ultraviolet spectroscopy and remote … spectroscopy and remote sensing cedar workshop boulder co...

ULTRAVIOLET SPECTROSCOPY AND REMOTE SENSING

CEDAR WORKSHOP

Boulder CO

June 22, 1993

Robert R. MeierCode 7640

Naval Research Laboratory202-767-2773

OVERVIEW

The Ultraviolet Earth: Images and Spectra

Background and Early History

Present Status of UV Remote Sensing

o Global Imaging from High Altitude: DE

o Limb Imaging from Low Altitude

Inversion Techniques

Global Change and Climatological Databases

Summary

NRL FUV CAMERA ON APOLLO-16

Observations: 21-23 April 1972

Location: Lunar Surface

Sun-Earth-Moon Angle: 105 deg

Broadband Imagery:

• 1250 - 1600 A

• 1050 - 1600 A

o

Spectroscopy: 500 - 1600 A

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U. IOWA EXPERIMENT ON DYNAMICS EXPLORER (DE) - I

Launch: 3 August 1981

Initial orbit: 570 km x 3.65 Rg

Initial latitude of apogee: 78.T

Spin-scan imaging with about 12 min per image at apogee

• Photometer A: visible

• Photometer B: visible

• Photometer C: Far UV

with 12 filters each

Photometer instantaneous field-of-view 0.32°

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EARTH ULTRAVIOLET SPECTRA

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H 100

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2 absorptionbands

Solar max

Solar min

ionization limits11 I I

1000 2000 3000

WAVELENGTH (A)4000

Heating of the Atnnosphere

by Variable Solar

Ultraviolet Radiation

300

250 -

200 -

150 -

100 z

50

NRL Codes 7640 & 7670

TEMPERATUREI I I I i I I I I I M I I I I I

Solarmin max

Thermosphere

Mesosphere

Stratosphere

TroposphereI I I I 1 ri I I 1,1-1 I 1 I I I I 1 I I 10 I I I I I I I itkI I I I 1I I I I I I I I I I I I I I t I

100 300 500 700 900 1100 1300

TEMPERATURE (K)

EXCITATION MECHANISMS

RESONANT SCATTERING OF SUNLIGHT

• SOLAR LINES: 01 1304, 1026; HI 1216, 1026; Hel 584, 540; Hell 304• SOLAR CONTINUUM: NO7; N2^ ING

ENERGETIC PARTICLE IMPACT

• PHOTO ELECTRONS: DAYGLOW

• PRECIPITATING ELECTRONS (AND PROTONS): AURORA

• HEAVY ATOM PRECIPITATION: NIGHTGLOW

PHOTO/ION CHEMISTRY

• PHOTO-IONIZATION: O + hi- ^ 0*+ + e 834 A• RADIATIVE RECOMBINATION: O"" + e ^ O (1356, 1304, 989, 911)

• ION-ION RECOMBINATION: O"" + O" ^ O* + O*

• CHEMILUMINESCENCE: N^S) + O (^P) « NO (C)O + O + M ^ O2 (A)

• DISSOCIATION: O2 + [hp or e] O + O*N2 + [hi* or e] N + N* or N + N"*" *+ e

1946

1949

1955

1960, 1963

EARLY HISTORY OF UV SPECTROSCOPY

Sun observed to 2100 A,O3 observed to 55 km

O2 extinction observed

H Lyman a discovered

01 & N, LBH discovered

Baum et al. [1946]

Friedman et al. [1951]

Byram et al. [1961]

Fastie et al. [1961, 1964]

Other early contributors: T.M. Donahue, R. Tousey, J.W. Chamberlain, J. Brandt, F.S. Johnson, I.S.Shklovsky, C. Barth, V.G.Kurt, S.A. Kaplan

VERY LONG MATURATION TIME FOR ROUTINE UV

REMOTE SENSING MISSIONS

because:

Reliable cross sections, oscillator strengths... required

High sensitivity imagers and spectrographs needed

Science models had to be developed

Retrieval algorithms necessary for parameter extraction

GLOBAL IMAGING MODEL

AIRGLOW MODEL

• MSIS-86 SPECIFIES GLOBAL CONCENTRATIONS

• HINTEREGGER SOLAR EUV FLUX ALGORITHM

• STRICKLAND AND MEIER PHOTOELECTRON MODEL

• RADL\TIVE TRANSPORT MODELS

- OI 1356: Strickland and Anderson

- 01 1304: Gladstone or Meier

IMAGING MODEL

• MODEL DESCRIBED BY: Strickland, Cox, Barnes, Paxton, Meier, Thonnard

-accepted in Applied Optics [1993]

• USES GEOGRAPHIC GRID WITH VARIABLE SPACING IN SOLAR ZENITH AND

AZIMUTH ANGLES

• PRE-COMPUTES INTENSITIES VS LOOK ANGLE AT EACH GRID POINT ANDINTERPOLATES TO DYNAMICS EXPLORER LOOK ANGLES

1250 1300 1350 1400 1450 1500 1550„ 1600 1650 1700 1750 1800Wavelength (A)

