
            *** CRUSH User's Manual Extension for SHARC-2 ***

                              Attila Kovacs
                      <attila[AT]submm.caltech.edu>

                      Last updated: 20 February 2016


Table of Contents
=================

1. Introduction

2. Locating Scans

  2.1 By file names
  2.2 By scan numbers

3. Opacity Corrections

  3.1 Tau scaling relations
  3.2 JCMT 183GHz water vapor lookup
  3.3 MaiTau lookup
  3.4 Direct tau
  3.5 Manually defined tau

4. Pointing Corrections

5. Glossary of SHARC-2 specific options

6. SHARC-2 specific log quantities




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1. Introduction
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This document contains information specific to using CRUSH-2 to reduce SHARC-2
data. It is assumed that you are already familiar with the contents of the main
CRUSH-2 README (inside the distribution directory), especially its Section 1
(Getting Started).

If you run into difficulty understanding the concepts in this document, you
will probably find it useful to study the main README document a little longer.




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2. Locating scans
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2.1 By file names

2.2 By scan numbers




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3. Opacity Corrections
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3.1 Tau scaling relations

3.2 JCMT 183GHz water vapor lookup (preferred)

3.3 Maitau lookup (2nd preferred)

3.4 Direct tau

3.5 Manually defined tau



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4. Pointing Corrections
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5. Glossary of SHARC-2 specific options
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   350um		Specify that the 350um filter was used (default). This
                        adjuts conversion factors, tau scaling relations for
                        calculating in-band line-of sight opacitites, and beam
                        sizes (see 'sharc2/default.cfg').
                        @See: 'jansky', 'tau.<?>', 'beam'.

   450um		Use if the 450um filter was used to observe with
                        SHARC-2, or to specify 450um imaging with SCUBA-2 and
                        MAKO-2.
                        @See: '350um' and '850um'
		
   850um		Specify that data was taken at 850um with SHARC-2, or
                        to reduce the data from the 850um array of SCUBA-2 and
                        MAKO-2.
                        @See: '350um' and '450um'
	
   block=NX,NY		@Expert
                        Specify a correlated block size for higher order
                        sky-noise removal, as two integer pixel numbers (rows
                        and columns) separated by a comma or 'x'. E.g.:

                           block=4x6

                        will correlated.signals on blocks that are 4 columns
                        wide and 6 rows tall (i.e. there will be 16 such blocks
                        on the 32x12 SHARC-2 array).

   blocks		@Alias -> correlated.blocks
			@Advanced
                        Decorrelate on rectangular block regions of the array,
                        as a way to remove higher order sky-noise. As such, it
                        can be used together with, or instead of 'gradients'.
                        @See: 'gradients', 'correlated.<?>'			

   chopper		@Alias -> correlated.chopper-x
			@Advanced
                        Remove signals that are correlated with chopper
                        movement. The moving secondary mirror changes the
                        telescope illumination, thus producing strong signals
                        when observing under a bright atmosphere. To first
                        order, such signals are linear with chopper
                        displacement. Since most telescopes chop in the
                        horizontal 'x' direction only, the 'chopper' keyword is
                        aliased to decorrelation on motion in that direction.
                        When a 2D chopper is used, you should correlated.in
                        both the 'x' and 'y' directions.
                        @See: 'correlated.<?>', 'detect.chopped'

   cols			@Alias -> 'correlated.cols'
			
   elevation-response   @Expert
                        Load and use an lookup table for the elevation
                        dependent forward efficiency of the telecscope. The
                        table is an ASCII file, as specified by Darren Dowell,
                        and is available from the SHARC-2 web-site. CRUSH
                        contains copies of the available tables and is
                        configured to use them as needed.

   excessload=X		@Expert
                        SHARC-2 can determine a line-of-sight opacity based on
                        the total-power response of its detectors. However, for
                        this to work well, all sources of optical loading on
                        the detectors must be understood. The load curves (see
                        'response') were determined at one time only, and
                        therefore this flag provides the means to specify a
                        different optical loading environment from then, as an
                        excess optical load (in Kelvins).
                        @See: 'response', 'tau.<?>'

   fazo			An alternative to 'center' for providing pointing
                        corrections. As opposed to 'center', which specifies
                        incremental corrections, this option takes an absolute
                        AZ pointing offset (i.e. FAZO at the CSO) which should
                        have been the correct one (as opposed to the value used
                        by the antenna computer during the observations).
                        @See: 'fzao', 'center'

   fzao			Specify a zenith pointing offset.
                        @See: 'fazo'

   maitau.fallback=<type>	@Advanced
                        Define which tau value to use in case the MaiTau lookup
                        fails. The possible values are:

                           direct         Calculate tau from the total-power
                                          loading of the detectors

                           225GHz         Use the 225GHz tipper value.

                           350um          Use the 350um tipper value.

                           pwv            Use precipitable water vapor.

