Magnier, E. A.Schlafly, E.Finkbeiner, DouglasJuric, M.Tonry, J. L.Burgett, W. S.Chambers, K. C.Flewelling, H. A.Kaiser, N.Kudritzki, R.-P.Morgan, J. S.Price, P. A.Sweeney, W. E.Stubbs, Christopher2014-02-042013Magnier, E. A., E. Schlafly, D. Finkbeiner, M. Juric, J. L. Tonry, W. S. Burgett, K. C. Chambers, and et al. 2013. The Pan-STARRS 1 Photometric Reference Ladder, release 12.0. The Astrophysical Journal Supplement Series 205, no. 2: 20.0067-0049http://nrs.harvard.edu/urn-3:HUL.InstRepos:11643694As of 2012 Jan 21, the Pan-STARRS1 \(3\pi\) Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in 5 filters, \(g_{\rm P1},r_{\rm P1},i_{\rm P1},z_{\rm P1},y_{\rm P1}\). Now at the end of the second year of the mission, we are in a position to make an initial public release of a portion of this unprecedented dataset. This article describes the PS1 Photometric Ladder, Release 12.01 This is the first of a series of data releases to be generated as the survey coverage increases and the data analysis improves. The Photometric Ladder has rungs every hour in RA and at 4 intervals in declination. We will release updates with increased area coverage (more rungs) from the latest dataset until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of \(\sim 1000\) objects per square degree in the rungs of the ladder. Saturation occurs at \(g_{\rm P1}, r_{\rm P1}, i_{\rm P1} \sim 13.5; z_{\rm P1} \sim 13.0;\) and \(y_{\rm P1} \sim 12.0\). Photometry is provided for stars down to \(g_{\rm P1}, r_{\rm P1}, i_{\rm P1} \sim 19.1\) in the AB system. This data release depends on the rigid `Ubercal' photometric calibration using only the photometric nights, with systematic uncertainties of (8.0, 7.0, 9.0, 10.7, 12.4) millimags in \((g_{\rm P1},r_{\rm P1},i_{\rm P1},z_{\rm P1},y_{\rm P1})\). Areas covered only with lower quality nights are also included, and have been tied to the Ubercal solution via relative photometry; photometric accuracy of the non-photometric regions is lower and should be used with caution.en-USJournal Article2014-01-17EA Magnier, E Schlafly, D Finkbeiner, M Juric, JL Tonry, WS Burgett, KC Chambers, HA Flewelling, N Kaiser, R-P Kudritzki, JS Morgan, PA Price, WE Sweeney, CW Stubbs2014-02-0410.1088/0067-0049/205/2/20