4 August 2010 Investigation of disturbance effects on space-based weak lensing measurements with an integrated model
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Many astrophysicists consider the mystery of accelerated expansion of the universe by a field called dark energy as the greatest challenge to solve in cosmology. Gravitational weak lensing has been identfied as one of the best methods to provide constraints on dark energy model parameters. Weak lensing introduces image shear which can be measured statistically from a large sample of galaxies by determining the ellipticity parameters. Several papers have suggested that a goal in the ability to measure shape biases should be <0.1% - this goal will be reviewed in terms of the observatory "transfer function" with comments interspersed regarding allocation inconsistencies. Time-varying effects introduced by thermoelastic deformations and vibration add bias and noise to the galaxy shape measurements. This is compounded by the wide field-of-view required for the weak lensing science which leads to a spatially varying point spead function (PSF). To fully understand these effects, a detailed integrated model (IM) was constructed which includes a coupled scene/ structure/ optics/ disturbance model. This IM was applied to the Joint Dark Energy Mission (JDEM) Omega design concept. Results indicate that previous models of vibration disturbance effects have been too simplified and the allocation for vibration needs to be re-evaluated. Furthermore, because of the complicated processing required to accurately extract shape parameters, it is argued that an IM is needed for maximizing science return by iterating the telescope/ instrument design against mission cost constraints, and processing e¤ectiveness of shape extraction algorithms, instrument calibration techniques and measurement desensitization of observatory effects.
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Michael Lieber, Michael Lieber, Michael Kaplan, Michael Kaplan, Michael Sholl, Michael Sholl, Gary Bernstein, Gary Bernstein, "Investigation of disturbance effects on space-based weak lensing measurements with an integrated model", Proc. SPIE 7738, Modeling, Systems Engineering, and Project Management for Astronomy IV, 773807 (4 August 2010); doi: 10.1117/12.856445; https://doi.org/10.1117/12.856445

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