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Changeset 40722


Ignore:
Timestamp:
May 7, 2019, 8:25:06 PM (7 years ago)
Author:
eugene
Message:

adding high-res figures

Location:
trunk/doc/release.2015/ps1.calibration
Files:
18 added
5 edited

Legend:

Unmodified
Added
Removed
  • trunk/doc/release.2015/ps1.calibration/Makefile

    r40714 r40722  
    44# remember to set \pdfoutput at the top
    55
    6 DO_BIBTEX = 1
     6DO_BIBTEX = 0
    77# remember to change from \bibliography to \input{.bbl} at the bottom
    88
     
    1313all: pdf tgz
    1414pdf: calibration.pdf
    15 tgz: calibration.tgz
     15
     16journal: calibration.journal.tgz
     17arxiv: calibration.arxiv.tgz
    1618
    1719quick: calibration.quick.pdf
    1820
     21PNGPICS = \
     22pics/gpc1.layout.pdf \
     23pics/A1.pdf \
     24pics/A4.pdf \
     25pics/photflat.example.v1.png \
     26pics/rings.v3.example.png \
     27pics/allsky.photom.v2.png \
     28pics/photom.pv3.3v4.png \
     29pics/KHexample.png \
     30pics/KHmap.png \
     31pics/DCR.example.png \
     32pics/astroflat.gri.v2.png \
     33pics/astroflat.zy.v2.png \
     34pics/allsky.astrom.pv3.3.png \
     35pics/astroflat.repair.png \
     36pics/allsky.histogram.astrom.compare.png \
     37pics/gaia.photom.v1.png \
     38pics/gaia.astrom.mean.png \
     39pics/gaia.astrom.sigma.png
     40
    1941PDFPICS = \
     42pics/gpc1.layout.pdf \
    2043pics/A1.pdf \
    21 pics/A3.pdf \
    22 pics/A4.pdf
     44pics/A4.pdf \
     45pics/photflat.example.v1.pdf \
     46pics/rings.v3.example.pdf \
     47pics/allsky.photom.v2.pdf \
     48pics/photom.pv3.3v4.pdf \
     49pics/KHexample.pdf \
     50pics/KHmap.pdf \
     51pics/DCR.example.pdf \
     52pics/astroflat.gri.v2.pdf \
     53pics/astroflat.zy.v2.pdf \
     54pics/allsky.astrom.pv3.3.pdf \
     55pics/astroflat.repair.pdf \
     56pics/allsky.histogram.astrom.compare.pdf \
     57pics/gaia.photom.v1.pdf \
     58pics/gaia.astrom.mean.pdf \
     59pics/gaia.astrom.sigma.pdf
    2360
    2461FILES = \
     
    2663../inputs/code.sty \
    2764../inputs/apj.bst \
    28 pics/rings.v3.example.png \
    29 pics/KHexample.png \
    30 pics/KHmap.png \
    31 pics/dcr.r2.g.png \
    32 pics/allsky.astrom.sigma.png \
    33 pics/gaia.photom.png \
    34 pics/gaia.astrom.png \
    35 $(PDFPICS) \
    3665calibration.tex
    37 
    38 # pics/photflat.example.sm.png \
    39 # pics/allsky.photom.sigma.sm.png \
    40 # pics/astroflat.gri.sm.png \
    41 # pics/astroflat.zy.sm.png \
    4266
    4367pics/%.pdf : pics/%.ps
     
    4872        ps2pdf -dEPSCrop $< $@
    4973
    50 pdfpics: $(PDFPICS)
     74# pdfpics: $(PDFPICS)
     75
    5176calibration.pdf: $(FILES)
    52 calibration.tgz: $(FILES)
     77
     78calibration.journal.tgz: $(FILES) $(PDFPICS) calibration.bbl
     79calibration..arxiv.tgz: $(FILES) $(PNGPICS) calibration.bbl
    5380
    5481include ../Makefile.Common
     82
  • trunk/doc/release.2015/ps1.calibration/calibration.tex

    r40714 r40722  
    2121%% NOTE: 2019 Feb versions of the figures are generated in /data/kukui.1/eugene/cal.paper.20190217
    2222
    23 %\def\picdir{/home/eugene/chipresid.20140404}
    24 \def\picdir{/data/pikake.2/eugene/chipresid.20140404}
     23%\def\picdir{pics}
     24\def\picdir{.}
    2525
    2626% Pick a terse version of the title here;
     
    247247\begin{figure}
    248248  \centering
    249   \includegraphics[width=0.9\hsize,angle=0,clip]{{pics/gpc1.layout}.pdf}
     249  \includegraphics[width=0.9\hsize,angle=0,clip]{{\picdir/gpc1.layout}.pdf}
    250250  \caption{Diagram illustrating layout of OTA devices in GPC1.  The
    251251    blue dots mark the locations of the amplifiers for xy00 cells in
     
