Minimize Data Extraction and Quality Checks

Data extraction and quality check processing aims to extract useful data from Instrument Source Packets (ISPs). Science data is extracted from the ISP's data field as well as information necessary for further processing and detection of anomalies in the data stream such as:

  • transmission error
  • format error
  • sequence error.

The OLCI measurement data are ordered and packaged, with additional information about the instrument status, into a sequence of strings of bits referred to as the OLCI ISPs.

The packets are input to the processing in the form of Level-0 product.
Level-0 products contain packets pertaining to a single instrument mode, nominally either Earth observation or calibration, with or without spectral relaxation. If a Level-0 product containing calibration data is submitted for Earth observation Level-1 processing, all its ISPs will be rejected by the data extraction step and processing will stop.
The Level-0 product may contain gaps (missing packets) of any size. Duplicates are assumed to have been removed by Level-0 processing.

Information in the packet header allows identification of:

  • OLCI operational mode: Earth observation or calibration modes (calibration mode packets are ignored)
  • events and exceptions in the operation of OLCI including disruptions in the clock or counter sequence, and instrument configuration changes.

No error correction code is applied at the packet level and so undetected invalid data may be present in the incoming packets.

Logical Flow of OLCI Data Extraction and Quality Checks