI Observations Glory TIM Instrument on Glory TIM Instrument TPS TIM Status Greg Kopp, Page 15

16 ...and then on NPOESS TIM S/C TSI Observations SIM Glory TIM Status Greg Kopp, Page 16

17 Summary TIM TSI values remain ~4.5 W/m 2 lower than other S/C TSI instruments. The NIST TSI Accuracy Workshop in July 2005 reaffirms our confidence in this value The TIM shows very little optical degradation from solar exposure, and the electronics show no signs of change since launch. TIM degradation is low at <50 ppm/yr This is tracked and corrected in data analysis Results from 1 March 2003 to the present are released regularly and are available 7 days after acquisition. TIM Status Greg Kopp, Page 17