Technical Note - IACiac.es/proyecto/IMaX/Public/OpticsCDR/SUN-IMaX-TN-GEN... · 2009. 11. 17. ·...

TITLE

IMaX Technical Note

Observing modes for IMaX

Code : SUN-IMaX-TN-GEN-003 Issue : 2B Date : 27/JUL/04 No. of pages : 18

Config. Doc. : No

IMaX – A Magnetograph for SUNRISE

http://www.iac.es/proyect/IMaX

IMaX Technical Note


Code: SUN-IMaX-TN-GEN-003 Issue: 1B Date: 27/JUL/04 Page: 2 of 18

Approval control

Prepared by

Valentín Martínez

IAC

Revised by

Manuel Collados

IAC

Approved by

Lieselotte Jochum

IAC

Authorized by

Valentín Martínez

Date:

IAC

27/JUL/04

IMaX is a joint development by a consortium of four institutions

Instituto de Astrofísica de Canarias (IAC)

Instituto de Astrofísica de Andalucía (IAA)

Instituto Nacional de Técnica Aeroespacial (INTA)

Grupo de Astronomía y Ciencias del Espacio (GACE)

IMaX Technical Note



Changes record

Issue Date Section Page Change description 1A 14/01/03 All All First Issue 1B 28/04/03 All All Template change 2A 26/05/04 All All Major revisions including new info on etalons and

ROCLIs 2B 27/07/04 5-7 New photon budget applied. Included deep

magnetograph mode and data rates.

IMaX Technical Note



Applicable documents

Nº Document title Code Issue

AD1 Sunrise Science Requirements SUN-MPAe-SP-GEN-003 1A

Reference documents

Nº Document title Code Issue

RD1 Elmore, D., 1994, Solar-B proposal, HAO internal communication.

RD2 del Toro Iniesta, J.C., Collados, M., 2000, Appl. Optics 39, 10, 1637 RD3 Technical Note on ROCLI modulation SUN-IMaX-TN-IX200-021 1A RD4 Photon Flux Budget SUN-IMaX-TN-GEN-002 4A

IMaX Technical Note



List of acronyms and abbreviations

IMaX Imaging Magnetograph eXperiment

TBD To Be Determined

TBC To Be Confirmed

IMaX Technical Note



CONTENTS

Approval control ......................................................................................................................... 2

1. INTRODUCTION............................................................................................................ 7

2. MODULATION SCHEMES WITH ROCLIS .............................................................. 7

3. SPECTRAL MODULATION WITH LINBO3 ETALONS........................................ 10

4. POLARIZATION AND WAVELENGTH TUNING.................................................. 12

4.1 FAST POLARIZATION TUNING MODE (FPTM).................................................................. 12

4.2 FAST WAVELENGTH TUNING MODE (FWTM)................................................................. 12

4.3 INTERMEDIATE TUNING MODE (ITM).............................................................................. 13 5. SCIENCE OBSERVING MODES FOR IMAX .......................................................... 13

5.1 MODE 1: VECTOR SPECTROPOLARIMETRY ....................................................................... 14

5.2 MODE 2: VECTOR MAGNETOGRAPH ................................................................................. 14

5.3 MODE 3: LONGITUDINAL SPECTROPOLARIMETER ............................................................ 15

5.4 MODE 4: LONGITUDINAL MAGNETOGRAPH...................................................................... 15

5.5 MODE 5: DEEP MAGNETOGRAPH MODE............................................................................ 16 6. IMAX DATA RATES .................................................................................................... 16

7. SUMMARY OF IMAX OBSERVING MODES ......................................................... 17

IMaX Technical Note



1. INTRODUCTION

The Imaging Magnetograph eXperiment (IMaX) should have a set of basic observing modes to comply with the Science Requirements Document (SRD, AD1). Each of these modes will observe a different subset of the Stokes parameters, achieve a certain S/N, observe a number of wavelength points during a given observing mode time.

In this TN, we describe these observing modes and provide for each of them the associated science requirements and experiments as proposed in the SRD. Two important technical constrains in the definition of the observing modes are the performance of Liquid Crystal Variable Retarders (ROCLIs) for polarization modulation and the performance of LiNbO3 etalons for spectral modulation. These issues are discussed in sections 2 and 3 and have little description of the observing modes themselves. Section 4 describes how one can interlace polarization and wavelength tuning. Section 5 describes the observing modes themselves. Section 6 estimates the data rates produced in each mode and Section 7 summarizes their properties.

