deletions | additions       diff --git a/Performance Requirements.tex b/Performance Requirements.tex  index d888166..41d33c8 100644  --- a/Performance Requirements.tex  +++ b/Performance Requirements.tex 
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  \item \textbf{Absolute Photometric Calibration} Many of the ``bread and butter'' science goals of ZTF require a precise and accurate absolute photometric calibration (e.g., cosmography with Type Ia SNe, mapping Galactic structure with RRL). Recently, PS1 has demonstrated the ability to produce an absolute calibration, relative to the Sloan Digital Sky Survey and \textit{Hubble Space Telescope} Calspec stars of $\sim$30 mmag \citep{Tonry_2012}. The methodology available to PS1 can be employed by ZTF, and thus we require that the absolute photometric calibration of ZTF achieve an accuracy of $<$ 30 mmag relative to the photometric catalog produced by PS1.   \item \textbf{Relative Photometric Calibration} The dual grid of ZTF fields recommended above will provide significant overlap between every ZTF observation, which will, in turn, allow a precise calibration of the relative photometric system. \citet{Padmanabhan_2008} demonstrated that it was possible to use overlapping observations from SDSS to obtain a survey-wide relative photometric calibration of $\sim$10 mmag, while \citet{Schlafly_2012} demonstrated that the same algorithm could be applied to PS1 observations to obtain a relative precision $<$ 10 mmag. Given that there will be extensive overlap between ZTF observations, we require that the relative photometric precision achieve an accuracy of $<$ 10 mmag.   \item \textbf{Astrometric Calibration} The detection of moving objects is one of the major goals of ZTF, and the determination of their respective orbits requires an accurate calibration of the astrometric frame. For sources with $r \lesssim 20$ mag, SDSS was able to obtain an accuracy of 45 mas rms per coordinate when reduced against the USNO CCD Astrograph Catalog and 75 mas rms when reduced against Tycho-2, with an additional 20-30 mas systematic error in both cases \citep{Pier_2003}. SDSS utilized a larger aperture telescope than ZTF, thus we require ZTF to achieve a 75 mas rms when reduced against \textit{Gaia} for stars with $r \lesssim 19$ mag. \textbf{This should be checked/re-written by someone with further knowledge about astrometry}.  \item \textbf{Tolerance for Outliers}  \end{itemize}  % derive from bread & butter science? Ia cosmology, RR Lyr