Lecture 26 10 Imaging Radiometers

8/3/2019 Lecture 26 10 Imaging Radiometers

1/39

ECE 583Lecture 26

Imaging Visible and Infrared Radiometers

Multi-Spectral AnalysisActive/Passive


2/39

Ash Plume across the North AtlanticApril 15, 2010

MODIS


3/39

Elevated MODIS Aerosol Optical Depth near Iceland volcanic eruptionGiovanni AOD images and time-series show increase near location of eruption,

coinciding with eruption onset


4/39

Aerosol retrieval from space- the

MODIS aerosol algorithm

Uses bi-modal, log-normal aerosol size distributions.

5 small - accumulation mode (.04-.5 m) 6 large - coarse mode (> .5 m)

Look up table (LUT) approach

15 view angles (1.5-88 degrees by 6)

15 azimuth angles (0-180 degrees by 12)

7 solar zenith angles

5 aerosol optical depths (0, 0.2, 0.5, 1, 2)

7 modis spectral bands (in SW)

Ocean retrievals

compute IS and IL from LUT

find ratio of small to large modes ()andthe aerosol model by minimizing

1

1

0 . 0 1

(1 )

m cn

mj

c S L

I I

n I

w h e r e

I I I

=

=

+

= +

then compute optical depth fromaerosol model and mode ratio.

and Im is the

measured radiance.


5/39

+==

=

=

=

=

=

/1/m*,zwhere

)]mzexp()[(Pm

F),z(I

zzintegrate,andSubstitute

'dz]/)'zz(exp[),'z(I),z(I

zzpaththealongradiationaccumlatedTotal

)(P]/)'zz(exp[F

),'z(I

)(d]/)'zz(exp[),z(I)(P

),'z(I

z'levelteintermediaanAt

]/)'zz(exp[),z(I),'z(Ibeam)directlaw,(BeerscomponentdUnscattere

constantallare)(P

and,

,

/zr

text

texto

t

ext

z

1*

t

textsca1*

texttsca1*

textt

extsca

1

14

4

4

4

1

0

1

0

rr

rr

rr

rr

rr

rr

r

r

Example: reflection of sunlight from a

plane parallel atmosphere


6/39

Cloud

or aerosol

Surface

Multiple layers aerosolsurface contrast

The Problem:

Optical depth is obtained through the

relationship between reflected sunlight andoptical depth

To do so requires that reflections from

surface be removed.

This is difficult when there is littlecontrast between the surface and cloud oraerosol

Low contrast conditions occur frequently-e.g thin layers of cloud or aerosol overland, cloud over snow/ice


7/39

Land retrievals

Select dark pixels in near IR,

assume it applies to red and blue

bands.

Using the continental aerosol model,derive optical depth from the red

and blue bands (LUT approach

including multiple scattering.

Determine aerosol model usingsingle-scattering relationship

Adjust the optical depth according

to the new aerosol model.

The key to both ocean and

land retrievals is that the

surface reflection is small.


8/39

Measurement Requirements for Imaging Radiometers

Spatial resolution (pixel size)

Number and wavelength of channels

Spectral width of wavelength channels

Spatial alignment (registration) between wavelength channels

Minimum signal measurement accuracy (%)

Measurement accuracy of radiance (calibration)

Basic Type of Image Scanning Radiometer


9/39

Types of Optical Scanning


10/39

Whiskbroom Imaging

Pushbroom Imaging

Grating Spectrometer Pushbroom Imaging


11/39

Instrument Requirements for Imaging Radiometers(Derived from measurement requirements)

Instantaneous Field-of-View IFOV = d/R d Pixel resolution dimension

requirement

R Satellite nadir altitude

Line Frequency (mirror RPM) fL= V/d V Satellite velocity

Angular Rate v = 2/ fL (radians / second)

Sample Rate fc = v/ IFOV

Detector Electronic Bandwidth fb = fc/ 2 Nyquist frequency


12/39

Accuracy Requirement: Signal/Noise = 1 at minimum signal error or resolution (watts orTbrightness temperature ). Noise is the combination of signal shot noise and detector noise (as seenbefore).

