# IASI_L2

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `IASI_L2` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
datetime | double | {time} | [seconds since 2000-01-01] | The time of the measurement at end of integration time
orbit_index | int32 |  |  | absolute orbit number
longitude | double | {time} | [degree_east] | center longitude of the measurement
latitude | double | {time} | [degree_north] | center latitude of the measurement
longitude_bounds | double | {time, 4} | [degree_east] | corner longitudes of the measurement
latitude_bounds | double | {time, 4} | [degree_north] | corner latitudes of the measurement
solar_azimuth_angle | double | {time} | [degree] | solar azimuth angle at the surface
solar_zenith_angle | double | {time} | [degree] | solar zenith angle at the surface
sensor_azimuth_angle | double | {time} | [degree] | sensor azimuth angle at the surface
sensor_zenith_angle | double | {time} | [degree] | sensor zenith angle at the surface
CH4_column_density | double | {time} | [kg/m^2] | CH4 column mass density
CO_column_density | double | {time} | [kg/m^2] | CO column mass density
CO2_column_density | double | {time} | [kg/m^2] | CO2 column mass density
O3_column_density | double | {time} | [kg/m^2] | O3 column mass density
N2O_column_density | double | {time} | [kg/m^2] | N2O column mass density
scan_subindex | int8 | {time} |  | the relative index (0-119) of this measurement within an MDR
index | int32 | {time} |  | zero-based index of the sample within the source product

## Mapping description

The table below details where and how each variable was retrieved from the input product.

field name | mapping description
--- | ---
datetime | path | /MDR[]/MDR/RECORD_HEADER/RECORD_START_TIME
description | The time for a scan is the MDR start time + the scan id (0..29) times 8 / 37. Each part of the 2x2 matrix of a scan will get assigned the same measurement time (i.e. there are 30 unique time values per mdr)
orbit_index | path | /MPHR/ORBIT_START
longitude | path | /MDR[]/MDR/EARTH_LOCATION[,1]
latitude | path | /MDR[]/MDR/EARTH_LOCATION[,0]
longitude_bounds | path | /MDR[]/MDR/EARTH_LOCATION[]
description | the corner coordinates are rough estimates of the circle areas for the scan elements; the size of a scan element (in a certain direction) is taken to be half the distance, from center to center, from a scan element to its nearest neighboring scan element
latitude_bounds | path | /MDR[]/MDR/EARTH_LOCATION[]
description | the corner coordinates are rough estimates of the circle areas for the scan elements; the size of a scan element (in a certain direction) is taken to be half the distance, from center to center, from a scan element to its nearest neighboring scan element
solar_azimuth_angle | path | /MDR[]/MDR/ANGULAR_RELATION[,2]
solar_zenith_angle | path | /MDR[]/MDR/ANGULAR_RELATION[,0]
sensor_azimuth_angle | path | /MDR[]/MDR/ANGULAR_RELATION[,3]
sensor_zenith_angle | path | /MDR[]/MDR/ANGULAR_RELATION[,1]
CH4_column_density | path | /MDR[]/MDR/INTEGRATED_CH4[]
CO_column_density | path | /MDR[]/MDR/INTEGRATED_CO[]
CO2_column_density | path | /MDR[]/MDR/INTEGRATED_CO2[]
O3_column_density | path | /MDR[]/MDR/INTEGRATED_OZONE[]
N2O_column_density | path | /MDR[]/MDR/INTEGRATED_N2O[]