    476476\end{eqnarray}
    477477
    478 %% Include a description of the WCS keywords used to represent the fit elements?
    479 
    480 %% {\bf WCS Keywords} When this polynomial representation is written to
    481 %% the output files, a set of WCS keywords are used to define the
    482 %% astrometric transformation elements.  It is necessary to transform the
    483 %% simply polynomials above into an alternate form:
    484 %% \begin{eqnarray}
    485 %%   P & = & \sum_{i,j} C^P_{i,j} (X_{\rm chip} - X_0)^i (Y_{\rm chip} - Y_0)^j \\
    486 %%   Q & = & \sum_{i,j} C^Q_{i,j} (X_{\rm chip} - X_0)^i (Y_{\rm chip} - Y_0)^j
    487 %% \end{eqnarray}
    488 
    489 %% \note{need to complete this discussion of the WCS keywords, both
    490 %%   standard and non-standard, used to represent these polynomial
    491 %%   transformations}
    492 
    493 %% \begin{verbatim}
    494 %% Here is a list of the keywords
    495 %% and the related terms from Eqns above:
    496 %% CTYPE1,2 : RA---WRP, DEC--WRP
    497 %% CTYPE1,2 : RA---DIS, DEC--DIS
    498 %% CRVAL1,2 : C^{L,M}_{0,0}
    499 %% CRPIX1,2 : X_0, Y_0
    500 %% PC001001 : C^{L}_{1,0}
    501 %% PC001002 : C^{L}_{0,1}
    502 %% PC002001 : C^{M}_{1,0}
    503 %% PC002002 : C^{M}_{0,1}
    504 %% PCA1XiYj : C^{L}_{i,j}
    505 %% PCA2XiYj : C^{M}_{i,j}
    506 %% \end{verbatim}
    507 
    508478\subsection{Cross-Correlation Search}
    509479
     
    543513astrometry guess for the chip.
    544514
    545 %% \note{option to downweight based on photometric inconsistency : not used in PS1 analysis}
    546 
    547515\subsection{Pipeline Astrometric Calibration}
    548516
     
    586554representing the distortion. 
    587555
    588 %% \note{write out the math of the gradients}
    589 
    590556Once the common distortion coming from the optics and atmosphere have
    591557been modeled, \ippprog{psastro} determines polynomial transformations
     
    598564order for the final iterations. 
    599565
    600 %% \note{quality of the fits as a result of this stage}.
    601 
    602566\subsection{Pipeline Photometric Calibration}
    603 
    604 %% \note{define / describe the robust median}
    605567
    606568After the astrometric calibration is determined, the photometric
     
    671633Section~\ref{sec:synthdb}) was merged in.  Next, the full Tycho
    672634database was added, followed by the AllWISE database.  After the Gaia
    673 release in August 2016 \citep{2016AA...595A...2G}, we generated a DVO
    674 database of the Gaia positional and photometric information and merged
    675 that into the master PV3 $3\pi$ DVO database.
     635Data Release 1 (DR1) in August 2016 \citep{2016AA...595A...2G}, we
     636generated a DVO database of the Gaia positional and photometric
     637information and merged that into the master PV3 $3\pi$ DVO database.
    676638
    677639The master DVO database is used to perform the full photometric and
     
    869831\end{table*}
    870832
    871 %% \note{need to describe the assignment of flags, etc, for the external data sources}.
    872 
    873833\section{Photometry Calibration}
    874834
     
    1033993\subsection{Relphot Analysis}
    1034994
    1035 %% \note{how many exposures are not in ubercal?}
    1036 
    1037995Relative photometry is used to determine the zero points of the
    1038996exposures which were not included in the ubercal analysis.  The
     
    10591017is taken up as an additional element of the atmospheric attenuation.
    10601018
    1061 %% \note{color-color terms between chips?}
    1062 
    10631019We write a global $\chi^2$ equation which we attempt to minimize by
    10641020finding the best mean magnitudes for all objects and the best
     
    10951051rejections do not catch all cases of bad measurements.
    10961052
    1097 %% \citep[\code{PSF_QF} $< 0.85$, see][]{magnier2017.analysis};
    1098 %% \note{refer to the PSPHOT bad and poor psphot bits?} 
    1099 
    11001053After the initial iterations, we also perform outlier rejections based
    11011054on the consistency of the measurements.  For each star, we use a two
     
    11121065deviation (of the measurements used for the mean) greater than 0.005
    11131066mags or 2$\times$ the median standard deviation, whichever is greater.
    1114 
    1115 %% \note{is this true?}
    11161067
    11171068Similarly for images, we exclude those with more than 2 magnitudes of
     
    11341085dominates where they are present.
    11351086
    1136 % \note{do we drop this when calculating the final mean mags?}
    1137 % \note{do I need to present the math?}
    11381087\begin{equation}
    11391088  \mu = \frac{\sum m_i w_i \sigma_i^{-2}}{\sum w_i \sigma_i^{-2}}
     
    11751124% this is PV3.0 [pre-calibrations]
    11761125
     1126% updated version at:
     1127% /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh photflat.example
    11771128\begin{figure*}[htbp]
    11781129 \begin{center}
    11791130  \begin{minipage}{0.85\linewidth}
    1180    \includegraphics[width=\textwidth,clip]{{pics/photflat.example.v1}.png}
     1131   \includegraphics[width=\textwidth,clip]{{\picdir/photflat.example.v1}.\plotext}
    11811132  \end{minipage}
    11821133  \hspace{-3.0in}
     
