<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <!--Converted with LaTeX2HTML 98.1p1 release (March 2nd, 1998) originally by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds * revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan * with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --> <HTML> <HEAD> <TITLE>Data Reduction</TITLE> <META NAME="description" CONTENT="Data Reduction"> <META NAME="keywords" CONTENT="vol2"> <META NAME="resource-type" CONTENT="document"> <META NAME="distribution" CONTENT="global"> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <LINK REL="STYLESHEET" HREF="vol2.css"> <LINK REL="previous" HREF="node491.html"> <LINK REL="up" HREF="node489.html"> <LINK REL="next" HREF="node493.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html7569" HREF="node493.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html7566" HREF="node489.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html7562" HREF="node491.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html7568" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="icons.gif/contents_motif.gif"></A> <BR> <B> Next:</B> <A NAME="tex2html7570" HREF="node493.html">IRSPEC REDUCTION</A> <B> Up:</B> <A NAME="tex2html7567" HREF="node489.html">PISCO</A> <B> Previous:</B> <A NAME="tex2html7563" HREF="node491.html">Data Format</A> <BR> <BR> <!--End of Navigation Panel--> <H1><A NAME="SECTION002830000000000000000"> Data Reduction</A> </H1> After having enabled the PISCO context (command SET/CONTEXT PISCO), the basic reduction of PISCO data involves merely one command, REDUCE/PISCO, which starts a routine (pisco.prg) solely consisting of other MIDAS commands. So, the whole procedure can be followed when the ECHO facility is enabled (see description for ECHO/ON or ECHO/FULL). <BR> The essential steps are: (1) division of the data by the integration time (stored in descriptor O_TIME), (2) subtraction of the sky and the offset (using a sky measurement, if available, or a dark measurement), (3) calibration (division by calibration file) and (4) Fourier transformation. As is described in Appendix A of the PISCO Operating Manual, the last step, a simple Fourier transform using the MIDAS command FFT/POWER, is the core of the reduction of PISCO data. <BR> The procedure is designed to handle an entire set of data by operating on an input catalog and producing a single output table in which each row holds the results for one data frame in the input catalog. There are no free parameters except for a <EM>mode</EM>, which can be set to 1, 2, or 3 depending on whether the two sky channels X and Y shall be reduced separately, together, or separately and together, respectively. Normally, the X and Y channel should be treated together. <P> <BR> <DIV ALIGN="CENTER"><A NAME="27427"> </A> <TABLE> <CAPTION><STRONG>Table E.1:</STRONG> Format of output table produced by REDUCE/PISCO</CAPTION> <TR><TD> <TABLE CELLPADDING=3 BORDER="1"> <TR><TD ALIGN="LEFT">column label</TD> <TD ALIGN="LEFT">content</TD> </TR> <TR><TD ALIGN="LEFT">IDENT:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> identifier, copied from descriptor IDENT of raw data file</FONT></TD> </TR> <TR><TD ALIGN="LEFT">UT:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> universal time (hours), copied from descriptor O_TIME(5) of same data file</FONT></TD> </TR> <TR><TD ALIGN="LEFT">X_INTENSITY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> mean of 1<SUP><I>st</I></SUP> line from data file, divided by integration time O_TIME(7), sky subtracted</FONT></TD> </TR> <TR><TD ALIGN="LEFT">Y_INTENSITY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> mean of 2<SUP><I>nd</I></SUP> line from data file, divided by integration time O_TIME(7), sky subtracted</FONT></TD> </TR> <TR><TD ALIGN="LEFT">POLXY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> degree of polarisation in channels X+Y (mode=3)</FONT></TD> </TR> <TR><TD ALIGN="LEFT">ERRORXY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> error of :POLXY</FONT></TD> </TR> <TR><TD ALIGN="LEFT">ANGLEXY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> position angle of E-vector in channels X+Y (mode=3)</FONT></TD> </TR> <TR><TD ALIGN="LEFT">POLX:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> degree of polarisation in channel X (mode=1)</FONT></TD> </TR> <TR><TD ALIGN="LEFT">ERRORX:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> error of :POLX</FONT></TD> </TR> <TR><TD ALIGN="LEFT">ANGLEX:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> position angle of E-vector in channel X (mode=1)</FONT></TD> </TR> <TR><TD ALIGN="LEFT">POLY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> degree of polarisation in channel Y (mode=2)</FONT></TD> </TR> <TR><TD ALIGN="LEFT">ERRORY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> error of :POLY</FONT></TD> </TR> <TR><TD ALIGN="LEFT">ANGLEY:</TD> <TD ALIGN="LEFT"><FONT SIZE="-1"> position angle of E-vector in channel Y (mode=2)</FONT></TD> </TR> </TABLE> <A NAME="T1"> </A></TD></TR> </TABLE> </DIV> <BR> <P> The program attempts an error estimate from the noise level in the Fourier-transform. The polarisation angles still have an arbitrary zeropoint and need to be transformed to a standard system by means of observations of standard stars. Apart from the comparison with calibration data, the results of REDUCE/PISCO should be final. <P> The output table is a standard MIDAS table so that all applicable table commands can be used to further process the results. The columns of this table are shown in Table <A HREF="node492.html#T1">E.1</A>. <P> <P> =01 =11 =1992 <HR> <!--Navigation Panel--> <A NAME="tex2html7569" HREF="node493.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html7566" HREF="node489.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html7562" HREF="node491.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html7568" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="icons.gif/contents_motif.gif"></A> <BR> <B> Next:</B> <A NAME="tex2html7570" HREF="node493.html">IRSPEC REDUCTION</A> <B> Up:</B> <A NAME="tex2html7567" HREF="node489.html">PISCO</A> <B> Previous:</B> <A NAME="tex2html7563" HREF="node491.html">Data Format</A> <!--End of Navigation Panel--> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
