SMAP – Handbook

“A rare characteristic of the SMAP Project is its emphasis on serving both basic Earth System science as well as applications in operational and practice-oriented communities.”

Contents of Full Handbook

1. Introduction and Background
2. Mission Overview
3. Instrument Design and L1 Data Products
4. Soil Moisture Data Products
5. Value-Added L4_SM Soil Moisture Product
6. Carbon Cycle Data Products
7. Science Data Calibration and Validation
8. NASA SMAP Applications Program
9. SMAP Project Bibliography

SMAP Handbook Excerpts on ASF's Roles

The Alaska Satellite Facility (ASF) is one of four ground stations that support the SMAP mission and one of two NASA DAACs that distribute SMAP data. The SMAP baseline science data products will be generated within the project’s Science Data System and made available publicly through the two NASA-designated Earth-science data centers. The ASF Synthetic Aperture Radar (SAR) Distributed Active Archive Center (DAAC) will provide Level 1 radar products, and the National Snow and Ice Data Center (NSIDC) DAAC will provide all other products. The excerpts below from the SMAP Handbook focus on ASF’s roles.

About ASF
ASF, part of the University of Alaska Fairbanks (UAF) Geophysical Institute, operates the SAR DAAC for NASA. For more than 20 years, ASF has worked in conjunction with the SAR research community and scientists across the globe providing near-real-time and archive data from several key Earth-observing satellites. In support of this user community, ASF offers interactive web resources for data search and download, and creates custom software tools for data interpretation and analysis.

ASF’s DAAC is one of 12 Data Centers supported by NASA and specializes in the processing, archiving, and distribution of SAR data to the global research community. In recent years, the ASF DAAC has moved from a process-on-demand to a download-on-demand data system that provides direct access to over 1 PB of SAR data. The ASF data system, comparable to the EOSDIS Core System, provides ingest, cataloging, archiving, and distribution of ASF DAAC’s complete data holdings. ASF distributes focused and unfocused SAR data products, browse images, and relevant metadata in multiple formats through the Vertex data search portal. 

Ground Data System (GDS)
The primary path for commanding the SMAP observatory and returning science and engineering data is through three northern-hemisphere tracking stations and one southern-hemisphere station in Antarctica. Data return at the northern-hemisphere stations is via 11.3-m antennas located at Wallops, Virginia (WGS), Fairbanks, Alaska (ASF), and Svalbard Island, Norway (SGS). Data return at the southern-hemisphere station is via the 10-m antenna at McMurdo Station, Antarctica (MGS). The table below gives characteristics of the four stations and average contact statistics from the science orbit. Because SMAP is in a near-polar orbit, the higher latitude stations have more frequent contact opportunities.

Ground Station Antenna Latitude Average # of Contacts per day* Average Coverage Minutes/day*
Svalbard (SGS) Norway 11.3 m 78.2ºN 10.3 88.3
Fairbanks (ASF) Alaska 11.3 m 64.9ºN 6.8 53.7
Wallops (WGS) Virginia 11.3 m 37.9ºN 3.3 25.8
McMurdo (MGS) Antarctica 10.0 m 77.8ºS 10.4 90.7

ASF DAAC Support of NASA Missions
The ASF DAAC provides support for NASA and NASA-partner missions assigned to it by the Earth Science Data and Information System (ESDIS) Project. The ASF DAAC has extensive experience managing diverse airborne and spaceborne mission data, working with various file formats, and assisting user communities to further the use of SAR data.

These efforts are facilitated, in part, by ASF Scientists and Data Managers, who interact with mission teams, provide subject matter expertise, inform data and metadata formats, evaluate data structure and quality, and address data support needs. A key project component at ASF is the core product team, which provides integration of new datasets into the ASF data system and ensures efficient coordination and support of each mission. The team members have mission-specific expertise and consist of the following personnel:

  • The Project Manager is the team leader who oversees mission activities at ASF and coordinates with external groups.
  • The Product Owner is a primary product stakeholder and oversees ingest, archive, documentation, and distribution of data products as well as managing interactions with mission and ASF scientists and other stakeholders.
  • The User Services Representative (uso@asf.alaska. edu) supports data users with products and software tools and communicates user feedback or suggestions for improvement to the Project Manager and Product Owner. 
  • Software Engineers design, develop, and maintain software for the acquisition, processing, archiving, and distribution of satellite and aerial remote sensing data.
  • Software Quality Assurance Technicians provide software and web-based-application testing prior to delivery to the production data system to ensure integrity, quality, and overall proper functionality through testing methods to uncover program defects, which in turn are reported to software engineers.
  • The Technical Science Writer composes and edits a variety of ASF materials, from newsletter articles to technical documentation.

