Sentinel-1 Payload Data Ground Segment

Operations Concept

B. Rosich, Sentinel-1 PDGS Project ManagerN. Miranda, G. Sabella, C. Putignano, P. Potin

Outlook• Overall context• Key role• Main operations concepts• Challenges and status

Sentinel-1 PDGS Overall Context

FOS

Sentinel-1A

TT&C Stations

Sentinel-1

PDGS

Acquisition Stations

GSC Coordinated Data Access System

TM/TCISPs

GMES Collaborativ

e Ground Segment

Collaborative

Centre A

GSCS-1 Core Ground

Segment

GCM GSGCM GS

GCM GSGCM GS

GCM GSGCM GS

GM

ES Con

tribut

ing

Mis

sions

(ESA, E

UMETS

AT, N

atio

nal

mem

ber-s

tate

s m

issi

ons, e

tc)

GCM GS

Collaborative Centre A

Collaborative Centre A

Collaborative Centre A

Collaborative Centre A

Collaborative Centre A

GMES Space Component

EO Data Users

GSC Data Request GSC Data Provision GMES Services

Users

EO Sentinel-1 Data Users

GMES Service Entities

EO Data Users

Sentinel-1B

The GSC Operations Concept will rely on a GSC Ground Segment consisting of:

• a GSC Core Ground Segment, with GSC-funded functions and operations, providing:– the primary access to all Sentinel Missions core products as well as

– the coordinating access functions to Contributing Missions and Sentinels data,

• a GSC Collaborative Ground Segment, with non GSC-funded operations, providing through dedicated operational interfaces:– a supplementary access to Sentinel Missions data, i.e. either through specific acquisition services (e.g. with shorter

timeliness), or specific products,

– the frame for international cooperation

Sentinel‐1 PDGS

Data Archiving

Data Circulation and Dissemination

Mission Performance

Configuration, Monitoring and Control

Precise Orbit Determination

Mission Access User Interface

MissionPlanning

Data Processing

Data Reception and Ingestion

X‐band raw data

Products

The Sentinel-1 PDGS as a component of the overall GMES Space Component (GSC) Ground Segment, in charge of the following key activities:

• Implementing the Sentinel-1 mission observation scenario

• X-Band data reception

• Generating the operational core ground segment products

• Reacting to emergency orders with rush instrument tasking and processing

• Providing access to Sentinel-1 data

• Ensuring the long term mission data archiving

• Monitoring the instrument and mission performance

• Ensuring Sentinel-1 core operational user products meet the expected quality, with necessary calibration and validation activities

Sentinel-1 PDGS Key Role

Predefined

instrument

planning

Systematic

Data

Processing

On-line data accessOn-line data access

Data timelinessData timeliness

PDGS LayoutPDGS Layout

Core GS operational user productsCore GS operational user products

Sentinel-1 PDGS main operations concepts

Predefined

instrument

planning

Systematic

Data

Processing

On-line data accessOn-line data access

Data timelinessData timeliness

PDGS LayoutPDGS Layout

Core GS operational user productsCore GS operational user products

• The Sentinel-1 PDGS provides a set of Core operational SAR user products.

• These user products are made available in an harmonised format based on XFDU, wrapping a set of annotation files in XML and image file/s in binary (L0), geotiff (L1) , NetCDF (L2)

• Other products (supported products) are generated by the Sentinel-1 Core PDGS for internal purposes or to fulfil specific GMES requirements (e.g. stack products for emergency).

• Additionally:

- Hosted processing will be supported within available resources, allowing the generation of other user-”defined & implemented” products as part of the systematic processing flow.

- Other products/services may be provided by the collaborative GS

Sentinel-1 Core PDGS Operational User Products (1)

LEVEL-0 PRODUCTSLevel 0 products contain the compressed, unprocessed instrument source packets, with additional annotations and auxiliary information to support the processing.Only SAR Level-0 products for SAR SM, IW and EW modes are made available to the S-1 users.