2. MODULATION SCHEMES WITH ROCLIS

IMaX will use liquid crystal variable retarders (ROCLIs) to produce the polarization modulation. We baseline here the use of 2 ROCLIs (produced by TECDIS Display Ibérica in collaboration with the IAC) to produce the modulation schemes needed by the observing modes.

Modulation schemes using two ROCLIs have been extensively studied in the past (Elmore, 1994). A very flexible configuration uses a first LCVR with its fast axis at 0o (i.e. aligned with the final linear polarizer) and retardance ρ (depending on the input voltage V1) and a second LCVR with the fast axis at 45o and retardance σ (for an input voltage V2). Finally, the IMaX polarizing beamsplitter makes the linear polarization analysis. In this configuration the detected intensity is a linear combination of the Stokes parameters as given by:

ρρσσ

ρρ

σσ

ρσρσσ

sin,cossin,cos

====

−++=

scsc

VcsUssQcII D

(1)

Figure 1: LCVR ρ LCVR σ Linear Polarizer

IMaX will have an observing mode (vector mode hereafter) where the full Stokes vector (I,Q,U,V) will be measured and, also, a longitudinal mode where only I and V will be observed (longitudinal mode). The former configuration allows easily arranging both modes.

IMaX Technical Note



For the vector mode, we look for four independent linear combinations (I1, I2, I3, I4) where all four Stokes parameters are equally weighted. By equating the coefficients that multiply the Stokes parameters one finds that the retardance values needed are ρ=[45,135,225,315], σ=[54.736,125.264,234.736,305.264].

Using these angles the coefficients multiplying the Stokes parameters in equation (1) are all equal to

31

± .

Noting that ROCLIs at low voltage have high retardance values and that large jumps increasing the retardance (decreasing voltage) correspond to long ROCLIs switching times, we propose to use the following set of retardance values:

[ρ1, ρ2, ρ3, ρ4]=[315,315,225,225]

[σ1, σ2, σ3, σ4]=[305.264, 54.736, 125.264, 234.736], (2)

which produce four accumulation states given by:

VUQII

VUQII

VUQII

VUQII

31

31

31

31

31

31

31

31

31

31

31

31

4

3

2

1

−+−=

+−−=

−−+=

+++=

(3)

From the accumulated intensities (I1, I2, I3, I4) one recovers the Stokes parameters by simple inversion:

4321

4321

4321

4321

43

43

43

43

43

43

43

43

43

43

43

43

41

41

41

41

IIIIV

IIIIU

IIIIQ

IIIII

−+−=

+−−=

−−+=

+++=

(4)

Using this vector modulation scheme the so-called modulation efficiencies (see del Toro Iniesta and Collados, 2000) attain their maximum values:

[εI, εQ, εU, εV]=[1, 3

1 ,3

1 ,3

1 ]. (5)

In practice, these efficiencies will only be achieved if the switching times were infinitely small and the applied voltages exactly correspond to the retardances given in (2). Finite switching times and voltage-retardance calibration miss calibrations will decrease the efficiencies by an

IMaX Technical Note



amount that is TBD. However, extensive laboratory measurements with the TECDIS-IAC ROCLIs have been carried out including changing the order of the combination in (2). The results (as explained in RD3) are that all the combinations have a slow change (30-40 ms), an intermediate transition (20 ms) and two fast transitions (less than 10 ms). The differences between the modulation efficiencies of these combinations are indeed very small and they are always larger than 0.5 (vector mode), which is perfectly acceptable. So the order proposed in (2) must be chosen as IMaX baseline.

Figure2: calibration of one of the ROCLIs of TECDIS showing the voltages and retardance values given in equations

6 and 2 (ρ values in solid line; σ values in dotted lines).

If we use an LCVR from TECDIS with a 6 µm gap and liquid crystal of type ZLI-3449-100 (see Figure 2), the voltages needed for the retardances of equation (2) are (in volts):

[V(ρ1), V(ρ2),V( ρ3),V(ρ4)]=[2.444,2.444,3.101,3.101]

[V(σ1), V(σ2),V(σ3), V(σ4)]=[2.510,7.630,4.234,3.017] (6)

These voltages will be produced with an electronics that has a 5 mV resolution and an error of ±3 mV. Given the typical calibration curve of an LCVR these voltage errors produce, in the end, calibration matrices that differ from the expected one (equation 3) by only a few 10-3.