    15921543
    15931544% generate from :
    1594 % /data/kukui.1/eugene/czw.paper.images.20181130 (see .dvo)
     1545% /data/kukui.1/eugene/cal.paper.images.20190217/rings.sh
    15951546
    15961547\begin{figure*}[htbp]
    15971548  \begin{center}
    1598  \includegraphics[width=\hsize,clip]{{pics/rings.v3.example}.png}
     1549 \includegraphics[width=\hsize,clip]{{\picdir/rings.v3.example}.\plotext}
    15991550  \caption{\label{fig:rings.v3.example} Illustration of overlapping
    16001551    skycells and the identification of the ``primary'' detections.}
     
    18281779\subsection{Photometry Calibration Quality}
    18291780
     1781% /data/kukui.1/eugene/cal.paper.images.20190217/scatter.sh : allsky.scatter.photom
    18301782\begin{figure*}[htbp]
    18311783  \begin{center}
    18321784%width=\hsize
    1833  \includegraphics[height=\vsize,clip]{{pics/allsky.photom.v2}.png}
     1785 \includegraphics[height=\vsize,clip]{{\picdir/allsky.photom.v2}.\plotext}
    18341786  \caption{\label{fig:allsky.photom.sigma} Consistency of photometry
    18351787    measurements across the sky.  Each panel shows a map of the
     
    1876182818)$ millimagnitudes.
    18771829
     1830% /data/kukui.1/eugene/cal.paper.images.20190217/kronrepair.sh : full.figure
    18781831\begin{figure*}[htbp]
    18791832  \begin{center}
    1880   \includegraphics[width=\hsize,clip]{{pics/photom.pv3.3v4}.png}
     1833  \includegraphics[width=\hsize,clip]{{\picdir/photom.pv3.3v4}.\plotext}
    18811834  \caption{\label{fig:photom.pv3.3v4} Sample comparison of PV3.3 and
    18821835    PV3.4 photometry illustrating the impact of the issues identified
     
    19191872
    19201873\section{Astrometry Calibration}
    1921 
     1874\label{sec:astrometry}
     1875
     1876% /data/kukui.3/eugene/pv3.stats.20161202/mana.sh
    19221877\begin{figure*}[htbp]
    19231878  \begin{center}
    1924  \includegraphics[width=\hsize,clip]{{pics/KHexample}.png}
     1879 \includegraphics[width=\hsize,clip]{{\picdir/KHexample}.\plotext}
    19251880  \caption{\label{fig:KHexample} Illustration of the Koppenh\"ofer Effect
    19261881    on OTA04.  {\bf Bottom left} X-direction before correction.  The solid line shows the measured
     
    19331888\end{figure*}
    19341889
    1935 % from: /data/kukui.3/eugene/pv3.stats.20161202/
    1936 
     1890% /data/kukui.3/eugene/pv3.stats.20161202/mana.sh
    19371891\begin{figure}[htbp]
    19381892  \begin{center}
    1939  \includegraphics[width=\hsize,clip]{{pics/KHmap}.png}
     1893 \includegraphics[width=\hsize,clip]{{\picdir/KHmap}.\plotext}
    19401894  \caption{\label{fig:KHmap} Map of the amplitude of the
    19411895    Koppenh\"ofer Effect on chips across the focal plane.  In the
     
    20772031% /data/ipp094.0/eugene/pv3.cam.20150607/astrom.corrections/dcr.meas.20151203.0.fits
    20782032
     2033% /data/kukui.3/eugene/dcr.20141205/dvo.dcr.sh : figure8
    20792034\begin{figure}[htbp]
    20802035  \begin{center}
    2081  \includegraphics[width=\hsize,clip]{{pics/dcr.r2.g}.png}
     2036 \includegraphics[width=\hsize,clip]{{\picdir/DCR.example}.\plotext}
    20822037  \caption{\label{fig:DCRexample} Example of the DCR trend in the
    20832038    g-band.  {\bf top:} DCR trend in the parallactic direction {\bf
     
    21182073% /data/ipp105.0/eugene/astrom.20170225/astroflat.20170217/astroflat.20170217.med.cam.dX.g.fits
    21192074
     2075% last version in :
     2076% /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh astroflat.example
    21202077\begin{figure*}[htbp]
    21212078 \begin{center}
    2122  \includegraphics[width=0.85\textwidth,clip]{{pics/astroflat.gri.v2}.png}
     2079 \includegraphics[width=0.85\textwidth,clip]{{\picdir/astroflat.gri.v2}.\plotext}
    21232080 \caption{\label{fig:astroflat.gri} High-resolution astrometric flat-field correction images for $gri$.}
    21242081 \end{center}
    21252082\end{figure*}
    21262083
     2084% /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh astroflat.example
    21272085\begin{figure*}[htbp]
    21282086 \begin{center}
    2129  \includegraphics[width=0.85\textwidth,clip]{{pics/astroflat.zy.v2}.png}
     2087 \includegraphics[width=0.85\textwidth,clip]{{\picdir/astroflat.zy.v2}.\plotext}
    21302088 \caption{\label{fig:astroflat.zy} High-resolution astrometric flat-field correction images for $zy$.}
    21312089 \end{center}
     