LEVEL-1 PRODUCTSLevel-1 Slant-Range Single-Look Complex Products (SLC):SLC products provide focused data in slant-range geometry, single look, containing phase and amplitude information.

Level-1 Ground Range Detected Geo-referenced Products (GRD):Focused data is projected to ground range, detected (phase information is lost) and multi-looked. Data is projected to ground range using an Earth ellipsoid model, maintaining the original satellite path direction and including complete geo-reference information.

LEVEL-2 PRODUCTSLevel-2 Ocean (Wind, Wave and Currents) productsOcean wind field, swell wave spectra and surface currents information as derived from SAR data.L2 ocean products are available for all modes (although information content may slightly vary per mode)

Sentinel-1 Core PDGS Operational User Products (2)

Predefined

instrument

planning

Systematic

Data

Processing

On-line data accessOn-line data access

Data timelinessData timeliness

PDGS LayoutPDGS Layout

Core GS operational user productsCore GS operational user products

LTA

MMUS

POD

Sentinel-1 PDGS Layout

The Sentinel-1 PDGS is a distributed system, with elements deployed in various core PDGS centres

CGS

CGS

CGS

PAC

PAC

MPC

PDMC

PACPACCGS

RPF

In addition the Sentinel-1 PDGS includes the following services:

•Long Term Archiving Service (LTA)•Precise Orbit Determination Service (POD)•Multi-Mission User Services (MMUS)

Processing and Archiving Centres

Fast-24h processing and dissemination

Medium term archiving

Mission Performance Centre

Instrument performance, calibration and quality control

Payload Data Management Centre

Mission Planningand management

Core Ground Stations

Data receptionNRT processing and dissemination

Reference Platform Centre

Reference facility for AIV activities

Predefined

instrument

planning

Systematic

Data

Processing

On-line data accessOn-line data access

Data timelinessData timeliness

PDGS LayoutPDGS Layout

Core GS operational user productsCore GS operational user products

S1-A

CGS

X-Band downlink

X-Band downlink

CGS

S1 NRT data

Inst. sensing

Inst. sensing

< 3h 10 min / 1 h

S1 NRT data

PAC

S1 24h data

<24h

time

Sentinel-1 PDGS Data Timeliness

Data access to systematically generated products is provided according to the following timeliness:

Standard timeliness: within 24h from sensing for all systematic products NRT timeliness:

< 3h from sensing (within 1h from downlink) < 1h from sensing for data acquired in direct downlink over specific areas (e.g. European waters).

Predefined

instrument

planning

Systematic

Data

Processing

On-line data accessOn-line data access

Data timelinessData timeliness

PDGS LayoutPDGS Layout

Core GS operational user productsCore GS operational user products

Predefined instrument planningBased on the Sentinel-1 mission observation requirements from GMES Services, National Users, continuity needs, a pre-defined Long Term Plan is built up by the Sentinel-1 PDGS and used as baseline for instrument tasking.

This Long Term Plan:

-defines the instrument sensing and downlink activities during the LTP period, solving any observation conflicts and ensuring compliance with spacecraft constraints

-is defined in line the available downlink resources & affordable instrument sensing activity (up to 25 min of HBR mode dual polarisation per orbit)

-is expected to be interrupted only to satisfy emergency/crisis requests whenever they can be fulfilled by the Sentinel-1 mission

-is updated regularly in time to follow the evolution of the user observation needs and the availability of GS resources.

-is available for consultation through the Sentinel-1 access interface (ngEO)

(*) The Sentinel-1 Core Ground Stations network is currently being selected through open ITT.

IW1

IW1

Full synchronisation

TOPS cycle time2.7 sec

IW acquisition #N

IW acquisition #N+1

Partial synchronisation

IW2

IW3

TOPS burst synchronization is essential to exploit TOPS data for interferometry

Synchronization is achieved by defining a set of tie points around the orbit (separated by the TOPS cycle time) and ensuring the TOPS acquisitions start in one of these tie points.

Mission planning is performed by the PDGS based on position, rather than absolute time.

