010

2030

4050

60C

ross

Trac

kPo

sitio

n

-3

-2

-10123

N-eul avt ne mt s uj A

l=31

4.4

nml=

313.

2nm

l=31

1.9

nml=

310.

8nm

Vol

cani

c SO

2 D

etec

tion

•O

MI v

s. A

IRS:

Man

am(P

apua

New

Gui

nea)

-O

ct 2

4, 2

004

•O

MI v

s. EP

-TO

M: A

mbr

ymvo

lcan

o, V

anua

tu –

Oct

24,

200

4

SO2

Inde

x

For t

his s

tudy

, we

show

map

s of S

O2

inde

x, d

efin

ed a

s the

resi

dual

diff

eren

ces b

etw

een

sele

cted

pa

irs o

f wav

elen

gths

, whi

ch h

ave

larg

e di

ffer

entia

l sen

sitiv

ity to

the

SO2

abso

rptio

n.Firs

t Loo

k at

the

SO

2 in

dex

Cal

cula

ted

from

OM

I Obs

erva

tions

Fi

rst L

ook

at th

e S

O2

inde

x C

alcu

late

d fr

om O

MI O

bser

vatio

ns

K. Y

ang1

* , N

.A. K

rotk

ov2 ,

S. C

arn2

, A. K

rueg

er2 ,

and

P.K

. Bha

rtia3

1. S

cien

ce S

yste

ms

and

Appl

icat

ions

, Inc

., La

nham

, MD

US

A2.

JE

CT/

GES

T, U

nive

rsity

of M

aryl

and,

Bal

timor

e C

ount

y, B

altim

ore,

MD

, USA

3. N

ASA

God

dard

Spa

ce F

light

Cen

ter,

Gre

enbe

lt, M

D, U

SA

* Ka

i_Ya

ng.1

@gs

fc.n

asa.

gov

A33

A-0

137

-2

2

150

400

010

0

Tot

al C

olum

n O

zone

Ref

lect

ivity

@ 3

31 n

m

Pair

2 S

O2

inde

x

Thre

e pa

irs o

f wav

elen

gths

are

sele

cted

for O

MI

SO2

inde

x ca

lcul

atio

n, a

s illu

stra

ted

in th

e fig

ure

show

n on

the

right

. Thi

s plo

t sho

ws t

he N

-val

ue

resi

dual

s fo

r 1.0

DU

of S

O2

is p

rese

nt a

t 15

km o

f al

titud

e. N

ote

that

the

resi

dual

diff

eren

ces,

i.e.,

the

SO2

indi

ces s

how

a d

istin

ct p

atte

rn: p

air 1

and

pai

r 3

indi

ces a

re e

xpec

ted

to b

e ne

gativ

e, w

hile

pai

r 2 in

dex

is e

xpec

ted

to b

e po

sitiv

e, w

hen

SO2

is p

rese

nt in

the

atm

osph

ere.

Man

y ot

her f

acto

rs m

ay c

ontri

bute

the

resi

dual

s, bu

t whe

n th

e th

ree

pairs

show

the

dist

inct

pa

ttern

illu

stra

ted

here

, one

can

be

reas

onab

ly

conf

iden

t tha

t SO

2 is

det

ecte

d.30

030

531

031

532

032

533

0wl

Hnm

L

0

0.2

0.4

0.6

0.81

1.2

N-eul av

p1 -p2 +

p3 -w

l=(3

10.8

, 311

.9, 3

13.2

, 314

.4) n

mp1

p2

p3

Res

idua

ls: 1

.0 D

U S

O2

@ 1

5 km

INT

RO

DU

CT

ION

The

Ozo

ne M

onito

ring

Inst

rum

ent (

OM

I) on

boar

d th

e A

ura

spac

ecra

ft m

akes

hyp

er-s

pect

ral

radi

ance

mea

sure

men

ts in

the

Ultr

a-V

iole

t (U

V) a

nd V

isib

le (V

IS) r

ange

. The

OM

I mea

sure

men

ts

cove

rs th

e gl

obe

daily

and

has

a n

adir

reso

lutio

n of

13x

24 k

m2 .

Thes

e ch

arac

teris

tic o

f OM

I off

er a

n im

prov

ed c

apab

ilitie

s for

mon

itorin

g oz

one

and

othe

r tra

ce g

ases

, suc

h as

SO

2, in

the

atm

osph

ere.