For the longitudinal mode, the situation becomes simpler. Inspection of equation (1) shows that by zeroing the effect of the first LCVR (i.e. setting ρ to 0o or, in practice, to 360o) and making a quarter wave plate of the second LCVR (i.e. setting σ to 90o or to 270o) only the Stokes V parameter is measured, with no contributions from Q and U.

In this case only two accumulation states are used with the retardance values:

[ρ1, ρ2]=[360,360]

[σ1, σ2]=[90,270] (7)

now that one measures the accumulation states:

IMaX Technical Note



VIIVII

+=−=

2

1 (8)

that provide I and V in trivial ways.

Figure3: calibration of one of the ROCLIs of TECDIS showing the voltages and retardance values given in equations

9 and 7 (ρ values in solid line; σ values in dotted lines).

Note that for the first LCVR we cannot use 0o as uncompensated ROCLIs always produce some residual retardance even at very high voltages. Instead, one sets this LCVR to a retardance of 360o. The voltages that one uses in this longitudinal mode can be seen in Figure 3, whose exact values are (in volts):

[V(ρ1), V(ρ2)]=[2.199,2.199]

[V(σ1), V(σ2)]=[5.221,2.750] (9)

Although this set-up easily allows switching from vector mode to longitudinal mode with minor efforts, we caution that in this longitudinal mode we are switching half of the time between 90o→270o. This switching mode has proven to be very slow in the response time measurements at IAC, with values not smaller than 40 ms which represents 20% of a typical exposure time of 200 ms. This must be borne in mind when defining the IMaX observing modes.

3. SPECTRAL MODULATION WITH LINBO3 ETALONS

LiNbO3 etalons are solid etalons very suitable to perform spectral selection in observing platforms where stable conditions cannot be granted. In particular, the commercially available CSIRO etalons with a thermally controlled enclosure are a robust option with good optical performance and has been selected for the spectral modulation in IMaX: They can be tuned within our spectral line by applying adequate voltages, easily reaching a resolution better than 50000, and allowing for a repeatable performance (due to their solid nature). In the definition of the observing modes the most important property of the LiNbO3 is the tuning speed, the time needed to tune the etalon a given amount. To see the constraints imposed by this tuning speed it is necessary to define the wavelengths where IMaX will be mapping the spectral profile.

IMaX Technical Note



Figure4: Spectral scans proposed by IMaX: Mode with 5 wavelengths (4+continuum, left) and Mode with 3 wavelengths (2+continuum, right).

The proposed spectral positions for the IMaX scans are shown in Figure 2. The Stokes I and V profiles correspond to FTS data convolved with the instrument profile given in red. Two scans are baseline. The first uses 5 wavelength positions with locations from line center (5250.665 Å) of [–0.20, -0.09, -0.04, 0.04, 0.09] Å, with the first one corresponding to a continuum window and the other four to points within the line (dotted and dashed lines in left of Fig. 4). The mode with three wavelength positions uses the locations [-0.20, -0.06, 0.06] Å (dotted and dashed lines in right of Fig. 4). The wavelength jumps used by these scanning modes are:

5 wavelengths: [0.11,0.05,0.08,0.05,0.29] Å

3 wavelengths: [0.14,0.12,0.26] Å

It is clear that there are two groups of tuning ranges. The first one is in the range 0.05 to 0.14 Å and the second corresponds to the large steps needed to reach the continuum at the end of the line scans, which amount to 0.29 Å and 0.26 Å. CSIRO has used a tuning speed of at most 1500 V/s. If we consider that one typically needs 4000 V to tune 1 Å, tuning of 0.14 Å needs 0.37 seconds and 0.29 Å needs 0.77 seconds. The CCD exposure time is 0.2 seconds and the easiest way to accommodate these tuning times is by throwing away those images taken while we tune the etalon. Then, for a 0.14 Å we would be using two CCD exposures lasting 0.4 seconds and for 0.29 Å, four exposures. These numbers are indeed too large and would impose long delay times in the observing sequence. We have thus decided to test higher tuning speeds with a raw etalon of the same thickness as the real ones. This raw etalon will be tested for tuning speeds of 3000 V/s. In this case, the 0.14 Å step would require 0.187 seconds (one CCD exposure). The 0.29 Å would need 0.387 seconds or two CCD exposures. Making this biggest jump in only one CCD exposure would require driving the etalon at 6000 V/s, which seems too risky with our current knowledge. The delay times inferred for the 3000 V/s (or 0.75 Å/s) will be adopted when computing the total exposure time of each observing mode.

