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Top > Suzaku > process > criteria(XIS)

Screening criteria for the XIS data in the version 2.0 processing

2007-07-01 by the XIS team
2007-10-01 revised by the XIS team

Screening of unfiltered XIS event files to create cleaned event files has four steps, as shown in the processing log file (aeNNNNNNNNN_joblog.html, which is in the "log" subdirectory. "NNNNNNNNN" represents a sequence number of the observation). The flow of the screening is as follows:
(1)Event selection based on the grade and pixel status
(2)Creation of Good Time Intervals (GTIs) in which some criteria are simultaneously satisfied
(3)Event extraction with the GTI
(4)Rejection of hot/flickering pixels
Thus, we provide here screening criteria adopted in the version 2.0 processing, for users to screen the unfiltered event files. We summarize the screening criteria below, followed by an example for creating the cleaned event files using XSELECT.

A. Summary of the screening criteria

Selection criteria for each XIS event are summarized in Table 1. Each XIS event is classified by the ASCA grades on the basis of the 3x3 pixel patterns. This task is performed with "xispi", the XIS-specific tools. Grade 0, 2, 3, 4, and 6 are selected as X-ray events. Furthermore, a pixel status is given for each event by "xisputpixelquality". In the cleaned event files, bad CTE (Charge Transfer Efficiency) columns and the Spaced-row Charge Injection (SCI) and its adjacent rows are already removed by the status selection. The ASCA grade and pixel status are defined as "GRADE" and "STATUS" columns in the event files.

Table 1: Selection criteria for each XIS event
Criterion Parameter meaning Responsible files
GRADE=0:0 2:4 6:6 ASCA grades.
Grade 0, 2, 3, 4, 6 are selected as X-ray events.
aeNNNNNNNNNxi[0-3]_N_{5x5,3x3,2x2}[nb]MMMZ_uf.evt.gz
(Unfiltered event file#)
STATUS=0:524287
or
STATUS<2**19
Pixel status(*).
Bad CTE columns are removed. For the observations with the SCI, the SCI and its preceding/trailing rows are also filtered out.
(*)Status values assigned to each XIS event is described in the help file of "xisputpixelquality".
(#)File name convention for the science data is described in the following URL: http://darts.isas.jaxa.jp/astro/suzaku/seq_v2data.html

Screening criteria to create the GTI file are given in Table 2. The listed items are related to the XIS data rate, the SAA passages, the satellite attitude, and the satellite position in orbit. The attitude sometimes has an offset of a few arcmin to the pointing position, just after the maneuver. Fine tuning of the attitude is done when the star tracker (STT) locks reference stars. Thus, we remove the initial settling period using "ANG_DIST".

Table 2: Screening criteria to create Good Time Intervals (GTIs)
Criterion Parameter meaning Responsible files
AOCU_HK_CNT3_NML_P==1 Attitude is controlled in the pointing mode.
Time intervals during maneuvers are removed.
aeNNNNNNNNN.hk
(common HK file)
ANG_DIST<1.5 Distance from the mean pointing position. (in unit of arcmin)
The initial settling period after the maneuver is removed.
aeNNNNNNNNN.ehk
(Extended HK file)
S[0-3]_DTRATE<3 Telemetry bit rate (Super High : 0, High : 1, Medium : 2, Low : 3).
Since small amount of telemetry is allocated to X-ray events, the telemetry is easily saturated in the data rate "Low". Therefore, time intervals in this data rate are removed.
aeNNNNNNNNNxi[0-3]_0.hk
(XIS HK file)
SAA_HXD==0 && T_SAA_HXD>436 Satellite is out of South Atlantic Anomaly (SAA).
Related parameters are defined as follows;
SAA_HXD: Passage of SAA for the HXD. (03: deep)
T_SAA_HXD: Elapsed time after a SAA passage for the HXD. (in unit of seconds)
aeNNNNNNNNN.ehk
(Extended HK file)
ELV>5 && DYE_ELV>20 Earth elevation angle and Day-earth elevation angle.
(in unit of degrees)

In the pipeline processing, the XIS data with some submodes for an editing mode is split based on the parameters in aeNNNNNNNNNxi[0-3]_0.hk (XIS HK file). The submode ID corresponds to "Z" in aeNNNNNNNNNxi[0-3]_0_{5x5,3x3,2x2}[nb]MMMZ_uf.evt.gz. However, most of the observations have only a single submode. Hence, the data split by the submode is usually unnecessary for users to reprocess the unfiltered event files. We show here the screening criteria applied to the "general" observations in Table 3. If you have the cleaned event files with some submode IDs and want to reprocess the data, please contact the Suzaku Help Desk (URL: http://cosmic.riken.jp/suzaku/help/index_e.html)

