eve calibrations: on-orbit calibrationslasp.colorado.edu/eve/eve_workshop/2005/... · dark, or...

EVE Calibrations:

On-Orbit Calibrations

Frank Eparvier

LASP / University of Colorado

[email protected]

EVE CalibrationsEparvier - 2EVE Science Workshop

November 9-11, 2005

Reminder that Calibration is a Lifetime Commitment

The Calibration Essentials:Understand the Measurement Equation:

Know all the parameters that go into the measurement to irradiance conversionand assess how to best quantify each

Do a thorough error analysis and uncertainty budget

Calibrate pre-flight:

Use a standard radiometric EUV source

Primary standards, such as NIST SURF-III source, are preferred (note: SURFbeam flux known to <1% for EUV ranges)

Track in-flight:

Any instrument changes that will affect results

E.g. detector flat fields, temperature effects, background signals, …

Re-Calibrate in-flight:

As close after launch as possible (changes since pre-flight calib.)

On a regular basis thereafter in order to track absolute changes

E.g. redundant channels, on-board sources, rocket underflights, proxy models

Validate:

With measurements made with other instrumentation

Comparisons with models


November 9-11, 2005

Levels of EVE Calibrations

Component Level:

Verification and selection testing on optical components and detectors

Instrument Level:

Calibrate parameters in measurement equation

Spacecraft Level:

Aliveness and functional testing only

On-Orbit Level:

Track changes in key parameters and re-calibrate with underflights


November 9-11, 2005

MEGS-A & B Parameter Calibrations and Tracking

X0.02%1-AU Correctionf1AU

XX2%Slit Image WeightfImage

X0.02%Integration Timet

XXXX34%SignalS

25%Irradiance

Product

EMeasured

2%

0.2%

18%

10%

12%

6%

8%

20%

20%

0.2%

2%

1%

Error

Budget

XXOrder SortingEOS

XXWavelength

XDegradation

Correction

fDegrad

XXFOV CorrectionfFOV

XXResponsivity at

Center

RC

XXDispersion

XSlit AreaASlit

XXXScattered LightCSL

XXXXBackgroundCBkg

XXDetector LinearityfLin

XXXXFlatfieldfFF

Spacecraft

Level

On-Orbit

Level

X

Instrument

Level

XGainG

Component

Level

Parameter

DescriptionSymbol


November 9-11, 2005

On-Orbit Level Calibrations

Inflight Tracking of ParametersFlatfield

Background

Scattered Light

Slit Image

Dispersion and Wavelength

1-AU

FOV Map

Order Sorting

Re-CalibrationDegradation

Responsivity

Validation


November 9-11, 2005

Flatfield

Need:

Track pixel-to-pixel changes that may occur due to burn-in,

contamination, radiation damage, ...

Method:

Built-in LED lamps:

Two LEDs per CCD (405 nm and 470 nm)

Do flatfields with each lamp on a daily basis


November 9-11, 2005

Why two flatfield lamps? Penetration Depths in Silicon


November 9-11, 2005

Background

Need:

Dark, or background signal may change over time due to changing

radiation background, damage, or other drift.

Method:

Shutter (filter wheel dark position) all channels at least once a day

MEGS-P and ESP also have dark (covered) diodes for continuous

background monitoring

MEGS-P and ESP darks may be correlated with shuttered MEGS CCD darks

to get a continuous relative background measurement for CCDs


November 9-11, 2005

Scattered Light

Need:

Degradation of the gratings may cause scattered light properties to

change

Method:

Similar analysis as pre-flight calibrations, but using solar spectrum and

built-in filters


November 9-11, 2005

Slit Image

Need:

Need to understand shape and locations of slit images on detector for

data processing

Note: don’t expect this to change with time, but will change with pointing,

on-orbit determination is check for pre-flight determination gathered at

LASP and SURF

Method:

Analysis of whole CCD images

Solar spectrum has lots of isolated lines to give slit image shape at different

wavelengths across detectors

FOV mapping provides information on how slit image moves and changes with

pointing.


November 9-11, 2005

Simulated CCD Images

MEGS-A

MEGS-B


November 9-11, 2005

Dispersion and Wavelength Scale

Need:

Determine wavelength scale for each spectrum, changes with FOV and

other factors

Don’t expect wavelength dependancies to change, but on-orbit

determination will be check for pre-flight (and will be better than pre-flight)

Method:

Each solar spectrum itself has lots and lots of lines for determining

wavelength scale.


November 9-11, 2005

1-AU

Need:

Want solar irradiance at a fixed distance from the Sun to isolate variability

due to Sun alone, but Earth and satellite orbital motions constantly

change that distance.

Note: this isn’t really an instrument calibration, but it is a tracking of a

parameter in the measurement equation.

Method:

Use satellite location information and Earth ephemeris


November 9-11, 2005

FOV Map

Need:

Track changes in FOV Responsivity Map over time

Method:

Special s/c operations to perform off-nominal pointing map using the Sun

as the source and SAM as the pointing reference.

Maps done on a quarterly basis:

Cruciform Scans: ±150 arcmin in 3 arcmin steps

Gives gross FOV changes and locates edges of FOV for relative boresight

calibrations to SAM and AIA guide telescope

FOV Maps: ±10 arcmin in 5 arcmin steps (5x5 map)

Gives finer FOV changes over nominal FOV pointing area (with margin)

Also get bonus mapping when AIA and HMI require maneuvers (though their

mappings are different and not optimized for EVE needs).


November 9-11, 2005

Order Sorting

Need:

Track any changes in higher order contributions as optics degrade.

