WAC1 Problems, Advantages of Swapping out with WAC2

1. WAC1 Problems, Advantages of Swapping out with WAC2 June 4, 2008

2. Visible Flat Field - WAC1 415 nm 560 nm 600 nm 650 nm 690 nm Median merge of flat mosaic acquired on August 16 with Xenon source and integrating sphere, areas of saturation are zeroed out (top to bottom 415, 560, 600, 650, 690 nm). Mirrored left to right to match images after processing. Out-of-band leak in in 560 nm filter - degrades spectral and spatial resolution Tears in 640 and 680 nm filters degrade spatial resolution

3. WAC Performance Concerns • Some areas of concern were noted during WAC Calibration efforts: • Dark current stability, pattern noise and time variable offset thought to be due to thermal effects - will verify in thermal vac • Filter response vs. position • Blemishes (560 nm, 640 nm, UV) • Out of band leak 560 nm • Scattered light glint • Affects first ~40 columns in all VIS bands • Most likely due to glint off light shield • Mitigate by zeroing affected columns, effectively reduces FOV by 4%, 8% for polar movies • Does not affect color data Confidential and Proprietary - MSSS 3 3

4. Artifacts in Filter Assembly • Tear in filter during removal of mask • Worst tear cases in 650 and 690 filters • Also uneven deposition of some layer(s) in 560 nm (swirls) • 415 and 600 nm filters relatively clean • UV filters • Manufacture defects • Integration contamination • Flats acquired with Xenon lamp (flat in VIS) 415 nm 560 nm 600 nm 650 nm 690 nm Blowup of Central Portion of VIS Region

5. Mask Removal Tears During interlayer mask removal some regions of existing layers were torn off or damaged. The most serious tear is found in the middle of the 650 nm filter (A). Note that damage was extensive enough in areas A through D such that saturation occurs in much of the damaged area during nominal exposures. Regions that were saturated in the mosaic data were set to zero in the composite flat field. Note: the left side of the array is contaminated with scattered light (extremes set to zero). We do not understand the source.

6. Out-of-Band 560 nm • Red data for nominal portion of filter • Blue data centered on blemish (swirl) • Note leak in the 585 to 680 region

7. 560 nm Row Profiles • Blue, line 44 through the swirls • Red, line 33 through clean region • Note that leak is 2x nominal in extreme cases

8. 560 nm Row Ratios • Red line is ratio of line one over line 12 • Blue line is ratio of line one over line 13 • Will need to mask rows 12 and 13 and probably portions of 11 and 10 • Plus and minus 2% represents normal flat variation - most trouble in columns 160 to 380 (0 to 200 in color mode) Note: only showing color columns

9. 560 nm, Good Rows Ratio • Median 1.03 • Stdev 0.013

10. Color Chart and Slabs Above: Lab setup photo

11. RGB Composite 650, 560, 415 • Note that image has been mirrored left to right, thus worse 560 swirls now on right side of image • Since 560 nm swirls are due to 585 to 680 nm leaks redder squares should have greater artifacts. Pure green materials should have no artifacts. • Artifacts in box “A” are 30% lower than nominal area in box • Red = 650 nm, Green = 560 nm, Blue=415 nm • Arrow indicates leak in 650 associated with central tear A White speckles in ratio in lower left box (white square) represent saturated data

12. VIS Flat Remediation Strategy Median merge of flat mosaic acquired on August 16, areas of saturation are zeroed out (top to bottom 415, 560, 600, 650, 690 nm). From above with thresholding, editing, and best zones indicated with horizontal lines. http://lroc.sese.asu.edu/WORK/CALB/WAC1/FLAT/index.html

13. 560 nm, 14 lines, no overlap Vertical lines represent color region Repeat mosaic of flat to show remaining artifacts

14. 560 nm, 14 lines, 1 overlap 560 nm band may be a complete loss? The remaining bright swirls are out of band leaks

15. UV Filters Summed 4x Stretched and annotated UV flat field (073007). Note the edge band at the bottom of the 315 nm filter. Sizes of the marked blemishes are listed below.The center of these blemishes are typically at 25% of the background. The curved strand of foreign material in the middle of the 360 nm band was introduced during integration of the filter assembly to the CCD. Nature of the circular blemishes (yellow arrow shows example) is not understood, do not know if such will flat filed out or not. Blemish sizes in pixels: A x=5 y=5, B x=7 y=8, C x=5 y=5, D x=7 y=8, E x=6 y=7, F x=5 y=7, G x=5 y=4

16. Glint - Contamination 40 Columns Frame 2OFS7.DDD showing artifact when fat point was outside field at (az=342, el=43.3). Exposure time was ~600x that of normal exposure. Note: as fat point source moved vertically glint also moves. Enlargement of frames 2OFS53 and 2OFS24 showing sharp edge of glint. Both images were stretched 75 and 400 to 0 to 255. In normally exposed images ~40 columns in all VIS bands are seriously degraded.

