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Suomi NPP VIIRS On-Orbit

Geometric Performance Validation

NASA VIIRS Calibration Support Team (VCST)

Geometric Calibration Group

Robert E. Wolfe, NASA/GSFC Code 619

Mash Nishihama, Sigma Space/GSFC

Guoqing (Gary) Lin, Innovim/GSFC

Krishna P. Tewari, Innovim/GSFC

James C. Tilton, NASA/GSFC Code 606

and

Northrop Grumman Aerospace Systems (NGAS)Lushalan Liao, Stephanie Weiss

Suomi NPP VIIRS SDR Product Review (Validated Maturity) 19 December 2013

Outline

• Major accomplishments since Provisional

• Geolocation Validation for I-/M-Bands and DNB

• Band-to-band co-registration

• Spatial responses

• Discrepancy Reports (DRs), quality flags, challenges and

potential improvements

• Conclusions

• Backup

o DR list, Trending of orbit parameters, RTA/HAM encoder

performance, Land PEATE reprocessing, DNB geospatial

performance (by NGAS)

Wolfe et. al., 19 Dec 2013 VCST/GEO 2

Major Accomplishments since Provisional

• Fine tuned I-/M-bands SDR/GEO LUTs and DNB geo LUT (by NG)

• Updated LUTs in responses to • Scan control electronics (SCE) side A (switched from side B in November 2012)

• Star tracker re-alignment in April 2013

• Worked DNB TC geolocation to be implemented in IDPS expected March

2014 (already in NASA Land PEATE since May 2013)

• Reduced geolocation bias from (up to) 20 km to (up to) 1.5 km when SC

diaries were delayed to and TLE used in IDPS

• Added quality flags for sync loss and sector rotation

• Verified (further) on-orbit BBR and LSF

• Trended (2 years) SC ephemeris (mean altitude 838.8 ±0.2 km)

• Published papers and made conference presentations

• 2 peer reviewed papers (TGRS + JGR)

• 1 SPIE talk/paper and 1 AGU presentation


Geolocation Requirements


D45143 NPOESS System Pointing Error

Budgets (Document Date: 04/13/2009)

Figure 3.1 VIIRS Pointing Knowledge

Budget for NPOESS 1330 Satellite

3.1 VIIRS POINTING KNOWLEDGE

UNCERTAINTY

The geolocation mapping uncertainty for VIIRS

EDRs is specified as 400 meters (3 sigma) at the

satellite Nadir and 1500 meters (3 sigma) at the

VIIRS Edge-of-Scan (EOS) which is 56.0

degrees from Nadir.

Figure 3.1 shows the VIIRS pointing knowledge

budget which rolls up requirements and

capabilities for the NPOESS 1330 spacecraft

and the VIIRS sensor..

On-orbit Geolocation LUT Updates

Wolfe et. al., 19 Dec 2013

Update Date Description Comments

1/19/2011 Cryo-radiator door openAll VIIRS band available,

LPEATE re-process start date

1 2/23/2012 Initial mounting coef. update Removed bias ~ 1.3 km

2 3/30/2012 Initial DNB FPA center update Removed bias ~ 1 km

11/22/2012Scan control electronics (SCE) was switched

from B-side to A-SideCaused bias ~ 300 m

3 12/11/2012Correction after SCE was switched from B-

Side to A-sideRemoved bias ~ 300 m

4 2/15/2013 Second, fine DNB FPA center update Removed DNB bias ~ 300 m

5 4/18/2013 Second, scan angle dependent, fine Geo LUT

update

Fine tuned and removed scan

dependent biases

4/25/2013 Star tracker maintenance/re-alignment Caused bias ~ 25 m

6 8/22/2013 Correction to the star tracker re-alignment Removed bias ~ 25 m

VCST/GEO 5

DNB onlyAll bands impactedKey: External event

DNB Geolocation

As of Nov 4, 2013, the DNB geolocation accuracy is

Scan: 8 ± 33 μrad Track: -35 ± 68 μradScan: 7 ± 28 m Track: -29 ± 57 m

(nadir equivalent with mean altitude of 838.8 km)

