Solar Spectral Irradiance (SSI)
Variations Workshop

Feb. 28 Mar. 1, 2012

There are interesting and conflicting differences for the Solar Spectral Irradiance (SSI) variations during the SORCE mission. The SORCE team in collaboration with NIST and GSFC is planning a series of SSI Workshops involving a small number of SSI scientists and calibration experts to address these SSI variation differences. Unlike the Total Solar Irradiance (TSI) or UARS-era SSI studies that concentrated on absolute scale offsets in irradiance, this first SSI workshop of the series focused on issues primarily related to differences in understanding degradation trends that affect the solar cycle variations in irradiance. For this first SSI workshop, we:

  • Discussed SSI instrument observations, capabilities, their estimated irradiance uncertainties
  • Discussed how each instrument team analyzed the spectral data to separate out instrument effects (e.g. degradation) from intrinsic solar variations
  • Established a better understanding of the SSI differences and refinement of their uncertainties
  • Made plans on how to identify the significant differences (new studies, new calibrations, etc.) and refine uncertainties

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Download the Workshop Summary

Day 1 – Feb. 28, 2012

Introduction to Instruments used in SSI Comparison
7:30 – 8:15 a.m. Welcome / Continental Breakfast
8:15 – 9:15 a.m. Introduction to Workshop Topic and SSI Variability Differences – Gary Rottman (LASP)
 
UV Instruments (100-300 nm) and Visible/Infrared Instruments Part 1
Session Chair: Joe Rice

With the Generalized Measurement Equation as a guide, each instrument lead discussed how the instrument adheres to the terms in this equation, and additional contributions and/or omissions. Discussion was held throughout each briefing.

9:15 – 10:35 a.m. SOLSTICE I (UARS) and II (SORCE) – Marty Snow, Tom Woods, Bill McClintock (LASP)
10:35 – 10:50 a.m. Break
10:50 – 12:25 p.m. UARS / ATLAS SUSIM – Linton Floyd (NRL)
12:30 – 1:30 p.m. Lunch (NIST Cafeteria Buffet)
1:30 – 2:55 p.m. SBUV / SSBUV – Matt DeLand (SSAI, GSFC)
2:55 – 3:45 p.m. ATLAS / ISSI SOLSPEC – Gerard Thuillier (LATMOS-CNRS)
3:45 – 4:00 p.m. Break
4:00 – 5:30 p.m. SORCE SIM – Jerry Harder, Juan Fontenla (LASP)
 

Day 2 – Feb. 29, 2012

Breakdown of Contributions to the Generalized Measurement Equation Understanding Degradation: Part 1
Session Chair: Jerry Harder

Advancements in laboratory studies characterizing material damage and analysis of degradation mechanisms for space flight missions provide an independent perspective on root causes of degradation in instruments that measure SSI.

7:45 – 8:20 a.m. Continental Breakfast / Welcome
8:20 – 8:35 a.m. Capabilities of NIST / SURF calibrations for SSI UV instruments – Uwe Arp (NIST)
8:35 – 9:10 a.m. NIST / SURF capabilities in the VUV degradation (C deposition) – Shannon Hill (NIST)
9:10 – 9:45 a.m. Detector degradation – Ping Shaw (NIST)
9:45 – 10:05 a.m. Capabilities of NIST SIRCUS calibrations for SSI Vis-IR instruments – Allan Smith (NIST, for Steve Brown)
10:05 – 10:35 a.m. NIST capabilities regarding polymer-based degradation – Joannie Chin (NIST)
10:35 – 10:50 a.m. Break
10:50 – 11:50 a.m. Radiation testing for the TSIS SIM instrument – Erik Richard (LASP)
 
Visible/Infrared Instruments Part 2 (300-2400 nm)
Session Chair: Howard Yoon
11:50 – 12:30 p.m. SOHO VIRGO filter radiometers – Christoph Wehrli (PMOD/WRC)
12:00 – 12:30 p.m. Working Lunch (Box Lunch delivered)
 
Understanding Degradation: Part 2: Question and Answer Session with NASA Contamination Experts
1:00 – 2:10 p.m. Degradation / contamination effects – David Hughes/Therese Errigo (GSFC) (no slides)
 
Visible/Infrared Instruments Part 3 (300-2400 nm)
2:10 – 3:10 p.m. ATLAS / ISSI SOLSPEC – Gerard Thuillier (LATMOS-CNRS)
3:10 – 3:20 p.m. Break
 
Understanding Differences in the Time Series of Different Bands
Session Chair: Tom Woods

Topic-by-topic discussion encompassing systematic and time dependent components and "unpack" uncertainties in absolute accuracy, stability, and precision. This included time, temperature, wavelength, and optical performance at specific wavelengths common to the instruments employed in this study.

3:20 – 3:40 p.m. Comparison of SSI UV observations in relevant bands (120-400 nm) - Marty Snow
3:40 – 4:05 p.m. Comparison of SSI UV observations in relevant bands (120-400 nm) - Matt Deland
4:05 – 4:30 p.m. Comparison between SUSIM and SIM – Jeff Morrill
4:05 – 4:30 p.m. Decoupling degradation and solar cycle variability – Tom Woods
5:00 – 5:30 p.m. "Where do we go from here?" discussion – Led by Tom Woods
 

Day 3 – March 1, 2012

Session Chair: Tom Woods
7:45 – 8:15 a.m. Continental Breakfast
8:15 – 8:35 a.m. PREMOS Instrument status and results – Gail Cessateur (PMOD/WRC)
8:35 – 9:15 a.m. Discussion - using "SSI Workshop Discussion Options" slides – Led by Tom Woods
9:15 – 10:15 a.m. Comparison of SSI observations in relevant bands – new plots - Marty Snow
10:15 – 10:30 a.m. BREAK
10:30 – 12:00 p.m Discussion –SSI VIS-NIR variability Research Topics/degradation/ Summary/Comments/Additional assessments/Action Items/SSI Workshop #2/