Add EMIT emit_l1b reader

satpy/etc/readers/emit_l1b.yaml

@@ -0,0 +1,154 @@
+reader:
+  name: emit_l1b
+  short_name: EMIT L1B NetCDF4
+  long_name: Earth Surface Mineral Dust Source Investigation (EMIT) Level 1B data in netCDF4 format
+  description: >
+    Reader for EMIT Level 1B files in NetCDF4 format.
+  status: Beta
+  supports_fsspec: false
+  sensors: [emit]
+  reader: !!python/name:satpy.readers.yaml_reader.FileYAMLReader
+
+file_types:
+  emit_l1b_rad:
+    file_reader: !!python/name:satpy.readers.emit_l1b.EMITL1BFileHandler
+    file_patterns: ['{sensor:4s}_{level:3s}_RAD_{product_version:s}_{start_time:%Y%m%dT%H%M%S}_{orbit:s}_{scene:s}.nc']
+    requires: [emit_l1b_obs]
+  emit_l1b_obs:
+    file_reader: !!python/name:satpy.readers.emit_l1b.EMITL1BFileHandler
+    file_patterns: ['{sensor:4s}_{level:3s}_OBS_{product_version:s}_{start_time:%Y%m%dT%H%M%S}_{orbit:s}_{scene:s}.nc']
+
+datasets:
+  elev:
+    name: elev
+    file_type: [emit_l1b_rad, emit_l1b_obs]
+    standard_name: elev
+    long_name: surface elevation
+    units: m
+    nc_group: location
+    _FillValue: -9999.0
+
+  glt_x:
+    name: glt_x
+    file_type: [emit_l1b_rad, emit_l1b_obs]
+    standard_name: glt_x
+    long_name: GLT sample Lookup
+    units: pixel location
+    nc_group: location
+    _FillValue: -9999
+
+  glt_y:
+    name: glt_y
+    file_type: [emit_l1b_rad, emit_l1b_obs]
+    standard_name: glt_y
+    long_name: GLT sample Lookup
+    units: pixel location
+    nc_group: location
+    _FillValue: -9999
+
+  radiance:
+    name: radiance
+    file_type: [emit_l1b_rad]
+    standard_name: radiance
+    units: uW cm-2 sr-1 nm-1
+    nc_group:
+    _FillValue: -9999.0
+
+  sza:
+    name: sza
+    file_type: [emit_l1b_obs]
+    standard_name: solar_zenith_angle
+    long_name: To-sun zenith (0 to 90 degrees from zenith)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  saa:
+    name: saa
+    file_type: [emit_l1b_obs]
+    standard_name: solar_azimuth_angle
+    long_name: To-sun azimuth (0 to 360 degrees CW from N)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  vza:
+    name: vza
+    file_type: [emit_l1b_obs]
+    standard_name: sensor_zenith_angle
+    long_name: To-sensor zenith (0 to 90 degrees from zenith)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  vaa:
+    name: vaa
+    file_type: [emit_l1b_obs]
+    standard_name: sensor_azimuth_angle
+    long_name: To-sensor azimuth (0 to 360 degrees CW from N)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  path_length:
+    name: path_length
+    file_type: [emit_l1b_obs]
+    standard_name: sensor_height
+    long_name: Path length (sensor-to-ground in meters)
+    units: m
+    nc_group:
+    _FillValue: -9999.0
+
+  solar_phase:
+    name: solar_phase
+    file_type: [emit_l1b_obs]
+    standard_name: solar_phase
+    long_name: Solar phase (degrees between to-sensor and to-sun vectors in principal plane)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  surface_slope:
+    name: surface_slope
+    file_type: [emit_l1b_obs]
+    standard_name: surface_slope
+    long_name: Slope (local surface slope as derived from DEM in degrees)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  surface_aspect:
+    name: surface_aspect
+    file_type: [emit_l1b_obs]
+    standard_name: surface_aspect
+    long_name: Aspect (local surface aspect 0 to 360 degrees clockwise from N)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  cosine_i:
+    name: cosine_i
+    file_type: [emit_l1b_obs]
+    standard_name: cosine_i
+    long_name: Cosine(i) (apparent local illumination factor based on DEM slope and aspect and to sun vector)
+    units: degree
+    nc_group:
+    _FillValue: -9999.0
+
+  time:
+    name: time
+    file_type: [emit_l1b_obs]
+    standard_name: time
+    long_name: UTC Time (decimal hours for mid-line pixels)
+    units:
+    nc_group:
+    _FillValue: -9999.0
+
+  earth_sun_distance:
+    name: earth_sun_distance
+    file_type: [emit_l1b_obs]
+    standard_name: earth_sun_distance
+    long_name: Earth-sun distance (AU)
+    units: AU
+    nc_group:
+    _FillValue: -9999.0