±

by NGAS4

2/15/20132

3/30/2012

4/25/20135

4/18/20136

8/22/2013


89

89

VCST/GEO 6

Star tracker

induced shift

Star tracker

shift corrected

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0

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150

200

12.0 12.2 12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0

Tra

ck r

esid

ua

ls (

m)

Years since Jan. 1, 2000

VIIRS (I1 Band) Residual Trend


11/22/20121

2/23/2012

5

4/18/2013

4/25/20136

8/22/20133

12/11/2012

4

2/15/2013

2

3/30/2012

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Sca

n r

esid

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R² = 0.2462

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res

VIIRS (I1 Band) Scan Angle Residuals


Starting 8/22/2012

R² = 0.016

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VCST/GEO 8

Overall Uncertainty

Residuals Error

(Nadir)

Spec

(Nadir)

Error

(EOS)

Spec

(EOS)

Track mean -9 m -20 m

Scan mean -7 m -46 m

Track RMSE 73 m 133 m 161 m 500 m

Scan RMSE 61 m 133 m 398 m 500 m

• RMSE: Root Mean Square Error (equivalent to unbiased 1 s)

• Data-days: 632, excluding 18 days right after A/B side switch

• Mean errors are small

• Nadir uncertainties of ~70 m (1 s) meet spec of 133 m (1 s) [400 m (3 s)]

• Edge-of-scan (EOS) uncertainties of ~ 400m (1 s) meet spec of 500 m (1 s)

[1500 m (3 s)]


On-Orbit LSF – Bridge

Gaussian functions are

used to model pre-

aggregated scan LSFs

(Line Spread Functions)

Up to 14 scenes for each

band each aggregation

zone having robust

statistics

Bands (3,2,1) = (R,G,B)

21 November 2012

I-Bands (3,2,1) = (R,G,B)

18 November 2012VIIRS pixels (cyan) around the

Landsat bridge (red - linear fit)Stripes are due to Landat 7 scan

line corrector failure. But the

center portion is fine.

Images are co-geolocated

& histogram equalized

Landsat 7 VIIRS

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tial

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pons

e (n

.d.)

Position (post_agg HSI)

On-orbit Measured

Double Gaussian Fit

Pre-launch Test

I3, Agg2x1 M10, Agg2x1


On-orbit scan GDFOV (with robust statistics)


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On-Orbit

Ground Test

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DF

OV

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I R

ati

o


On-Orbit

Ground Test

M1 M2 M16M14 M15M13M11 M12M3 M4 M5 M6 M7 M8 M9 M10

VCST/GEO 11

GDFOV:

Ground

Distance

Field of View

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dirS

can

Off

set (

I-H

SI

wrt

I3)


On-Orbit

Ground Test

Scan Band Offsets from LSF Retrievals

12

I1 I2 I3 I4 I5


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dir

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n O

ffse

t (M

-H

SI w

rt M

10

)


On-Orbit

Ground Test

M1 M2 M16M14 M15M13M11 M12M3 M4 M5 M6 M7 M8 M9 M10

VCST/GEO 12

-0.2

-0.1

0

0.1

0.2

M1

M2

M4

M3 I1 I2

M7

M5

M6

M1

3

M1

2 I4 I3

M1

0

M1

1

M8

M9 I5

M1

6A

B

M1

5

M1

4Tra

ck B

BR

(M-S

amp

_In

tvl)

Band Name

-0.2

-0.1

0

0.1

0.2

Scan

BB

R (M

-Sam

p_

Intv

l) Prelaunch Mean, Min, Max

VIIRS Band to Band Registration (BBR)

S/MWIR LWIRVisNIR

M1

Tra

ck

(M

-sa

mp

intv

l)S

ca

n (

M-s

am

pin

tvl)

Band average BBR (wrt. Band I1) compares well to prelaunch performance

(Some M/LWIR bands are saturated by moon)


Agg1x1 (non-aggregated)

DRs and Quality Flags

• DR 4924 adds DNB Terrain Corrected (TC) Geolocation is being

worked: CCR-13-1362 discussed at AERB and planned for Mx8.3

(March 2014)

• DR 4767 added flags and fills in both SDR and GEO when

RTA/HAM synchronization loss occurs (35 events so far, 100

seconds or less each). New situation was found and DR 7484 will

flag additional scans.