The number of frames lost for each mode is:

5 wavelengths: [1,1,1,1,2] total of 6 frames

3 wavelengths: [1,1,2] total of 4 frames

IMaX Technical Note



4. POLARIZATION AND WAVELENGTH TUNING

From the previous section it can be seen that the typical tuning times of the etalon are in the range of 200 ms while for the ROCLIs one typically uses tuning times that are one order of magnitude slower. This indicates that in order to produce the fastest possible tuning of wavelength and polarization it is advisable to run with the fastest speed for the polarization tuning and used the minimal number of wavelength steps. Modes that produce faster wavelength scanning and slower polarization modulation are also explained in this section but they offer a slower performance.

In what follows, the CCD will be taking data with a cadence τ . This time corresponds to the time needed to obtain one frame at a given wavelength, modulation state and per accumulation. We then observe wavelength points, polarization modulation states and accumulate frames until the desired S/N (1000 unless specified otherwise) is reached.

λN pN AN

4.1 Fast Polarization Tuning Mode (FPTM)

In this mode one fixes the wavelength λ and tunes over all polarization modulation states (4 in vector mode, equation 2, and two in longitudinal mode, equation 7). This is repeated a number of times to increasing the S/N to the final target. Then one tunes the etalon to the next wavelength. If the tuning jump is smaller than 0.15 Å a delay time of is introduced (expected to be one CCD exposure). When the final wavelength has been reached, a jump of almost 0.3 Å is needed, requiring a delay time of t (two CCD exposure times). The total time expend in one single wavelength is clearly

AN

dt

D

Ap NNτ . If we now include the wavelength scanning with the delay times as before, the total time of FPTM is:

DdApFPTM ttNNNN +−+= )1( λλττ (10)

and where the effective time expend measuring solar photons is

λττ NNN Apeff = . (11)

The duty cycle is normally referred to as the ratio FPTMeff ττ / .

The accumulation is done here in the polarization modulation states, so one needs to keep in the memory of the system a total of images (the factor 2 corresponds to the 2 detectors used). The ROCLIs are run at a frequency of 5 Hz while the etalon goes at a much slower frequency. The number of CCD frames thrown out while tuning the etalon is

pN2

τλ /))1 Dd ttN +(( − . Note that in this mode the time expend between the observations of the first wavelength and the last one is considerably large. This must be compatible with the scientific objectives.

4.2 Fast Wavelength Tuning Mode (FWTM)

In this mode one fixes the ROCLIs polarizations to one of the modulation states ( ρσ ) and tunes over all wavelengths (with the required delay times). The time needed for one modulation state is

λN

Dd tNtN +−+ )1( λλτ . This process is repeated a number of times to AN

IMaX Technical Note



reach the desired the S/N as before. Only after this, one tunes the ROCLIs to the next modulation state. The total time needed for FWTM is:

))1(( DdApFWM ttNNNN +−+= λλττ (12)

the effective time used measuring solar photons is, of course, the same as before whereas the duty cycle is FWTMeff ττ / .

The accumulation is done here in selected wavelength points, so one needs to keep in the memory of the system a total of images. Now the etalon performs the fastest modulation and, due to the slower tuning times (compared to ROCLIs), the total times employed in this mode will be much larger (note that the delay times are multiplied by ).

λN2

Ap NN

The number of CCD frames not used is τλ /))1(( DdAp ttNNN +− . Note that in this mode the time expend between the different wavelengths is minimized but the different polarization modulation states, at a given wavelength, will have a maximum separation in time. Once again, this must be compatible with the scientific objectives.

4.3 Intermediate Tuning Mode (ITM)

This mode offers an intermediate solution between the two previous modes. In this mode one fixes the etalon at one wavelength and tunes the ROCLIs over the polarization modulation states. After each cycle is completed, the etalon is tuned to the next wavelength and one repeats the polarization modulation as before. This is done for all wavelengths in a time of

pN

Ddp tNtNN +−+ )1( λλτ and the whole process is repeated a number of times to reach the desired S/N. The total time needed for the ITM is:

AN

))1(( DdpAITM ttNNNN +−+= λλττ (13)

the effective time stays the same and the duty cycle is ITMeff ττ / .

Note that now the delay times are multiplied only by so this mode makes a better use of the observing time than FWTM. Both, wavelengths and polarization modulation states are distributed over the total observing mode and none of them suffers from extreme lags between the first and the last modulation time. In this sense, this is the most balanced observing mode. The number of unused CCD frames is also intermediate

AN

τλ /))1(( DdA ttNN +− . The main disadvantage of this mode is that now accumulations are made in the frames and the amount of memory needed is considerably larger.

