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NPP ATMS Prelaunch Performance Assessment and Sensor Data Record Validation

W. J. Blackwell, L. Chidester (SDL), C. Cull, E. J. Kim (NASA GSFC), R. V. Leslie,

C.-H. Lyu (NASA GSFC), T. Mo (NOAA STAR), and I. Osaretin

IGARSS

July 25, 2011

This work was sponsored by the National Oceanographic and Atmospheric Administration under Air Force Contract FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the

authors and are not necessarily endorsed by the United States Government.

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Outline

• ATMS Overview– Background and development– Performance

• Prelaunch testing– Antenna– Radiometric TVAC

• Post-launch validation of sensor/product performance– Planning/schedule/objectives– Tasks

• Summary

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NPP (NPOESS Preparatory Project)Oct. 25, 2011 Launch

National Polar-orbiting Operational Environmental Satellite

System → Joint Polar Satellite System

National Polar-orbiting Operational Environmental Satellite

System → Joint Polar Satellite System

NPOESS Preparatory Project

• Launch site: Vandenberg AFB

• Launch vehicle: Boeing Delta II

• Spacecraft: Ball Aerospace Commercial Platform 2000

• Instruments: VIIRS, CrIS, ATMS, OMPS, & CERES

• Orbits: 824 km (NPP); sun-synchronous with a 1:30 p.m. local-time ascending node crossing

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NPOESS Preparatory ProjectOctober 25, 2011 Launch

Photo courtesy of Ball Aerospace, Boulder, CO.

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Advanced Technology Microwave Sounder (ATMS)

ATMS is a 22 channel MW sounder

Frequencies range from 23-183 GHz

Total-power, two-point external calibration

Continuous cross-track scanning, with torque & momentum compensation

Orbits: 833 km (JPSS); 824 km (NPP); sun-synchronous

Thermal control by spacecraft cold plate

Contractor: Northrop Grumman Electronics Systems (NGES)

70 cm

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ATMS Development

• ATMS NPP unit (“F1") developed by NASA/Goddard– ATMS NPP unit delivered in 2005– ATMS JPSS-1 unit (“F2”) currently in development

(antenna and TVAC testing in 2011/12, delivery in 2012)

• Principal challenges/advantages:– Reduced size/power relative to AMSU

Scan drive mechanism MMIC technology

– Improved spatial coverage (no gaps between swaths)– Nyquist spatial sampling of temperature bands (improved

information content relative to AMSU-A)

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ATMS Design Challenge

– 70x40x60 cm – 110 W– 85 kg– 8 year life

AMSU-A1

AMSU-A2

MHS

Reduce the volume by 3xReduce the volume by 3x

• 75x70x64 cm• 24 W• 50 kg• 3-yr life

• 73x30x61 cm• 67 W• 54 kg• 3-yr life

• 75x56x69 cm• 61 W• 50 kg• 4-yr life

Figure courtesy NGES, Azusa, CA

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Atmospheric Transmission at Microwave Wavelengths

The frequency dependence of atmospheric absorption allows different altitudes to be sensed by spacing channels along absorption lines

ATMS channels

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Spectral Differences: ATMS vs. AMSU/MHS

Ch GHz Pol Ch GHz Pol

1 23.8 QV 1 23.8 QV

2 31.399 QV 2 31.4 QV

3 50.299 QV 3 50.3 QH

4 51.76 QH

4 52.8 QV 5 52.8 QH

5 53.595 ± 0.115 QH 6 53.596 ± 0.115 QH

6 54.4 QH 7 54.4 QH

7 54.94 QV 8 54.94 QH

8 55.5 QH 9 55.5 QH

9 fo = 57.29 QH 10 fo = 57.29 QH

10 fo ± 0.217 QH 11 fo±0.3222±0.217 QH

11 fo±0.3222±0.048 QH 12 fo± 0.3222±0.048 QH

12 fo ±0.3222±0.022 QH 13 fo±0.3222±0.022 QH

13 fo± 0.3222±0.010 QH 14 fo±0.3222 ±0.010 QH

14 fo±0.3222±0.0045 QH 15 fo± 0.3222±0.0045 QH

15 89.0 QV

16 89.0 QV 16 88.2 QV

17 157.0 QV 17 165.5 QH

18 183.31 ± 1 QH 18 183.31 ± 7 QH

19 183.31 ± 3 QH 19 183.31 ± 4.5 QH

20 191.31 QV 20 183.31 ± 3 QH

21 183.31 ± 1.8 QH

22 183.31 ± 1 QH

Exact match to AMSU/MHS

Only Polarization differentUnique Passband

Unique Passband, and Pol. different from closest AMSU/MHS channels

MH

SAM

SU-A

AMSU/MHS ATMS

• ATMS has 22 channels and AMSU/MHS have 20, with polarization differences between some channels