• DR 7023 reduced geolocation bias from (up to) 20 km to (up to) 1.5

km when S/C diary from Svalbard does not arrive at IDPS in time

and the backup two line elements (TLE) is used. Scan quality flag

was checked and found ~0.2% of products used TLE data. DRs

7145, 7146 and 7147 were filed for changes in IDPS production

rules or Svalbard SC diary data delivery rules.


Challenges and Potential Improvements

• Challenging to accurately measure on-orbit BBR for all band pairs,

especially for those LWIR bands saturated by the moon

• Challenging to accurately measure spatial response characterization

for all bands, especially LWIR bands – expect no significant change

from pre-launch and no significant impacts on EDRs

• Within orbit thermal correction is likely to be needed – code updated

needed

• Long-term monitoring is needed for accurate geolocation and for

responses to possible on-orbit events – we are trending and fine

tuning as needed

• Digital Elevation Model (DEM) and Land/Water (L/W) mask should

be updated (such as those in MODIS Collection 6)

• Geolocation accuracy issues during and right after spacecraft

maneuvers needs to be better understood and clearly identified


Conclusions

• VIIRS geometric performance is as expected

• Geolocation mean errors for I-/M-bands are near 0 and

uncertainties are ~ 70 m at nadir, meeting specifications at

nadir and edge-of-scan

– Caveat: DNB terrain corrected geolocation product is expected in Mx8.3

in March 2014

• Encoder and scan time/period are nominal

• Orbit and attitude are nominal

• Quality flags are well-understood

• Limited verification of on-orbit spatial responses and BBR

agrees with prelaunch measurements

• VIIRS SDR/Geometric performance maturity should be rated

as Validated (except for DNB TC geolocation)


Publications1. Wolfe, R. E., G. Lin,M. Nishihama, K. P. Tewari, J. C. Tilton, and A. R. Isaacman (2013),

Suomi NPP VIIRS prelaunch and on-orbit geometric calibration and

characterization, J. Geophys. Res. Atmos., 118, 11508–11521, doi:10.1002/jgrd.50873.

2. Cao, C., F.DeLuccia, X. Xiong, R.Wolfe, and F.Weng (2013), Early on-orbit performance

of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National

Polar-orbiting Partnership (S-NPP) satellite, IEEE Trans. Geosci. Remote Sens.,

doi:10.1109/TGRS.2013.2247768.

3. Guoqing Lin, James C. Tilton, Robert E. Wolfe, Krishna P. Tewari, Masahiro Nishihama

(2013), SNPP VIIRS spectral bands co-registration and spatial response

characterization, Earth Observing Systems XVIII, edited by James J. Butler, Xiaoxiong

Xiong, Xingfa Gu, Proc. of SPIE Vol. 8866, 88661G,· doi: 10.1117/12.2023367.

4. Wolfe, R.E., G. Lin, M.Nishihama, K.P. Tewari, E. Montano (2012), “NPP VIIRS Early On-

Orbit Geometric Performance”, Earth Observing Systems XVII, edited by J. J. Butler, X.

Xiong, X. Gu, Proc. of SPIE Vol. 8510, 851013, doi: 10.1117/12.929925.

5. Wolfe, R. E., M. Nishihama, G. Lin, K. P. Tewari, and E. Montano (2012), MODIS and

VIIRS geometric performance comparison, IEEE International Geosci. and Remote

Sens. Symposium, Munich, Germany, July, 2012. doi:10.1109/IGARSS.2012.6352484.

6. Lin, G., R. E. Wolfe, M. Nishihama (2011), "NPP VIIRS Geometric Performance Status,”

Earth Observing Systems XVI, edited by James J. Butler, Xiaoxiong Xiong, Xingfa Gu,

Proc. of SPIE, Vol. 8153, pp. 81531V-81531V-14, doi:10.1117/12.894652.


