Search and Discovery of AVIRIS Data

Summary

This notebook will demonstrate how to search, discover, subset, and access NASA airborne imaging spectrometer data derived from the AVIRIS (Airborne Visible / Infrared Imaging Spectrometers) suite of instruments. AVIRIS data are archived to NASA Earthdata collections, but but given the many years of flights in support of varied NASA campaigns, can be a challenge to discover and access.

The earthaccess Python library simplifies programmatic discovery and access of NASA Earthdata data including the many AVIRIS instrument’s radiance, reflectance, and further derived campaign data. earthaccess is a useful Python library that facilitates finding and downloading or streaming data over HTTPS or s3. earthaccess searches NASA’s Common Metadata Repository (CMR) which is a metadata system that catalogs Earth Science data and associated metadata records. This can then be used to download granules or generate lists of granule search result URLs.

With areas and times of interest identified, flight metadata will be used to build and visual flight paths within those subset parameters.

Background

Developed at the NASA Jet Propulsion Laboratory (JPL), the Airborne Visible / Infrared Imaging Spectrometers (AVIRIS) are a unique suite of optical sensors that collect data while mounted on airborne platforms such as the B200 LARC or an ER-2 AFRC. Imaging spectrometers collect light reflected off of an object (the Earth in this case) and then analyze the intensity of the wavelengths present at each pixel. As their names suggest, the AVIRIS instruments collect light in the visible to infrared wavelenths. These data can be used for characterization of the Earth’s surface and atmosphere and applied to studies in the fields of oceanography, environmental science, snow hydrology, geology, volcanology, soil and land management, atmospheric and aerosol studies, agriculture, and limnology.

Green, R.O., M.L. Eastwood, C.M. Sarture, T. G. Chrien, M. Aronsson, B.J. Chippendale, J.A. Faust, B.E. Pavri, C. J. Chovit, M. Solis, M.R. Olah, and O. Williams. 1998. Imaging Spectroscopy and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Remote Sensing of Environment 65:227- 248. Green et al. (1998)

Chadwick KD, Brodrick PG, Grant K, et al. Integrating airborne remote sensing and field campaigns for ecology and Earth system science. Methods Ecol Evol. 2020; 11: 1492–1508. Chadwick et al. (2020)

AVIRIS imaging spectrometers break down light into hundreds of narrow spectral bands, providing a spectrum for each point (or pixel) in the image. The resulting data are typically stored in a 3-dimensional array sometimes referred to as a data cube. The x and y dimensions represent the spatial dimensions of the image and the z dimension represents the wavelength information. JPL processes and provides data as radiance (L1B) and reflectance (L2A) which are archived and publically available through NASA Earthdata Facility Instrument Collections. These data files are historically distributed in a popular remote sensing ENVI file format and more recently as a standardized netCDF file format.

AVIRIS Data Processing Levels

NASA Earthdata AVIRIS Project Data Facility Instrument Links

• AVIRIS-Classic: L1B Calibrated Radiance, Facility Instrument Collection, V1

• AVIRIS-Classic: L2 Calibrated Reflectance, Facility Instrument Collection, V1

• AVIRIS-NG L1B Calibrated Radiance, Facility Instrument Collection, V1

• AVIRIS-NG L2 Surface Reflectance, Facility Instrument Collection, V1

• AVIRIS-3 L1B Calibrated Radiance, Facility Instrument Collection

• AVIRIS-3 L2A Orthocorrected Surface Reflectance, Facility Instrument Collection

Notebook Requirements

A NASA Earthdata Login account is required

Learning Objectives

• login and authenticate to NASA Earthdata Login using earthaccess

• construct searches of the NASA Common Metadata Repository (CMR) for specific airborne instruments

• construct searches of the NASA Common Metadata Repository (CMR) for specific NASA Projects/Campaigns

• narrow a search of the CMR to for files from AVIRIS instrument flights based on a spatial area of interest

• programmatically discover specific AVIRIS- file access URLs based on metadata and spatial/temporal parameters

• create flight line bounding boxes from a search result using CMR file(granule)-level metadata

Set Up¶

Import the required Python libraries

earthaccess is a Python library that simplifies data discovery and access to NASA Earthdata data by providing an abstraction layer to NASA’s APIs for programmatic access.

earthaccess will be used to:

• Authentication: - handles a user’s identity (authentication) with NASA’s Earthdata Login (EDL),

• Search: search the NASA Earthdata Data holdings using NASA’s Common Metadata Repository (CMR), and

• Access: provide direct cloud file download and access

Earthdata Login

NASA Earthdata Login is a user registration and profile management system for users getting Earth science data from NASA Earthdata. If you download or access NASA Earthdata data, you need an Earthdata Login.

Authentication¶

Using earthaccess we’ll login and authenticate to NASA Systems.

• For this exercise, we will be prompted for and interactively enter our Eathdata Login credentials (login, password)

Searching by Collection¶

The earthaccess search_datasets function with the keyword argument can be used to search collections.

Given the many Instruments and Campaigns, there are several AVIRIS-* collections or datasets available within the NASA Earthdata cloud archive.

Printing the collections object explores all of the json metadata.

We can create a list of the short-name, concept-id, version, and EntryTitle of each result collection using list comprehension. These fields are important for specifying and searching for data within collections.

Searching by Instrument¶

The collection concept-id or short_name are unique to each collection. After finding the collection you want to search, you can use the short_name or concept-id to search for granules (or files) within that collection.

Searching by Project¶

Search AVIRIS-3 Instrument (only) for Specific Project/Campaign¶

• AVIRIS-3 datasets contain campaign information at the granule level within the Unified Metadata Model-Granule (UMM-G) AdditionalAttributes

• For AVIRIS-3 L1B data, this next code block lists the campaigns and number of granules in each campaign

• Note that at the time of writing this Notebook, this functionality is specific to AVIRIS-3 Datasets

If you know a NASA Project or Campaign employed the AVIRIS-3 instrument, you can directly query the AdditionalAttributes

Setting Search Parameters for Granules¶

We’ll use a NEON AOP Flight Boundary to search for AVIRIS data in a spatial area of interest.

NEON AOP Flight Boundaries

Use the NEON AOP Boundary file to search for AVIRIS-Classic L2 Reflectance data within that boundary

For our search parameters, let’s explore the granules found

• Let’s look at the first result

You can download these files directly to your local machine by clicking on any of the files

• We also see that these data are Cloud Hosted: True

Create and Visualize the Bounding Boxes of the subset of files¶

From each granule, we’ll use the CMR Geometry information to create a plot of the AVIRIS-3 flight lines from our temporal and spatial subset

Below, we convert NASA’s Unified Metadata Model (UMM) geometry to a geopandas dataframe to plot the search results over a basemap.