MODIS Preprocessing (before L1B) Changes over the Last Year (and looking forward)

MODIS Preprocessing (before L1B) Changes over the Last Year

(and looking forward)

Chris Moeller and others

CIMSS; Univ. Wisconsin

July 13, 2004

Thanks to MCST for their help

MODIS L1B Issues/Changes• Terra RSB Calibration using SD screen

down (since June 2003).

• DSM RVS implemented for Terra (since 04059) in Collect 5.

• Detector/Mirror side TEB destriping. Applied in MOD06, MOD35. No plan for applying to L1B at this time.

• Terra MODIS RSB calibration based on trend instead of discrete in Collect 5.

MODIS L1B Issues/Changes• Detector failures in PVLWIR (B28 Det 1,

10). May need to stop using B28 for 5um leak surrogate.

• RSB m1 values changing after Day 04158 (mswg040616.ppt).

• Change to Terra 5um leak correction (offset forced to zero) for SWIR bands 5,6,7,26. Small impact flows down into B26 correction, causing B26 to be slightly more negative (0-1.4%) after correction for OOB and striping. May be “fixed” by adjusting correction coefficients.

May 6, 2003: the Terra MODIS Solar Diffuser (SD) door telemetry showed an anomaly, indicating the door was not operating. This was found not to be true; however it caused concern about the future operability of the SD door and associated 8% transmission screen.

July 2, 2003: decided to operate Terra MODIS with the SD dooropen and transmission screen in place for remainder of the mission.

Courtesy of MCST

The effects are:The SD plate is exposed to sun light on every orbit, hastening degradation of the Spectralon coating. Degradation will be greatest in the blue spectral region; it will be small in longer wavelengths. The degradation will be monitored by SDSM.

The RSB calibration is limited to the low signal end by the screen being in place. This accommodates ocean color band calibration at the expense of high signal calibration. Low signal calibration is being used to track calibration change for those bands that previously used high signal calibration.

Courtesy of MCST

Terra MODISDay 041530025 UTC

Band 51km aggregated

Striping appears to be a function of signal.Suggests a calibration slope error.

Striping in this image is ~10% of scene signal

Courtesy of MCST

RSB calibration (m1) in Terra Collect 5 will be based on trends in SD calibration, not discrete

MODIS Scan Mirror Reflectance Measurement

Scan mirror reflectance depends on angle of incidence (AOI) on the mirror

Response Vs. Scan (RVS) of Terra MODIS

Terra MODISDay 030941740 UTCBand 35Old RVS

Terra MODISDay 030941740 UTCBand 35

DSM RVS

Terra MODISDay 030941740 UTCBand 36Old RVS

Terra MODISDay 030941740 UTCBand 36

DSM RVS

Mirror side “1”

Mirror side “1”

Mirror side “2”

Mirror side “2”

Mirror side “1”

Mirror side “1”

Mirror side “2”

Mirror side “2”

Cross Track Frame Number

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Mirror side “2”


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DSM RVS impact on PVLWIR bands is typically small except for B29. A scene temperature dependence is also apparent.

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DSM RVS impact on PCLWIR bands is large in atmospheric bands, and small in window bands.

Mirror side “2”

Old RVS

Terra MODIS Clear Sky Radiance Bias (MODIS – model prediction)Band 25 (4.54 um)

DSM RVS


Old RVS


DSM RVS


Old RVS


DSM RVS


Old RVS


The biases have a distinct dependence on scan angle

DSM RVS

Using DSM RVS largely removes the bias dependence on scan angle


MODIS TEB destriping impact

• Destripe all MODIS thermal bands using Empirical Distribution Function (EDF). Destriping is done on a granule by granule basis (no knowledge from one granule to next).

• Look at change in radiances, including at granule interfaces.

B 22

B 27

B 29

B 34

B 36

Before Destriping

After Destriping

Before Destriping

After Destriping

Figure 1

Red: Median restore on

Blue: Median restore off

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MODIS Scan Line Counter

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destriping application to RSB

Along track profile taken at yellow line

Terra MODISJune 20, 2002

Day 021711425 UTC

Band 7

GDAAC Aggregated

1km L1B

Along track profile taken at yellow line

Terra MODISJune 20, 2002

Day 021711425 UTC

Band 7

Destriped Aggregated

1km L1B

Terra Band 28 New Noisy Detectors

Page 64

MCST/MsWG

• Terra (PFM) Band 28 product order Ch 1 became noisy on granule 2004175.0205 (night time over SAA, orbit#: 24009)

• Will affect SWIR OOB correction

• Scan-to-scan b1 (MS-1)

• Scan-to-scan NEdT (MS-1)

X Ch 1

Courtesy of MCST

Band 28 Status – (*) noisy Ch3, Ch8;(**) b1 unstable and very noisy: Ch1, Ch10

Page 65

MCST/MsWG

Ch10 unstable on day 118, alreadyset to noisy in L1B QA flag Courtesy of MCST

Page 66

Day 2004 158(No Terra S/C,

MODIS Activity)

Courtesy of MCST

Page 67Courtesy of MCST

SURVEY

• What are the remaining L1B issues seen in Atmosphere Group products?

• Can these issues get relief in Terra MODIS Collect 5 L1B?

Terra MODIS L2 issues that flow down from L1B

• Detector and mirror side striping?

• RVS (scan angle dependence) effects?

• Noisy detector influence?

Documents

MODIS Preprocessing (before L1B) Changes over the Last Year (and looking forward)