The controling document for TES Level 2 data processing algorithms is the Level 2 Algorithm Theoretical Basis Document (ATBD) [pdf File].

At Level2, vertical concentration profiles of the selected species are extracted from the Level 1B spectral data through a process of retrieval: iteratively fitting an atmospheric radiative transfer model results with the observed radiances considering the measurement noise and some known characteristics of the atmospheric parameters.

The Forward Model (F):

->  the model spectral radiance,

->  the Jacobians,  (the sensitivity of spectral radiance to the perturbations of retrieved parameters).

->  some characteristics of the TES forward model

• Tabulated Absorption Coefficients for line, continua, and cross-section species
• Jacobians are calculated analytically
• Micro-windows are used to reduce processing time and error from interfering species

The Retrieval Method:

• The cost function C(x) is minimized iteratively from an initial guess of x,

  

• Gauss-Newton or Levenberg-Marquardt solution,

  

TES Level 2 Processing Flowchart

The following flowchart describes the TES L2 data processing and its related operational support activities. The Task Scheduler controls the data production via scheduling observation scenes and coodinating with all the processing components. The basic architecture of L2 consists of three major functional components: (1) Binning and Ordering, (2) Retrieval, and (3) Standard Product Generation. The target scene binning and ordering is to organize data available in a defined time period (e.g. one day) to latitude / longitude bins for the retrieval process. The retrieval process is the core in L2. This process is controled by the retrieval strategy engine which builds sequential retrieval steps. The Earth Limb And Nadir Operational Retrieval (ELANOR) is the TES Level 2 operational retrieval program with tabulated instrument and physics data as supplies. The Retrieval Strategy engine is also supported by data products from the external sources. The Level 2 standard products are generated after target scene data are processed for a single day.

(click to enlarge)