We

have

app

lied

the

TOM

S to

tal o

zone

alg

orith

m to

the

OM

I UV

2 sp

ectra

l rad

ianc

e m

easu

rem

ents

, w

ith sp

ectra

l ran

ge fr

om 3

06 to

370

nm

at a

sam

plin

g di

stanc

e of

0.15

nm

/pix

el a

nd a

reso

lutio

n of

0.4

5 nm

. We

exam

ine

the

resi

dual

s tha

t are

cal

cula

ted

as th

e di

ffer

ence

bet

wee

n th

e m

easu

red

and

the

com

pute

d th

eore

tical

radi

ance

s tha

t acc

ount

for t

he e

ffec

ts o

f ozo

ne, R

ing,

and

surf

ace

refle

ctiv

ity.

Ana

lysi

s of t

hese

resi

dual

s is v

ery

usef

ul in

det

ectin

g in

stru

men

t arti

fact

s and

cal

ibra

tion

erro

rs a

s wel

l as

unu

sual

atm

osph

eric

con

ditio

ns. S

ulfu

r dio

xide

(SO

2) h

as a

stro

ng a

bsor

ptio

n in

the

wav

elen

gth

rang

e 30

6-34

0 nm

. Res

idua

ls in

this

wav

elen

gth

rang

e sh

ow d

istin

ctiv

e fe

atur

es if

a si

gnifi

cant

am

ount

of

SO

2 is

pre

sent

in th

e at

mos

pher

e, su

ch a

s in

the

case

of v

olca

nic

clou

ds o

r air

pollu

tion.

How

ever

, SO

2 is

abs

ent o

ver m

ost o

f the

Ear

th a

nd re

sidu

als a

re se

nsiti

vedi

agno

stics

of i

nstru

men

t per

form

ance

.

OM

I Dai

ly G

loba

l Map

s •T

OM

S-V

8 al

gorit

hm, w

hich

use

s a sm

all s

et o

f dis

cret

e w

avel

engt

hs, i

sapp

lied

to th

e O

MI d

ata

to

deriv

e to

tal c

olum

n oz

one

and

othe

r rel

ated

par

amet

ers.

Thes

e se

t of m

aps s

how

s the

tota

l col

umn

amou

nt o

zone

, sur

face

refle

ctiv

ity a

t 331

nm

, and

the

pair

2 SO

2in

dex.

The

se a

re th

e re

sults

afte

r N-

valu

e ad

just

men

ts w

hich

rem

oves

the

cros

s-tra

ck b

ias.

Man

am

Aqu

a/A

IRS

SO

2co

lum

n04

00U

T(c

ourte

sy A

.J. P

rata

, CS

IRO

, Aus

tralia

)

Aur

a/O

MI S

O2

colu

mn

0412

UT

Sum

mar

y•A

naly

sis o

f the

ear

ly re

sults

from

OM

I ind

icat

es th

at th

is in

stru

men

t is p

erfo

rmin

g ve

ry w

ell.

•OM

I L1B

nee

ds t

o be

cor

rect

ed fo

r cro

ss-tr

ack

bias

. N-v

alue

adj

ustm

ent w

orks

wel

l for

this

co

rrec

tion.

•SO

2 de

rived

from

OM

I mea

sure

men

t sho

ws g

ood

agre

emen

t with

that

from

AIR

S.

•OM

I vs.

EP-

TOM

S co

mpa

rison

dem

onst

rate

s the

hig

her s

ensit

ivity

of O

MI m

easu

rem

ents

with

less

ba

ckgr

ound

noi

se th

an th

ose

of E

P TO

MS.

N-v

alue

Adj

ustm

ent f

or S

O2

inde

x

Sout

h A

tlant

icA

nom

aly

•N-v

alue

= -1

00 L

og10

(Rad

/Irra

d)

•Cro

ss-T

rack

bia

s is p

rese

nt in

OM

I L1

B d

ata

due

to c

alib

ratio

n im

perf

ectio

n.

•N

-val

ue a

djus

tmen

ts c

an b

e de

rived

to

cor

rect

sca

n bi

as. F

or a

det

ail

desc

riptio

n of

this

tech

niqu

es, p

leas

e se

e po

ster

#

A33

A-0

133.

•Fo

r SO

2 in

dex

calc

ulat

ion,

N-v

alue

ad

just

men

ts sh

own

here

are

the

aver

age

of th

e re

sidu

al a

t the

re

spec

tive

wav

elen

gth

in th

e eq

uato

rial r

egio

n.

Oct

ober

24,

200

4

Ack

now

ledg

men

tTh

is w

ork

is su

ppor

ted

unde

r NA

SA c

ontra

ct N

AS5

-002

20.

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