sciamachy los mispointing modelling m. gottwald & e. krieg – dlr-imf - dlr/ife iup-ife,...

SCIAMACHYLoS MispointingModelling

M. Gottwald & E. Krieg – DLR-IMF

- DLR/IFE S S T

IUP-IFE, Bremen, 30 November 2006

SCIAMACHY Operations Support

M. Gottwald & E. Krieg – DLR-IMF, 30 November 2006 page 2

Known LoS Anomalies

several measurements display small LoS anomalies auf (known since Commissioning Phase)

all of them, except BIAS in limb tangent height, are classified as ‘uncritical’

approach to use LoS anomalies to understand limb BIAS

what can cause LoS anomalies?

- extra instrument misalignment (pitch, roll, yaw)

- platform attitude misalignment

- FOCC planning and scheduling s/w (CFI, SCIACAL)

- scanner control s/w

- Sun Follower



LoS Anomalies – Measured Jumps

Jump-history Sun-states (LoS)

-0,07

-0,05

-0,03

-0,01

0,01

0,03

0,05

0,07

0,09

0,11

9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000

Orbit

jum

p [

deg

- L

oS

an

gle

]

ASM_jump (ID49) ESM-Jump (ID47) ESM_subsolar (ID53) ASM_jump (ID47)SCIA-OFF SCIA_Idle-OCM decontamination SCIA_Idle-MPS

Jump-history Sun-states (LoS)

-0,07

-0,05

-0,03

-0,01

0,01

0,03

0,05

0,07

0,09

0,11

9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000

Orbit

jum

p [

deg

- L

oS

an

gle

]

ASM_jump (ID49) ESM-Jump (ID47) ESM_subsolar (ID53) ASM_jump (ID47)SCIA-OFF SCIA_Idle-OCM decontamination SCIA_Idle-MPS



Coordinate Systems

+Y

-X

+Z

ESM:in X-Z plane-X (Z = 0): 0°+X (Z = 0): 180°

ASM:in Y-X plane+X (Y = 0): 0°-X (Y = 0): 180°

+X

+Y

-X

+ZElevationfrom X-Y plane+Z: -90°-Z: +90°

Azimut+ in X-Y plane-Y: 0°+Y: 180°

+X

Scanner CFI

-Y

Target



Observed Anomalies (LoS angle)

- limb: elevation = -0.016 deg1

‘SCIAMACHY is pointing too low tangent heights are too large’1 possibly larger

- solar occultation: azimuth = 0.1 deg2 elevation = -0.04 deg3

jumps of the ASM and ESM readings when switching to Sun Follower(State 47)

2 at 17.2 km3 at 100 km

- subsolar: azimuth = 0.05 deg4 elevation = -0.02 deg

jump of the ESM readings when switching to Sun Follower and temporal shift of maximum signal (State 53)

4 derived from temporal shift of maximum signal of about 5 BCPS



‘Modelling the Jumps’ (1)

assumption

- jumps, temporal shift in subsolar signal and limb BIAS are caused by extra misalignment

(known misalignment LoS: pitch = 0.00065°, roll = 0.00167°,

yaw = -0.22746°)

- azimuth jump in occultation may be a special case (acquisition at 17.2 km = well within the atmosphere)

misalignment budget- pitch: pt = pi + pp + pe (t = total misalignment, i = instrument, p = platform, e = extra)

- roll: rt = ri + rp + re

- yaw: yt = yi + yp + ye




Modelling

- derive solar azimuth and elevation for occultation and subsolar viewing using the ENVISAT CFIs

- option 1: CFI without any misalignment = reference for subsolar azimuth

- option 2: CFI with instrument misalignment = reference for subsolar elevation and occultation elevation

- option 3: CFI with instrument misalignment, platform misalignment and variable extra misalignment

- combination of option 1/2 and option 3 = simulation of Sun Follower acquisition

determine ‘best fit’ extra misalignment which produces measured jump or time shift




option 1 and 2 = scanner control with FOCC prediction

option 3 = scanner control with Sun Follower

absolute values of azimuth/elevation from SOST-CFIs and FOCC-CFIs are not fully identical (additional corrections at FOCC)

difference in absolute values about several 0.01°

jumps are relative changes jumps can be modelled with SOST-CFIs



Which Jump results from which Misalignment?

subsolar elevation roll

subsolar azimuth = time of maximum signal yaw and pitch

Sun occultation azimuth: not analysed

Sun occultation elevation pitch and roll



Modelling

20 orbits with state 53 (subsolar)