− QV = Quasi-vertical; polarization vector is parallel to the scan plane at nadir

− QH = Quasi-horizontal; polarization vector is perpendicular to the scan plane at nadir

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Spatial Differences: ATMS vs. AMSU/MHS

Beamwidth (degrees)

ATMS AMSU/MHS

23/31 GHz 5.2 3.3

50-60 GHz 2.2 3.3

89-GHz 2.2 1.1

160-183 GHz 1.1 1.1

Spatial sampling

ATMS AMSU/MHS

23/31 GHz 1.11 3.33

50-60 GHz 1.11 3.33

89-GHz 1.11 1.11

160-183 GHz 1.11 1.11

Swath (km) ~2600 ~2200

ATMS scan period: 8/3 sec; AMSU-A scan period: 8 secATMS measures 96 footprints per scan (30/90 for AMSU-A/B)

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Summary of Key Sensor Parameters

Parameter PFM Measurement

Envelope dimensions 70x60x40 cm

Mass 75 kg

Operational average power 100 W

Operational peak power 200 W

Data rate 30 kbps

Absolute calibration accuracy 0.6 K

Maximum nonlinearity 0.35 K

Frequency stability 0.5 MHz

Pointing knowledge 0.03 degrees

NEDT 0.3/0.5/1.0/2.0 K

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ATMS Data Products

Data Product Description

RDR (Raw Data Record) FOV1 antenna temperature (counts)

TDR (Temperature Data Record) FOV1 antenna temperature (K)

SDR (Sensor Data Record) FOR1 brightness temperature (K)

EDR (Environmental Data Record) P/T/WV profile

“CDR” (Climate Data Record) “Climate-optimized” product

IP (Intermediate Product) Used to generate EDR/CDR

1FOV = ATMS “Field of View”; FOR = CrIMSS “Field of Regard”RDR, TDR, SDR, and EDR products will be available via CLASS

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Outline

• ATMS Overview– Background and development– Performance

• Prelaunch testing– Antenna– Radiometric TVAC

• Post-launch validation of sensor/product performance– Planning/schedule/objectives– Tasks

• Summary

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ATMS Pre-Launch Testing

• Essential for two objectives:– Ensure sensor meets performance specifications– Ensure calibration parameters that are needed for SDR processing are

adequately and accurately defined

• PFM testing revealed several issues that will require calibration corrections in the SDR:– Non-linearity (temperature-dependent for 31.4-GHz channel)– Cross-polarization (sometimes 10X higher than AMSU)– Antenna beam spillover from secondary parabolic reflector approaching

2% for some channels

• A variety of prelaunch testing is performed to assess performance and reliability– EMI/EMC - anechoic chamber for both emitted and susceptible

measurements – Mechanical – mass, CG, vibration, & torque on various fixtures– Radiometric – thermal vacuum (TVac) testing– Antenna – Compact Antenna Test Range (CATR)

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Compact Antenna Range Testing

• Compact Antenna Test Range– RF source illuminates the Antenna Under

Test (AUT), i.e., ATMS antenna subsystem– Uses a parabolic reflector to collimate the

electromagnetic radiation to illuminate the AUT in the far-field region

– AUT is attached to a positioner to rotate the AUT into the proper orientation

• Test measures the power received by the AUT compared to a standard antenna with a known antenna gain pattern

• Specifications verified: – Beam pointing accuracy– Beamwidth– Beam efficiency– Earth intercept

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Thermal Vacuum Parameters

• Dynamic range (brightness temperature range of 93-320 K)

• NEΔT (sensitivity)• Calibration accuracy (bias)• Linearity (deviation from linear

regression)• Short term gain fluctuation

(ΔG/G) (gain stability or 1/f noise)

• Hysteresis (repeatability)

NASA/LARC

• Measure the calibration parameters that are needed by the SDR algorithm (e.g., non-linearity correction factor)

• Validate that the sensor meets performance requirements• Provide pre-launch performance validation in a flight-like

environment

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Outline

• ATMS Overview– Background and development– Performance

• Prelaunch testing– Antenna– Radiometric TVAC

• Post-launch validation of sensor/product performance– Planning/schedule/objectives– Tasks

• Summary

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Post-Launch Cal/Val Timeline

L+13

L+90

IPO/NGAS ATMS

L+ 40L+12

NASA/NGES NGES/NASA

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ATMS Post-Launch Calibration/Validation in a Nutshell

• Post-launch is Cal/Val has four phases: Activation, Checkout, Intensive Cal/Val, and Long-term Trending

• Tasks within the phases can be categorized:– Sensor Evaluation: interference, performance evaluation, etc.– TDR/SDR Verification: geolocation, accuracy, etc.– SDR Algorithm Tunable Parameters: bias correction, space view

sector, etc.

