EMIT Methane Downloader

EmitDownloader fetches NASA EMIT (Earth Surface Mineral Dust Source Investigation) Level-2B methane products for any bounding-box AOI from NASA's LP DAAC and stages them into a Unity Catalog Volume.

EMIT is an imaging spectrometer on the International Space Station that resolves methane plumes at 60 m. Two EMIT L2B products are fetched together: EMITL2BCH4ENH (per-scene CH4 enhancement COGs) and EMITL2BCH4PLM (per-plume complex products — a COG plus a GeoJSON outline with JPL's emission-rate estimate).

Requires an Earthdata Login token

Unlike the Planetary-Computer-backed downloaders (NaipDownloader, DemDownloader, TropomiDownloader), EMIT is served from NASA's LP DAAC via earthaccess and requires authentication. EmitDownloader reads the token from the EARTHDATA_TOKEN environment variable (earthaccess.login(strategy="environment"), via the internal databricks.labs.gbx.earthdata.EarthdataClient). Populate it from a Unity Catalog secret before calling download():

import os

token = dbutils.secrets.get("<catalog>", "<schema>", "earthdata_token")
os.environ["EARTHDATA_TOKEN"] = token

Create an Earthdata Login account and token first if you don't have one.

Prerequisites

GeoBrix installed with the [earthdata] extra (e.g. %pip install "geobrix[light_env6,earthdata] @ file:///Volumes/…"), which bundles earthaccess — wheel includes databricks.labs.gbx.sample. See Installation.
Unity Catalog Volume already exists at /Volumes/{catalog}/{schema}/{volume}/...
EARTHDATA_TOKEN set in the environment (see above) before calling download()

How It Works

EmitDownloader is a thin wrapper over the generic EarthdataClient — the Earthdata analog of StacClient — supplying only the EMIT-specific CMR short names, an asset classifier, and a validation function:

discover(bbox, temporal=None) — CMR search (earthaccess.search_data) for both EMITL2BCH4ENH and EMITL2BCH4PLM over the AOI. Each granule's data links are classified into an asset label (ch4enh, plm_cog, or plm_geojson) or skipped. Returns a metadata-only DataFrame: item_id, asset_name, href.
download(bbox, out_dir, temporal=None, force=False, ...) — logs in (EARTHDATA_TOKEN), runs discover() internally, then fetches each asset driver-side (EMIT/LP DAAC auth mints short-lived per-request credentials that don't fan out like anonymous hrefs, so download is not Spark-distributed). Each asset is validated: the enhancement/plume COGs need a rasterio window read to succeed above a size floor; the plume GeoJSON needs to parse and carry at least one feature. Returns the shared result DataFrame: item_id, asset_name, out_file_path, out_file_sz, is_out_file_valid, last_update.
Two readers, because EMIT ships two different product shapes:
- read_enh(out_dir) — loads the CH4 enhancement COGs as raster_gbx tiles ((source, tile) schema).
- read_plumes(out_dir) — loads the plume-complex GeoJSON metadata (geojson_gbx) into a typed, per-plume frame with the outline as WKB.

Serverless-safe: no spark.conf.set, _jvm-bridge access, or runtime Spark-config mutation.

API Reference

`EmitDownloader`

from databricks.labs.gbx.sample.emit import EmitDownloader

downloader = EmitDownloader()
# Defaults: EMITL2BCH4ENH + EMITL2BCH4PLM short names, version "002"

Parameter	Type	Description
`enh_short`	`str`	CMR short name for the enhancement product. Default `"EMITL2BCH4ENH"`.
`plm_short`	`str`	CMR short name for the plume-complex product. Default `"EMITL2BCH4PLM"`.
`version`	`str`	CMR product version. Default `"002"`.
`_earthaccess`	injectable	Mock `earthaccess`-like module for offline unit tests.
`_client`	injectable	Mock `EarthdataClient` for offline unit tests.