    23252283
    23262284For the initial PV3 analysis, we again used the 2MASS coordinates as
    2327 an external astrometric reference.  After the DR1 object parameters
    2328 were ingested into the PSPS database, the Gaia DR1 astrometry was
    2329 released \citep{2016AA...595A...4L}.  This gave us the option to use
    2330 the Gaia positions for the external astrometric reference.  We re-did
    2331 the astrometric analysis and generated a Gaia-based astrometry table
    2332 for the Pan-STARRS DR1.  For Pan-STARRS DR2, the average object
    2333 coordinates are based on the analysis using the Gaia coordinates.  The
    2334 Gaia DR1 coordinates used a fixed 2015 epoch.  Coordinates were
    2335 propagated from that epoch to the epoch for each PS1 image as
    2336 described above.
     2285an external astrometric reference.  After the Pan-STARRS DR1 object
     2286parameters were ingested into the PSPS database, the Gaia DR1
     2287astrometry was released \citep{2016AA...595A...4L}.  This gave us the
     2288option to use the Gaia positions for the external astrometric
     2289reference.  We re-did the astrometric analysis and generated a
     2290Gaia-based astrometry table for the Pan-STARRS DR1.  For Pan-STARRS
     2291DR2, the average object coordinates are based on the analysis using
     2292the Gaia DR1 coordinates.  The Gaia DR1 coordinates used a fixed 2015
     2293epoch.  Coordinates were propagated from that epoch to the epoch for
     2294each PS1 image as described above.
    23372295
    23382296\subsection{Object Astrometry}
     
    23472305PS1 \ippstage{chip}-stage measurements were used for the astrometry
    23482306measurement (no stack or forced-warp measurements).  If available, the
    2349 2MASS and Gaia astrometry for an object was also used in the
     23072MASS and Gaia DR1 astrometry for an object was also used in the
    23502308calculation of the astrometry.  Measurements which were kept for the
    23512309astrometric fit for an object were marked with the bit-flags
     
    23552313the bit flag \code{ID_MEAS_POOR_ASTROM}.
    23562314
    2357 If 2MASS or Gaia astrometry measurements
     2315If 2MASS or Gaia DR1 astrometry measurements
    23582316were available for an object, {\em all} measurements for that object
    23592317are marked with the bit-flag \code{ID_MEAS_OBJECT_HAS_2MASS} or
     
    24942452\subsection{Astrometry Calibration Quality}
    24952453
     2454% /data/kukui.1/eugene/cal.paper.images.20190217/scatter.sh : allsky.scatter.astrom
    24962455\begin{figure*}[htbp]
    24972456  \begin{center}
    2498  \includegraphics[width=\hsize,clip]{{pics/allsky.astrom.pv3.3}.png}
     2457 \includegraphics[width=\hsize,clip]{{\picdir/allsky.astrom.pv3.3}.\plotext}
    24992458  \caption{\label{fig:allsky.astrom.sigma} Consistency of astrometry
    25002459    measurements across the sky.  Each panel shows a map of the
    25012460    standard deviation of astrometry residuals for stars in each
    25022461    pixel.  The median value of the standard deviations across the sky
    2503     is $(\sigma_\alpha, \sigma_\delta) = (22, 23)$ milliarcseconds.
     2462    is $(\sigma_\alpha, \sigma_\delta) = (16, 16)$ milliarcseconds.
    25042463    These values reflect the typical single-measurement errors for
    25052464    bright stars.  See discussion regarding the astrometric flat which
     
    25082467\end{figure*}
    25092468
     2469% /data/kukui.1/eugene/cal.paper.images.20190217/flatplots.sh : astroflat.repair
    25102470\begin{figure*}[htbp]
    25112471  \begin{center}
    2512   \includegraphics[width=\hsize,clip]{{pics/astroflat.repair}.png}
     2472  \includegraphics[width=\hsize,clip]{{\picdir/astroflat.repair}.\plotext}
    25132473  \caption{\label{fig:astroflat.repair} Comparison of the
    25142474    high-resolution astrometric flat-field images used for PV3.2
     
    25352495%% filter y : 42867074 stars
    25362496
     2497% /data/kukui.1/eugene/cal.paper.images.20190217/scatter.sh : allsky.histogram.astrom.compare
    25372498\begin{figure*}[htbp]
    25382499  \begin{center}
    2539   \includegraphics[width=\hsize,clip]{{pics/allsky.histogram.astrom.compare}.png}
     2500  \includegraphics[width=\hsize,clip]{{\picdir/allsky.histogram.astrom.compare}.\plotext}
    25402501  \caption{\label{fig:allsky.astro.histogram} Illustration of the
    25412502    impact of the astrometric flat-field correction used for PV3.2 vs
     
    25772538photometry, we attribute this to failure of the PSF fitting due to
    25782539crowding.  The celestial North pole regions have somewhat elevated
    2579 errors in both R.A. and DEC, with some specifc structures.  Some of
     2540errors in both R.A.\ and DEC, with some specifc structures.  Some of
    25802541these structures may be due to the larger typical seeing at these high
    25812542airmass regions, but some are due to astrometric failures which stem
     
    25832544Section~\ref{sec:pole.problems} for further details).  Several
    25842545features can be seen which appear to be an effect of the tie to the
    2585 Gaia astrometry: the stripes near the center of the DEC image and the
    2586 right side of the R.A. image.  The mesh of circular outlines one the 2
     2546Gaia DR1 astrometry: the stripes near the center of the DEC image and the
     2547right side of the R.A.\ image.  The mesh of circular outlines one the 2
    25872548degree scale is due to the outer edge of the focal plane where the
    25882549astrometric calibration is poorly determined. 
     