Table 3: Screening criteria used for the data split based on the submode
Column Extension name (No.) Parameter meaning Default value
For event thresholds:
S[0-3]_EVTHLW_[A-D] XIS_EXPCND (5) Lower limit of event threshold 20(XIS1), 100(XIS0, 2, 3)
S[0-3]_EVTHUP_[A-D] Upper limit of event threshold 3583
For area discriminator:
S[0-3]_AREA_DSC_[A-D] XIS_EXP_MODEINF (6) Area discriminator status. Enable: 1, Disable: 0 0
S[0-3]_ADHST_[A-D] XIS_EXPCND (5) Horizontal start-pixel address for area discriminator 0
S[0-3]_ADHEND_[A-D] Horizontal end-pixel address for area discriminator 255
S[0-3]_ADVST_[A-D] Vertical start-pixel address for area discriminator 0
S[0-3]_ADVEND_[A-D] Vertical end-pixel address for area discriminator 1023
S[0-3]_DSC_INOUT_[A-D] Target position to area discriminator. Outside: 1, Inside: 0 0
For grade discriminator(*):
S[0-3]_GRADE_DSC_[A-D] XIS_EXP_MODEINF (6) Grade discriminator status. Enable: 1, Disable: 0 0
S[0-3]_GDSC_OTHERS XIS_EXPCND (5) Flag to output grade "Others" events to the telemetry (On: 1, Off: 0) 1
S[0-3]_GDSC_TRAIL_SP Flag to output grade "Trailing split" events to the telemetry (On: 1, Off: 0) 1
S[0-3]_GDSC_LEAD_SP Flag to output grade "Leading split" events to the telemetry (On: 1, Off: 0) 1
S[0-3]_GDSC_SINGLE Flag to output grade "Single" events to the telemetry (On: 1, Off: 0) 1
(*)Grade discriminator is available only for the data in P-sum mode.

The XIS team needs the trend data for the purpose of the XIS calibration. The trend data is also extracted in the pipeline processing and is open to the public. We summarize the substituted screening criteria to extract the trend data in Table 4.

Table 4: Substituted screening criteria to extract the trend data
Substituted criteria Products
55Fe calibration source data:
GRADE=0:0 2:4 6:6 aeNNNNNNNNNxi[0-3]_0_{5x5,3x3,2x2}[nb]MMMZ_fe_evt.gz
STATUS=65536:131071 196608:262143 327680:393215 458752:524287
or
STATUS<2**19 && (STATUS%(2**17))>=2**16
Day-earth event data:
SAA_HXD==0 && T_SAA_HXD>436 aeNNNNNNNNNxi[0-3]_0_{5x5,3x3,2x2}[nb]MMMZ_de_evt.gz
ELV<0 && NTE_ELV>0(*)
Telemetry is not saturated
(screened with unsaturated GTI file: aeNNNNNNNNNxi[0-3]_0_tel_uf.gti)
Night-earth event data:
SAA_HXD==0 && T_SAA_HXD>436 aeNNNNNNNNNxi[0-3]_0_{5x5,3x3,2x2}[nb]MMMZ_ne_evt.gz
ELV<-5 && DYE_ELV>100
Telemetry is not saturated
(screened with unsaturated GTI file: aeNNNNNNNNNxi[0-3]_0_tel_uf.gti)
(*) NTE_ELV represents a night-earth elevation angle in unit of degree, which becomes NTE_ELV=120 when the night-earth is not visible, namely, the earth view from the satellite is completely sunlit.