`discover(bbox, temporal=None, spark=None) → DataFrame`

Parameter	Type	Description
`bbox`	`(minx, miny, maxx, maxy)`	AOI in EPSG:4326 (WGS84 longitude/latitude)
`temporal`	`str \| (str, str) \| None`	CMR temporal window. Accepts a STAC-style `"start/end"` string (normalized internally) or a 2-tuple. `None` searches all available EMIT coverage.
`spark`	`SparkSession \| None`	Active SparkSession. Defaults to `SparkSession.getActiveSession()`.

Returns a DataFrame with columns: item_id (str), asset_name (str — "ch4enh", "plm_cog", or "plm_geojson"), href (str) — one row per classified data link.

`download(bbox, out_dir, temporal=None, force=False, spark=None) → DataFrame`

Parameter	Type	Description
`bbox`	`(minx, miny, maxx, maxy)`	AOI in EPSG:4326
`out_dir`	`str`	Output directory — a UC Volume path (e.g. `/Volumes/...`) or local path
`temporal`	`str \| (str, str) \| None`	CMR temporal window, same as `discover()`.
`force`	`bool`	Re-download even if a valid file already exists at the destination. Default `False`.
`spark`	`SparkSession \| None`	Active SparkSession.

Calls EarthdataClient.login() (reads EARTHDATA_TOKEN) before searching and downloading. Returns a metadata DataFrame with columns: item_id, asset_name, out_file_path, out_file_sz, is_out_file_valid, last_update.

`repair(target, where="is_out_file_valid = false", spark=None, out_dir=None) → DataFrame`

Parameter	Type	Description
`target`	`str \| DataFrame`	A Delta table name (repairs are `MERGE`d back in place) or a DataFrame (returns the repaired rows without persisting).
`where`	`str`	Filter selecting rows to re-fetch. Default `"is_out_file_valid = false"`.
`spark`	`SparkSession \| None`	Active SparkSession.
`out_dir`	`str \| None`	Destination directory for re-fetched files. `None` infers it from an existing valid row's `out_file_path`.

Re-downloads invalid/missing assets (force=True internally) and, when target is a table name, MERGEs the repaired rows into it by (item_id, asset_name). Requires item_id, asset_name, and href columns on the target.

`read_enh(out_dir, spark=None) → DataFrame`

Parameter	Type	Description
`out_dir`	`str`	Root directory written by `download()`
`spark`	`SparkSession \| None`	Active SparkSession.

Loads the CH4 enhancement COGs (filterRegex=r".*CH4ENH.*\.tif$") via raster_gbx, repartitioned 64-way by source. Returns a DataFrame with source and tile columns — one row per EMIT overpass segment.

`read_plumes(out_dir, spark=None) → DataFrame`

Parameter	Type	Description
`out_dir`	`str`	Root directory written by `download()`
`spark`	`SparkSession \| None`	Active SparkSession.

Reads each *CH4PLMMETA*.json plume-metadata file individually via geojson_gbx (per-file schema divergence rules out a single multi-file read), normalizes JPL's raw property names to typed columns, and unions the results. Raises FileNotFoundError if no matching files exist under out_dir. Output columns:

Column	Type	Source property
`plume_id`	string	`Plume ID`
`utc_observed`	string	`UTC Time Observed`
`orbit`	string	`Orbit`
`dcid`	string	`DCID`
`max_conc_ppmm`	double	`Max Plume Concentration (ppm m)`
`lat_max`	double	`Latitude of max concentration`
`lon_max`	double	`Longitude of max concentration`
`wind_speed_ms`	double	`Wind Speed (m/s)`
`wind_speed_std_ms`	double	`Wind Speed Std (m/s)`
`wind_speed_source`	string	`Wind Speed Source`
`emission_rate_kg_hr`	double	`Emissions Rate Estimate (kg/hr)`
`emission_rate_uncert_kg_hr`	double	`Emissions Rate Estimate Uncertainty (kg/hr)`
`fetch_length_m`	double	`Fetch Length (m)`
`plume_geom`	binary (WKB)	plume outline geometry

Numeric columns are try_cast to double — plumes with no wind match store those fields as the string "NA" in the source GeoJSON, which becomes null.