λNN p

5. SCIENCE OBSERVING MODES FOR IMAX

In this section, we describe the 5 science observing modes of IMaX and compute the time needed for each one of the modulation sequences described above. Calibration modes for IMaX are not included here. Here it is assumed that the CCD frame rate is 5 Hz or 2.0=τ seconds. The delay times for tuning the etalon are 2.0=dt seconds and 4.0=Dt seconds. To these times, it is TBD if another delay time must be added to the observing modes in order to comply with the bandwidth assigned to IMaX (see section 6). This bandwidth (600 KB/s) falls a factor 2 too short if these modes were to run continuously.

IMaX Technical Note



For each observing mode we also provide the expected time needed to compress the images used in each one of them. It is expected that IMaX needs 1.2 seconds to compress one image and the time of each of the modes needs to be larger than the time needed for the compression of all the images. Actually image compression speed becomes one of the major speed limitations in IMaX.

For each observing mode, we explain the degree of compliance of IMaX requirements and also point out which of the prototypical SUNRISE experiments explained in document AD1 do apply.

5.1 Mode 1: vector spectropolarimetry

This mode is considered to provide data that can be introduced into some form of inversion code for the retrieval of atmospheric parameters, either Milne-Eddintong type or, in some cases, SIR-like code with a small number of depth nodes.

In this mode we have for vector polarimetry and 4=pN 5=λN with 4 points scanning the spectral line and one in the continuum. In RD4, it is shown that the actual photon flux budget imposes and the modulation schemes have a timing of: 7=AN

• 20.29=FPTMτ seconds with a 96 % duty cycle.

• 60.61=FWTMτ seconds with a 45 % duty cycle.

• 40.36=ITMτ seconds with a 77 % duty cycle.

The IMaX requirements (IMaX-4) ask for this mode to be done in 20-30 seconds. As it can be seen only the FPTM reaches a similar value, on the close side of the upper limit. We believe this is within the acceptable range for this mode, but an effort should be made not to increase this time. The only option in which this time can be reduced is by getting a higher photon throughput in IMaX (see RD4) and, may be, combining this with a CCD running at 7 Hz (the limit in the present cameras). But there is a lower limit to how fast this mode can run set by the compression of the images. Note that the total number of images is requiring at least 24 seconds for them to be compressed.

20=λNN p

In FPTM only 4 images (polarization modulation states) are stored in memory during the accumulations (per CCD camera). ITM is in principle excluded, but the better integrity of the data in this mode (that combines polarization and wavelength scanning) should be traded off scientifically. In this case one would store 20 images per CCD camera in the system memory.

Relevant to prototypical experiments: A3, B4, C3, D1

5.2 Mode 2: vector magnetograph

When, from a scientific point of view, one needs vector magnetic fields and LOS velocities at a higher cadence, this mode should be preferred. No inversions are planned for this type of data. In this mode we have for vector polarimetry but 4=pN 3=λN . As before . The resulting exposing times are:

7=AN


IMaX Technical Note





IMaX requirements (IMaX-4) ask for this mode to be done in 10-20 seconds and it is clear that only one mode is within this range. FPTM offers the fastest performance and is again selected as baseline. The number of images is now, 12=λNN p which requires a minimum time of 14.4 seconds. As before, 4 memory locations are needed for this mode.

Relevant to prototypical experiments: A1, A2, A3, B2, B3, C1, C2, D3

5.3 Mode 3: longitudinal spectropolarimeter

This mode uses the longitudinal modulation scheme explained in section 2, where only I and V are observed. In this mode we have 2=pN and 5=λN . Inversion methods are envisaged also for this mode. As only two Stokes parameters are observed the modulation efficiencies are higher and now 4=AN . The resulting exposing times are accordingly much smaller:



• 80.12=ITMτ seconds with a 63 % duty cycle

IMaX requirements (IMaX-4) ask for this mode to be done in less than 10 seconds. Only FPTM complies with this requirement. But the time needed for the compression now is 12 seconds as one uses . Thus we recommend here to use ITM. This has an additional bonus in terms of the tuning of the ROCLIs in this mode. One of the ROCLIs transition needed for the longitudinal modulation is particularly slow (the 90

10=λNN p

o→270o). By using ITM, the etalon tuning step can also be used to tune this ROCLI transition.

