Payload Data Segment (PDS)

PDS role
Architectural elements
PDS product distribution
Processing and archiving centres (PAC)
Processor algorithms

The PDS comprises all ground segment elements related to payload data acquisition, processing, and archiving. It also includes the user interface facilities which offer Envisat services to the user community.

For more detailed information see the PDS Detailed Description.

PDS role

The PDS provides all services related to the exploitation of the data produced by the instruments embarked on-board the Envisat satellite:

• all payload data acquisition for the global mission
• all regional data acquisition performed by ESA stations
• processing and delivery of ESA near real time products
• archiving, processing and delivery of ESA off-line products with support of processing and archiving centres (PACs)
• interfaces with national and foreign stations acquiring regional data
• interfaces to the user community from order handling to product delivery

Architectural elements

Overview of the PDS architectural elements

The PDS comprises:

ESA provided centres and stations:

• the payload data control centre (PDCC) at Esrin;
• the payload data handling station (PDHS) at Esrin and Kiruna;
• the payload data acquisition station (PDAS) at Fucino;
• the low-rate reference archive centre (LRAC) at Kiruna.

Centres and stations procured nationally:

• the processing and archiving centre (PAC's) located at ESA member states;
• the national stations providing ESA services (NSES) and located in programme participating states.

The PDS also interfaces with national and foreign stations duly authorised to receive Envisat regional data.

All PDS centres and stations is coordinated by the payload data control centre (PDCC) which is in charge of instrument and ground segment planning and of the overall PDS monitoring and control. The PDCC interfaces with the flight operation control center (FOCC) for all mission planning activities.

PDS product distribution

Two categories of product distribution services are provided by the PDS:

	Near real time services
	typically three hours from sensing for data used in forecasting or tactical operations (global and regional products produced and distributed systematically); typically one to three days from sensing, for applications requiring high resolution images (agriculture, forestry, soil moisture, etc.) with production and delivery to users on request.
	Note: All regional data (ASAR HR and MERIS FR) acquired at the two PDHSs are systematically processed in NRT as medium-resolution stripes (150-m resolution for ASAR and 1200-m resolution for MERIS
	Off-line service
	Continuity of services from near real time to off-line: delivery a few days to weeks from data take; product commonalities (same format, same processing algorithms whenever possible); off-line products benefit from a posteriori knowledge of calibration, auxiliary data, and precise orbit.
	Payload data handling stations for off-line users

Processing and archiving centres (PAC)

The processing and archiving centres, located in ESA member states, archive and process off-line high rate data and generate off-line geophysical products for the regional high-rate and full-resolution instruments and for the global low-rate instruments.

Their respective roles are as follows:

Processor algorithms

The algorithms and processors used in the PDS are developed and validated independently of the PDS industrial activities.
See Algorithm Development Approach for more information.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry