Sentinel-1 Mission Overview Pierre Potin Sentinel-1 Mission Manager, ESA Advanced Course on Radar Polarimetry ESRIN, Frascati, 19 January 2011
Global Monitoring for Environment and Security GMES is established to fulfil the growing need amongst European policy-makers to access accurate and timely information services to better manage the environment, understand and mitigate the effects of climate change and ensure civil security
Goal of GMES GMES aims at developing operational services, following the example of meteorology, but for other domains such as: emergency management air quality monitoring land monitoring ocean & sea ice monitoring etc In addition, science is needed to create and continuously improve operational services
GMES dedicated missions: Sentinels Sentinel 1 SAR imaging All weather, day/night applications, interferometry Continuity of ERS and ENVISAT 2012 (A), 2014+ (B) Sentinel 2 Multispectral imaging Land applications: urban, forest, agriculture,.. Continuity of Landsat, SPOT 2013 (A), 2015+ (B) Sentinel 3 Ocean and global land monitoring Ocean colour, vegetation, sea/land surface temperature, altimetry - Continuity of ERS and ENVISAT 2013 (A), 2015+ (B) Sentinel 4 Geostationary atmospheric Atmospheric composition monitoring, transboundary pollution 2018 Sentinel 5 and Precursor Low-orbit atmospheric Atmospheric composition monitoring 2014 (5P), 2019
Sentinel 1: C-band SAR mission Data continuity of ERS and ENVISAT missions GMES radar imaging mission for ocean and land services Applications: monitoring sea ice zones and the arctic environment surveillance of marine environment monitoring land surface motion mapping in support of humanitarian aid in crisis situations mapping of land surfaces: forest, water and soil, agriculture, etc. The Sentinel-1 mission is based on a constellation of 2 satellites Sentinel-1A to be launched end 2012 Sentinel-1B under procurement, launch date is TBD (indicatively 2014/2015)
Sentinel 1 satellite system 2300 Kg spacecraft mass 7 years design life time, consumables for 12 years Sun synchronous dawn-dusk orbit at 693 Km mean altitude 12 days repeat cycle (1 satellite), 6 days for the constellation The two satellites are in the same orbit but with a different mean anomaly C-Band SAR Payload with centre frequency 5.405 GHz
Sentinel 1 SAR operational modes Data recording / transmission capabilities Four nominal SAR operation modes: Strip map 80 km swath, 5x5 m res. Interferometric wide swath 250 km swath, 5x20 m res. Extra wide swath 400 km swath, 20x40 m res. Wave 5X5 m res (TBC), sampled images of 20x20 km at 100 km along the orbit, alternating into 2 incidence angles Note: above resolutions are (single look) mode resolutions. See slide 12 for expected product resolution. SAR Duty cycle: up to 25 min/orbit in high rate acquisition modes Data recording / transmission capabilities : On-board data storage capacity of 1400 Gbit Two X-band RF channels of 260 Mpbs each Equipped with an Optical Communication Terminal for GEO laser link with European Data Relay System
Sentinel-1 SAR Modes and Production 19 o Sentinel-1 SAR can be operated in 4 exclusive 46 o imaging modes with different resolution and coverage: Extra Wide Swath Mode (EW) 19 o 30 o S1 400 Km 250 Km 400 Km 80 Km 45 o 46 o Interferometric Wide Swath Mode (IW) S6 Stripmap Mode (SM) Mode Rate High Bit Rate (HBR) Low Bit Rate (LBR) SAR Mode For all of these operating modes, the same family of products is available to users. IW EW SM (S1 S6) WV 23 o 36 o 100 Km 200 Km Wave Mode (WV) The systematic processing into specific product type is done according to pre-defined areas definition while other product types will be available on request in offline. 8
Example of average revisit capability Revisit frequency for S1A and S1B (IW mode) Days Per revisit Two satellites in a 12 day orbit Repeat frequency: 6 days (important for coherence) Revisit frequency: (asc/desc & overlap): 3 days at the equator, <1 day at high latitudes (Europe ~ 2 days)
Mission Performance Mode Access Angle GR Single Look Resolution Swath Width Polarisation Strip Map 20-45 deg. Range 5 m > 80 km HH or VV or Azimuth 5 m HH+HV or VV+VH Interferometric Wide Swath > 25 deg. Range 5 m Azimuth 20 m > 250 km HH or VV or HH+HV or VV+VH Extra Wide Swath > 20 deg. Range 20 m > 400 km HH or VV or Azimuth 40 m HH+HV or VV+VH Wave mode 23 deg. Range 5 m (TBC) > 20 x 20 km HH or VV & Azimuth 5 m (TBC) Vignettes at 36.5 deg. 100 km intervals For All Modes Radiometric accuracy (3 σ) Noise Equivalent Sigma Zero Point Target Ambiguity Ratio Distributed Target Ambiguity Ratio 1 db -22 db -25 db -22 db
Planned ESA Operational Products available to users LEVEL-0 PRODUCTS Compressed, unprocessed instrument source packets, with additional annotations and auxiliary information to support the processing. LEVEL-1 PRODUCTS Level-1 Slant-Range Single-Look Complex Products (SLC): Focused data in slant-range geometry, single look, containing phase and amplitude information. Level-1 Ground Range Detected Geo-referenced Products (GRD): Focused data projected to ground range, detected 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 PRODUCTS Level-2 Ocean products Ocean wind field, swell wave spectra and surface radial velocity information as derived from SAR data.
