NCC Status December 04, 2012 Calvin Liang Stephanie Weiss NGAS A&DP

2 Path Forward to Investigate NCC EDR Issues Proposed steps to investigate NCC issue: 1. Collect SVDNB, GDNBO, and IVOBC granules from August th, 2012 – Around new moon 2. Construct stray light correction lookup table (LUT) from new moon data 3. Apply stray light correction LUT to new moon granules using NGAS stray light correction algorithm 4. Determine best functional fit to corrected radiances and account for night glow. (In work right now) 5. Produce a new GVVSSE/GVVSLE LUT based on the new functional fits. 6. Remove stray light in problematic granules 7. Run the latest version of the NCC EDR algorithm in ADL on stray light corrected granules (results are shown using ADL 3.1) 8. Inspect output to determine whether some of the problems identified in the granules go away with stray light correction 9. If it is found that fixing stray light does not completely solve the problems, then we will delve into the NCC EDR algorithm logic (Wrote offline NCC code for testing) Completed In Work Planned

3 Radiance vs Solar Zenith After Stray Light Correction Noise floor 7e-11 Current SZA cutoff = 105 Straylight removed Some overcorrection but very little C. Liang, NGAS New Lunar table to account for night glow

4 Issues with NCC Algorithm: Currently the solar and lunar tables are identical. If there were no night glow, this would not be an issue. –Dynamic range between the solar radiances (~10 -2 ) and night glow (~10 -9 to ~ ) span 7-9 orders of magnitude vs. the dynamic range between the lunar radiances (10 -7 ) is only about 2-4 orders of magnitude. This causes many of the NCC albedos to fall out of range because assuming the lunar and solar tables to be identical creates too large a gain difference between maximum lunar radiances and the night glow. –Possible solutions: Either we need to subtract out night glow in the GVVSSE and GVVSLE LUT and add a night glow term into the NCC algorithm Rescale the lunar table such that the night glow starts at an earlier lunar angle such that when the night glow portion of the curve is rescaled by the lunar irradiance, the night glow is at the proper level (method used for the subsequent results). Given the NCC albedo range of [0,5] auroras get cut out (too bright) Algorithm truncates negative radiances (darkest of scenes)

5 VNCCO-npp-d t e b03229-c ng-sw.png Aurora overwhelms albedo because aurora radiances are ~10 -7, roughly what you expect from a bright full moon image with lunar zenith angles near 0.

6 VNCCO-npp-d t e b03229-c ng-sw.png If aurora is in the scene where both the solar and lunar zenith angles are around 105, the albedos on the lunar side will overwhelm the solar side. Lunar Solar Lunar Solar

7 VNCCO-npp-d t e b03229-c ng-sw.png NCC works well when solar conditions dominate. Data that spans ~4-6 orders of magnitude now only span 1.

8 Aurora Imagery (NCC)

9 Aurora Imagery (SDR)

10 Summary For lunar conditions, the albedo range limit of [0,5] cuts out –Negative radiances which leads to removal of real features that are observable in the DNB SDRs –Auroras because they are too bright Conditions for which the sun’s illumination dominates, the NCC product produces good results. Results in the terminator are satisfactory Question: How do the end users want to use the NCC product? –The DNB SDR radiances, though they are not projected onto their respective geolocation, produce very nice imagery for day and night conditions. Auroras are particularly nice using the SDR imagery (can easily be geolocated) –NCC really serves to reduce the dynamic range of atmospheric/ground features in the terminator where the SDR imagery span ~4-6 orders of magnitude. –Aurora conditions will be problematic for NCC.