Instrument Checkout / Performance Verification for XRT

&Control of XRT Observation

R. Kano for the XRT Team

Control of XRT Observation

On-board functions for XRT Obs.

Mission Data Processor

DR ImageCompression

Pre-FlareBuffers

Autonomous Functions

FLDARSAEC

XRTObservationTables

Data PacketEdition

SOT

EIS

Mission Data Processor (MDP) has many functions for XRT.• Management of XRT exposures by “Observation Table”• Autonomous Functions for XRT observations

– Automatic Exposure duration Control (AEC)– Automatic Region Selector (ARS)– FLare Detection (FLD)

• Image processing– Edition of Image data packets– Image compression– Pre-Flare Buffers

Observation Table

Program No.1“Normal Obs.”1. SUB1　 loop=102. SUB3　 loop=13. SUB2　 loop=104. SUB3　 loop=1

SEQ1: global structure of 1MK corona• Exp. for thin-Al-mesh & full FOV• Exp. for thin-Al-poly & full FOV

SEQ2: AR’s temperature structure• Exp. for thin-Al-poly & small FOV (AR)• Exp. for med-Be-mesh & small FOV (AR)

SEQ3: 1MK corona in AR• Exp. for thin-Al-mesh & small FOV (AR) • Exp. for thin-Al-poly & small FOV (AR)

SEQ100: CCD dark calibration

Sequence Table (100 sequences)Observation Program (20 programs)

SUB11. SEQ1　 loop=12. SEQ2　 loop=20

SUB21. SEQ1　 loop=12. SEQ3　 loop=20

SUB31. SEQ100　 loop=1

：

•XRT exposures are managed by one observation table in the Mission Data Processor (MDP).

•The structure of XRT observation table is essentially the same with those for SOT.

Automatic Exposure Control (AEC)

Exposure duration is adjusted by using the intensity histogram.

LLT 　　 ULT

Intensity I

Num

ber

of p

ixel

)(IF

LLT 　　 ULT

Intensity I

Num

ber

of p

ixel

)(IF

4095

ULT

)(I

IFU

LLT 　　 ULT

Intensity I

Num

ber

of p

ixel

)(IF

4095

LLT

)(I

IFL

Under Exposure

Normal Exposure

Over Exposure

If U is too much, shorten the exposure duration.

If L is not enough, lengthen the exposure duration.

duration

Automatic Region Selector (ARS)

• XRT will take an “ARS patrol image” (the full CCD-frame and 2”-resolution) once per orbit (every 90 min typically).

• Two modes of ARS run in parallel each other.– “Global Search” mode to fine the

brightest region.

– “Local Search” mode to track bright regions.

ARS: Global Search

Steps to derive a new FOV

•Take a new patrol image.•Define the search area.(The default is all CCD.)

•Make a macro-pixel image.•Pick up the brightest macro-pixel.

•Calculate a fine position in the original image around the selected macro-pixel.

New FOV

Automatic Region Selector (ARS)

• XRT will take an “ARS patrol image” (the full CCD-frame and 2”-resolution) once per orbit (every 90 min typically).

• Two modes of ARS run in parallel each other.– “Global Search” mode to fine the

brightest region.

– “Local Search” mode to track bright regions.

ARS: Local Search

Steps to derive a new FOV

•Take a new patrol image.•Define the search area.(Just around the current FOV)

•Calculate a fine position in the search area.

Current FOVNew FOVNew FOV

30 sec (typically) 30 sec (typically)

Flare Detection (FLD)• XRT will take a FLD patrol image every 30 sec (typically).• MDP derives a difference image between a new patrol image and the

running averaged patrol image, and searches any intensity enhancement in it.

• Once a flare occurred, MDP informs the flare position to SOT and EIS also.• (FLD function is useful to avoid strong irradiation to CCD.)

difference difference difference

average averageaverage

Flare has detected!

Flare is lasting.

Flare has terminated.

FLD patrol image FLD patrol image FLD patrol image

Averaged image Averaged image Averaged image Averaged image

Pre-Flare Buffers

Buffer0

Buffer1

Buffer2

Buffer3

“SW1”

“SW2”

“SW3”

XX−100sX−200sX−300s

time

Total

Buffer0

Buffer1

Buffer2

Buffer3

Data Recorder

Four buffers is available for the image transfer to the Data Recorder.• Buffer0 is prepared for the normal image transfer.• Buffer1, 2, and 3 for ring buffers to freeze the pre-flare images.

Instrument Checkout&

Performance Verification

Detailed Items

Instrument checkout

Performance verification

Front Door Opens

Launch

Science Obs. Starts

Instrument checkout• Launch to Orbit Stabilization: ~ 3weeks

– Turn on CCD heater and survival heaters just after the launch.

– Survival mode until orbit is stabilized

• Orbit Stabilization to Door Opening: ~ 1week – Turn on the electronics for XRT. – Functional tests

(focus mechanism not tested. VLS not tested.)

– CCD noise/dark characterization– Observation control check (partially)

Performance verification• Door Opening and First Light: 1day

– Door open (1day after the SOT top door open)– Initial X-ray and Visible light images

• First Light to Science Ops: 1 ~ 3weeks– X-ray focus check and adjustment– Exposure duration check– Filter light leak check– Alignment check– Observation control check– Autonomous functions check

• Automatic Exposure Control (AEC)• Automatic Region Selector (ARS)• FLare Detection (FLD)

Mercury Transit

• Instrument– Alignment check.

• Science– Sub-pixel structure?

End, but..

END

Observation Table (detail)

ObservationProgram

(OBS PRG)

SequenceTable(SEQ)

ParameterTable(PAR)

Region of InterestTable(ROI)

AEC ThresholdsTable(AET)

AEC ControlTable

(AEC CTL)

ARS ControlTable

(ARS CTL)

FLD ControlTable

(FLD CTL)

20 programs

100 sequences

100 tables 16 tables 7 tables

Filter Dimming Parameter Table

(FLT)

ObservationControl

(OBS CTL)

Current ControlTable

(CUR CTL)

Micro-VibrationTable(MVB)

To Control Observation To Control Onboard Process

Group Refer

(internal table)