17. Artifact RemediationStrategies • Zero out 40 columns of glint (BW mode) • 14 line readout to minimize contaminated zones • Zero out remaining bad zones • Process to 100 m/pixel maintaining bad zones as nulls (appear as black holes in data) • 560 nm band may be a complete loss? • Strategy 1: Create lower resolution continuous products for global color assesment (still use full resolution in conjunction) • Rxample: If largest bad area is 4 lines “tall” resample at 6 line resolution - need good data above and below to interpolate. 100 meter data resampled to 500 meter map product • Strategy 2: merge data taken at different times • Photometric challenges • Sub-pixel registration challenges • Produc delivery schedule degradation

18. Law of Unintended Consequences • Strategy to readout 14 lines mitigates much of the bad areas • Requires speed up electronics • Results in degradation of 415 nm band through increased noise • Might be fixable through firmware upgrade

19. ALL VIS BANDS MEDIAN - LINE 2 STD AT EACH PIXEL – LINE 2 Line 0 and 2 have anomalously high dns, ~10% of dynamic range with worst pixels 40% of dynamic range (8-bit companded data) 19

20. Line 0, 415 nm Max value is ~600 DN out of 1800, average scene at 900 DN (de-companded 11-bit data) 20

21. Line 1, 415 nm Unusually low, something is wrong 21

22. Line 2, 415 nm Similar to line 0 22

23. Line 3, 415 nm Background back to normal, note column noise 23

24. Line 4, 415 nm Background back to normal, note column noise 24

25. Consequences Either accept saturation in lines 0 and 2 and have acceptable SNR across array, result in loss of 3 lines of data out of 14 in 415 filter, effectively degrade resolution to something like 400 m/pixel Or, cut down integration by 2x and keep all 14 rows, however lower SNR by 2x across all bands and line 1 is probably unusable Either option significantly degrades color data Increased noise in 415 nm does not effect BW mode Global basemap Polar multi-temporal imaging Possible firmware fix? Being worked by MSSS EEPROM patch after integration to LRO 25

26. Science DegradationOverview • Degradation of 560 nm (out-of-band leak) and 415 nm (increased noise) degrades characterization of broad opaque minimum • Tears in 650 and 690 result in localized loss of data and/or overall degradation of mosaic resolution • Glint off light shield results in narrowing of BW FOV by 4% thus degrading polar temporal observations coverage (by 8%)

27. Global Multispectral Mapping • WAC UV / Visible • 315, 360, 415, 560, 600, 640, 680 nm bandpasses • Acquire global dataset at 100 m/pixel VIS, 400 m/pixel UV • Map TiO2 soils (hold H, He) • Pyroclastic glasses (volatiles) • Olivine (magmatic processes) • Meshes with Clementine • 100-200 m/pixel • 415, 750, 900, 950, 1000 nm bandpasses • 415 and 560 nm bands critical to assessing UV slope and opaque minima Ilmenite Basalt LROC WAC bandpasses and key lunar mineral spectra (12063R Rock, 12070S Soil)

28. Tie to Apollo Sample Sites • Spectral interpretations depend on tie to soil chemistry from Apollo stations • Loss of resolution and local “holes” in data degrade parameter calibration Clementine (A) and HST (B) images of AP17 showing sample stations at 100 m/pixel, WAC will obtain 75 m/pixel

29. New WAC Filter Assemblies • Inspected by Mark Robinson (ASU) and Joe Calabrese (GSFC) May 22, 2008 • Eight VIS+UV filter assemblies • Assemblies one and two show significant improvement over that installed in WAC1, though assemblies have numerous blemishes • Best four assemblies delivered to MSSS on May 24 • MSSS inspection completed • Assemblies 1 and 2 successfully attached to CCDs on June 3

30. WAC2 - Assembly #1 Visible band portion of Barr WAC Filter Assembly 1 (WAC2_001), the shortest wavelength is at the bottom while the longest is at the top. The black vertical wedge on the left is a gore in the mosaic, the gray shaded areas on the left and right indicate approximate regions outside the color readout zone. The gray shaded areas on the left and right indicate approximate regions outside the color readout zone. The 600, 640, and 680 nm filters are the best candidates for BW full frame imaging.

31. UV2 - Assembly #1 WAC Filter Assembly 1 UV2 (top, nearest VIS filters). The black box shows the size of the 512 x 16 area that will be read out, not necessarily from that particular location. We will want to readout as near to the bottom of this filter as possible.

32. UV1 - Assembly #1 WAC Filter Assembly 1 UV1 (bottom). The black box shows the size of the 512 x 16 area that will be read out, not necessarily from that particular location. We will want to readout as near to the top of this filter as possible.