OMICalibration Status

18th OMI science team meeting

KNMI, de Bilt, 11 march 2014

KNMI, de Bilt, 11 march 201418th OMI science team meeting2

Overview

1. Instrument thermal control and stability

2. CCD thermal control and stability

3. CCD pixel quality statistics

4. OMI degradation monitoring principle

5. ELU gain ratios

6. CCD LED monitoring

7. WLS monitoring

8. Irradiance monitoring

9. Radiance monitoring

10.Wavelength calibration monitoring

11.OMI calibration status overview

KNMI, de Bilt, 11 march 201418th OMI science team meeting3

Instrument thermal control and stability

•Radiant cooler degrades

•no active thermal control

•Temperature follows ELU power consumption

KNMI, de Bilt, 11 march 201418th OMI science team meeting4

Instrument thermal control and stability

+0.80 K290.30 K289.50 KAUX electronics ELU

+0.80 K292.30 K291.50 KVIS electronics ELU

+0.90 K290.90 K290.00 KUV electronics ELU

+1.20 K265.20 K264.00 KOptical bench

trend20142004

KNMI, de Bilt, 11 march 201418th OMI science team meeting5

CCD thermal control and stability

ATC control loop imperfect(PI instead of PID)

Temperature follows OBMOBM follows cooler

KNMI, de Bilt, 11 march 201418th OMI science team meeting6

CCD thermal control and stability

-15 perc5 %20 %UV CCD ATC PWM

-14 perc10 %24 %VIS CCD ATC PWM

+0.05 K265.26 K265.21 KVIS channel CCD

+0.05 K265.18 K265.13 KUV channel CCD

trend20142004

•OMI has never been switched off over 10 years

•Near-perfect detector temperature control

•PWM margin can last until end of mission

KNMI, de Bilt, 11 march 201418th OMI science team meeting7

CCD pixel quality statistics (binned)

5%5%5%5%5%5%5%5%5%RTS

7%7%7%6%6%6%20%16%7%BAD

ARCTICMIDLATTROPARCTICMIDLATTROPARCTICMIDLATTROP

VISUV2UV1

• Detector degradation mainly occurs in SAA and polar belts

• Degradation on individual pixel level

• Caused by CCD bulk radiation damage by protons

• Shows increased darkcurrent

• Shows increased RTS

KNMI, de Bilt, 11 march 201418th OMI science team meeting8

CCD pixel quality statistics (unbinned)

Reduced performance Unusable pixels

• Operational CCD temperature were lowered• Detector shielding increased with 8 kg aluminum• Daily updates of background images to correct increased darkcurrent• Automatic updates of pixel quality maps• After 10 years 0.8 % is unusable (dead)• After 10 years 2.0 % has reduced performance (bad)

KNMI, de Bilt, 11 march 201418th OMI science team meeting9

OMI degradation monitoring principle

QVD diffuser D1ALU1 diffuser D2ALU2 diffuser D3

spectrometerS

telescopeM1

telescopeM2

folding mirrorFM

radiance = M1*M2*S*Eirradiance = D1*FM*M2*S*E

detector &electronics

E

KNMI, de Bilt, 11 march 201418th OMI science team meeting10

ELU gain ratios - UV

•Video chain gain switchable inflight

•4 discrete gains available

•Monitored using DLED and WLS

•Stability much better than 0.2%

KNMI, de Bilt, 11 march 201418th OMI science team meeting11

CCD LED monitoring (excludes spectrometer)

•degradation higher than irradiance -> not Quantum Efficiency effect

•Led voltage stable

•LED radiation damage / aging

KNMI, de Bilt, 11 march 201418th OMI science team meeting12

WLS monitoring (includes spectrometer)

•WLS voltage increasing

•Current source

•Power steadily increasing

•Tungsten filament ‘necking’

•Close to filament burn-out?

•Current source �voltage source

KNMI, de Bilt, 11 march 201418th OMI science team meeting13

Irradiance monitoring•QVD � daily

•ALU1 � weekly

•ALU2 � monthly

•Degradation includes D1 * FM * M2 * S * E

•Exposure based degradation

•Backup ALU does not degrade

•Degradation may include electronic effects

-2.3 %-3.0 %-4.5 %QVD total

-0.6 %-1.4 %-2.5 %QVD

-1.7 %-1.6 %-2.0 %other inc FM

0.9830.9840.980ALU2 path

0.9810.9820.974ALU1 path

0.9770.9700.955QVD path

VISUV2UV1

KNMI, de Bilt, 11 march 201418th OMI science team meeting14

Radiance monitoring

•Antarctic and Greenland Ice sheet reflectance model

•De-trended zonal ozone averages

•Degradation includes M1 * M2 * S * E

•Set of equations cannot be solved without assumptions or detailed model for degradation

UV1 : -1.0%UV2 : -0.5%VIS : -0.5%

Glen Jaross & Sergey Marchenko

KNMI, de Bilt, 11 march 201418th OMI science team meeting15

Wavelength calibration monitoring

0.002 nm0.002 nm0.002 nmseasonal [pp]

0.001 nm0.000 nm0.015 nmtrend

VISUV2UV1

•spectral stability in general good

•folding mirror anomaly from 28/02/2006 to 11/06/2006

•row anomaly

•spectral calibration switched on in L01b processor

KNMI, de Bilt, 11 march 201418th OMI science team meeting16

OMI calibration status conclusion

•Very low contamination levels in OMI result in record low degradation

•No measurable degradation of aluminum diffusers

•Very low degradation of novel Quartz Volume Diffuser

•Not possible to uniquely identify the degrading component

•Detector radiation damage monitored

•TMCF/TDOPF software solution for inflight calibration

•Daily updates for dark current

•Daily updates for bad and dead pixels

•Spectral stability very good

http://www.knmi.nl/omi/research/calibration/instrument_status_v3/index.html