Preparing for JPSS-1/ATMS Direct Readout Readiness

Acknowledgments: This work was performed under contract NAS5-01089, sponsored by NASA

Nikisa S. George & Kent AndersonNorthrop Grumman Electronic Systems, Azusa CA, 91702, U.S.A.

Overview• The Advanced Technology Microwave Sounder (ATMS),

manufactured by Northrop Grumman Electronic Systems (NGES) in Azusa CA, was launched on October 28, 2011 aboard the Suomi National Polar-orbiting Partnership (NPP) spacecraft

• ATMS works in conjunction with the Cross-track Infrared Sounder (CrIS) to measure atmospheric temperature and humidity profiles and is the follow-on to the Advanced Microwave Sounding Units -A and -B

• The next ATMS, currently in system-level testing, will be on the Joint Polar Satellite System-1 (JPSS-1), planned for launch in 2017

• This study reviews:

• Our performance assessments from Cal-Val activities

• Scan-dependent radiometric biases and “striping”

• Preliminary algorithm options that may be useful for direct readout users

Summary of NPP On-orbit Assessments• Radiometric Sensitivity: Channels 1-16 reduced by 1/3, for direct comparison to AMSU-A (Figure 2a)

• Radiometric Accuracy: Analytic model, with parameter updates based on On-orbit Data (Figure 2b)

Figure 1. a) ATMS Channelization Compared to AMSU, b) ATMS Proto-flight Model, and c)Ch 18 TB of Hurricane Isaac

Figure 3. Channel 1 and channel 17 scan-dependent radiometric biases, observed during pitch-maneuver

Figure 4. ATMS Striping example

Conclusions• Stability of critical temperature-dependent parameters is

significantly better than predicted

• Sensitivity (NEDT) is consistent with ground tests, and is an improvement over AMSU when averaged for equivalent footprint sizes

•Other phenomena, such as scan-dependent biases and striping, are being characterized and modeledBasis for deriving related requirements for future unitsAlgorithm enhancements are under development to mitigate their effects

ATMS Description• Total-power radiometer, two-point external calibration• Continuous cross-track scanning• Functional-equivalent follow-on to AMSU-A and MHS, with

improved sampling and coverage

Figure 2. a) NEDT compared to requirements and AMSU-A / MHS and b) Radiometric Accuracy, with & without quadratic corrections

“Striping” Noise• “Striping” is due to scan-to-scan (down-track) variations

that are greater than sample-to-sample variations within a scan (cross-track) (see Figure 4)

No requirement has yet been established, but it is now recognized that such a requirement needs to be developed

Phenomenon is due to low-frequency gain fluctuations, predominantly in front-end LNAs

•Associated issue of multi-channel correlation of gain fluctuations is also under investigation

ATMS Chan

AMSU-A,B Chan

Center Freq (GHz)Pre-Detection

Bandwidth (MHz)

Pol

1 1 23.8 270 QV

2 2 31.4 180 QV

3 3 50.3 180 QH

4 51.76 400 QH

5 4 52.8 400 QH

6 5 53.596±0.115 170 QH

7 6 54.4 400 QH

8 7 54.94 400 QH

9 8 55.5 330 QH

10 9 57.290344 155 QH

11 10 57.290344±0.217 78 QH

12 11 57.290344±0.3222±0.048 36 QH

13 12 57.290344±0.3222±0.022 16 QH

14 13 57.290344±0.3222±0.010 8 QH

15 14 57.290344±0.3222±0.0045 3 QH

16 15 88.2 2000 QV

17 17 165.5 1150 QH

18 20 183.31±7.0 2000 QH

19 183.31±4.5 2000 QH

20 19 183.31±3.0 1000 QH

21 183.31±1.8 1000 QH

22 18 183.31±1.0 500 QH

b)

c)

a)

a)

b)

• Scan-dependent Radiometric BiasPrimarily due to scanning reflector polarized emissivityMinor secondary effect, may be due to reflector spillover (TBD)Causes both a systematic angle-dependent error and an overall bias

(due to radiometric offset of cold-calibration measurement)

Potential Algorithm Options for JPSS• Corrections for the scan-dependent bias, based on modeled

effect of reflector emissivity

• Multi-channel processing to reduce correlated errors

• Corrections for polarization angle errors and cross-pol contamination

•More sophisticated techniques (TBD) to reduce striping

Feb 20, 2012 - ATMS Pitch Maneuver; Ch 3 in Kelvin

Cros

s Tr

ack

Beam

Pos

ition

Down Track Scan

2

Ref sin2/ TT nQV 2

Ref cos2/ TT nQH e: Emissivity = 0.37%Tref: Reflector Temperature = 0.0° Cy: Scan Angle

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-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

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Scan Angle (degrees)

Chan 1 (QV)On-orbit DataSimulated EmissivitySimulated, with 0.2 K quadr corr

0.0

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-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

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Chan 17 (QH)On-orbit DataSimulated EmissivitySimulated, with 0.2K quadr corr