NODC Jason-2 Archive

Introduction

This site contains an overview of the NOAA archive services being provided for the Ocean Surface Topography Mission (OSTM). These services are being provided by the National Oceanographic Data Center (NODC) and the Comprehensive Large-Array data Stewardship System (CLASS). The Jason-2 satellite launched 20 June 2008 and is the latest in a series of ocean altimeter missions designed to observe ocean circulation, sea level rise, and wave heights. Earlier missions included Geosat, which flew in the 1980s, and TOPEX/Poseidon, which was launched in 1992 and continued through 2005. Jason-1 was launched in 2001 and continues to operate today.

Archive Requirements

As part of the Four Partner Agreement with NASA, EUMETSAT, and CNES, NOAA committed to provide Satellite Command, Control and Communications; Near real time operational product processing and distribution; and Archive and Access. Within the NOAA Polar Ground Segment (NPGS) plan for OSTM, NOAA agreed to numerous specific archive requirements, including for example, "NPGS-3.1.9-040: The NPGS shall archive the Science Data products received from CNES" and "NPGS-3.1.9-010: The NPGS shall archive NOAA-generated NRT products." In addition to these contractual obligations, a range of scientific requirements encourage the archive of the OSTM observations, which will carry on the more than 16 years of continuous ocean measurements made by the TOPEX/Poseidon and Jason-1 missions.

Archive Strategy

Under the new NOAA Data Center - CLASS relationship, CLASS focuses on information technology in support of the archive, but the NOAA Data Center is responsible for the overall archive services. In the case of Jason-2/OSTM, NODC is the lead Data Center responsible for meeting the archive requirements of the mission. The basic strategy involves CLASS providing a wide range of Open Archival Information System (OAIS) archive functions, including functions across all six OAIS Functional Entities but with a focus on Ingest, and Archival Storage, and Access. NODC provides leadership in Preservation Planning and some aspects of Administration, particularly with respect to negotiating Submission Agreements. In addition, NODC provides stewardship oversight of the entire process, including efforts to ensure the quality of the data and its connection with data from the other altimeter missions, including Geosat, which is also preserved for the long-term in the NODC archive.

Submission Agreement

In early 2005, based on a Request to Archive process under consideration by the Data Archive Board (now known as the Data Management Committee), it was agreed that the drafting of an archive Submission Agreement would be the appropriate way to clearly establish and document the OSTM archive strategy. This Submission Agreement would document the relationships between the Archive, consisting of CLASS and NODC, and the Producer, consisting of the NOAA Environmental Satellite Processing Center (ESPC), which generates the local OSTM products and provides those created by CNES. The negotiations to create this Submission Agreement were conducted by Kenneth Casey for NODC, Jeremy Throwe for CLASS, and John Lillibridge of NESDIS STAR, who represented the NOAA, EUMETSAT, and CNES producers. The process of drafting the OSTM Submission Agreement gained momentum as the partners realized that the negotiations were addressing critical questions related to the short-term usability and the long-term understanding and preservation of the data. The partners all agreed that standards-compliant formats would be critical, and netCDF with Climate/Forecast (CF) file-level metadata attributes was chosen to store the mission products. Standard names for altimetry observations were debated within the CF community and are now under consideration for approval. Greater unrestricted access to the full mission data was advocated, with some successes (the great majority of the mission data and all mission products are publicly available, but CNES still requires limited access to some ancillary fields provided by ECMWF and to telemetry data).

Archive Services

All critical archive functions necessary for the preservation of OSTM data have been established and rigorously tested through the comprehensive NOAA and Four Partner Operational Readiness Reviews. An FGDC description for each OSTM data family has been generated and is available in CLASS. CLASS is prepared to support User Services functions for basic requests, with identified external experts at STAR, JPL, and CNES for more scientifically oriented issues. In addition, the Quality Assurance function within the Ingest Functional Entity is being maintained using a system known as NRTAVS, which was developed by JPL under contract with NOAA. It extends the near real time quality monitoring established for Jason-1 to include Jason-2/OSTM and is being run operationally at ESPC. Related work by NODC is also being conducted, to establish a Rich Inventory monitoring system for Jason-2/OSTM using Geosat and Jason-1 data as test beds. While more interoperable connections are being established between CLASS and NODC information technology systems, NODC archive accessions are being generated that direct users to the CLASS access mechanisms for OSTM. These accessions are available below:

1. Level-2 X-Geophysical Data Records (O/I/GDR)
2. Ancillary Files
3. Auxiliary Files
4. Near Real-Time Altimetry Validation System (NRTAVS) QA Reports
5. Orbital Information
6. Telemetry

• HTTP: http://data.nodc.noaa.gov/jason2/
• FTP: ftp://data.nodc.noaa.gov/pub/data.nodc/jason2/
• OPeNDAP: http://data.nodc.noaa.gov/opendap/jason2/