# IAS_02_SO2

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `IAS_02_SO2` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
orbit_index | int32 |  |  | absolute orbit number
datetime | double | {time} | [s since 2020-01-01] | on-board time in UTC
longitude | double | {time} | [degree_east] | geocentric longitude at sounder pixel centre
longitude_bounds | double | {time, 4} | [degree_east] | corner longitudes of the measurement
latitude | double | {time} | [degree_north] | geodetic latitude at sounder pixel centre
latitude_bounds | double | {time, 4} | [degree_north] | corner latitudes of the measurement
solar_azimuth_angle | double | {time} | [degree] | solar azimuth angle at sounder pixel centre
solar_zenith_angle | double | {time} | [degree] | solar zenith angle at sounder pixel centre
sensor_azimuth_angle | double | {time} | [degree] | measurement azimuth angle at sounder pixel centre
sensor_zenith_angle | double | {time} | [degree] | measurement zenith angle at sounder pixel centre
SO2_column_number_density | float | {time} | [DU] | SO2 column
SO2_layer_height | float | {time} | [m] | retrieved plume altitude
validity | int8 | {time} | [] | general retrieval quality flag
index | int32 | {time} |  | zero-based index of the sample within the source product

## Ingestion options

The table below lists the available ingestion options for `IAS_02_SO2` products.

option name | legal values | description
--- | --- | ---
so2_column | 7km, 10km, 13km, 16km, 25km | whether to ingest the SO2 column consistent with the SO2 layer height (default), the SO2 column from the 7km box profile (so2_column=7km), from the 10km box profile (so2_column=10km), from the 13km box profile (so2_column=13km), from the 16km box profile (so2_column=16km), or from the 25km box profile (so2_column=25km)

## Mapping description

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

field name | mapping description
--- | ---
orbit_index | path | /@orbit_start
datetime | path | /data/geolocation_information/onboard_utc[]
longitude | path | /data/geolocation_information/sounder_pixel_longitude[]
longitude_bounds | path | /data/geolocation_information/sounder_pixel_longitude_bounds[]
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 (within the same 2x2 subgrid inside a Field of Regard (FOR))
latitude | path | /data/geolocation_information/sounder_pixel_latitude[]
latitude_bounds | path | /data/geolocation_information/sounder_pixel_latitude_bounds[]
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 (within the same 2x2 subgrid inside a Field of Regard (FOR))
solar_azimuth_angle | path | /data/geolocation_information/sounder_pixel_sun_azimuth[]
solar_zenith_angle | path | /data/geolocation_information/sounder_pixel_sun_zenith[]
sensor_azimuth_angle | path | /data/geolocation_information/sounder_pixel_azimuth[]
sensor_zenith_angle | path | /data/geolocation_information/sounder_pixel_zenith[]
SO2_column_number_density | condition | so2_column unset
path | /data/so2_col[]
condition | so2_column=7km
path | /data/so2_col_at_altitudes[0]
condition | so2_column=10km
path | /data/so2_col_at_altitudes[1]
condition | so2_column=13km
path | /data/so2_col_at_altitudes[2]
condition | so2_column=16km
path | /data/so2_col_at_altitudes[3]
condition | so2_column=25km
path | /data/so2_col_at_altitudes[4]
SO2_layer_height | path | /data/so2_altitude[]
validity | path | /data/so2_qflag[]
description | the uint8 data is cast to int8