PSRCHIVE user documentation: pcm
Measurement Equation Modeling (MEM) Degeneracy
Due to the degeneracy described in Appendix B of van Straten (2004),
it is necessary to make two assumptions:
- To constrain the mixing of Stokes I and V, it is assumed that either:
- 1.A) the noise diode has zero circular polarization; or
- 1.B) while pointing at a standard candle, the system temperature
has zero circular polarization.
- To constrain the mixing between Stokes Q and U (rotation about
line of sight), it is assumed that either:
- 2.A) the orientation offset of the first receptor is zero; or
- 2.B) the orientation offset of the noide diode is zero.
Assumption 1.A is made by default if no
are provided, or if the -v command line option is specified.
In this case, Stokes V of the noise diode is fixed at zero.
Assumption 1.B is made by default if a
Signal::FluxCalOn observation is included as a
constraint. In this case, Stokes V of the noise diode is allowed to
vary as a free parameter.
Assumption 2.A is made by default. In this case, Stokes Q of the noise
diode is allowed to vary as a free parameter.
Assumption 2.B is made if the -q command line option is specified.
Equally valid solutions are derived regardless of the above assumptions;
that is, there is no change in the goodness of fit.