LocalSkyModel

The Local Sky Model

For now we will work with a LSM containing apparent fluxes. This postpones the problem of the unknown beam shape. Note that each telescope / station has its own beam shape. In general these beams will slightly differ from one another.

Initial Implementation

A prototype Local Sky Model is under construction. It is connected to an existing ParmTable (a mep-table). It is not yet available from cvs, but if you want to play with it ask RJN.

Two documents describing the LSM have been produced: a functional description document () and an implementation document. The implementation document can be downloaded here:

The ParmTable consists of data for some Calibrator sources.

# A MEPTable with CPS parameters using the Baars flux scale (Baars et al., A&A 61, 99-106, 1977)
#
# Available sources: 
#
# The A-team: CasA, CygA, VirA, TauA
#
# WSRT Calibrator Sources: 3C48, 3C147, 3C286, 3C295
#
# ATCA Calibrator Source: 1934-638
#
# Intensity (given as ISIF=Log(I)) is a PolcLog with l_scale 10^6 (1 MHz).
#
# For 3C286 coefficients for StokesQ and StokesU are given. These are taken from the MYRIAD routine 'calstoke'.
# They are based on unpublished data from Perley/Killeen, 1991.
# StokesQ and StokesU (given as QSIF=Q, USIF=V) are PolcLogs with l_scale 10^9 (1 GHz).
#
# StokesV is zero for all sources.
#

Below is some preliminary decription of the protolsm object.

#   the protolsm always contains
#
#      self.mep       : A meptable object that is linked to an AIPS++ Table containing LSM parameters.
#      self.tablename : Name of the meptable. Needed for creating MeqParms.
#
#   and may additionally contain the following objects:
#
#      self.LSM_Trees[q=xyz][RA_Tree = defrec1,
#                            Dec_Tree = defrec2,
#                            StokesI_Tree = defrec3,
#                            StokesQ_Tree = defrec4,
#                            StokesU_Tree = defrec5,
#                            StokesV_Tree = defrec6
#                           ]
# 
#               defrec1.name     = 'RA[q=xyz]'
#               defrec1.default  = meq_polc
#               defrec1.groups   = 'Parm'
#
#               defrec2.name     = 'Dec[q=xyz]'
#               defrec2.default  = meq_polc
#               defrec2.groups   = 'Parm'
#
#               defrec3.class    = 'MeqPow'
#               defrec3.name     = 'StokesI[q=xyz]'
#               defrec3.children = meq.list()
#
#               defrec4.name     = 'StokesQ[q=xyz]'
#               defrec4.default  = meq_polclog
#               defrec4.groups   = 'Parm'
#
#               defrecs 5,6 just like defrec4
#
#   Furthermore, the protolsm contains the following public functions:
#
#       public.done()
#       public.show()            : browse the LSM mep-table 
#       public.plot(...)         : plot one of the Stokes parameters as function of frequency for all sources in the LSM  
#       public.qnames()          : returns a list of source names
#       public.defrec('treename'): returning the defrec of the Tree asked for, e.g. 'StokesI[q=RJN1]'
#       public.go()              : build and execute all 6 LSM trees for all sources