satpy/readers/emit_l1b.py

@@ -0,0 +1,176 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (c) 2022-2023 Satpy developers
+#
+# This file is part of satpy.
+#
+# satpy is free software: you can redistribute it and/or modify it under the
+# terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# satpy is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# satpy.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Reader for the EMIT L1B NetCDF data."""
+
+import logging
+from datetime import datetime
+
+import numpy as np
+from pyresample.geometry import SwathDefinition
+from satpy.readers.netcdf_utils import NetCDF4FileHandler
+from satpy.utils import get_legacy_chunk_size
+
+logger = logging.getLogger(__name__)
+CHUNK_SIZE = get_legacy_chunk_size()
+
+DATE_FMT = "%Y-%m-%dT%H:%M:%S%z"
+
+
+class EMITL1BFileHandler(NetCDF4FileHandler):
+    """File handler for EMIT L1B netCDF files."""
+
+    def __init__(self, filename, filename_info, filetype_info, *req_fhs):
+        """Prepare the class for dataset reading."""
+        super().__init__(filename, filename_info, filetype_info)
+        self.area = None
+
+        self._load_bands()
+
+    def _load_bands(self):
+        """Load bands data and attributes."""
+        if self.filetype_info["file_type"] == "emit_l1b_rad":
+            bands_name = "wavelengths"
+        elif self.filetype_info["file_type"] == "emit_l1b_obs":
+            bands_name = "observation_bands"
+
+        self.bands = self[f"sensor_band_parameters/{bands_name}"].rename("bands")
+
+        # add other parameters as coords of bands
+        if self.filetype_info["file_type"] == "emit_l1b_rad":
+            # add wavelength
+            self.bands.coords["fwhm"] = self["sensor_band_parameters/fwhm"]
+
+    @property
+    def start_time(self):
+        """Get observation start time."""
+        return datetime.strptime(self["/attr/time_coverage_start"], DATE_FMT).replace(tzinfo=None)
+
+    @property
+    def end_time(self):
+        """Get observation end time."""
+        return datetime.strptime(self["/attr/time_coverage_end"], DATE_FMT).replace(tzinfo=None)
+
+    @property
+    def platform_name(self):
+        """Get platform name."""
+        return self["/attr/platform"]
+
+    @property
+    def sensor(self):
+        """Get sensor."""
+        return self["/attr/instrument"]
+
+    @property
+    def spatial_ref(self):
+        """Get spatial_ref."""
+        return self["/attr/spatial_ref"]
+
+    @property
+    def geotransform(self):
+        """Get geotransform."""
+        return self["/attr/geotransform"]
+
+    @property
+    def attrs(self):
+        """Return attributes."""
+        return {
+            "filename": self.filename,
+            "start_time": self.start_time,
+            "end_time": self.end_time,
+            "platform_name": self.platform_name,
+            "sensor": self.sensor,
+            "geotransform": self.geotransform,
+            "spatial_ref": self.spatial_ref,
+        }
+
+    def _standardize_dims(self, dataset):
+        """Standardize dims to y, x."""
+        if "downtrack" in dataset.dims:
+            dataset = dataset.rename({"downtrack": "y"})
+        if "crosstrack" in dataset.dims:
+            dataset = dataset.rename({"crosstrack": "x"})
+        if dataset.dims[0] == "x":
+            dataset = dataset.transpose("y", "x")
+        if "bands" in dataset.dims:
+            dataset.coords["bands"] = self.bands
+            dataset = dataset.transpose("bands", ...)
+
+        return dataset
+
+    def get_metadata(self, dataset, ds_info):
+        """Get metadata."""
+        metadata = {}
+        metadata.update(dataset.attrs)
+        metadata.update(ds_info)
+        metadata.update(self.attrs)
+
+        return metadata
+
+    def get_dataset(self, dataset_id, ds_info):
+        """Get dataset."""
+        name = dataset_id["name"]
+        file_type = self.filetype_info["file_type"]
+
+        if ds_info["nc_group"] is None:
+            var_path = name
+        else:
+            var_path = ds_info["nc_group"] + "/" + name
+
+        if file_type == "emit_l1b_obs":
+            # because the "obs" DataArray includes the varname as the "bands" dim
+            #   we need to reset the var_path to "obs"
+            var_path = 'obs'
+
+        logger.debug(f"Reading in file to get dataset with path {var_path}.")
+        dataset = self[var_path]
+
+        dataset.attrs = self.get_metadata(dataset, ds_info)
+        fill_value = dataset.attrs.get('_FillValue', np.float32(np.nan))
+
+        # preserve integer data types if possible
+        if np.issubdtype(dataset.dtype, np.integer):
+            new_fill = fill_value
+        else:
+            new_fill = np.float32(np.nan)
+            dataset.attrs.pop('_FillValue', None)
+
+        # mask data by fill_value
+        good_mask = dataset != fill_value
+        dataset = dataset.where(good_mask, new_fill)
+
+        # standardize dims
+        dataset = self._standardize_dims(dataset)
+
+        # only load the variable by selecting bands dim
+        if file_type == "emit_l1b_obs":
+            dataset = dataset.sel(bands=ds_info['long_name']).rename(name)
+
+        # add area
+        self.get_lonlats()
+        dataset.attrs['area'] = self.area
+
+        return dataset
+
+    def get_lonlats(self):
+        """Get lonlats."""
+        if self.area is None:
+            lons = self['location/lon']
+            lats = self['location/lat']
+            self.area = SwathDefinition(lons, lats)
+            self.area.name = '_'.join([self.sensor, str(self.start_time)])