Chapter 1

SDI Overview

The SSEC Desktop Ingestor (SDI) takes a simple approach to satellite data ingesting. A fast PC plus a modified third party interface card receives clock and data from a bit sync. For high data rate satellites, such as GVAR and POES, the entire serial data stream is ingested into memory, blocked into 1 Mbyte files, and written to disk. These files are called Stretched Data Format (SDF) files. An independent program analyzes the SDF files to build index files to the information in the SDFs. Data access is handled by an ADDE server running on the ingest processor without interfering with the ingest process. For low data rate satellites, such as METEOSAT PDUS, image files are built directly as the data is received. The image files contain the raw satellite transmission aligned on byte boundaries with sync removed.

The advantages to these approaches are:

No frame synchronizer or SAS (Satellite Acquisition System) is required. The frame synchronization is done in software.
For the high data rate approach, SDF files usually use less disk space than area files; therefore, more data can be stored on-line.
The SDI runs without operator intervention, i.e., it is a black box. After attaching the clock and data cables to the card and booting up the PC, data ingestion begins.
The same hardware works for multiple satellite families; i.e., the same hardware that handles GVAR handles POES, Meteosat, etc. Only the software running in the black box varies.

This chapter is divided into the following sections:

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