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Mission/InstrumentsScience Requirement Absolute TimeTiming System DesignTiming Calibration StatusIn-orbit Timing
Calibration Targets
Reported IssuesReference
RequirementGoalGPS ReceiverClock Stability(Absolute Timing Precision)
RXTE/PCA (star)        
Chandra / ACIS        
Chandra / HRC        
XMM-Newton/EPIC-MOS        
XMM-Newtion/EPIC-PN        
INTEGRAL/SPI        
INTEGRAL/IBIS        
Swift/BAT        
Swift/XRT        

Suzaku/XIS(star)

No science requirement defined.No

1.9 x 10^-9 s/s
(measured)

Not confirmed.A0535+262, Her X-1, etcN/A
Y.Terada et al 2008
(10.1093/pasj/60.sp1.S25)
Suzaku/HXD(star)360±150 μsec
(270±130  μsec in condition)
Crab for coordinated
PSR1509-58
Timing shift by a failure
in time stamp at the
ground station during
2012-2014
(Shu Koyama, Fixed)
NuSTAR/FPMShould be 100 msnoneNo

Freely drifting by ~3 ms/day.
Reduced to 20 us/day using
the clock correction file

65 us (1-sigma)

Crab
B1821-24A
B1937+21

~5ms offset using
millisecond pulsars
(Lucien Kuiper)

Corrected through
clock correction file
v108+

Bachetti+ in prep
(can distribute early copy) 
Astrosat        
HXMT        
Hitomi/SXS, SXI, HXI, SGD(star)350 μsec
35 μsecYes

0.01μsec(GPSR)
<3.0 μsec(SpW)
0.3 ns (orbit)

~ 120-230 μsec

Crab (with radio)
note: using out-of-time
event for SXI
absolute timing
accuracy is much
larger than expected
on ground (3 μsec)
Y.Terada et al 2018
(10.1117/1.JATIS.4.1.011206)
NICER       100 ns (RMS)noneYesN/AApprox. 3 µsCrab Pulsar
PSR B1821-24A
PSR B1937+21
Precise 1-second offset
in on-board timestamps
due to flight software bug;
corrected using TIMEZERO
keyword in pipeline-processed
FITS data files.
Markwardt  et al. (in prep.) 
eROSITA        
XRISM/Resolve (blue star)1 msecnoneYessame as Hitomi

 (under discussion)  
XRISM/Xtend (blue star)10 msecnoneYes (under discussion)  

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