Tie points position remains fixed during the mission and selected start position is converted in time on-the-fly by the spacecraft using the on-board GNSS.

Predefined instrument planning for TOPS interferometry

Predefined

instrument

planning

Systematic

Data

Processing

On-line data accessOn-line data access

Data timelinessData timeliness

PDGS LayoutPDGS Layout

Core GS operational user productsCore GS operational user products

Systematic Data Processing (1)

Based on a baseline observation scenario, after resolving potential conflicting observation needs, Sentinel-1 data is acquired in a pre-defined mode/polarisation and frequency around the world.

From the same data acquired according to this plan, multiple processing requirements can be fulfilled in terms of regional areas and product type.

Accordingly, the Sentinel-1 data processing scenario is based on a pre-defined set of products systematically generated over well defined areas and timeliness in a data driven mode, constituting the Sentinel-1 data sets or collections, e.g.:

•Collection 1: IW SLC products generated for all IW data acquired over Saint Andreas Fault and made available within 24h from sensing

•Collection 2: IW SLC products generated for all IW data acquired over the Etna and made available within 24h from sensing

•Collection 3: IW GRD products generated for all IW data over Italy and made available within 24h from sensing

•Collection 3: IW GRD products generated for all IW data acquired over Artic sea-ice areas and made available within 3h from sensing•….

Global: Applies to all acquired dataRegional: Applies to data acquired over well defined geographical areas, including areas required in NRT, (cf. HLOP)Local: Applies to well defined geographical areas fulfilling specific constraints (e.g. within the stations coverage area) (cf. HLOP)

Processing Concept

Instrument mode

Product Type Timeliness (availability

after sensing)Comment

Systematic Global

SM, IW, EWSAR L0

SAR L1 GRD<24h All acquired data

WV SAR L2 OCN <3h All acquired WV mode data (oceans areas)

Systematic Regional

SM,IW,EW

SAR L2 OCN <3hFor regional maritime surveillance areas in HBR mode defined

through HLOP

SAR L0SAR L1 GRDSAR L1 SLC

<3hData available in 3h from sensing from the core PDGS for regional

areas defined through HLOP

SAR L1 SLC<24h

Data available in 24h from sensing from the core PDGS for regional areas defined through HLOP

Systematic Local

SM,IW,EWSAR L0

SAR L1 GRD<10 min

Only for data acquired in direct downlink over the S-1 Core Ground Stations when not addressed by collaborative stations

ArchiveSM,IW,EW,

WV

SAR L0SAR L1 GRDSAR L1 SLCSAR L2 OCN

Offline

All systematically generated data is available on-line on a Non Time Critical basis (e.g. nominally ˜24h)

Products non systematically generated (e.g. SLC outside the systematic regional areas) can be requested from L0

Systematic Data Processing (2)

Sentinel‐1 instrument operations:‐ High Bit Rate (HBR) modes (SM/IW/EW) are operated for max 25 min / orbit‐WV mode is operated continuously over ocean

6 m

in IW

15 m

in IW

2 m

in IW

Data processing strategy (1)

Sentinel‐1 systematic observation scenario results in large acquisition segments (data takes of few minutes)

`

For Sentinel-1 access to long product stripes (e.g. similar to ASAR MR WSM or IMM products today systematically disseminated) would result in an unmanageable product size for Sentinel-1 L1 HBR modes.

As a matter of example:

Sentinel‐1 Level‐0 and Level‐1 products will be segmented and made available in “slices” of defined length along track, optimised per instrument mode.

Sev

eral

min

utes

IW d

ata

take

L0 products

L0 slice#1

L0 slice#2

L0 slice#3

L0 slice#4

L0 slice#5

L0 slice#6

L1 slice#1

L1 slice#2

L1 slice#3

L1 slice#4

L1 slice#6

L1 slice#5

L1 products

Data processing strategy (2)

Sliced GRD L1 products Slices are referred to the start of

each acquisition segment.