    26972658
    26982659\subsection{Comparison to Gaia}
     2660\label{sec:gaia.tie}
    26992661
    27002662After the full relative astrometry analysis was performed for the PV3
     
    27042666observations.  Gaia DR1 objects which are bright enough to have proper
    27052667motion and parallax solutions are in general saturated in the PS1
    2706 observations.  Thus, we are limited to using the Gaia mean positions
    2707 reported for the fainter stars.  We extracted all Gaia sources not
     2668observations.  Thus, we are limited to using the Gaia DR1 mean positions
     2669reported for the fainter stars.  We extracted all Gaia DR1 sources not
    27082670marked as a duplicate from the Gaia archive and generated a DVO
    2709 database from this dataset.  We then merged the Gaia DVO into the PV3
     2671database from this dataset.  We then merged the Gaia DR1 DVO into the PV3
    27102672master DVO database.  We re-ran the complete relative astrometry
    2711 analysis using Gaia as an additional measurement.  We applied the
     2673analysis using Gaia DR1 as an additional measurement.  We applied the
    27122674analysis described above, applying the estimated distances to
    2713 determine preliminary proper motions.  The Gaia mean epoch is reported
     2675determine preliminary proper motions.  The Gaia DR1 mean epoch is reported
    27142676as 2015.0, so all Gaia measurements were assigned this epoch.  We
    27152677wanted to ensure the Gaia measurements dominated the astrometric
     
    27232685even at a lower weight, helps to tile over those gaps.
    27242686
     2687% /data/kukui.3/eugene/pv3.stats.20161022/plots.sh
     2688
    27252689\begin{figure*}[htbp]
    27262690  \begin{center}
    2727   \includegraphics[width=\hsize,clip]{{pics/gaia.photom.v1}.png}
    2728   \caption{\label{fig:gaia.photom} Comparison with Gaia
    2729     photometry. {\bf Left} Mean of PS1 - Gaia, {\bf Right} Standard
    2730     deviation of PS1 - Gaia.  For pixels with $|b| > 30$ and $\delta >
    2731     -30$, the standard deviation of the PS1 - Gaia mean values is 6.9
     2691  \includegraphics[width=\hsize,clip]{{\picdir/gaia.photom.v1}.\plotext}
     2692  \caption{\label{fig:gaia.photom} Comparison with Gaia DR1
     2693    photometry. {\bf Left} Mean of PS1 - Gaia DR1, {\bf Right} Standard
     2694    deviation of PS1 - Gaia DR1.  For pixels with $|b| > 30$ and $\delta >
     2695    -30$, the standard deviation of the PS1 - Gaia DR1 mean values is 6.9
    27322696    millimagnitudes, while the median of the standard deviations is 12.4
    27332697    millimagnitudes.  The former is a statement about the consistency
    2734     of the Gaia and Pan-STARRS\,1 photometry, while the latter
     2698    of the Gaia DR1 and Pan-STARRS\,1 photometry, while the latter
    27352699    reflects the combined bright-end errors for both systems.  }
    27362700  \end{center}
     
    27382702
    27392703Figure~\ref{fig:gaia.photom} shows a comparison between the Pan-STARRS
    2740 photometry in $g,r,i$ and the Gaia photometry in the $G$-band.  To
     2704photometry in $g,r,i$ and the Gaia DR1 photometry in the $G$-band.  To
    27412705compare the PS1 photometry to the very broadband Gaia G filter, we
    27422706have determined a transformation based on a 3rd order polynomial fit
     
    27792743\begin{figure*}[htbp]
    27802744  \begin{center}
    2781   \includegraphics[width=0.45\hsize,clip]{{pics/gaia.astrom.mean}.png}
    2782   \includegraphics[width=0.45\hsize,clip]{{pics/gaia.astrom.sigma}.png}
     2745  \includegraphics[width=0.48\hsize,clip]{{\picdir/gaia.astrom.mean}.\plotext}
     2746  \includegraphics[width=0.48\hsize,clip]{{\picdir/gaia.astrom.sigma}.\plotext}
    27832747  \caption{\label{fig:gaia.astrom} Comparison with Gaia
    2784     astrometry. {\bf Left} Mean of PS1 - Gaia, {\bf Right} Standard
    2785     deviation of PS1 - Gaia.  The median value of the standard
     2748    astrometry. {\bf Left} Mean of PS1 - Gaia DR1, {\bf Right} Standard
     2749    deviation of PS1 - Gaia DR1.  The median value of the standard
    27862750    deviations is $(\sigma_\alpha, \sigma_\delta) = (4.8, 3.1)$
    27872751    milliarcseconds. }
     
