Motivation

• Measurements of Radiant Flux Physical Properties of Complex Systems

• Required Scientific Accuracy State of the Art Measurements

• International, Multi-platform, Multi-instrument Long Time Series Data

• Manufacturer or PI Responsible for Characterization and Calibration of Sensor Verification Program

Oceans from Space 9-13 October 2000

Spectral Radiance from NIST Standards

Optical Sensor

IrradianceLamp

Standard

Prism-GratingSpectroradiometer

IntegratingSphereSource

FlipMirror

DiffuseReflectanceStandard

BafflesSensor

Calibration

SourceCalibration

Plaque

Measurement Chains

Standards Calibrations

Research

SXR, VXR, SLMs

Standards Laboratories

MOBY, MOS

MODIS,

SeaWiFS

Ocean Sites

(Lanai, HI)

Lw

LwCal Sources

Traditional—Multiple steps

NIST/OA Programs—Direct verification in the field

Instrument Vendors

Cal Sources

Visible Transfer Radiometer (VXR)

Objectivelens

Entrancepupil

Wedgedmirrors

Filter andphotodiode

Fieldstop

HandleTemperature

controlled plate

Eye-piece

Voltage amplifiercircuit

Relaylens

Preamplifier andreadout circuits

14 cm

VXR and SXR Channels

300 400 500 600 700 800 900 1000 11001E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

Rel

ativ

e S

pec

tral

Rad

iance

Res

ponse

Wavelength [nm]

VXR and NPR in the Field

• VXR (or SXR or SLMs) transfer NIST radiance scales to the field

• NPR is a stable, portable, calibrated source, with monitor photodiodes, for verifying VXR in the field

NPR (NIST Portable Radiance Source)

VXR on Tripod

Comparisons at Snug Harbor

• September 1996

• January 1999

• February 2000

• NIST & SXR

• SLMs, MOBY, MOS, OL420

• NIST & VXR, NPR

• SLMs, MOBY, MOS, MD5, Diver’s Lamps, OL420, OL425

• NIST & VXR, NPR

• SLMs, MOBY, MOS, OL425

MOBY Spheres

• OL420– Calibrated in terms of spectral radiance, L()– External lamp (90 to exit aperture)– Continuously variable (translate lamp or change throughput

between lamp and the sphere)– No monitor photodiode

• OL425– Calibrated in terms of the relative spectral shape and the output of

the monitor photometer– External lamp and interior baffle plate (lamp is on-axis)– Continuously variable (change throughput between lamp and the

sphere)

Sphere Radiance

200 300 400 500 600 700 800 900 1000 1100 1200-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Spec

tral

Rad

ianc

e [W

cm

-2 s

r-1 n

m-1]

Wavelength [nm]

OL420 W5D100 OL420 W6D40 OL425 W6D100 OL425 W5D100

Solid Lines—from calibration laboratory

Symbols—from NIST transfer radiometers

OL420 in 1996

350 400 450 500 550 600 650 700 750 800 850 9000.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04

1.05

1.06 OL420 S3W5D40

SXR

or S

LM

Rad

ianc

e / O

L R

adia

nce

Wavelength [nm]

SXR11Sep96T SXR11Sep96 SLM11Sep96T SLM11Sep96

350 400 450 500 550 600 650 700 750 800 850 9000.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04

1.05 OL420 S3W5D100

SXR

or S

LM

Rad

ianc

e / O

L R

adia

nce

Wavelength [nm]

SXR11Sep96 SXR12Sep96 SXR13Sep96 SLM11Sep96 SLM12Sep96 SLM13Sep96

OL420 is calibrated by Optronic Laboratories at the S3W5D100 setting; numeric ratios are provided for all other settings: W5D40 = 1.5 * W5D100. The SXR-SLM results give 1.52.

k = 1

OL420 in 1999

350 400 450 500 550 600 650 700 750 800 850 9000.95

0.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04OL420 S3W5D100

VX

R o

r SL

M R

adia

nce

/ OL

Rad

ianc

e

Wavelength [nm]

VXR25Jan99A VXR28Jan99D VXR29Jan99A SLM25Jan991 SLM27Jan991 SLM28Jan994 SLM28Jan995

350 400 450 500 550 600 650 700 750 800 850 9000.95

0.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04 OL420 S3W6D40

VX

R o

r SL

M R

adia

nce

/ OL

Rad

ianc

e

Wavelength [nm]

VXR25Jan99C SLM26Jan992

Calibrated at S3W5D100 Relate to S3W5D100 using OL numeric factors: S3W6D40 = 1.5*3.1 S3W5D100

k = 1

OL425 in 1999

350 400 450 500 550 600 650 700 750 800 850 9000.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04 OL425 S3W5D40

VX

R o

r SLM

Rad

ianc

e / O

L R

adia

nce

Wavelength [nm]

VXR26Jan99A VXR28Jan99C SLM26Jan994 SLM29Jan991

350 400 450 500 550 600 650 700 750 800 850 9000.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04 OL425 S3W6D40

VX

R o

r SLM

Rad

ianc

e / O

L R

adia

nce

Wavelength [nm]

VXR26Jan99B SLM26Jan994

Calibrated at S3W5D100; scaled using OL425 Photometer

Calibrated at S3W6D100; scaled using OL425 Photometer

k = 1

OL425 in 2000

350 400 450 500 550 600 650 700 750 800 850 9000.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04 OL425 S3W5D100

VX

R o

r SLM

Rad

ianc

e / O

L R

adia

nce

Wavelength [nm]

VXR8Feb00C VXR8Feb00D SLM8Feb001 SLM8Feb002

350 400 450 500 550 600 650 700 750 800 850 9000.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04 OL425 S3W6D100

VX

R o

r SL

M R

adia

nce

/ OL

Rad

ianc

e

Wavelength [nm]

VXR8Feb00B SLM8Feb001 SLM8Feb002 VXR8Feb00E

Calibrated at S3W5D100 Calibrated at S3W6D100

k = 1

Conclusions

• Spectral radiances of MOBY calibration sources are accurate to within +/- 3% from 410 nm to 870 nm

• Commercial calibration laboratory is providing standards that are within their stated expanded (k = 2) uncertainties

• OL420 appears to have a spectral component compared to NIST; the OL425 does not, but the variations are within the uncertainties

• Periodic comparisons with EOS/NIST should continue