24 orbits with state 47 (occultation)

platform attitude information from AUX_FRA

pitch, roll and yaw extra misalignment variations around expected values (limits defined by maximum observed anomalies)

search for best fit extra misalignment in pitch, roll and yaw



Example: Subsolar Azimuth – Yaw

Azimuth Sun (at subsolar az = 270.0°); extra misalignment: p = - 0.016; r = - 0.020; y = variable

269,20

269,40

269,60

269,80

270,00

270,20

270,40

270,60

270,80

271,00

-100 -75 -50 -25 0 25 50 75 100

Sun_Max Elapsed Time (BCPS)

Azi

mu

th (

°)

y = instrument misalignment+platform y =-0,04 y =-0,08y =-0,12 y =-0,16 y =-0,20y =-0,24 y =-0,28 y =-0,32y =-0,36 y =-0,40 instrument misalignmentsignal maximum 270,0 deg reference = no mislignment

Azimuth Sun (at subsolar az = 270.0°); extra misalignment: p = - 0.016; r = - 0.020; y = variable

269,20

269,40

269,60

269,80

270,00

270,20

270,40

270,60

270,80

271,00

-100 -75 -50 -25 0 25 50 75 100


Azi

mu

th (

°)

y = instrument misalignment+platform y =-0,04 y =-0,08y =-0,12 y =-0,16 y =-0,20y =-0,24 y =-0,28 y =-0,32y =-0,36 y =-0,40 instrument misalignmentsignal maximum 270,0 deg reference = no mislignment



Example: Subsolar Azimuth – Pitch

Azimuth Sun (at subsolar az = 270,0°); misalignment: p = variable; r = -0.020; y = 0.000

269,20

269,40

269,60

269,80

270,00

270,20

270,40

270,60

270,80

271,00

-100 -75 -50 -25 0 25 50 75 100


Azi

mu

th (

°)

pitch = instrument misalignment + platform pitch -0,004 pitch -0,008pitch -0,012 pitch -0,016 pitch -0,02pitch -0,024 pitch -0,028 pitch -0,032

pitch -0,036 pitch -0,04 signal maximum270,0 deg reference = no misalignment instrument misalignment

Azimuth Sun (at subsolar az = 270,0°); misalignment: p = variable; r = -0.020; y = 0.000

269,20

269,40

269,60

269,80

270,00

270,20

270,40

270,60

270,80

271,00

-100 -75 -50 -25 0 25 50 75 100


Azi

mu

th (

°)

pitch = instrument misalignment + platform pitch -0,004 pitch -0,008pitch -0,012 pitch -0,016 pitch -0,02pitch -0,024 pitch -0,028 pitch -0,032

pitch -0,036 pitch -0,04 signal maximum270,0 deg reference = no misalignment instrument misalignment



Example: Subsolar Elevation – Roll

Elevation Sun (at subsolar az = 270.0°); extra misalignment: p = -0.016; r = variable; y = 0.000

-60,35

-60,30

-60,25

-60,20

-60,15

-60,10

-60,05

-400 -300 -200 -100 0 100 200 300 400 500

Sunpass Elapsed Time (BCPS)

Ele

va

tio

n (

°)

roll reference roll -0,004 roll -0,008 roll -0,012 roll -0,016

roll -0,020 roll -0,024 roll -0,028 roll -0,032 roll -0,036

roll -0,04 ESM_scan ESM-corr_scan

Elevation Sun (at subsolar az = 270.0°); extra misalignment: p = -0.016; r = variable; y = 0.000

-60,35

-60,30

-60,25

-60,20

-60,15

-60,10

-60,05

-400 -300 -200 -100 0 100 200 300 400 500

Sunpass Elapsed Time (BCPS)

Ele

va

tio

n (

°)

roll reference roll -0,004 roll -0,008 roll -0,012 roll -0,016

roll -0,020 roll -0,024 roll -0,028 roll -0,032 roll -0,036

roll -0,04 ESM_scan ESM-corr_scan



Solar Occultation Elevation – Assymetric Signal

PMD 4 LG State 47 (orbit 19822)

-10

10

30

50

70

90

110

130

150

0 200 400 600 800 1000

BCPS

PM

D_

4 s

ign

al

PMD_4 Read-Out

PMD 4 LG State 47 (orbit 19822)

-10

10

30

50

70

90

110

130

150

0 200 400 600 800 1000

BCPS

PM

D_

4 s

ign

al

PMD_4 Read-Out



Example: Solar Occultation Elevation – Pitch

Elevation Sun (at ESM acquisition); extra misalignment: p = variable ;r = - 0.020; y = 0.000

25,15

25,20

25,25

25,30

25,35

25,40

25,45

440 450 460 470 480 490 500 510 520 530 540 550

ASM-acquisition Elapsed Time (BCPS)

