Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/external/xmm_sw_cal/icwg/presentations/Integral_walter.pdf Дата изменения: Wed Jun 14 23:07:16 2006 Дата индексирования: Sat Dec 22 14:59:16 2007 Кодировка:

INTEGRAL
Launched in October 2002, could last for > 10 years Best spatial resolution at hard X-rays Best narrow-line sensitivity Large field of view i.e. long effective exposure Broadest energy range

X-ray monitor (JEM-X) 3-35 keV Optical monitor (OMC) V band


INTEGRAL performance

5 deg

GRANAT/SIGMA Limit. sens: ~ 10 mCrab

RXTE

INTEGRAL/ISGRI Limit. sens: ~ 0.1 mCrab


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In flight calibration strategy
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Performance verification (12.11.02-29.12.02)
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Continuous calibration (instr. background)
Gain calibration Spectral resolution Noisy pixel handling

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Crab observations (2-3 days every 6 months)
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Spectral response Geometrical calibration Absolute/relative timing calibration

Table II.a: Main information about the data used in this work ! !!!!!!!!!!!!!!"#4!+,9!!!!!!!!!!!!!!!!!!!!!!!"#4!3W+!!!!!!!!!!!!!!!!!!!!!!!!!"#4!V-Y!!!!!!!!!!!!!!!!!!!!!!!!!"#4!-++!!!!!!!!!!!!

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II-a: Dithering patterns for the revolutions used in this work (the Crab position is 0,0)

Empty field & earth observations
Background modeling OMC flat fields

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Calibration status

(OSA 6 - Sept 2006)

SPI is a very stable instrument. Systematics on results are linked with analysis assumptions rather than calibration issues. IBIS/ISGRI: the calibrations have improved to a level adequate for scientific analysis of all types of sources excepting in a few areas: - ARF to be adjusted to new LUT2/RMF and agreed Crab model - PSF modeling still to be improved IBIS/PICSIT calibration effort is limited because of the small number of detected sources (4 compact objects and about 35 GRB) JEM-X calibration and modeling effort need to be pursued to match various instrumental instabilities. Specific calibrations have been performed recently Standardized high energy Crab spectrum would be very useful


JEM-X calibration
JEM-X is affected by some instabilities which affect software and calibrations: microstrip erosion ( decreased HV and S/N) microstrip ions diffuse into glass plate ( HV adjustments) gain variation ( electronic efficiency to be determined on short time scales) memory effect on microstrips transient hot spots Observations are used to calibrate the instrument geometry: - detector and mask alignment vs star tracker (thermal effect), - collimator tilt (effect underestimated before launch) - photon detection accuracy instrument background: collimator effect ARF: physical properties understood above 15keV. Below 15keV the electronic efficiency is important and it can be determined by observations at different gains. This has been performed recently.
2.3. The Microstrip Plate 2.4. On-Board Event Selection
Figure 1. The JEM­X detector.

copper. The internal dimension of each collimator cell is 6.6в6.6 mm and the height is 57.0 mm. The collimator is circular with a diameter of 250 mm.

The microstrip plate has orthogonal strip patterns on the upper and lower sides. The primary micro-strip pattern on the upper side has a pitch of 1062 µm and alternating 10 µm wide ano de strips and 458 µm wide catho de strips. The pattern on the lower side has 1 mm wide strips with a 2 mm pitch. The strip patterns are formed in a 0.2 µm thick chromium layer sputtered on a D 263 glass substrate from Schott Glass Works (Germany). The signals from the ano de strips are used for event triggering, energy determination and pulse-shape determination employed in the on-board event selection. The signals from the cathode strips and the lower side strips are used for X- and Y-position determination respectively.

The detector requires a drift voltage applied between the detector window (at ground potential) and the cathodes on the microstrip plate. A second voltage is applied between the ano de and catho de strips on the microstrip plate which controls the electron gas multiplication on the microstrip plate.

The count rates of the JEM-X detectors are dominated by events caused by cosmic ray proton and alpha particles. Particle events are about 50 times as numerous as the X-ray induced events. It is therefore essential to ensure a very efficient on-board rejection of the particle background - otherwise the telemetry channel would be completely clogged by particle data. The particle rejection has three elements, all based on the signals from the micro-strip detector:

Issues: Crab is an extended source that requires special treatment. Instrument characteristics evolve faster than the frequency of Crab observations


IBIS/ISGRI geometric calibration
Instrument geometry: detector and mask alignment vs star tracker Current systematics: 10" Nomex geometrical model. Current systematics on flux measurement: 2-3% Image defects indicate that the instrument modeling is not yet perfect Systematic error on the PSF: 1%