Apr 17-22, 20061SOT17 @ NAOJ

Dopplergram from Filtergram (FG) Observation

Y. Katsukawa (NAOJ)SOT Team

Apr 17-22, 2006 SOT17 @ NAOJ 2

SOT Dopplergrams (DGs)

Narrowband Filter Imager (NFI) on SOT provides Dopplergrams (DGs) which are images of Doppler (line-of-sight) velocities. Observations with DGs are critically important in studies of photospheric dynamics and helioseismology.

The primary photospheric line used for DGs is Fe I 5576 Å which is a line insensitive to the Zeeman effect (Lande g=0).

FOV:80”x160” (1Kx2K) for no summing320”x160” (2Kx1K) for 2x2 summing

4 uniform wavelength samplings are a standard observable. It takes about 12 secs to make one Dopplergram. 1 30m/s for 2x2 summ.

Two wavelength sampling is also available when higher temporal resolution is required.

Apr 17-22, 2006 SOT17 @ NAOJ 3

5576A 4-wavelengths Dopplergrams

The nominal wavelength sampling for 5576A F1: -90mA, F2: -30mA, F3: +30mA, F4: +90mAUp to 3km/s velocities are detectable by this sampling.

The velocity index R is calculated using the 4 images

In order to reduce the telemetry amount, the denominator and the numerator are calculated on-board, and sent to the ground.

Denominator: F1-F2-F3+F4 Numerator: F1+F2-F3-F4

4321

4321

FFFF

FFFFR

DG obtained at Palo Alto in April, 2005

Apr 17-22, 2006 SOT17 @ NAOJ 4

5576A 4-wavelengths Dopplergrams

Fe I 5576A spectrum and the transmission profiles of TF at 4 wavelength positions.

The relation between the actual Doppler velocities V and the velocity indexes R are calculated using the ideal TF profiles and the atlas spectrum.

The Doppler velocities are derived from the velocity indexes R using LUT.

5575.0 5575.5 5576.0 5576.5 5577.0wavelength (A)

0.0

0.2

0.4

0.6

0.8

1.0

norm

aliz

ed inte

nsi

ty

-4 -2 0 2 4Velocity indenx

-4

-2

0

2

4

Dopple

r velo

city

(km

/s)

QSUmbra

QSUmbra

Apr 17-22, 2006 SOT17 @ NAOJ 5

Quantitative evaluation of DGs

The data used here were obtained by FPP in April 19-20, 2005 at Palo Alto.

2x2 summing mode, 1Kx1K partial images Magnification is different from the actual telescope, and

the solar diameter is around 600 pixels (1/3 of full FOV). The Doppler velocity is evaluated along the latitudinal

lines at 0, 30, and 60.

Raw data of FG Dopplergram

Velocity index (R)

Apr 17-22, 2006 SOT17 @ NAOJ 6

Solar rotation speed obtained by SOT DGs

H1804/#17: Vel Index

-300 -200 -100 0 100 200 300-3-2-10123

velo

city

Index

H1804/#17: Velocity

-300 -200 -100 0 100 200 300-3-2-10123

velo

city

(km

/s) Lat=+60deg: -1.46 km/s

Lat=+30deg: -1.85 km/sLat= 0deg: -2.01 km/s

Lat= -30deg: -1.88 km/sLat= -60deg: -1.53 km/s

H1804/#17: Velocity residual

-300 -200 -100 0 100 200 300(pix)

-2

-1

0

1

2ve

l resi

dual (

km/s

)

H1804/#17: Vel Index

800 900 1000 1100 1200 1300(pix)

200

300

400

500

600

700

(pix

)

Apr 17-22, 2006 SOT17 @ NAOJ 7

Solar rotation speed obtained by SOT DGs

H1648/# 9: Vel Index

800 900 1000 1100 1200 1300 1400(pix)

200

300

400

500

600

700

800

(pix

)

H1648/# 9: Vel Index

-300 -200 -100 0 100 200 300-3-2-10123

velo

city

In

dex

H1648/# 9: Velocity

-300 -200 -100 0 100 200 300-3-2-10123

velo

city

(km

/s) Lat=+60deg: -1.12 km/s

Lat=+30deg: -1.58 km/sLat= 0deg: -1.65 km/s

Lat= -30deg: -1.56 km/sLat= -60deg: -1.39 km/s

H1648/# 9: Velocity residual

-300 -200 -100 0 100 200 300(pix)

-2

-1

0

1

2vel re

sid

ual (k

m/s

)

Apr 17-22, 2006 SOT17 @ NAOJ 8

The velocity profiles exhibit linear dependence on positions along the longitudinal lines as expected.

The velocities of the solar rotation obtained by FPP are roughly consistent with the expected one. Systematic difference is 200m/s

But there is time variation in the obtained velocity, and the deviation from the theoretical prediction is about 400m/s in the worst case.

Apr 17-22, 2006 SOT17 @ NAOJ 9

Intensity ripple through wavelength scan

2.0

4.0

6.0

8.0

0.1

no

rma

lize

d in

ten

isty

0001- 005- 0 005 0001)Am(

0.8

0.9

1.0

1.1

1.2

norm

alize

d inte

nis

ty

-1000-500 0 500 1000(mA)

Solar spectrum

Lamp source

Apr 17-22, 2006 SOT17 @ NAOJ 10

Effect of the intensity ripple on DGs

The intensity ripple can be reproduced by including errors in the wide field elements of the calcite blocks in TF.

The relation between the velocity indexes and the Doppler velocities is reexamined using the TF profiles including the ripple. The deviation from the ideal case is 1 km/s in the worst case.