Method:

Built-in Order-Sorting filters for each MEGS channel

Use on a daily basis as check compared to pre-flight


November 9-11, 2005

Degradation Tracking with On-Board Means

Reminder: EVE Primary

Measurements:

ESP Central Order: 0.1-7 nm

MEGS-A: 5-37 nm

MEGS-B: 34-105 nm

But EVE has other channels:

MEGS-SAM: 0.1-7 nm

ESP: 17.5, 25.6, 30.4, 36 nm

MEGS-P: 121.6 nm0.1

1

4

7

10

nm


November 9-11, 2005

On-Board Tracking

ESP, MEGS-P, and MEGS-SAM are nearly continuously observing.

These are fundamentally different instruments from the spectrographs.

ESP and MEGS-P diodes are reference detectors and not expected to

change rapidly or unexpectedly.

SAM is a pinhole camera with only a filter and the detector to degrade.

Comparisons of simultaneous measurements by primary and redundant

channels allow for tracking of relative changes between them.

MEGS-P Lyman- measurement is used as a proxy

Model based on TIMED-SEE data shows Ly- can be used to predict relative

irradiance changes in H and He emissions from 45-103 nm to better than 4%

Note: Since these extra channels are also on-board, they are subject to

drift and degradation and only provide a means for relative tracking.


November 9-11, 2005

Sounding Rocket Underflights

Sounding Rocket Payload:

Contains all EVE Channels: MEGS-A, B, SAM, P, and ESP

Will fly on a regular basis during the SDO mission

Note: first flight is fall 2006 as a test and to help calibrate TIMED-SEE

Will be calibrated at NIST-SURF before and after every rocket flight

Simultaneous measurements by SDO-EVE and Rocket EVE will allow for

transfer of ground calibration to satellite instruments

Multiple flights over mission allow for fitting of degradation curves to all

instruments (more frequent early on, since degradation tends to be

exponential)

Rocket timing for nominal mission: L+2 months, L+10, L+22, L+38,L+62


November 9-11, 2005

EVE Validation

Comparisons with other instruments that are potentially flying

SOHO-SEM: 0-50 nm, 26-34 nm

TIMED-SEE: 0-194 nm

SORCE: 0-27 nm, Ly-a

GOES-EUVS: Various EUV bands

SDO AIA: Integrated images at AIA bandpasses

GOES-SXI: Integrated images at SXI bandpasses

Non-US instruments: SOL-ACES, others?

Comparisons with models

NRLEUV

SOLAR2000

FISM

EUVAC, HEUVAC

Others?


November 9-11, 2005

Backup Slides


November 9-11, 2005

MEGS A & B Measurement Equation & Verification

Solar SpectrumSURF beam, Manson, and hollow cathode lampsOrder Sorting CorrectionEOS

Solar SpectrumSURF beam, Manson, and hollow cathode lampsWavelength

Orbit-1-AU Correctionf1AU

FOV mapsSURF FOV mapsFOV CorrectionfFOV

ESP, MEGS-P, Rocket

underflights-Degradation CorrectionfDegrad

Rocket underflight SURF

calibration transferSURF beam calibrationResponsivity at Center of FOVRCenter

Solar SpectrumSURF beam, Manson, and hollow cathode lampsWavelength Dispersion

-LASP metrologySlit AreaA

Solar SpectrumSURF beam, Manson, and hollow cathode spectraSlit Image Contributing PixelsfImage

Solar SpectrumSURF beam, Manson and hollow cathode lamp spectraScattered light CorrectionCSL

Dark mode calsDark mode calsDark CorrectionCDark

-SURF beam current adjustmentLinearity CorrectionfLin

MEGS LED lampsMEGS LED lampsFlat-field CorrectionfFF

-Electronics measurementGain CorrectionG

-Electronics measurementIntegration Timet

In-Flight Cal/TrackingPre-Flight Test/CalParameterSymbol

E =f Image S

t G fFF fLin CDark CSL( )[ ]A RCenter fDegrad fFOV f1AU

hcEOS


November 9-11, 2005

MEGS-SAM Measurement Equation & Verification

Solar SpectrumSURF beam, Manson

source, and hollow

cathode lamps

Wavelength


ESP, MEGS-P, Rocket underflights-Degradation CorrectionfDegrad

Rocket underflight transfer of SURF

calibrationSURF beam calibrationResponsivityR

Solar SpectrumSURF beam, Manson

source, and hollow

cathode lamps

Wavelength Dispersion

LASP metrologySlit AreaA

Dark mode calsDark mode calsDark CorrectionCDark

-SURF beam current

adjustmentsLinearity CorrectionfLin

MEGS LED lampsMEGS LED lampsFlat-field CorrectionfFF

-Electronics measurementGain CorrectionG

-Electronics measurementIntegration Timet


E =

St G fFF fLin

A R fDegrad f1AU

hc


November 9-11, 2005

ESP and MEGS-P Measurement Equation & Verification

Solar Spectrum

SURF beam, Manson

source, and hollow

cathode lamps

Wavelength Dispersion

Assumed shape/MEGS spectrumAssumed spectral shapeSpectral WeightingfWeight

Solar Spectrum

SURF beam, Manson

source, and hollow

cathode lamps

Wavelength


Rocket underflights-Degradation CorrectionfDegrad

Rocket underflight transfer of SURF

calibrationSURF beam calibrationResponsivityR

-LASP, JPL metrologySlit AreaA

ESP dark diode calsESP dark diode calsDark Current CorrectionSDark


E =S SDark

A R fWeight fDegrad( ) f1AU

hc

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