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
Day 1 – Feb. 28, 2012 – Introduction to Instruments used in SSI Comparison
7:30 – 8:15 a.m.
8:15 – 9:15 a.m.
Welcome / Continental Breakfast
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.
10:35 – 10:50 a.m.
10:50 – 12:25 p.m.
12:30 – 1:30 p.m.
1:30 – 2:55 p.m.
2:55 – 3:45 p.m.
3:45 – 4:00 p.m.
4:00 – 5:30 p.m.
SOLSTICE I (UARS) and II (SORCE) – Marty Snow, Tom Woods, Bill McClintock (LASP)
Break
UARS / ATLAS SUSIM – Linton Floyd (NRL)
Lunch (NIST Cafeteria Buffet)
SBUV / SSBUV – Matt DeLand (SSAI, GSFC)
ATLAS / ISSI SOLSPEC – Gerard Thuillier (LATMOS-CNRS)
Break
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.
8:20 – 8:35 a.m.
8:35 – 9:10 a.m.
9:10 – 9:45 a.m.
Continental Breakfast / Welcome
Capabilities of NIST / SURF calibrations for SSI UV instruments – Uwe Arp (NIST)
NIST / SURF capabilities in the VUV degradation (C deposition) – Shannon Hill (NIST)
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.
3:40 – 4:05 p.m.
4:05 – 4:30 p.m.
4:05 – 4:30 p.m.
5:00 – 5:30 p.m.
Comparison of SSI UV observations in relevant bands (120-400 nm) - Marty Snow
Comparison of SSI UV observations in relevant bands (120-400 nm) - Matt Deland
Comparison between SUSIM and SIM – Jeff Morrill
Decoupling degradation and solar cycle variability – Tom Woods
“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.
8:15 –8:35 a.m.
8:35 – 9:15 a.m.
9:15 – 10:15 a.m.
10:15 – 10:30 a.m.
10:30 – 12:00 p.m.
Continental Breakfast
PREMOS Instrument status and results – Gail Cessateur (PMOD/WRC)
Discussion – Led by Tom Woods using “SSI Workshop Discussion Options” slides
Comparison of SSI observations in relevant bands – new plots - Marty Snow
Break
Discussion –SSI VIS-NIR variability Research Topics/degradation/
Summary/Comments/Additional assessments/Action Items/SSI Workshop #2/