NOAA KLM User's Guide

Section 6.2

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6.2 Pre-Processing

Data pre-processing is a set of functions which combine to create the Level 1b datasets. The software formats, error checks, calibrates, and appends earth locations and otherwise manages the ingested data. Raw spacecraft data are processed via Polar Acquisition and Control Subsystems (PACS) and made available to the Pre-Processing operation via the Ingest System as Level 1a data sets. The transformation of ingested data of Level 1a format into one or more data sets of Level 1b format primarily consists of the addition of instrument calibration coefficients and earth location information to the raw data stream. The transformation also provides supplemental data about the calibration process and thus indirectly about the instruments onboard the satellite. Data in the Level 1b format are made accessible for products, archival, file transfer and are used by the meteorological and climatological communities.

6.2.1 System Improvements

The pre-NOAA KLM series of TIROS polar spacecraft have retained the same basic format of raw data streams for over 20 years. The new series of TIROS polar spacecraft (NOAA KLM) has new formats and somewhat larger volumes of data. The NOAA KLM Pre-Processing system processes both old and new spacecraft data. The software is modular and structured to allow platform independence. Program structures are designed to take advantage of modern operating systems with distributed processing providing faster availability of data products.

6.2.2 Level 1b Database Improvements

Enhancements have been made to the methods of access and storage of the Level 1b data. With the old system (pre-NOAA KLM), a change made in spacecraft or instrument configuration, would result in a change in the format of the encapsulation of the Level 1b data. When such a change was made in the up-front systems, the change had to ripple to the end user. A new Level 1b generating system (Level 1b*) provides a centralized database which contains the basic elements of the Level 1b and the associated supporting ancillary data. The database provides end-to-end accountability for data and data products to managers and users. The new system (Level 1b*) provides a universal access to the component elements of the dataset, thus providing transparency to the Level 1b format. Access to the Level 1b* database is facilitated by a library of utilities layered in a tree structure.

The facilities and services provided by the Level 1b* offers a means of simplifying and improving the interfaces of the Calibration Monitoring System. Specifically, these interfaces are between the Pre-processing input to the monitoring and monitoring output of status reporting to the users. The calibration process performed by the Pre-Processor passes resulting parameters to the offline monitoring system. The parameters transit an interface referred to as History Files. The Level 1b* database library has structures and utilities defined specifically to contain and access the information sent to the History File. This provides for a modifiable and maintainable system that is much more flexible than the old version.


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