• Activation Phase: Sensor is turned on and a sensor functional evaluation is performed; ATMS is collecting science data

• Checkout Phase: Performance evaluation and RFI evaluations

• Intensive Cal/Val: Verification of SDR attributes such as geolocation, resampling, brightness temperature accuracy (Simultaneous Nadir Overpass, Double Difference, radiosondes/NWP simulations, aircraft verification campaigns), and satellite maneuvers

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ATMS On-Orbit FOV Characterization

• Spacecraft maneuvers (constant pitch up or roll, for example) could be used to sweep antenna beam across vicarious calibration sources– Moon (probably too weak/broad for pattern assessment)– Earth’s limb (requires atmospheric characterization)

Focus of today’s presentation– Land/sea boundary (good for verification of geolocation)

• With knowledge of the atmospheric state, the antenna pattern can be recovered with deconvolution techniques

• Objectives of this study - quantitatively assess:– The benefits of various maneuvers

How accurately can the pattern be recovered?– The limitations of this approach

How much roll/pitch is needed for an adequate measurement? The error sources and their impact

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TB’s Across Earth/Space Transition

62.1

7°

BE

YO

ND

STA

ND

AR

D A

TM

OS

PH

ER

E

SURFACE

LIMB(STANDARD

ATMOSPHERE)

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NPOESS Airborne Sounder Testbed

OBJECTIVES

• Satellite calibration/validation

• Simulate spaceborne instruments

(i.e. CrIS, ATMS, IASI)– Preview high resolution products

– Evaluate key EDR algorithms

INSTRUMENTS: NAST-I & NAST-M

NAST- I: IR Interferometer Sounder

NAST- M: Microwave Sounder5 Bands: 23/31 (to be added), 54, 118, 183, 425 GHz

118

18354

425

NAST- M

NAST

~100km

Cruising altitude: ~17-20 km

Cross-track scanning: - 65º to 65º

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MetOp Satellite Validation

April 20th, 2007 collection

MetOp

path

Gulf of Mexico

NAST-M [Kelvin]

AM

SU

-A (

Met

Op

) [K

elvi

n] Tb Comparison AMSU-A

50.352.853.7554.454.94

-0.25K1.4K

-0.2K-0.2K-0.9K

GHz Bias

JAIVEx

<20min

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Summary

• All key radiometric requirements were satisfied

• Radiometric accuracy exceeds 1K

• Radiometric sensitivity exceeds requirements– Similar to AMSU for similar effective footprint sizes

• Linearity performance generally exceeds AMSU

• Antenna pattern testing indicates good performance– Opportunity for spacecraft maneuvers allows improved

characterization of ATMS spatial response function

• Post-launch cal/val plans are well defined– Readiness exercises ongoing– Areas to watch have been illuminated during prelaunch testing

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Backup Slides

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Utility of Aircraft Underflights

What do aircraft measurements provide that we cannot get anywhere else?– Why not just compare to radiosondes or NWP?

• Direct radiance comparisons– Removes modeling errors

• Mobile platform– High spatial & temporal coincidence achievable

• Spectral response matched to satellite– With additional radiometers for calibration

• Higher spatial resolution than satellite• Additional instrumentation deployed

– Coincident video data– Dropsondes

Example video image

Solar glint

Ocean

Clouds

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Synergistic Use of MW+IR:

Infrared Provides High Spatial Resolution

For example, CrIS provides 15km horizontal and 1km vertical resolution

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Passive Microwave Measurements Provide Low

Spatial Resolution, but Penetrate Clouds

For example, ATMS provides 33km horizontal and 3km vertical resolution

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AMSU-A: Large, Positive Forecast Impact

Source: Gelaro, Rienecker et al., 2008, NASA GMAO

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ATMS Storm Mapping:Improvements Relative to AMSU

Source: Surussavadee and Staelin, NASA PMM Presentation, 7/08