    27902754
    27912755Figure~\ref{fig:gaia.astrom} shows a comparison between the Pan-STARRS
    2792 mean astrometry positions in $\alpha,\delta$ and the Gaia astrometry.
     2756mean astrometry positions in $\alpha,\delta$ and the Gaia DR1 astrometry.
    27932757For this comparison, we have seleted all PS1 stars with Gaia
    2794 measurements with $14 < i < 19$ and with at least 10 total
     2758measurements with $14 < \ips < 19$ and with at least 10 total
    27952759measurements.  For Figure~\ref{fig:gaia.astrom}, we calculate the
    2796 difference between the position predicted by PS1 at the Gaia epoch
     2760difference between the position predicted by PS1 at the Gaia DR1 epoch
    27972761(using the proper motion and parallax fit) and the position reported
    27982762by Gaia.  For each pixel, we determine the histogram of these
    2799 differences in the R.A\. and DEC directions, and calculate the median
     2763differences in the R.A.\ and DEC directions, and calculate the median
    28002764and the 68\%-ile range.  In Figure~\ref{fig:gaia.astrom}, these
    28012765values are plotted as a color scale.
    28022766
    2803 There is good consistency between the PS1 and Gaia astrometry.  There
     2767There is good consistency between the PS1 and Gaia DR1 astrometry.  There
    28042768are patterns from the Galactic plane (though not very strongly at the
    28052769bulge).  There are also clear features due to the PS1 exposure
     
    28102774statisics of the per-exposure measurement residuals
    28112775(Figure~\ref{fig:allsky.astrom.sigma}.  The standard deviations of the
    2812 median differences are ($\sigma_\alpha, \sigma_\delta) = (4, 3)$
     2776median differences are ($\sigma_\alpha, \sigma_\delta) = (4.8, 3.1)$
    28132777milliarcseconds.
    28142778
    28152779For a future data release, we will recalibrate the Pan-STARRS $3\pi$
    2816 astrometry using the Gaia DR2 release.  The addition of Gaia-measured
    2817 proper motions will obviate the need to correct for the Galactic rotation.
     2780astrometry using the Gaia DR2 release \citep{2018AA...616A...1G}.  The
     2781addition of Gaia-measured proper motions will obviate the need to
     2782correct for the Galactic rotation.
    28182783
    28192784\section{Polar Astrometry Issues}
    2820 
    2821 Internal consistency testing of the PV3 stacks measurements indicated
     2785\label{sec:pole.problems}
     2786
     2787Internal consistency testing of the PV3 stack measurements indicated
    28222788potential problems with the astrometric registration of the exposures
    28232789in small areas near the North Pole.  These issues were originally
     
    28272793these anomalous sources demonstrated the presence of significant
    28282794misalignments between exposures; one of the worst cases is shown in
    2829 Figure~\ref{fig:pole.issue.exampe}.  While such sources appeared to be
     2795Figure~\ref{fig:pole.issue.example}.  While such sources appeared to be
    28302796rare, astrometric registration errors have the potential to affect
    28312797several different source properties: morphology and photometry in
    28322798addition to astrometry.  Therefore we carried out an astrometric
    2833 regsitration test for all skycells North of $ \delta=+70\deg$.
     2799regsitration test for all skycells North of $\delta=+70\mathdegree$.
    28342800
    28352801\begin{figure*}[htbp]
    28362802  \begin{center}
    2837   \includegraphics[width=\hsize,clip]{{pics/A1}.pdf}
     2803  \includegraphics[width=\hsize,clip]{{\picdir/A1}.pdf}
    28382804  \caption{\label{fig:pole.issue.example} Example of a stack source badly affected by polar astrometry failures.  Source from multiple detections from skycell 2643.093.}
    28392805  \end{center}
     
    28412807
    28422808This test was based primarily on the ``original detection positions'',
    2843 \ie, the positions of sources (detections) found in individual
    2844 exposures as measured after each exposure's astrometric calibration,
    2845 but before recalibration of the combined values to the Gaia reference
    2846 frame (described in Section 7.3).  We started by collecting the
    2847 original detection positions (as defined above) for each skycell.  To
    2848 ensure good signal-to-noise ratios and minimize potential spurious
    2849 detections, we used only the top quartile (in flux) of detections
    2850 within each chip.  We grouped these detections on a filter-by-filter
    2851 basis within a radius of $ 2\farcs5 $ (10 pixels), ensuring that each
    2852 group contained only one source per exposure, and retaining only
    2853 groups with at least five detections; we then recorded the 2-D
    2854 position dispersion for each group.  The mean positions for each group
    2855 were cross-correlated against the Gaia DR2 sources, showing that these
    2856 were real sources and providing information on their absolute
    2857 astrometry.
    2858 
    2859 \begin{figure*}[htbp]
    2860   \begin{center}
    2861 %  \includegraphics[width=\hsize,clip]{{pics/A2}.pdf}
    2862   \caption{\label{fig:pole.issue.example} Example of a stack source badly affected by polar astrometry failures.}
    2863   \end{center}
    2864 \end{figure*}
     2809\ie, the positions of detections found in individual exposures as
     2810measured after each exposure's astrometric calibration, but before
     2811recalibration of the combined values to the Gaia reference frame
     2812(described in Section~\ref{sec:gaia.tie}) since that step had the
     2813opportunity to repair any astrometric failures.  We started by
     2814collecting the original detection positions (as defined above) for
     2815each skycell.  To ensure good signal-to-noise ratios and minimize
     2816potential spurious detections, we used only the top quartile (in flux)
     2817of detections within each chip.  We grouped these detections on a
     2818filter-by-filter basis within a radius of $ 2\farcs5 $ (10 pixels),
     2819ensuring that each group contained only one source per exposure, and
     2820retaining only groups with at least five detections; we then recorded
     2821the 2-D position dispersion for each group.  The mean positions for
     2822each group were cross-correlated against the Gaia DR2 sources \citep{2018AA...616A...1G}, showing
     2823that these were real sources and providing information on their
     2824absolute astrometry.
    28652825
    28662826Overall, the vast majority of the detection groups thus defined have
     
