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Ocean Color Science Team Meeting

Ocean Color Science Team Meeting. August 1, 2011 MOBY 2008 Stray Light SIRCUS Characterizations C. Johnson, NIST; M. Ondrusek, NOAA. MOBY Stray Light Correction. Traveling SIRCUS deployed to Snug Harbor multiple times in 2001 and 2002; resulting data set is very limited in wavelength coverage

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Ocean Color Science Team Meeting

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  1. Ocean Color Science Team Meeting August 1, 2011 MOBY 2008 Stray Light SIRCUS Characterizations C. Johnson, NIST; M. Ondrusek, NOAA

  2. MOBY Stray Light Correction • Traveling SIRCUS deployed to Snug Harbor multiple times in 2001 and 2002; resulting data set is very limited in wavelength coverage • Fits and approximations to the laser data set were used to generate modeled data suitable for the stray light correction algorithm • It became clear the stray light performance was changing in time • Solution was to bring MOBY to NIST for full characterization (June and Nov 2008)

  3. Tasks • Analyze 2008 laser characterization data sets taken at NIST for LuTOP, even and odd buoy • Extend analysis to other fibered inputs; Analyze LuMOS data sets • Investigate other algorithms to validate approach • Evaluate impact of new stray light characterization on 2008 deployments • Validate results using 2008 Es data (B241 - B244) and by including “blue” calibration sources in current calibration cycles (B247, B248) • Document and publish results, include estimation of uncertainties

  4. Odd Buoy Data Set - Example • Odd buoy at NIST June 2008 (MOBY241/243) • 386 laser data sets collected over 10 days • Colored source validation data also collected

  5. Processing SIRCUS Data Sets • Quality checking is applied (spikes and suspect scans are removed, if possible) • Data are adjusted by darks, integration time, and bin factor to get ADU/pix/sec • Problem data are fixed (oscillations, noise in scans, out-of-band noise/level) • Single spectrum analysis algorithm is used to smooth the data • Each laser scan is normalized using the in-band area and interpolated to fill in the missing laser data (started with 58, need 512, one for each CCD column)

  6. Matrix-based Algorithm A is the SLC matrix, B is the in-water data for Lu in ADU/Pix/Sec, here shown for the blue spectrograph Pixel 1 (B) is multiplied by row 1 (A), the pixel 2 (B) x row 2 (A), ... to 512 Matrix C is the result. Summing the rows in C produces the SLC results in D (red & green); blue is uncorrected This procedure must be done for both the laboratory calibration data and the in-water deployment data E shows the matrix C with the in-band removed and normalized to the total out-of-band

  7. LuMOS Data No optical fibers, which causes square reflection peaks Data sets have been processed and smoothed Interpolation algorithm has been developed and processing is in progress

  8. Extension to all Fibered Inputs • The laser data set is “fine” for LuTOP (and LuMOS) and “coarse” for the remaining fibered inputs • Analysis shows the stray light correction for the “coarse” fibered inputs can be implemented using the LuTOP matrix • Slight variations are observed around the reflection peaks

  9. Status – August 2011 • Stray Light Correction Matrices • LuMOS remains to be completed • Impact on 2008 deployments • Complete; remaining issue with first 10 pixels of MOS205 (odd buoy); “overshoot” • Validation Activities • alternate algorithm studies are complete • consistency of Es and “overlap” for B239 to B242 (2008 deployments) was assessed • NIST blue LED source being revised • Uncertainty estimations, documentation, publication • detailed documentation of processing is up to date • preliminary investigations of uncertainty budget underway

  10. Better Agreement in Overlap

  11. Ratio New/Old SLC

  12. Even and Odd Buoy Now Consistent in CIE Space for Es Old (existing) SLC New (2008 SIRCUS) SLC

  13. Summary Milestones • Year 1 – Develop a new MOBY stray-light correction matrix based on 2008 SIRCUS characterizations. • Year 2 – Validate the new MOBY stray light correction matrix using colored sources and other methods, estimate and assign uncertainties in the stray light correction for 2008 MOBY deployments, and publish these results

  14. Team • NIST • Steve Brown & Keith Lykke, SIRCUS • Al Parr (consultant) algorithm and uncertainties • Eric Shirley & David Harris, algorithm and interpolation • Bob Saunders & Zhigang Li, measurement support • Carol Johnson, lead • MLML • Mike Feinholz, Mark Yarbrough, Stephanie Flora, MOBY instrument, data analysis, documentation • NOAA • Mike Ondrusek, funding and oversight

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