                           sharc2         Use the value specified by tau.sharc2

                        Other than the 'direct' flag, the values may be
                        specified with the corresponding tau settings.
                        @See: 'maitau.server', 'tau.225GHz', 'tau.350um',
                              'tau.sharc2'

   maitau.server=IP	@Expert
                        Specify the MaiTau server to use, either as an IP
                        address, or server name. This should probably be set to
                        'agn.caltech.edu', or to the equivalent
                        'fangorn.submm.caltech.edu'. MaiTau is a server-based
                        lookup of the CSO opacities, based on dailly polynomial
                        fits to the measured 225GHz and 350um tipper data. The
                        polynomials smooth out short-term fluctuations and
                        measurement errors, providing a smoothly varying
                        function of tau with time. When using MaiTau, CRUSH
                        will try use the 350um fit, and then the 225GHz fit (if
                        available), from which it calculates an appropriate
                        in-band zenith tau value.
                        @See: 'tau.<?>.a', 'tau.<?>.b'

   mux			@Alias -> correlated.mux
			@Advanced
                        Decorrelate on MUXes, or set options for it.
                        @See: 'correlated.<?>'

   nochopper		@Advanced
                        @Since:2.16-1
                        Ignore the chopper position signal (if at all present).

   nogaps		@Advanced
                        Terminate the reading of the data at the first
                        gap. During the early SHARC-2 runs when JSharc was used
                        for the acquisition of the data, there was an
                        occasional damaging timing bug resultuing from the
                        wraparound of an internal buffer. The bug manifested in
                        a sudden jump in the timestamps, making it relatively
                        easy to diagnose if this happened during the scan.

   pcenter=row,col	@Advanced
                        Defines the pointing center used, in terms of the
                        instrument pixel row and colum coordinates. Pixel 1,1
                        designates the top-left corner of the array in
                        horizontal (AZ/EL) or equivalent Nasmyth coordinates.
                        Columns increase to the right, while row numbers
                        increase downward. Thus, the center of the
                        SHARC-2 array is 6.5,16.5, while the center of GISMO is
                        8.5,4.5. The 'pcenter' option is not used if the pixel
                        positions are loaded from an RCP data file, instead of
                        being calculated (since a rectangular grid can no
                        longer be assumed).
                        @See: 'rcp', 'rcenter', 'pixelsize', 'rotate'

   pixelsize=X		@Since: 2.17
                        @Expert
                        Specify the pixel spacing in arcseconds.

   pixelsize=X,Y	@Expert
                        Specify the size of rectangular pixels in a grid. This
                        is used for calculating pixel positions on a rectangular
                        grid. The information is ignored when positions are
                        loaded from an RCP data file (as a regular grid can no
                        nonger be assumed).
                        @See: 'rcp', 'pcenter', 'rcenter'

   rcenter=dX,dY	@Expert
                        Specify a rotation center, in the coordinate system of
                        the array (AZ,EL or Nasmyth coordinates). Works
                        similarly to 'pcenter'
                        @See: 'pcenter'

   response=<filename>	@Expert
                        Specify the <filename> containing the pixel
                        loading information, based on which in-band
                        line-of-sight opacities may be calculated.
                        @See: 'response.calc', 'tau', 'tau.<?>'

   response.calc	@Expert
                        Allows the recalculation of pixel responses, based on an
                        initial 'response' provided in a file, and a 'tau'
                        value. Scans on very faint or deep-field sources are
                        most suited for such recalculations. Use this option
                        only if you really understand what it is meant to do.
                        @See: 'response', 'tau', 'tau.<?>'

   rot0			@Expert
                        Specifies the reference (zero point) of the rotator (if
                        available). This option applies only for the early
                        SHARC-2 runs, when the instrument was still mounted on
                        the Cassdegrain platform. The values should be correcly
                        configured in the default SHARC-2 configuration
                        ('sharc2/default.cfg'), and there should be no reason
                        for the user to change these settings...
                        @See: 'rotation'

   rows			@Alias: -> correlated.rows
			@Advanced
                        Decorrelate on detector rows, or set options for it.
                        @See: 'correlated.<?>'

   tau.jctables=<spec>	@Advanced
			Specify the location (folder) of the JCMT 183 GHz tau
                        tables. The argument can point to a local directory
                        or an online resource on the web (URL). E.g.:

                          http://www.jach.hawaii.edu/weather/opacity/mk/archive      
                        If the JCMT lookup fails (e.g. because no data is
                        available for the specific date, or using CRUSH
                        offline), then a fallback option may be specified via
                        the 'maitau.fallback' key.
                        @See: 'tau.tables', 'maitau.fallback'

   tau.window=X		@Expert
			@Since: 2.13
                        Set the 1-sigma Gaussian weighting window (in hours)
                        for deriving local weighted average tau values from a
                        table of skydip/tau measurements.
                        @GISMO: since 2.15-2.
                        @See: 'tau', 'scale.window'



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6. SHARC-2 specific log quantities
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	bias		The bias amplitude (mV) of the first detector row.

	dsos?		Whether DSOS was used.

	FAZO		FAZO during observation (arcsec).

	FZAO		FZAO during observation (arcsec).

	filter		Filter setting.

	foc.mode	Focum mode.

	foc.dY		Focus Y offset (mm).

	foc.dZ		Focus Z offset (mm).

	foc.X		Focus X (mm).

	foc.Y		Focus Y (mm).

	foc.Z		Focus Z (mm).

	load		The excess optical load in K (calculated or assumed).

	pnt.FAZO	FAZO pointing offset.
	
	pnt.FZAO	FZAO pointing offset.

	rot		Rotator angle (deg).

	rot0		Zero rotation angle (deg).

	rotmode		Rotator mode.

	rotoff		Rotator offset (deg).


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Copyright (C)2016 -- Attila Kovacs <attila[AT]submm.caltech.edu>