`download_emit_aoi` (convenience function)

Constructs a default EmitDownloader and downloads in a single call:

from databricks.labs.gbx.sample.emit import download_emit_aoi

download_emit_aoi(
    spark,
    bbox,
    out_dir,
    temporal="2023-07-15/2023-08-20",
    # **kw forwarded to EmitDownloader.download() — e.g. force=
)

Copy-Paste Example

The example below fetches EMIT CH4 enhancement scenes and plume-complex metadata for a Delaware Basin (Permian, TX) AOI, then quantifies each plume against the enhancement raster.

# earthaccess is bundled in the [earthdata] extra:
# %pip install "geobrix[light_env6,earthdata] @ file:///Volumes/<catalog>/<schema>/<volume>/geobrix/geobrix-<version>-py3-none-any.whl"

import os

from pyspark.sql import functions as F

from databricks.labs.gbx.rasterx import functions as rx
from databricks.labs.gbx.sample.emit import EmitDownloader

# EMIT needs the Earthdata token — populate it from a UC secret first.
os.environ["EARTHDATA_TOKEN"] = dbutils.secrets.get(
    "<catalog>", "<schema>", "earthdata_token"
)

# Delaware Basin AOI, TX (lon/lat, EPSG:4326)
AOI_BBOX = (-103.25, 31.30, -102.85, 31.62)
DATE_WINDOW = "2023-07-15/2023-08-20"  # anchored on a known EMIT overpass

VOLUME = "/Volumes/main/default/geobrix_samples/emit"

downloader = EmitDownloader()

# Step 1 — discover: see which EMIT assets cover this AOI + window
items = downloader.discover(AOI_BBOX, temporal=DATE_WINDOW)
items.groupBy("asset_name").count().show()
# +----------+-----+
# |asset_name|count|
# +----------+-----+
# |    ch4enh|    2|
# |   plm_cog|    3|
# |plm_geojson|    3|
# +----------+-----+

# Step 2 — download: fetch enhancement COGs + plume COGs + plume GeoJSON
meta = downloader.download(AOI_BBOX, VOLUME, temporal=DATE_WINDOW)
meta.select("item_id", "asset_name", "out_file_path", "is_out_file_valid").show(truncate=False)

# Step 3a — read the plume metadata (outline + JPL's emission-rate estimate)
plumes = downloader.read_plumes(VOLUME)
plumes.drop("plume_geom").orderBy(F.col("max_conc_ppmm").desc()).show()

# Step 3b — read the enhancement scenes (source, tile)
enh = downloader.read_enh(VOLUME)
enh.printSchema()

One-shot convenience

from databricks.labs.gbx.sample.emit import download_emit_aoi

meta = download_emit_aoi(
    spark,
    bbox=AOI_BBOX,
    out_dir=VOLUME,
    temporal=DATE_WINDOW,
)
meta.show()

Quantify each plume against the enhancement raster

Clip each plume's outline against the enhancement raster and summarize it with RasterX, cross-checking GeoBrix's measured enhancement against JPL's reported values:

clipped = (
    plumes.crossJoin(enh.select(F.col("tile").alias("scene")))
    .withColumn("clip", rx.rst_clip("scene", "plume_geom", F.lit(True)))
    .withColumn("summary", rx.rst_summary("clip"))
    .withColumn(
        "gbx_max_ppmm", F.get_json_object("summary", "$.bands[0].max").cast("double")
    )
)
clipped.select(
    "plume_id", "emission_rate_kg_hr", "max_conc_ppmm", "gbx_max_ppmm"
).show()

Two products, two readers

EMITL2BCH4ENH (raster) and EMITL2BCH4PLM (COG + GeoJSON) are different shapes of data — read_enh and read_plumes load them separately rather than forcing one schema on both.

Notebook Reference

EmitDownloader is used in the Vapor-Eyes example (notebook 03) to confirm and quantify a candidate methane plume at 60 m resolution — cross-checking GeoBrix's clipped-raster enhancement against JPL's reported emission rate — after Sentinel-5P screening and Sentinel-2 detection narrow the search area.