    28692829having an internal dispersion $ > 1 $ pixel, can result from spurious
    28702830sources or other anomalies, and are generally rare (fewer than a few
    2871 percent of al groups).  However, some skycells have a significant
     2831percent of all groups).  However, some skycells have a significant
    28722832fraction ($ > 10\%$) of bad groups.  Direct inspection demonstrates
    28732833that the incidence of bad groups is related to astrometric
    2874 registration failures.  Figure~\ref{fig:pole.astrom.failures} shows an
    2875 example of a good and of a bad group.
    2876 
    2877 %% [Note: the rest of this
    2878 %%   paragraph, and Figure A3, may be too much information for this
    2879 %%   paper.]  It also appears that registration problems, when present,
    2880 %% are not uniform within a skycell; Figure (A3) shows the difference
    2881 %% between mean group position and the position of individual detections
    2882 %% for all G band exposures overlapping skycell 2637.088, which has one
    2883 %% of the worst-case mismatches in the g band.
    2884 
    2885 % caption: Map of astrometric displacement for all g-band exposures
    2886 %    overlapping skycell 2637.088, with one of the worst astrometric
    2887 %    registration issues. [Optional]
     2834registration failures.
    28882835
    28892836\begin{figure*}[htbp]
    28902837  \begin{center}
    2891   \includegraphics[width=\hsize,clip]{{pics/A4}.pdf}
     2838  \includegraphics[width=\hsize,clip]{{\picdir/A4}.pdf}
    28922839  \caption{\label{fig:pole.bad.histogram} Histogram of the fraction of bad groups for each skycell (red line).}
    28932840  \end{center}
     
    28952842
    28962843Bad skycells, defined as those with more than 10\% bad groups, are
    2897 essentially limited to the North polar cap ($ \delta > +80^{\degree}$).
     2844essentially limited to the North polar cap ($ \delta > +80\mathdegree$).
    28982845Of the 2500 skycells in this region, 164, or 6.6\%, have more than 10\%
    28992846bad groups; 64 of these have more than 20\% bad groups.  By comparison,
    2900 essentially no skycells between $ +70^\degree $ and $ +80^\degree $ have
     2847essentially no skycells between $+70\mathdegree$ and $+80\mathdegree$ have
    29012848more than 10\% bad groups.  Figure~\ref{fig:pole.bad.histogram} shows a histogram
    29022849of the fraction of bad groups for each skycell.
     
    29042851In order to have an independent validation of the impact of this
    29052852astrometric alignment issue, we also carried out a photometric test
    2906 based on a comparison of stack to mean object photometry.  In the
     2853based on a comparison between stack and mean object photometry.  In the
    29072854presence of modest registration errors, mean object photometry would
    29082855not be affected, as individual detection woulds have the correct
     
