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42.10 Expected Accuracies of HSP Data
HSP photometric accuracies are strongly dependent on the observational setup and observing conditions, such as spacecraft jitter. Absolute photometry can be done only with a one sigma limiting accuracy of approximately 5%, but relative photometry is possible with an accuracy of 1-2%.
Estimated HSP Calibration Accuracies
Attribute
Estimated Accuracy
Comments
Absolute Timing
~10 millisec
Can be achieved from science headers if HST/UTC timing regression coefficients appropriate to observation date were used in post-observation calibration; otherwise, use methods from
HSP ISR 12
.
Relative Timing
(timing resolution)
Digital modes: 10.7 microsec
Analog modes: ~1 millisec
For PRISM mode: relative timing given by science headers must be corrected for format-dependent read-beam switching time (see page 42-
2
).
Detector stability:
Detector linearity:
Sensitivity: UV1, UV2, POL all constant within 1%; VIS: factor of 3 decrease then recovery
linearity: +/- 0.01 mag
1991 through summer 1993 monotonic decrease,
post-August 1993 complete recovery
VIS 551W for magnitude range 5.11 < V < 12.79
Absolute photometry
(flux calibration)
5% (one sigma)
Limited by breathing effects and small differences in telescope pointing at different standard star observing epochs
Relative photometry
1-2%
Limited by guiding, re-acquisition centering, orbital effects (breathing, jitter)
Polarimetry: q,u,p
0.3% (one sigma)
F327M and F277M
Add in quadrature with photon statistical uncertainty
Aperture Location
Absolute: <50 milliarcsec
Relative: <20 milliarcsec
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Last updated: 01/14/98 16:01:49