5575.0 5575.5 5576.0 5576.5 5577.0wavelength (A)

0.0

0.2

0.4

0.6

0.8

1.0

norm

aliz

ed inte

nsi

ty

5575.0 5575.5 5576.0 5576.5 5577.0wavelength (A)

0.0

0.2

0.4

0.6

0.8

1.0

norm

aliz

ed inte

nsi

ty

-4 -2 0 2 4Velocity indenx

-4

-2

0

2

4

Dopple

r ve

loci

ty (

km/s

)

5575.0 5575.5 5576.0 5576.5 5577.0wavelength (A)

0.0

0.2

0.4

0.6

0.8

1.0

norm

aliz

ed inte

nsi

ty

-4 -2 0 2 4Velocity indenx

-4

-2

0

2

4

Dopple

r ve

loci

ty (

km/s

)

Ideal

with ripple

difference

Ideal

with ripple

difference

Apr 17-22, 2006 SOT17 @ NAOJ 11

Errors caused by I-ripple and satellite revolution

Fine tuning of the wavelength against solar originated absorption lines is important for deriving physical parameters from the obtained data by NFI. Adjustment of TF wavelength is performed in FPP by using Doppler velocities value calculated in MDP.

The largest velocity is caused by the revolution of the satellite around the earth. The maximum velocity is 3.9 km/s in a period of about 95mins.

In the worst case, about 1 km/s velocity offset is produced by the intensity ripple.

-4 -2 0 2 4velocity index

0.0

0.2

0.4

0.6

0.8

1.0

ph

ase

of

the r

evo

luti

on

-4 -2 0 2 4velocity index

0.0

0.2

0.4

0.6

0.8

1.0

-2

-1

0

1

2

Dop

ple

r velo

city (km/s)

Simulated error of the Doppler velocities caused by the intensity ripple and the Doppler motion of the satellite.

Apr 17-22, 2006 SOT17 @ NAOJ 12

FOV non-uniformity

Full-FOV DG with 2x2 summing

The solar diameter is 1.5 times larger than FOV

Velocity profiles along the latitudinal lines show relatively large FOV non-uniformity than expected.

Apr 17-22, 2006 SOT17 @ NAOJ 13

Calibration of the intensity ripple

When the intensity ripple is caused by the halfwave plates in the calcite blocks, the intensity modulation can be represented as a function of the motor positions (provided by encoders) of the tuning elements.

Calcite block Motor pos

Calcite-02*(Motor-0)+(Motor-1)

Calcite-1 (Motor-1)

Calcite-22*(Motor-2)+(Motor-3)

Calcite-3 (Motor-3)

Calcite-42*(Motor-4)+(Motor-5)

Calcite-5 (Motor-5)

Calcite-62*(Motor-6)+(Motor-7)

Calcite-7 (Motor-7)

)sin(7

00 i

iiii baII

ia

ib

: Intensity amplitude for ith calcite block (Position dependent)

: Phase of the motor position for ith calcite block (Position dependent)

i : Motor positions corresponding to ith calcite block

ai (x,y) and bi (x,y) will be stored in the data base.

Apr 17-22, 2006 SOT17 @ NAOJ 14

5576A: Amplitude and phase map

Calcite-2: Amplitude

0 500 1000 1500 20000

200

400

600

800

1000

0.03 0.04 0.05 0.06 0.07Calcite-2: Phase

0 500 1000 1500 20000

200

400

600

800

1000

70 75 80

Calcite-3: Amplitude

0 500 1000 1500 20000

200

400

600

800

1000

0.010 0.015 0.020 0.025 0.030Calcite-3: Phase

0 500 1000 1500 20000

200

400

600

800

1000

-10 -8 -6 -4 -2 0 2 4

Calcite-6: Amplitude

0 500 1000 1500 20000

200

400

600

800

1000

0.02 0.04 0.06 0.08Calcite-6: Phase

0 500 1000 1500 20000

200

400

600

800

1000

-20 0 20 40

Calcite-6

Calcite-2Amplitude Phase

Amplitude Phase

Amplitude Phase

Calcite-3

Apr 17-22, 2006 SOT17 @ NAOJ 15

Spectra after calibration of I-ripple: 5576A

Fe I 5576A

Black: After correctedRed: Atlas +TF ideal profiles

Black: Measured Red: Atlas +TF ideal profiles

0.2

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alize

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ty

-1000-500 0 500 1000(mA)

2.0

4.0

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no

rma

lize

d in

ten

isty

0001- 005- 0 005 0001)Am(

Apr 17-22, 2006 SOT17 @ NAOJ 16

Position-dependent LUT

Dopplergram FITS data will have the motor positions of the tuning elements for the 4 exposures.

From the motor positions in a FITS data and the stored I-ripple function (amplitude and phase), generate a position-dependent look-up-table.

Doppler velocity: V(R, X, Y)

-4.0

-2.0

0.0

2.0

4.0

Dopple

r vel (k

m/s

)

-4 -2 0 2 4V index

-4

-2

0

2

4

Y

XV index

Vel

ocity

R: Velocity index(X, Y): Position in FOV

Apr 17-22, 2006 SOT17 @ NAOJ 17

DG after I-ripple calibration

Velocity offsets and linearity are　improved.

More improvement might be possible.

Before calibration After calibration

Apr 17-22, 2006 SOT17 @ NAOJ 18

Current status

The data sets necessary to build the calibration function were obtained in the ground-based test.

The preliminary calibration data base and the S/W to generate the position-dependent LUT have been produced, but are still necessary to be tested.