    29172864in poor stack photometry for the affected skycells.
    29182865
    2919 \note{discuss the cause of the failure due to the duplicates in the reference catalog, and the original polar astrometry failures}
    2920 
    2921 As a result of these tests, we decided to 1) exclude from the main DR2
    2922 catalogs all sources in the skycells with more than 10\% bad groups,
    2923 and 2) to reprocess all such skycells with an improved procedure.  The
    2924 reprocessing was carried out in late 2018, and the astrometric
    2925 registration test was repeated on the reprocessed exposures.  The
    2926 reprocessing greatly ameliorated the registration issue, as shown
    2927 Figure (A4).  Here the red line shows the histogram of the fraction of
    2928 bad groups for each skycell {\sl before reprocessing}, while the black
    2929 line refers to the results {\sl after reprocessing}.  The improvement
    2930 is apparent.  After reprocessing, only 23 cells, instead of the
    2931 original 164, exceed 10\% of bad groups, and even for these the
    2932 fraction of bad groups is substantially reduced.  Sources in the
    2933 previously bad, now fixed skycells will be included in an upcoming
    2934 partial release.
    2935 
    2936 \note{the above is not quite accurate -- a test reprocess demonstrated
    2937   partial improvement, but did not use a totally repaired ref catalog.
    2938   we are running a new analysis based on a DR2-tied catalog with
    2939   pristine source set.}
     2866Further investigaion revealed that the cause of these failures was an
     2867error in the internal reference catalog used for the PV3 analysis (see
     2868Section~\ref{sec:synthdb}).  This reference catalog used PS1
     2869observations to generate a catalog of \grizy\ photometry tied to the
     28702MASS astrometric system.  The astrometry used for this catalog was
     2871generated using the analysis discussed in Section~\ref{sec:astrometry}
     2872to define a collection of reference stars with a coordinate system
     2873tied to 2MASS but with the higher accuracy of the Pan-STARRS
     2874measurements on small spatial scales.  Unfortunately, in the vicinity
     2875of the celestial north pole, this reference catalogs was contaminated
     2876by a number of poor measurements.  In this portion of the sky, the
     2877astrometric registration of the exposures is more challanging due to
     2878the degeneracy between boresite position errors and field rotation.
     2879In addition, the PS1 telescope suffers from larger pointing errors
     2880near the celestial north pole, largely for the same reason.  Because
     2881of these two factors, a number of exposures near the celestial pole
     2882were included in the reference database with invalid astrometry,
     2883injecting apparently good reference stars in the database with
     2884positions displaced from the true position by 1-2 arcseconds.
     2885Sometimes a chip processed in this region would find an astrometric
     2886solution using only good reference stars.  Sometimes the solution
     2887would use only bad reference stars, resulting in a chip apparently
     2888displaced from the truth position by 1-2 arcseconds.
     2889
     2890To correct the astrometry failures that caused the original errors in
     2891the reference catalog, we extended the field rotation search range for
     2892the polar exposures.  We also added tests to the analysis of the
     2893exposures to ensure they would not fail in a marginal way and
     2894introduce poor solutions into the calibration database.  We then ran a
     2895test to confirm that we could generate good astrometry in this region
     2896with an acceptable reference catalog.
     2897
     2898We first used the PV3 mean astrometry and photometry to define a new
     2899reference catalog in the assumption that the bulk of the failures
     2900would be eliminated by the astrometric recalibration.  We reprocesed a
     2901section of the polar cap data using this PV3-based reference catalog
     2902and re-ran the astrometric registration test was repeated on the
     2903reprocessed exposures.  The reprocessing greatly ameliorated the
     2904registration issue, as shown in Figure~\ref{fig:pole.bad.histogram}.
     2905Here the red line shows the histogram of the fraction of bad groups
     2906for each skycell {\sl before reprocessing}, while the black line
     2907refers to the results {\sl after reprocessing}.  The improvement is
     2908apparent.  After reprocessing, only 23 cells, instead of the original
     2909164, exceed 10\% of bad groups, and even for these the fraction of bad
     2910groups is substantially reduced.
     2911
     2912To further improve the astrometric calibration reliability in this
     2913region, we have generated a new reference catalog combining the PS1
     2914PV3 photometry with astrometry from Gaia DR2 \citep{2018AA...616A...1G}.  We are reprocessing all
     2915images from the region North of $+70\mathdegree$ and will provide a
     2916complete Polar Region release using the same data as used for DR2.
     2917This updated release is expected to be available from MAST near the
     2918end of summer 2019.
     2919
     2920We consider skycells with more than 10\% bad groups to have been
     2921adversely affected by this problem.  Uses of DR2 should be aware that
     2922the affected skycells have poor astrometry and effective image
     2923quality.  However, as these images may be useful to the community,
     2924they are available from the MAST cutout server.  Users who attempt to
     2925download these problem skycells will see a warning message and should
     2926avoid using the skycell images for quantitative measurements without
     2927extreme caution.  Since stack measurements from these skycells are
     2928significantly damaged, the DR2 release has set the measured stack
     2929properties of these objects to a null value.  Again, users should
     2930exercise caution with sources from the affected skycells. 
    29402931
    29412932\section{Conclusion}
    29422933
    2943 \note{WRITE THIS}
     2934The Pan-STARRS Data Release 2 provides astromtry and photometry of
     2935roughly 3 billion astronomical objects across the $3\pi$ survey
     2936region.  The photometry system has been shown to be reliable across
     2937the sky at the level of (8.0, 7.0, 9.0, 10.7, 12.4) millimags in
     2938(\grizy).  The median value of the measure standard deviations for
     2939stars across the sky is $(\sigma_g, \sigma_r, \sigma_i, \sigma_z,
     2940\sigma_y) = (14, 14, 15, 15, 18)$ millimags, reflecting the systematic
     2941floor on the accuracy of individual measurements of bright stars.  The
     2942astrometric calibration is tied to the Gaia DR1 frame with a
     2943systematic error floor of ($\sigma_\alpha, \sigma_\delta) = (4.8,
     29443.1)$ milliarcseconds.  The median residual astrometric scatter for
     2945bright objects across the sky is 16 milliarcseconds in both R.A.\ and
     2946DEC.  Caution should be used for 164 skycells in the celestial north
     2947pole regions where the reference catalog was contaminated with
     2948astrometric failures.  The Pan-STARRS DR2 photometry and astrometry
     2949will be a valuable resource for many years for the astronomical
     2950community.
    29442951
    29452952\acknowledgments
     
    29632970\ref{fig:allsky.photom.sigma}, \ref{fig:photom.pv3.3v4},
    29642971\ref{fig:astroflat.gri}, \ref{fig:astroflat.zy},
    2965 \ref{fig:allsky.astrom.sigma}, and \ref{fig:astroflat.repair} from
    2966 Peter Kovesi \citep[Good Colour Maps: How to Design Them.][]{2015arXiv150903700K}.
     2972\ref{fig:allsky.astrom.sigma}, and \ref{fig:astroflat.repair} are
     2973based on the matplotlib ``magma'' colormap with additional guidance
     2974from Peter Kovesi's work \citep[Good Colour Maps: How to Design
     2975  Them.][]{2015arXiv150903700K}.
    29672976
    29682977\bibliographystyle{apj}
    2969 \bibliography{lib}{}
    2970 % \input{calibration.bbl}
     2978% \bibliography{lib}{}
     2979\input{calibration.bbl}
    29712980
    29722981\end{document}
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