Slices cover a sub-set of the data take in along-track direction and the complete data take area in the across track direction.

Slices are standard independent products.

Slices can be seamlessly concatenated by the user into a continuous product or “stripe”covering up to the complete data take.

Data processing strategy (3)

Predefined

instrument

planning

Systematic

Data

Processing

On-line data accessOn-line data access

Data timelinessData timeliness

PDGS LayoutPDGS Layout

Core GS operational user productsCore GS operational user products

On-line Data Access – Main concepts

•In line with the Sentinels Data Policy, the Sentinel-1 products will be made available on-line to registered users.

•Data access is mainly based on a concept of “subscription” to a set or sub-set of products systematically generated (podcast concept).

•Additionally, data discovery and download of any product systematically generated is possible through the user data access interface (ngEO)

•In case the selected product to be downloaded is not available in the GS (i.e. in case it was not part of the systematic processing scenario), the product is generated on-the-fly from the source L0 product, transparently to the user. However, limited GS resources may be available to support this scenario.

•The next generation user services for Earth Observation (ngEO) will be the main user data access interface for Sentinel users.

•It will provide:

- A web based interface for:- Data discovery- Interactive data selection and download- Definition of “personal subscription” (identifying an area of interest and a

mode/product type)

- A download manager application, which the user installs and runs as a daemon in its own premises, which is in charge of downloading any new product matching the user defined order

- The possibility to download only a set of product components (e.g. only one polarisation for dual polarisation products, or only one sub-swath for TOPS SLC products)

- Information on interferometric baseline and burst synchronisation

On-line Data Access – Main mechanisms

On-line Data Access – Main scenarios

GMES Services requiring regular access to a pre-defined “collection” of systematically generated S1 products:-The user will be able to “subscribe” to the desired collection/data set through the CDS-the user will have transparent on-line download capability for any new product associated to the subscribed data sets through a transparent data access client

Users requiring access to regular access to S1 products systematically generated but over a limited user-specific area:-The user will be able to define his personal data set (e.g. any IW SLC over a user defined area) through ngEO-Any new product systematically generated matching the user request definition will be automatically downloaded by the ngEO download manager.

Users requiring occasional access to S1 products:-The user will be able to discover Sentinel-1 acquired data through the ngEO front-end and select a past acquisition and product type to be downloaded-If the selected product type

- is available in the GS archives, it is made available on line to be downloaded by the user

- is not available in the GS archives, it is generated on-the-fly from the source L0 product transparently to the user (within available resources)

Main challenges and Status

• Challenging requirements in terms of data volume (~ 1 TB/day of data downlinked, > 1 TB/day of new products generated) and data policy implementation

• Largely distributed system, with core ground segment centres being selected

• New capabilities to be exploited in terms of collaborative interfaces

• Operational products with traceable and maintained quality through the mission

• Extremely demanding data access needs for an open and free access to all systematically generated data….… but also new challenges for Sentinel-1 users to be ready to make the best use of it !!!!

Sentinel-1 PDGS challenges

S1-A

ENVISAT ASAR

0

100

200

300

400

500

600

GB

Systematic NRT(Average S-1 Scenario) [GB/day]

Systematic NRTFor Systematic Real time (~1h from downlink) : The Sentinel-1 represents a volume increase of a factor 30 compared to the most demanding ESA EO SAR Scientific mission(under a minimum systematic S-1 product generation scenario)

=> GS Operational requirements never achieved worldwide for SAR missions (volume, availability, reliability,…)

Sentinel-1 PDGS Status

• System Requirements Review: April 2009 ✔

• Preliminary Design Review: Nov 2010 ✔

• Core Ground Stations and PACs selection

• Critical Design Review: Dec 2011

• v1 Factory Acceptance: Dec 2011 – reference platform

• v2 Acceptance Review: Jun 2011 – first partial deployed system

• v3 Acceptance Review: Oct. 2011 – system deployed for CP operations

• Satellite Launch & Commissioning

• v4 Acceptance review: Launch + 3 months

Thank you