Backup Slides


• DR list

• Trending of orbit parameters

• RTA/HAM encoder performance

• Land PEATE reprocessing

• DNB geospatial performance (by NGAS)

Major Geometric related DRs & Status


DR # Status Description

4423 Fixed RTA/HAM timestamps reversal

4428 Resolved Rotation Matrix in LUT Used by SDSM Code

4629 Completed Initial on-orbit update of the VIIRS DNB GEO LUT

4703 Completed (Mx6.2) Add mirror side to VIIRS geolocation products

4737 LUTs ready for SCE switch Scan Encoder Electronics (SCE) A-side missing in geolocation parameter LUTs

4759 Being verified (Mx6.3/4) Determine Scan Encoder Electronics Side in Geolocation products

4767 Completed (Mx7.0) SDR/GEO should be fill and flagged when HAM/RTA sync is lost

4776 Completed (Mx7.0) Sector Rotation caused erroneous geo results

4795 Completed (Mx7.0) VIIRS SDR Cal: Add major HAM/RTA sync loss flag to VIIRS SDR Cal

4894In-Progess (for Mx7.1)

confirmation neededUnexpected high values of Satellite zenith angles

4917 IDPS alerted (June 2013) – closed IDPS Incorrect Handling of Leap Seconds

4924 In-Progess (for Mx8.3) VIIRS DNB Geolocation Terrain Correction is needed

7145 In-Progess VIIRS SDR Controller should wait for the Spacecraft Diary

7146 In-ProgessReplacement VIIRS SDR Granules should be manufactured if the Spacecraft Diary

become available post-production

7147 In-Progess Maintain an IDPS Production History

7203 Completed (Mx7.0) Degraded VIIRS (and possibly other instruments) geolocation from backup TLE

7443 In-Progess VIIRS GEO FILL diferences noted in Maneuver granules

7484 In-ProgessObserved toggling in the VIIRS engineering packet sync loss indicator as the

instrument is recovering from sync loss

VCST/GEO 19

838.6

838.7

838.8

838.9

839

0 60 120 180 240 300 360 420 480 540 600 660 720

Mea

n A

ltit

ude

(km

)

Time (Days since Launch on Oct 28, 2011)

Trends of Orbit Parameters

• Altitude (km)

• Mean: 838.8 ±0.2 Peak-to-Valley

• Min: 828.5 ±0.6 P-V; Max: 856 ±0.6 P-V; Equator: 829.8 ±1.0 P-V

• Drag make-up (DMU) maneuvers keeps altitude from falling and 16-day ground track

repeatable (±20 km P-V)

• Local time of ascending node (LTAN) drifts from 13:25:24 in Nov 2011 westward 66

km to 3:23:02 in Nov 2012 then back eastward 104 km to 13:26:46 in 4 Dec 2013,

continues eastward

• Orbital period: 101.5 min ±0.3 sec P-V

• Inclination angle drifts 98.65 98.72 deg (0.07 degrees away from the poles) in 2

years, and continues to move away from the poles


-90

-72

-54

-36

-18

0

18

36

54

72

90

827

830

833

836

839

842

845

848

851

854

857

8:20:20 9:11:05 10:01:50

Lati

tud

e(d

eg)

Alt

itu

de

(km

)

Time (GMT, 19 November 2013)

Altitude

LatitudeDMUDMU

DMUDMUDMU

VCST/GEO 20

23:00

23:30

24:00

24:30

25:00

25:30

26:00

26:30

27:00

0 60 120 180 240 300 360 420 480 540 600 660 720 780

Asc

Node

(1:m

m:s

s P

M)

Time (Days since Launch on Oct 28, 2011)

SNPP Equatorial Crossing Time

142 sec

35.5 arcmin lon

66 km

Westward

?? sec

?? arcmin lon

?? Km

Eastward

350 days

?? days

Leap Second

1 July 2012

225 sec

56.3 arcmin lon

104 Km

Eastward

400 days

Equator-crossing local time


• SNPP Orbit ground track at equator drifted ~66 km westward in 350 days

• It then moves back eastward ~104 km as of 4 Dec 2013 (~ 40 km from launch date)

• SNPP continues moving eastward (sun zenith angle up). It will peak @ ?(future data)

VCST/GEO 21

Encoder characterization

Angle Residuals:

Deviation from linear trend for 1st Scan (Granule 05:45 on Nov. 8, 2011, doy 312)

Encoder residuals (non-linear motion)

-30

-20

-10

0

10

20

30

40

0 200 400 600 800 1000 1200 1400

Dev

iati

on f

rom

Lin

ear

Tren

d (A

rcse

c)

Encoder #

HAM

RTA

Combined (Approx.)

• The linear scan rate of telescope was 3.531 rad/sec on Nov 9, 2011.