The core product team’s responsibilities for data management include:

  • Ingesting, cataloging, archiving, and distributing data
  • Providing guidance on file formats and integration of new file formats into the ASF data system
  • Describing data products and producing user manuals and guide documents
  • Creating metadata and exporting it to CMR and GCMD (Global Change Master Directory)
  • Ensuring accurate metrics are reported to EMS (ESDIS Metrics System)
  • Designing, developing, and deploying specialized data portals that allow online access to data products and information 
  • Creating software tools for data interpretation and analysis
  • Assisting users with the selection and usage of data

ASF also supports NASA and partner missions through the operation of a ground station with two 11-m antennas, providing complete services, including data downlinking, commanding, and range/Doppler tracking. ASF is part of the NASA Near Earth Network (NEN) supporting a variety of low-Earth-orbit spacecraft.

ASF DAAC Data Systems
The ASF DAAC operates a custom data system designed, implemented, and supported by DAAC personnel. During its evolution, the ASF data system has moved from using primarily custom software on capital equipment to commodity hardware and commercial off-the-shelf (COTS) software and hardware solutions. This has greatly lowered development and maintenance costs for the data system, while simultaneously providing a higher level of performance. The ASF DAAC data system provides the following capabilities:

Data Ingest

  • Automated data ingest occurs from the ASF ground station as well as external data providers in a variety of media and formats.
  • Ingested data are pre-processed when necessary, providing browse or derivative products.

Data Archive

  • The central ASF data system archive is provided by a Data Direct Networks gridscaler storage system.
  • This system provides direct access to over 1 PB of processed data as well as the capability for automated backups to an offsite location.
  • Raw data are held in a robotic silo for access by the processing system. ASF maintains a backup in an external location in case of silo failure.

Data Distribution

  • ASF provides direct http access to DAAC data products and utilizes NASA’s User Registration System (URS) for user authentication. 
  • NASA data are provided to public users with no restrictions. Partner data are provided to NASA-approved users through URS for authentication and ASF’s internal database for access control.
  • The data system provides web-based access to the archive through Vertex. Vertex supports the data pool with direct download of processed data.
  • Through custom portals and applications, the DAAC provides additional services such as mosaic subsetting, mosaicking, and time-series analysis.

Data Support 

  • ASF DAAC exports relevant metadata to NASA’s ECHO system.
  • ASF DAAC exports ingest, archive, and download metrics to NASA’s EMS system.
  • ASF DAAC assists users with data discovery and usage, maintains product documentation and use guides, and supports feedback between the ASF user community and the core product teams. 

SMAP at ASF DAAC
ASF provides a variety of services, software tools, and user support to address the needs of the SMAP user community. The ASF core project team will leverage on-going collaborations with the SMAP Project to identify and prioritize SMAP user community needs, which in turn will inform development and implementation of data support and value-adding services for the mission. The SMAP website at ASF will serve as an interactive data portal, providing users with relevant documentation, custom tools and services, and ancillary data and resources.

Post-Launch SMAP Data
ASF will ingest, distribute, archive, and support postlaunch Level 1 radar products for the SMAP mission. ASF will receive the Level 1 radar products from the SMAP Science Data System at the Jet Propulsion Laboratory (JPL) in Pasadena, California.

Non-SMAP Data of Interest to SMAP
ASF will cross-link from the SMAP website to data collections that complement SMAP data and are of interest to the user community. Some of these collections are distributed by ASF, including the following:

  • Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) data products
  • Jet Propulsion Laboratory Uninhabited Aerial Vehicle SAR (UAVSAR) data products
  • Making Earth System Data Records for Use in Research Environments Inundated Wetlands (MEaSUREs) data products
  • Advanced Land Observing Satellite-Phased Array L-band SAR (ALOS PALSAR)
  • Japanese Earth Resources Satellite-1 (JERS-1) image data and mosaics

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