Port of single scattering radar of ARTS2

examples/2-clearsky-radiative-transfer/2-zeeman/6-zeeman-sun-scattering.py

@@ -41,6 +41,9 @@
 ws.ray_path_observer_agendaSetGeometric()
 ws.spectral_propmat_scat_agendaSet(option="AirSimple")
 
+# %% Set up an air Rayleigh scatterer through the ScatteringSpecies interface.
+ws.scat_species = [pyarts.arts.RayleighScatterer(pyarts.arts.RayleighType("EarthAir"))]
+
 # %% Core calculations
 pos = [90e3, 0, 0]
 zens = np.linspace(0, 5, 21)

src/CMakeLists.txt

@@ -194,6 +194,7 @@ add_library(artsworkspace STATIC
   m_ppvar.cc
   m_propagation_path.cc
   m_propagation_path_observer.cc
+  m_radar.cc
   m_propmat.cc
   m_retrieval.cc
   m_rad.cc

src/core/geodesy/geodetic.cpp

@@ -668,7 +668,7 @@ bool terrain_occludes(Numeric obs_lat,
 }  // anonymous namespace
 
 std::vector<Vector2> visible_coordinates(Vector2 pos,
-                                         Vector2 ellipsoid,
+                                         Vector2,
                                          const GeodeticField2& hfield) {
   if (not hfield.ok()) return {};
 

src/core/matpack/CMakeLists.txt

@@ -18,7 +18,7 @@ add_library(matpack STATIC
   matpack_mdspan_algorithm.cc
 )
 
-find_package (Eigen3 3.4 REQUIRED NO_MODULE)
+find_package (Eigen3 REQUIRED NO_MODULE)
 message(STATUS "Found Eigen3: ${EIGEN3_INCLUDE_DIR}")
 
 target_link_libraries(matpack PRIVATE ${LAPACK_LIBRARIES})

src/core/options/arts_options.cc

@@ -1083,6 +1083,25 @@ where :math:`D(x)` is the Dawson function.
                  "Initialize an empty workspace - no variables are set."}},
   });
 
+  opts.emplace_back(EnumeratedOption{
+      .name = "RayleighType",
+      .desc =
+          R"(Selects the Rayleigh scattering model used by RayleighScatterer.
+
+To add a new model, add a value here and implement it in rayleigh_scatterer.cc.
+)",
+      .values_and_desc =
+          {Value{"EarthAir",
+                 R"(Empirical air molecular scattering.
+Pure scattering, no absorption.
+Number density from ideal gas law.
+)"},
+           Value{
+               "WaterDrop",
+               R"(Requires diameter. Number density from liquidcloud field.
+)"}},
+  });
+
   opts.emplace_back(EnumeratedOption{
       .name            = "ZeemanPolarization",
       .desc            = "A flag for the Zeeman polarization state.\n",

src/core/rtepack/rtepack_scattering.cc

@@ -167,7 +167,6 @@ void bulk_backscatter_commutative_transmission_rte(
   }
 }
 
-namespace {
 Numeric cos_scat_angle(const Vector2 &los_in, const Vector2 &los_out) {
   using Conversion::cosd;
   using Conversion::sind;
@@ -181,7 +180,6 @@ Numeric cos_scat_angle(const Vector2 &los_in, const Vector2 &los_out) {
   // Fix potential overflows by clamping numerical errors
   return std::clamp(theta, -1.0, 1.0);
 }
-}  // namespace
 
 muelmat rayleigh_scattering(const Vector2 &los_in,
                             const Vector2 &los_out,

src/core/rtepack/rtepack_scattering.h

@@ -24,6 +24,8 @@ void bulk_backscatter_commutative_transmission_rte(
     const Array<muelmat_matrix> &dT2,
     const Array<muelmat_matrix> &dZ);
 
+Numeric cos_scat_angle(const Vector2 &los_in, const Vector2 &los_out);
+
 muelmat rayleigh_scattering(const Vector2 &los_in,
                             const Vector2 &los_out,
                             const Numeric depolarization_factor);

src/core/rtepack/rtepack_surface.cc

@@ -223,7 +223,7 @@ stokvec nonspecular_radiance_from_patches(std::span<const Vector2> coords,
   constexpr Numeric pi = Constant::pi;
   using Conversion::deg2rad;
 
-  assert(static_cast<Index>(coords.size()) == sources.size());
+  assert(coords.size() == sources.size());
 
   const Vector& lats     = hfield.grid<0>();
   const Vector& lons     = hfield.grid<1>();

src/core/scattering/CMakeLists.txt

@@ -8,6 +8,7 @@ add_library(scattering STATIC
    utils.cc
    phase_matrix.cc
    henyey_greenstein.cc
+   rayleigh_scatterer.cc
    particle_habit.cc
    scattering_habit.cc
    bulk_scattering_properties.cc

src/core/scattering/general_tro_spectral.cc

@@ -1,6 +1,11 @@
 #include "general_tro_spectral.h"
 
+#include <arts_conversions.h>
+#include <legendre.h>
+
+#include <cmath>
 #include <memory>
+#include <numbers>
 
 #include "sht.h"