• The offset variation is consistent with pre-launch tests (more in NG slides)

• Rotating Telescope Assembly (RTA) and Half Angle Mirror (HAM) encoder

datasets had been erroneously swapped in the at-launch IDPS code. The

error was corrected, as plotted here, and implemented in IDPS drop Mx5.1

on Dec 19, 2011.Wolfe et. al., 19 Dec 2013 VCST/GEO 22

Scan to scan start angle

• Variations around -56.34º (used in the geolocation algorithm)

• Magnitude ~ 16 arcsec, half of an I-band scan sampling interval

• Data from one 48-scan (85-sec.) granule on data-day June 27, 2012

I-S

am

pli

ng

In

terv

al

~ 8

00 m

at

Sta

rt o

f S

can

-16

-12

-8

-4

0

4

8

12

16

0 8 16 24 32 40 48

An

gle

Var

iati

on

@ S

OS

(arc

sec)

Scan #

An Example VIIRS Start Angle


-200

-150

-100

-50

0

50

100

150

200

12.0 12.2 12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0

Tra

ck r

esid

ua

ls (

m)


VIIRS Residual Trend


IDPS

-200

-150

-100

-50

0

50

100

150

200

12.0 12.2 12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0

Tra

ck r

esid

ua

ls (

m)


Land PEATE Re-processed1/19/2012

11/22/2012

1

2/23/2012

5

4/18/2013

4/25/2013 6

8/22/20133

12/11/2012

4

2/15/2013

2

3/30/2012

VCST/GEO 24

-200

-150

-100

-50

0

50

100

150

200

12.0 12.2 12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0

Sca

n r

esid

ua

ls (

m)


-200

-150

-100

-50

0

50

100

150

200

12.0 12.2 12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0

Sca

n r

esid

ua

ls (

m)


res

VIIRS Residual Trend


Land PEATE Re-processed1/19/2012

IDPS11/22/20121

2/23/2012

5

4/18/2013

4/25/2013 6

8/22/20133

12/11/2012

4

2/15/2013

2

3/30/2012

VCST/GEO 25

R² = 0.8089

-200

-150

-100

-50

0

50

100

150

200

-60 -40 -20 0 20 40 60

Tra

ck r

esid

ua

ls (

m)

Scan angle (deg)

R² = 0.2462

-200

-150

-100

-50

0

50

100

150

200

-60 -40 -20 0 20 40 60

Tra

ck r

esid

ua

ls (

m)

Scan angle (deg)

res

VIIRS Scan Angle Residuals


IDPS

Land PEATE Re-processed

VCST/GEO 26

R² = 0.0149

-200

-150

-100

-50

0

50

100

150

200

-60 -40 -20 0 20 40 60

Sca

n r

esid

ua

ls (

m)

Scan angle (deg)

R² = 0.016

-200

-150

-100

-50

0

50

100

150

200

-60 -40 -20 0 20 40 60

Sca

n r

esid

ua

ls (

m)

Scan angle (deg)

res

VIIRS Scan Angle Residuals


IDPS

Land PEATE Re-processed

VCST/GEO 27

Overall ErrorResiduals Error

IDPS

Error

Land PEATE

Re-processed

Track mean -9 m 2 m

Scan mean -7 m 2 m

Track RMSE 73 m 69 m

Scan RMSE 61 m 58 m

• Nadir equivalent accuracy (RMSE – Root Mean Square Error)

• Data-days

IDPS: 632 Land PEATE: 637

• Average CP residuals per day (after filtering)

IDPS: 135 Land PEATE: 138

• Time period:

IDPS: Feb. 23, 2012 (VIIRS I/M-band LUT update) to Dec. 5, 2013;

excluding 18 days right after A/B side switch

Land PEATE: Jan. 19, 2012 to Oct. 18, 2013Wolfe et. al., 19 Dec 2013 VCST/GEO 28

DNB spatial characteristics

DNB HSR is approximately a constant multiple of the horizontal

sampling interval (HSI) for aggregation zones 1-24. This results

in approximately constant HSR in units of ground distance, with

saw tooth pattern that is inherent in the ground HSI. HSR meets

the requirement of 800 meters upto scan angle of 52 degrees.

by NGAS


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