From 0a9d4d8b45c42d004928751518a5f300d160b212 Mon Sep 17 00:00:00 2001
From: Joris van Zwieten <zwieten@astron.nl>
Date: Sat, 17 Mar 2012 10:34:27 +0000
Subject: [PATCH] Task #3165: Added linear to circular-RL conversion for LOFAR
observations.
---
.../BBSKernel/src/MeasurementExprLOFAR.cc | 85 ++++++++++++++++---
1 file changed, 73 insertions(+), 12 deletions(-)
diff --git a/CEP/Calibration/BBSKernel/src/MeasurementExprLOFAR.cc b/CEP/Calibration/BBSKernel/src/MeasurementExprLOFAR.cc
index 3ebca01db48..1d55e2ab11c 100644
--- a/CEP/Calibration/BBSKernel/src/MeasurementExprLOFAR.cc
+++ b/CEP/Calibration/BBSKernel/src/MeasurementExprLOFAR.cc
@@ -128,9 +128,6 @@ void MeasurementExprLOFAR::makeForwardExpr(SourceDB &sourceDB,
THROW(BBSKernelException, "No patches found matching selection.");
}
- // Create a linear to circular-RL transformation Jones matrix.
- Expr<JonesMatrix>::Ptr H(new LinearToCircularRL());
-
// Beam reference position on the sky.
Expr<Vector<2> >::Ptr exprRefDelay = makeDirectionExpr(refDelay);
Expr<Vector<3> >::Ptr exprRefDelayITRF =
@@ -156,6 +153,10 @@ void MeasurementExprLOFAR::makeForwardExpr(SourceDB &sourceDB,
itsScope);
}
+ // -------------------------------------------------------------------------
+ // Direction dependent effects (DDE).
+ // -------------------------------------------------------------------------
+
vector<MatrixSum::Ptr> coherenceExpr(itsBaselines.size());
for(size_t i = 0; i < patches.size(); ++i)
{
@@ -243,12 +244,6 @@ void MeasurementExprLOFAR::makeForwardExpr(SourceDB &sourceDB,
exprPatch->coherence(baseline, exprUVW[baseline.first],
exprUVW[baseline.second]);
- // Convert to circular-RL if required.
- if(circular)
- {
- patchCoherenceExpr = apply(H, patchCoherenceExpr, H);
- }
-
// Apply direction dependent effects.
patchCoherenceExpr = apply(exprDDE[baseline.first],
patchCoherenceExpr, exprDDE[baseline.second]);
@@ -263,10 +258,26 @@ void MeasurementExprLOFAR::makeForwardExpr(SourceDB &sourceDB,
}
}
+ // -------------------------------------------------------------------------
// Direction independent effects (DIE).
+ // -------------------------------------------------------------------------
+
+ // Create a linear to circular-RL transformation Jones matrix.
+ Expr<JonesMatrix>::Ptr H(new LinearToCircularRL());
+
+ const bool isLOFAR = (instrument->name() == "LOFAR");
+
vector<Expr<JonesMatrix>::Ptr> exprDIE(instrument->nStations());
for(size_t i = 0; i < instrument->nStations(); ++i)
{
+ // Convert from linear to circular-RL polarization. For the LOFAR array,
+ // which has linearly polarized antennae, this conversion is done at the
+ // end of the chain.
+ if(circular && isLOFAR)
+ {
+ exprDIE[i] = compose(exprDIE[i], H);
+ }
+
// Create a clock delay expression per station.
if(config.useClock())
{
@@ -289,12 +300,27 @@ void MeasurementExprLOFAR::makeForwardExpr(SourceDB &sourceDB,
config.usePhasors()));
}
- // Create a direction independent TEC expression per station.
+ // Create a direction independent TEC expression per station. Note that
+ // TEC is a scalar effect, so it commutes.
if(config.useTEC())
{
exprDIE[i] = compose(exprDIE[i],
makeTECExpr(itsScope, instrument->station(i)));
}
+
+ // Convert from linear to circular-RL polarization. It is assumed that
+ // for telescopes other than LOFAR, the polarization of the data is the
+ // same as the polarization of the antennae.
+ //
+ // The conversion from linear to circular would usually be part of the
+ // beam model. The conversion applied here is a hack for telescopes
+ // with circularly polarized antennae for which the beam model is not
+ // implemented. i.e. there is no telescope specific class derived from
+ // MeasurmentExpr.
+ if(circular && !isLOFAR)
+ {
+ exprDIE[i] = compose(exprDIE[i], H);
+ }
}
itsExpr = vector<Expr<JonesMatrix>::Ptr>(itsBaselines.size());
@@ -333,12 +359,29 @@ void MeasurementExprLOFAR::makeInverseExpr(SourceDB &sourceDB,
// Allocate space for the station response expressions.
vector<Expr<JonesMatrix>::Ptr> stationExpr(instrument->nStations());
+ // -------------------------------------------------------------------------
// Direction independent effects (DIE).
+ // -------------------------------------------------------------------------
+
+ // Create a linear to circular-RL transformation Jones matrix.
+ Expr<JonesMatrix>::Ptr H(new LinearToCircularRL());
+
const bool haveDIE = config.useClock() || config.useBandpass()
|| config.useGain() || config.useTEC();
+ const bool circular = buffer->isCircular();
+ const bool isLOFAR = (instrument->name() == "LOFAR");
+
for(size_t i = 0; i < instrument->nStations(); ++i)
{
+ // Convert from linear to circular-RL polarization. For the LOFAR array,
+ // which has linearly polarized antennae, this conversion is done at the
+ // end of the chain.
+ if(circular && isLOFAR)
+ {
+ stationExpr[i] = compose(stationExpr[i], H);
+ }
+
// Create a clock delay expression per station.
if(config.useClock())
{
@@ -361,15 +404,33 @@ void MeasurementExprLOFAR::makeInverseExpr(SourceDB &sourceDB,
config.usePhasors()));
}
- // Create a direction independent TEC expression per station.
+ // Create a direction independent TEC expression per station. Note that
+ // TEC is a scalar effect, so it commutes.
if(config.useTEC())
{
stationExpr[i] = compose(stationExpr[i],
makeTECExpr(itsScope, instrument->station(i)));
}
+
+ // Convert from linear to circular-RL polarization. It is assumed that
+ // for telescopes other than LOFAR, the polarization of the data is the
+ // same as the polarization of the antennae.
+ //
+ // The conversion from linear to circular would usually be part of the
+ // beam model. The conversion applied here is a hack for telescopes
+ // with circularly polarized antennae for which the beam model is not
+ // implemented. i.e. there is no telescope specific class derived from
+ // MeasurmentExpr.
+ if(circular && !isLOFAR)
+ {
+ stationExpr[i] = compose(stationExpr[i], H);
+ }
}
+ // -------------------------------------------------------------------------
// Direction dependent effects (DDE).
+ // -------------------------------------------------------------------------
+
const bool haveDDE = config.useDirectionalGain()
|| config.useBeam() || config.useDirectionalTEC()
|| config.useFaradayRotation() || config.useIonosphere();
@@ -735,7 +796,7 @@ void MeasurementExprLOFAR::setCorrelations(bool circular)
if(circular)
{
- LOG_DEBUG_STR("Visibilities will be simulated using circular (RL)"
+ LOG_DEBUG_STR("Visibilities will be simulated using circular-RL"
" correlations.");
itsCorrelations.append(Correlation::RR);
itsCorrelations.append(Correlation::RL);
--
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