Planned operational ESA Sentinel-1 products - L1 characteristics Acq. Mode SM IW EW WV Product Type Resolution Class Resolution [Rng x Azi] [m] Pixel Spacing [Rng x Azi] No. Looks [Rng x Azi] SLC - 1.7 x 4.3 to 3.6 x 4.9 1.5 x 3.6 to 3.1 x 4.1 1 x 1 1 FR 9 x 9 4 x 4 2 x 2 3.9 GRD HR 23 x 23 10 x10 6 x 6 34.4 MR 84 x 84 40 x 40 22 x 22 464.7 SLC - 2.7 x 22 to 3.5 x 22 2.3 x 17.4 to 3 x 17.4 1 1 HR 20 x 22 10 x 10 5 x 1 4.9 GRD MR 88 x 89 40 x 40 22 x 5 105.7 SLC - 7.9 x 42 to 14.4 x 43 5.9 x 34.7 to 12.5 x 34.7 1 x 1 1 HR 50 x 50 25 x 25 3 x 1 3 GRD MR 93 x 87 40 x 40 6 x 2 12 SLC - 2.0 x 4.8 and 3.1 x 4.8 1.7 x 4.1 and 2.7 x 4.1 1 x 1 1 GRD MR 52 x 51 25 x 25 13 x 13 139.7 ENL For Ground Range Products, the resolution corresponds to the mid range value at mid orbit altitude, averaged over all swaths. For SLC SM/IW/EW products, the resolution and pixel spacing are provided from lowest to highest incidence angle. For SLC WV products, the resolution and pixel spacing are provided for beams WV1and WV2. For SLC products, the range coordinate is in slant range. All the other products are in ground range.
Sentinel-1 mission key operational concepts Pre-defined and stable mission observation plan, to support operational activities (e.g. sea-ice monitoring, oil spill monitoring, ground motion monitoring, etc.) On-request satellite tasking, processing and dissemination capability limited to support exceptional cases (e.g. emergency situations) Systematic processing and dissemination of all acquired data within 24h Systematic NRT data access capability (from 3 h after data sensing to less than 1h after sensing) Easy access to systematic products flow Stable and traceable product quality meeting the quality requirements and accurate product calibration On line data access for fresh and past data
Examples of Sentinel-1 operations constraints (list not exhaustive) Instrument operations constraints: SAR modes exclusivity (incl. polarisation schemes) SAR mode transition time (2.4 sec.) SAR duty cycle (25 min/orbit for the 3 high rate modes) Data transmission / acquisition constraints: Huge volume of data, potentially up to 2.4 TB/day with the two satellites Data rate versus X-band downlink capacity (use of on-board data compression FDBAQ) Data downlink conflict between RT data transmission in dual-pol and download of on-board recorded data On-board memory sizing (1410 Gbits) X-band duty cycle (max. 30 min/orbit, max. 20 min consecutive) X-band downlink switches (X-Band system specified for a total of 150,000 operation cycles)
Sentinel-1 observation scenario definition Objective of the Sentinel-1 observation scenario Implement a pre-defined and conflict-free observation plan, aiming at fulfilling, to the max. feasible extent, the observation requirements from the various GMES and National services Need to find a priori the solutions on the potential conflict among services (e.g. different SAR operation modes / polarisation required over same geographical area)
Sentinel-1 observation scenario High level strategy optimum use of SAR duty cycle (25 min/orbit), taking into account the various constraints (e.g. limitation in the number of X-band switches, mode transition times) Wave Mode continuously operated over open oceans, with lower priority w.r.t. the other high rate modes IW or EW modes operated over pre-defined geographical areas: Over land: pre-defined mode is IWS Over seas and polar areas, and ocean relevant areas: pre-defined mode is either IWS or EWS In exceptional cases only, emergency observation requests may alter the pre-defined observation scenario, with e.g. the use of the Strip Map mode
Sentinel-1 observation scenario and impact on data volumes Sentinel-1 systematic observation scenario in one/two main high rate modes of operation will result in significanlty large acquisition segments (data takes of few minutes) 25min in high rate modes leads to about 2.4 TBytes of compressed raw data per day for the 2 satellites Wave Mode operated continuously over ocean where high rate modes are not used 46 GB for SLC 12 GB for GRD-HR 6 min IW 15 min IW 2 min IW 16 GB for SLC 4 GB for GRD-HR
Sentinel Data Policy ESA Member States have adopted a FREE and OPEN data policy Anybody can access Sentinel data; no difference is made between public, commercial and scientific use open access Sentinel data will be made available to the users via a generic online access mode free of charge This Data Policy still needs approval on the European Union side security restrictions might be implemented on the data distribution.
Synergy Sentinel-1 / RCM CSA-ESA discussions on-going to explore synergies between Sentinel-1 and Radarsat Constellation Mission and in view of interoperability between the missions RCM Sentinel-1interoperability would bring strong benefits to users The following interoperability items are explored: Joint / integrated pre-defined observation plans (complementarities in observations / modes, increased revisit, etc.) Level 1 Product format Harmonisation of catalogue interface Development of common tools Harmonised communication, joint publications etc. A joint calibration working group is being set up
Concluding remarks The Sentinel-1 mission will provide continuity to ERS and ENVISAT with improved performance and revisiting Sentinel-1 will be operated with a predefined systematic observation plan, with systematic processing to a predefined set of operational products On-line data access mechanism, through subscription for routine data flows Free and open access to Sentinel data for all users Cooperation with CSA is planned to achieve a certain level of interoperability between Sentinel-1 and RCM