B. Example of the screening

This is an example of the OBS_ID=101005010 observation, in which the SCI were not applied. The files used in the screening are as follows:

101005010/auxil/ae101005010.ehk.gz (Extended House Keeping file)
101005010/auxil/ae101005010.hk.gz  (Common House Keeping file)
101005010/xis/event_uf/ae101005010xi[0-3]_0_3x3n000z_uf.evt.gz
                                   (Unfiltered event files)
101005010/xis/hk/ae101005010xi[0-3]_0.hk.gz
                                   (XIS House Keeping files)

1. Screen with xselect (filter column), using GRADE and STATUS information.

unix% xselect
xsel:SUZAKU > set datadir .
xsel:SUZAKU > read event ae101005010xi0_0_3x3n000z_uf.evt.gz
xsel:SUZAKU-XIS0-STANDARD > filter column "GRADE=0:0 2:4 6:6 STATUS=0:524287"
or
xsel:SUZAKU-XIS0-STANDARD > select event "(GRADE==0||GRADE==2||GRADE==3||GRADE==4||GRADE==6)&&(STATUS<2**19)"

Calibration source areas are not removed in the pipeline processing. You are requested to do by yourself if needed. Substitute for the above command as follows;

xsel:SUZAKU-XIS0-STANDARD > filter column "GRADE=0:0 2:4 6:6 STATUS=0:65535 131072:196607 262144:327679 393216:458751" 
or 
xsel:SUZAKU-XIS0-STANDARD > select event "(GRADE==0||GRADE==2||GRADE==3||GRADE==4||GRADE==6)&&(STATUS<2**19&&(STATUS%(2**17))<2**16)"

2. Screen with xselect (select hk), using common HK, to discard the data during maneuver.

xsel:SUZAKU-XIS0-STANDARD > read hk hkfiles=ae101005010.hk.gz expand=yes
> HK file directory >[./]
xsel:SUZAKU-XIS0-STANDARD > select hk "AOCU_HK_CNT3_NML_P==1"
xsel:SUZAKU-XIS0-STANDARD > extract event
xsel:SUZAKU-XIS0-STANDARD > save event ae101005010xi0_0_3x3n000z_uf.evt_gsmnvcut
> Use filtered events as input data file ? >[no] yes

The common HK file is in "auxil" subdirectory.

3. Screen with xselect (select hk), using XIS HK, to discard the data during data rate low. The criteria are given by "Sn_DTRATE < 3", where n=0, 1, 2, 3, depending on the sensor ID.

xsel:SUZAKU-XIS0-STANDARD > read hk hkfiles=ae101005010xi0_0.hk.gz expand=yes
> HK file directory >[./]
xsel:SUZAKU-XIS0-STANDARD > select hk "S0_DTRATE<3"
xsel:SUZAKU-XIS0-STANDARD > extract event
xsel:SUZAKU-XIS0-STANDARD > save event ae101005010xi0_0_3x3n000z_uf.evt_dtratecut
> Use filtered events as input data file ? >[no] yes

4. Screen with xselect (select hk), using extended house keeping (EHK) file, to discard the data during SAA. Time intervals with large offset angles to the pointing position are also removed.

xsel:SUZAKU-XIS0-STANDARD > read hk hkfiles=ae101005010.ehk.gz expand=yes
> HK file directory >[./]
xsel:SUZAKU-XIS0-STANDARD > select hk "SAA_HXD==0 && T_SAA_HXD>436 && ANG_DIST<1.5"
xsel:SUZAKU-XIS0-STANDARD > extract event
xsel:SUZAKU-XIS0-STANDARD > save event ae101005010xi0_0_3x3n000z_uf.evt_saacut
> Use filtered events as input data file ? >[no] yes

The EHK file is in "auxil" subdirectory.

5. Then, cleaned events are selected with the following criteria:

xsel:SUZAKU-XIS0-STANDARD > read hk hkfiles=ae101005010.ehk.gz expand=yes
> HK file directory >[./]
xsel:SUZAKU-XIS0-STANDARD > select hk "ELV>5 && DYE_ELV>20"
xsel:SUZAKU-XIS0-STANDARD > extract event
xsel:SUZAKU-XIS0-STANDARD > save event ae101005010xi0_0_3x3n000z_uf.evt_elvcut
> Use filtered events as input data file ? >[no] no
xsel:SUZAKU-XIS0-STANDARD > exit
> Save this session? >[no]

6. Finally, "cleansis" is applied to remove hot/flickering pixels.

unix% cleansis datafile=ae101005010xi0_0_3x3n000z_uf.evt_elvcut \
               outfile=ae101005010xi0_0_3x3n000a_cl.evt \
               cellsize=5 logprob=-.53E+01 bthresh=3 \
               phamin=0 phamax=4095 \
               chipcol=SEGMENT

ISAS/JAXA Department of High Energy Astrophysics

Last Modified: Monday, 22-Oct-2007 18:17:39 JST