In this mode the number of images maintained in memory during the accumulation process is 10.

Relevant to prototypical experiments: B1, B2, D3

5.4 Mode 4: longitudinal magnetograph

This mode is the same as before but only three wavelengths are observed. Now we have and with also four accumulations as before. The resulting exposing times are: 2=pN 3=λN




IMaX Technical Note



IMaX requirements (IMaX-4) ask for this mode to be done in a time between less than 5 seconds. Again FPTM is the only one that approaches this value. The number of images is

which requires 7.2 seconds for compression, so indeed only ITM would be an option here. For the same reasons as before, we recommend to use ITM with 6 memory locations per CCD.

6=λNN p

Relevant to prototypical experiments: A1, B1, B3, D2

5.5 Mode 5: deep magnetograph mode

For various scientific reasons (see AD1) a mode where one could increase the S/N to much higher values is desirable. In this mode, only one wavelength point will be continuously observed with no etalon tuning. The observed wavelength will be one of the two wavelengths observed in the longitudinal mode inside the spectral line. The polarization modulation will be done only in longitudinal mode so in the end 2 images (equation 8) integrated for a long period of time will be obtained. It is advisable to use this mode sandwiched in between two runs of the longitudinal magnetograph mode that can be used for reference.

Figure5: Number of accumulations and total exposure time needed for a given S/N

The increased S/N will be achieved by changing the number of accumulated images depending on the desired S/N. Figure 5 shows the dependence between these variables. Of course the total exposure time increases linearly with the number of accumulated images. For example, for a S/N of about 10000, 400 accumulations are needed with an exposure time near 2.5 minutes. The IMaX sensitivity will be increased from <10 Mx cm-2 to <1 Mx cm-2.

Relevant to prototypical experiments: A2

6. IMAX DATA RATES

The IMaX data generation rates in each of the different observing modes must be compared with the 660 KB/s bandwidth given to the instrument. The IMaX CCDs are 1024x1024 pixels each (IMaX uses 2 CCDs) with 2 Bytes per pixel. The compression algorithm expects to

IMaX Technical Note



achieve a lossless compression factor of about 3. With this input, the data rates of each of the observing modes are

1. Vector spectropolarimeter: 20 images in 29.20 seconds. Data rate: 957 KB7s

2. Vector magnetograph: 12 images in 17.60 seconds. Data rate: 953 KB/s

3. Longitudinal spectropolarimeter: 10 images in 9.20 seconds. Data rate: 1520 KB/s

4. Longitudinal magnetograph: 6 images in 5.60 seconds. Data rate: 1498 KB/s

5. Deep magnetograph: 2 images in 160 seconds. Data rate: 17 KB/s

From these numbers it is clear that the average IMaX data rate (1300 KB/s) is about twice the available bandwidth. If no increase in bandwidth is produced, this implies in practice:

• IMaX can only work during half of the flight time

• The observing modes should include a dead time of an amount similar to the time needed for the observations (and when IMaX would do no further observations). In this case, the limitations imposed by the compression time would disappear and an improve photon performance could be achieved. For example the mode of vector spectropolarimetry could be done in 25 seconds or so and after that one has 35 seconds of quiet time where further compression and routine work could be done, but without acquiring more data. In this case, the effective cadence of the vector spectropolarimetric mode would be of order 1 minute.

7. SUMMARY OF IMAX OBSERVING MODES

We list in the following table the main properties of the five observing modes described in this TN.

Table 1. IMaX Observing Modes

Observing Mode Np Nλ NA τ(s) Images Memory Tuning Mode

Data rate

(KB/s)

Vector Spectropolarimeter

I,Q,U,V 5 7 29.20 20 4 FPTM 957

Vector Magnetograph

I,Q,U,V 3 7 17.60 12 4 FPTM 953

Longitudinal

Spectropolarimeter

I,V 5 4 9.20 10 10 ITM 1520

Longitudinal

Magnetograph

I,V 3 4 5.60 6 6 ITM 1498

Deep

Magnetograph

I,V 1 <400 <160 2 2 Fixed

λ

17

IMaX Technical Note



The columns on the table provide the observing modes, the observed polarizations, the number of wavelengths (including continuum), the number of accumulations used, the time used for this mode, the number of images produced during the operation of this mode, the number of memory buffers needed (of 1024 by 1024 pixels of 2 Bytes each), the polarization-wavelength tuning mode selected (see section 4) and the data rate associated with each mode.

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