Ele

vati

on

(°)

no misalignment instrument misalignment only p = -0,004 p = -0,008

p = -0,012 p = -0,016 p = -0,020 p = -0,024

p = -0,028 p = -0,032 p = -0,036 p = -0,040

ESM_scan ESM_scan-center

Elevation Sun (at ESM acquisition); extra misalignment: p = variable ;r = - 0.020; y = 0.000

25,15

25,20

25,25

25,30

25,35

25,40

25,45

440 450 460 470 480 490 500 510 520 530 540 550


Ele

vati

on

(°)

no misalignment instrument misalignment only p = -0,004 p = -0,008

p = -0,012 p = -0,016 p = -0,020 p = -0,024

p = -0,028 p = -0,032 p = -0,036 p = -0,040




Example: Solar Occultation Elevation – Roll

Elevation Sun (at ESM acquisition); misalignment: p = - 0.016; r = variable; y = 0.000

25,20

25,25

25,30

25,35

25,40

25,45

25,50

440 450 460 470 480 490 500 510 520 530 540 550


Ele

vati

on

(°)

no misalignment inst-mis-only r = -0,004 r = -0,008 r = -0,012

r = -0,016 r = -0,020 r = -0,024 r = -0,028 r = -0,032

r = -0,036 r = -0,040 ESM_scan ESM_scan-center

Elevation Sun (at ESM acquisition); misalignment: p = - 0.016; r = variable; y = 0.000

25,20

25,25

25,30

25,35

25,40

25,45

25,50

440 450 460 470 480 490 500 510 520 530 540 550


Ele

vati

on

(°)

no misalignment inst-mis-only r = -0,004 r = -0,008 r = -0,012

r = -0,016 r = -0,020 r = -0,024 r = -0,028 r = -0,032

r = -0,036 r = -0,040 ESM_scan ESM_scan-center



Example: Solar Occultation Elevation – Yaw

Elevation Sun (at ESM acquisition); misalignment: p = - 0.016; r = - 0.020; y = variable

25,15

25,20

25,25

25,30

25,35

25,40

25,45

440 450 460 470 480 490 500 510 520 530 540 550


Ele

vati

on

(°)

no misalignment instrument misalignment only y = -0,04 y = -0,08

y = -0,12 y = -0,16 y = -0,20 y = -0,24

y = -0,28 y = -0,32 y = -0,36 y = -0,40


Elevation Sun (at ESM acquisition); misalignment: p = - 0.016; r = - 0.020; y = variable

25,15

25,20

25,25

25,30

25,35

25,40

25,45

440 450 460 470 480 490 500 510 520 530 540 550


Ele

vati

on

(°)

no misalignment instrument misalignment only y = -0,04 y = -0,08

y = -0,12 y = -0,16 y = -0,20 y = -0,24

y = -0,28 y = -0,32 y = -0,36 y = -0,40




Example: Best Fit Roll – Subsolar Elevation (State 53)

Roll Variation vs Elevation

0,000

0,005

0,010

0,015

0,020

0,025

-0,040 -0,032 -0,024 -0,016 -0,008 0,000

Roll steps (°)

Sim

ula

ted

E

lev

ati

on

(°)

19822

19407

18978

18563

18148

17733

17303

15600

15170

14626

14326

13911

13481

13066

12651

12222

11806

11391

10962

10532

Roll Variation vs Elevation

0,000

0,005

0,010

0,015

0,020

0,025

-0,040 -0,032 -0,024 -0,016 -0,008 0,000

Roll steps (°)

Sim

ula

ted

E

lev

ati

on

(°)

19822

19407

18978

18563

18148

17733

17303

15600

15170

14626

14326

13911

13481

13066

12651

12222

11806

11391

10962

10532



Subsolar - Results

best fit extra misalignments

- pitch pe = -0.019° ± 0.004°

- roll re = -0.020° ± 0.004°

- yaw ye = 0.000° ± 0.000°



Solar Occultation – Results

best fit extra misalignments

- pitch pe = -0.027° ± 0.002°

- roll re = not sensitive

- yaw ye = not sensitive



Summary

observed LoS anomalies (except azimuth jump in solar occultation) can be explained by extra misalignment:

pitch pe = -0.023°, roll re = -0.020°, yaw ye = 0.000°

estimated uncertainties ± 0.002° - 0.003° (equivalent to about 200 m at limb distance)

further simulations with smaller pe, re, ye steps required

sciamachy los mispointing modelling m. gottwald & e. krieg – dlr-imf - dlr/ife iup-ife,...

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