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\begin{itemize}  \item \textbf{Scope} The first requirements for the survey concern the scope of the observations. ZTF must survey the entire sky visible from Palomar Observatory. In practice, this will cover nearly the entire footprint of the Pan-STARRS1 (PS1) 3$\pi$ survey. To enable the search for transients, it is essential that the full survey area be observed and reference images be created within the first year of the survey. Furthermore, a systematic grid of discrete fields should be developed prior to the start of the survey, and all observations should be confined to these fields. This will ensure that, once reference images are made, every frame taken by ZTF will be suitable for transient discovery. We recommend that the fields consist of two overlapping grids, offset by $\sim$half the length of the diagonal such that chip gaps can be filled and the corners of the FOV in one grid, which suffer the most from vignetting, correspond to the center of the FOV in the alternate grid. Alternative solutions may be appropriate, but they must be defined prior to the start of the survey.     \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 PTF achived 20\,mmag scatter compared with the SDSS. However, since PTF observed mostly in a single filter, one need  to PS1 can be employed by ZTF, and thus we require that know  the absolute photometric calibration of star color in order to achive the this accuracy.  The first requirment is that  ZTF achieve an accuracy will observe the sky in at least two bands.  The second requirment is that it will have uniformity  of $<$ 30 mmag relative better than 20\,mmag over the entire sky,  and we will be able  to calibrate this against  the photometric best  catalog produced by PS1. available for us.  The best way to achive this uniformity is using modifications of the ubber cal technique \citet{Padmanabhan_2008}.  \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} XXXX