# ARTS built-in documentation server

## Workspace Method yCalc

### Description

Calculation of complete measurement vectors (y). The method performs radiative transfer calculations from a sensor perspective. Radiative transfer calculations are performed for monochromatic pencil beams, following iy_main_agenda and associated agendas. Obtained radiances are weighted together by sensor_response, to include the characteristics of the sensor. The measurement vector obtained can contain anything from a single frequency value to a series of measurement scans (each consisting of a series of spectra), all depending on the settings. Spectra and jacobians are calculated in parallel. The frequency, polarisation etc. for each measurement value is given by y_f, y_pol, y_pos and y_los. The content of y_aux follows iy_aux_vars. See the method selected for iy_main_agenda for allowed choices. The geo-positions (y_geo) are set based on sensor_response. When an antenna pattern is considered, there are several pencil beams, and thus also several goe-positions, associated with each value of y. The geo-position assigned to a value in y is the geo_pos of the pencil beam related to the highest value in sensor_response. This means that mblock_dlos must contain the bore-sight direction (0,0), if you want y_geo to exactly match the bore-sight direction. The Jacobian provided (jacobian) is adopted to selected retrieval units, but no transformations are applied. Transformations are included by calling jacobianAdjustAndTransform.

**Authors: **Patrick Eriksson

### Synopsis

### Variables

OUT | y | (Vector) | The measurement vector. |

OUT | y_f | (Vector) | The frequencies associated with y. |

OUT | y_pol | (ArrayOfIndex) | The polarisation states associated with y. |

OUT | y_pos | (Matrix) | The sensor positions associated with y. |

OUT | y_los | (Matrix) | The line-of-sights associated with y. |

OUT | y_aux | (ArrayOfVector) | Data auxilary to y. |

OUT | y_geo | (Matrix) | The geo-position assigned to each element of y. |

OUT | jacobian | (Matrix) | The Jacobian matrix. |

IN | atmgeom_checked | (Index) | OK-flag for the geometry of the model atmosphere. |

IN | atmfields_checked | (Index) | OK-flag for atmospheric grids and (physical) fields. |

IN | atmosphere_dim | (Index) | The atmospheric dimensionality (1-3). |

IN | nlte_field | (EnergyLevelMap) | The field of NLTE temperatures and/or ratios. |

IN | cloudbox_on | (Index) | Flag to activate the cloud box. |

IN | cloudbox_checked | (Index) | OK-flag for variables associated with the cloudbox. |

IN | scat_data_checked | (Index) | OK-flag for scat_data. |

IN | sensor_checked | (Index) | OK-flag for sensor related variables. |

IN | stokes_dim | (Index) | The dimensionality of the Stokes vector (1-4). |

IN | f_grid | (Vector) | The frequency grid for monochromatic pencil beam calculations. |

IN | sensor_pos | (Matrix) | The sensor position for each measurement block. |

IN | sensor_los | (Matrix) | The sensor line-of-sight (LOS) for each measurement block. |

IN | transmitter_pos | (Matrix) | Transmitter positions. |

IN | mblock_dlos | (Matrix) | The set of angular pencil beam directions for each measurement block. |

IN | sensor_response | (Sparse) | The matrix modelling the total sensor response. |

IN | sensor_response_f | (Vector) | The frequencies associated with the output of sensor_response. |

IN | sensor_response_pol | (ArrayOfIndex) | The polarisation states associated with the output of sensor_response. |

IN | sensor_response_dlos | (Matrix) | The relative zenith and azimuth angles associated with the output of sensor_response. |

IN | iy_unit | (String) | Selection of output unit for radiative transfer methods. |

IN | iy_main_agenda | (Agenda) | Calculation of a single monochromatic pencil beam spectrum. |

IN | jacobian_agenda | (Agenda) | Pure numerical Jacobian calculations. |

IN | jacobian_do | (Index) | Flag to activate (clear-sky) Jacobian calculations. |

IN | jacobian_quantities | (ArrayOfRetrievalQuantity) | The retrieval quantities in the Jacobian matrix. |

IN | iy_aux_vars | (ArrayOfString) | Selection of quantities for iy_aux and when applicable also y_aux. |