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XRT’s Observational Parameters

This article provides information about the observational parameters of the X-ray Telescope (XRT) and its capability for full disk imaging. It also discusses the focus mechanism and camera performances of the XRT.

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XRT’s Observational Parameters

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  1. XRT’s Observational Parameters R. Kano (NAOJ)

  2. Contents • FOV & Full Disk Imaging • Time Cadence & Observation Table • New Items as Solar X-ray Telescopes • Pre-flare Buffer • Focus Mechanism • Camera Performances

  3. Field of View (FOV) • 10 different size: 64, 128, 192, 256, 384, 512, 768, 1024, 1536, & 2048 (arcsec). • A rectangular FOV is also available.(64arcsec is only for a square FOV.) 768 1024 1536 2048 arcsec

  4. Full Disk observation is rare. • The size of the largest FOV (2048”) is larger than the solar diameter. • However, it is rare to observe the full disk, because Solar-B usually pointing a feature on the solar disk for SOT. • This is an example of AR observation.

  5. For Full Disk Observation... • To take a full disk solar image regularly, it is necessary to change the Solar-B pointing. • I propose that we take the full disk solar image several times in a day. It takes about 5(TBR)min to change and stabilize the S/C pointing.

  6. Time Cadence • typical data rate = about 300k pixel / min • example-1 : AR observation = 294k pixel / min • 384”x384”, 1”-res., 2-filter images & 1min interval • example-2 : high speed AR obs. = 294k pixel / min • 384”x384”, 1”-res., 2-filter images & 10sec interval • 10min observation and 50min non-observation. • example-3 : AR & FFI observation = 287k pixel / min • 384”x 384”, 1”-res., 2-filter images & 80sec interval • 2048”x2048”, 4”-res. , 2-filter images & 8min interval

  7. Time Cadence • typical data rate = about 300k pixel / min • example-1 : AR observation = 294k pixel / min • example-2 : high speed AR obs. = 294k pixel / min • example-3 : AR & FFI observation = 287k pixel / min 1min AR 10min 50min AR 80sec AR FFI 8min

  8. Observation Table Obs. Program Main routine Subroutine-1 Sequence-1 Subroutine-1 Sequence-1 Exposure-1 Subroutine-2 Sequence-2 Exposure-2 Subroutine-3 Sequence-3 Exposure-3 Sub.- max8 Seq.- max8 Exp.- max8 20 programs for XRT 100 sequences for XRT

  9. Sequence-1: temperature analysis of active regions Sequence-2: temperature analysis of full frame images Exp.-1: FOV=384”x384”, Res.=1”, Fil.=Thin Al poly Exp.-1: FOV=2048”x2048”, Res.=4”, Fil.=Thin Al mesh Exp.-2: FOV=384”x384”, Res.=1”, Fil.=Medium Al Exp.-2: FOV=2048”x2048”, Res.=4”, Fil.=Thin Al poly Sequence tables are Building blocks. 100 Seqence tables for XRT are stored in MDP.

  10. An Example of Obs. Table Main routine-1 Subroutine-1: 2 times Sequence-1: T-ana. of AR 8 times Sequence-2: T-ana. of FFI 1 time Subroutine-2: 1 time Sequence-1: T-ana. of AR 8 times Sequence-3: Dark images 1 time AR FFI Dark

  11. Pre-flare Observation • FOV: 512x256 arcsec, 1”-res. • (You should predict the location of flare site.) • 13min Pre-flare images can be kept. • Time resolution before the flare onset(X) • X-780sec – X-260sec: 60sec interval • X-260sec – X-110sec: 20sec interval • X-110sec – X : 10sec interval (This is a typical example. You can adjust the duration and interval of pre-flare data.)

  12. Focus Mechanism • Focus Range: +/– 1mm • We can use this mechanism not onlyfor the engineering purpose(to cancel the focus shift by the launch env. etc.), but also for the observational purpose: • Better resolution only near the CCD center vs. • Moderate resolution over the whole CCD. • The usage rate is lower than 15 times in a day.

  13. Aberration at Different Focus Pos. (Only Geometrical Optics) φ512’’ φ1024’’ RMS=φ1’’ Distance from the Center

  14. Camera Performances • Dark Free • CCD temperature will be lower than –43 C. • 0.1 – 1 e/pixel/sec • <<1DN/pixel, if the exposure <<1min • Low Noise • 20 electron (= 0.4 DN) cf.) 1DN(Data Number)=50e

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