Signal S at detector in watts:

S () = Ipix() A [(IFOV)2/4] Ts Ipix() Spectral Intensity of pixelTs System optical transmissionA System effective aperture area

- Spectral Band pass requirementCalculated Aperture Requirement : Area calculated from Smin signal noise and Ipix,min measurementrequirement

Ar = Smin/(Imin A [(IFOV)2/4] Ts )

Higher spatial or spectral resolution requires larger aperturesHigher spatial resolution also requires faster scan rate and signal bandwidth, increasing noise.

But, multi element detectors increase through put by N the number of detectors, reducing theaperture requirement correspondingly.

Instrument Requirements for Imaging Radiometers(Derived from measurement requirements)


13/39

ER-2 Cloud and Aerosol Observation Experiment

Science Applications (1983-2000)

Height Structure from Lidar

Multi Sensor Observation Experiment

VIS

IR

Multi Spectral Radiance


14/39


15/39

Spatial Resolution:20 m


16/39


17/39

10.7 m2.16 m

1.64 m

0.76045 m

0.76346 m

0.75392 m


18/39

Stephens, Remote Sensing of the Lower Atmosphere, Chapter 6


19/39

Lidar and IR Radiance TechniqueActive/Passive Sensing

Multispectral Analysis of Cloud Particles

Thermal IR Cirrus Parameter Sensing

Temperature

BackscatterSource Function of IR Radiance


20/39

Thermal IR Particle Size


21/39

SPINHIRNE ET AL.: CONTRAIL CIRRUS FROM AIRBORNE REMOTESENSING, GRL 1998

Contrail Sensing Example

MODIS Airborne Simulator Data


22/39

Data MiningForty-three years after the Nimbus IIsatellite collected these data, a team fromNSIDC and NASA recovered a globalimage from September 23, 1966. In thisview over Antarctica, overlaid on GoogleEarth, the Ross Ice Shelf appears clearly

at left.

Early Weather Imaging Radiometers

HRIR High Resolution Imaging Radiometer


23/39

The single-channel dual-band pass scanning radiometer

uses a PBSe photoconductive detector cell and providesmeasurements of blackbody temperatures 210K 330K. TheScan mirror is inclined to 45 degrees with a scan rate of 44.7revolutions per minute. The Instantaneous field of view is 8.8milliradians and the scan line separation is 8.3 km. Theground resolution is 8 km at 1110 km.

The Nimbus III HRIR was designed to allow nighttime anddaytime cloud cover mapping by use of dual band-pass filterwhich transmits 0.7 to 1.3 micron, and 3.4 to 4.2 micronemitted radiation. The improvement of detector temperaturecontrol and electronics compensation has eliminated themultiple calibrations of previous instruments.

Early NASA Experimental Meteorological SatelliteNimbus I VII Launched (1964 1978)

Data Operations through 1994Some instruments:

Nimbus II Medium Resolution Infrared Radiometer (MRIR) (4.6-6.9 micron, 10-11 micron, 14-16 micron, 5-30 micron, 0.2-4.0 micron)

Nimbus II High Resolution Infrared Radiometer (HRIR) (3.5 to 4.1 micron)

Nimbus III single-channel dual band-pass High Resolution Infrared Radiometer (HRIR) (3.4 4.2 micron at nighttime, 0.7-1.3 micron at daytime)

Nimbus III Medium Resolution Infrared Radiometer (MRIR) (4.5-7.0 micron, 10-11 micron, 14.5-15.5 micron, 20-23 micron, 0.2-4.0 micron)

Nimbus IV Temperature and Humidity Infrared Radiometer (THIR) at 11.5 micron channel

Nimbus IV Temperature and Humidity Infrared Radiometer (THIR) at 6.7 micron channel

HRIR

Nimbus 3 Image of Australia (1969)