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CONCLUSIONS: 1230 - 1800 A DATA

» MODEL REPRODUCES DATA TO WITHIN ± 17%

• model scaling for individual images: 0.92 - 0.99

• deviations due to statistics or aurora

• SPATIAL VARIABILITY WELL-REPRODUCED BY MODEL

. 01 1304 A DOMINATES 85 %) DISK PORTION OF (FILTER 2)IMAGES

• 60 %(photoelec.) + 25 %(solar res.scat.) = 85%

• 01 1356 k ~ 1 %

• N2 LBH bands ~ 7 %

• 011356 AAND N^ LBH BANDS DOMINATE AT LIMB

• CAN PROCEED WITH CONFIDENCE TO DISTURBED-TIME IMAGES

IMRL-301 REMOTE ATMOSPHERIC &IONOSPHERIC DETECTION SYSTEM (RAIDS)NAVAL RESEARCH LAB-AEROSPACE CORPORATION"

• EVALUATE CONCEPT OF GLOBAL UV REMOTE IONOSPHERIC SENSING

• OBTAIN ELECTRON DISTRIBUTION FROM AIRGLOW MEASUREMENTS

• MEASURE THE ALTITUDE DISTRIBUTION OF:O•. O. N2. O2, N, NO. Na (75 750 km: 6km RESOLUTION)

. FLY STATE OF THE ART IMAGING SPECTROSCOPIC INSTRUMENTATION(500 8700 \)

400

350

^ 300

Q 250

200 -

150

100

SIMULATED RAIDS DATA & MODELS

SZA = 0 F,o = 70

10 100 1000COLUMN EMISSION RATE (R)

I I I I.

10000

O, O2 AND N2 CONCENTRATIONS FROM OI1356 AND LBH

01 1356 A

4^^356 =/ "O ^1356 «

Nj LBH (2,0) 1383 A

'̂ ^^383 " / "aTj ^1383 ^ ^

photoelectron g-factors are (non-linearly) proportional to total column densityto sun, N through the photoelectron flux, 4>:

g{z\ =/ a(£) ^(EMz]) dE

RAroS ALGORITHM APPROACH;

DISCRETE INVERSE THEORY

Fast, rigorous, systematic inversion technique for obtainingenvironmental data records (EDR's) from UV limb scans

Applicable to all RAIDS science data records (SDR's)

Straightforward approachfor obtaining uncertainties in EDR's

Uncertainties from statistics in retrieved neutral densities ofabout 3-10% between 150 and 350 km, and 2% forexospheric temperature

Validation will ultimately be with observational data andground truth

NONLDJEAR DISCRETE INVERSE THEORY

Model Equation:

G(m) = P''

P" = vector of length N, representing predictions of quantities which have beenobserved

G = vector function representing modelm = vector of length M, corresponding to the model parameters

Simple Iterative Approach; Use Taylor's Theorem:

• Taking inverse (overdetermined case):

mU - m] »

Generalized inverse:

învVG. = { VGÊcov/'̂ ^J-^VG VG '̂Ecov/"®^]-!

Covariance of Model Parameters:

ohsi Tin ^[cov m] = VG.^îcovI'""] VG^,

• Equivalent to Maximum Likelihood Method

DISCRETE INVERSE THEORY ALGORITHMFOR OI 1356 A AND N2 LBH

EXAMPLES: Limb scans from 65 to 325 km tangent altitude

- 65 measurement for each line

- Synthetic data with Gaussian noise (1 ct/s/R)

- Solar min, max; 0, 70 deg solar zenith angle, 850 km satellite

CASE 1: m represents 5 scaling parameters describing the MSIS model:

Itt — [ fjj2 ' ' ^02 ' ^10 ' ^euv^

CASE 2: m represents individual densities:

jn = [72^^(110) , . . . , il^^(500) , rZodlO) , . . . , i3o(500) ,Hq (110) , . . . , IIq (500) ]

dashecl:INITIAL, solid:FINAL

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-20 -10 0 10 20LOWER AND UPPER LIMITS (%)

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NRL UPPER ATMOSPHERE/IONOSPHERE MISSIONS

MISSION CY90 212292242S262798222QQfi 0102^

UVLIM (SHUTTLE)' a

HIRAAS (ROCKET)" a a a

RAIDS (TIROS-J)* • A

HIRAAS (ARGOS)* •-..a

GIMI (ARGOS)* •.. .A

SSULI I (DMSP) • ^

SSULI 2 (DMSP) • ^



SSULI 5 (DMSP) •

• DELIVERY

A LAUNCHMISSION

Space Test Program (STP)•• NASA

SUMMARY

UV remote sensing has evolved sufficiently that accurate,routine observations of the upper atmosphere (andionosphere) are possible on a global scale

Non-linear inversion methods show greatpromisefor retrievalof concentrations from airglow observations

Validation is underway with various data sets

DoD missions shouldprovide continuous observations over 1-2 solar cycles, beginning next year with RAIDS

ultraviolet spectroscopy and remote … spectroscopy and remote sensing cedar workshop boulder co...

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