24/39

NOAA 14 19 1994 to 2009


25/39

NOAA-19 CharacteristicsMain body: 4.2m (13.75 ft) long, 1.88m (6.2 ft) diameter

Solar array: 2.73m (8.96 ft) by 6.14m (20.16 ft)Weight at liftoff: 1419.8 kg (3130 pounds) including 4.1 kg of gaseous nitrogen

Launch vehicle: Delta-II 7320-10 Space Launch Vehicle

Launch date: February 06, 2009 Vandenburg Air Force Base, CAOrbital information: Type: sun synchronous

Altitude: 870 kmPeriod: 102.14 minutesInclination: 98.730 degrees

Sensors:Advanced Very High Resolution Radiometer(AVHRR/3)Advanced Microwave Sounding Unit-A (AMSU-A)

Microwave Humidity Sounder (MHS)High Resolution Infrared Radiation Sounder (HIRS/4)

Solar Backscatter Ultraviolet Spectral radiometer (SBUV/2)Space Environment Monitor (SEM/2)Search and Rescue (SAR) Repeater and ProcessorAdvance Data Collection System (ADCS)


26/39

AVHRR Advanced Very High Resolution Radiometer


27/39


28/39

Imaging Radiometer Detectors


29/39

Remote Sensing Group University of ArizonaThe Remote Sensing Group in the College of Optical Sciences at theUniversity of Arizona is best known for its work on the in-flight,

radiometric calibration of remote sensing imagers using ground-basedmeasurements at desert test sites. Radiometric calibration in thiscontext refers to the ability to take the data from a sensor and convertit to a standard energy scale. Such work allows for the comparison ofdata from an array of imagers (by last count more than 30 sensors).The methods of the group have been in use since the mid-1980s and

currently provide absolute radiometric calibration to better than 2%,both in accuracy and precision in the mid-visible.

Visible and near IR

Radiance Calibration


30/39


31/39

Terra Satellite


32/39

MODIS


33/39


34/39

VIRS on NPOESS follows MODIS

Vincent V. Salomonson et al.


35/39

Earth Observing System (EOS) PM Formation

Aqua EOS main platform with six imagers and sounders, UV microwaveAura EOS main stratospheric platform with 4 sounding instrumentsParasol CNES polarization imager

Cloudsat Cloud RadarCalipso Cloud LidarOCO Orbiting Carbon Observatory

GLORY- NASA Aerosol Polarization Imager


36/39

1 nm

A-band

Wavelength index

Ref

lection

The key is to make measurements

at high spectral resolution(0.01- 0.1 nm).

Actual aircraft data

from OBrien et al (1998)

Example OCO: Aerosol retrieval from oxygen absorption

Optical Depth of Overlapping


37/39

Optical Depth of OverlappingLayers

This is actual satellite data from MOS.

With better resolution (such as PABSI),

profiling of layers becomes even

more capable

Coded in A-band spectra is information

about cloud and aerosol layering

Optical Depth Under


38/39

Optical Depth UnderLow Contrast Conditions

Simulation of PABSImeasurement

for thin aerosol layer

overlying

land surface

Red wavelengths respond mostly to surface albedo changes(reflecting the capabilities of most existing instruments)

Yellow wavelengths respond mostly to aerosol changes.

Key point: The ability to see into the absorption lines provides a way of

discriminating surface from atmosphere.

Thus surface reflection as well as optical depth is obtained

from PABSI.

wavenumber cm-1sensitivity to

optical depth

sensitivit

y

to

surfacea

lbedo


39/39

aerosol optical depth error surface albedo error

absolute

err

or

relative

erro

r

Aerosol retrieval is difficult:

small signature in observed

spectrum. instrument noise.

instrument convolution

(smearing or averaging of

observations).

uncertainties in a priori data.

Retrieval simulation

Best case scenario

(assume we know asymmetry

parameter, single-scattering

albedo, and location of aerosol

layer).

Lecture 26 10 Imaging Radiometers

Documents

Transcript of Lecture 26 10 Imaging Radiometers