Sentinels and Waves. GMES Sentinel-1 SAR GMES Sentinel-3 Altimeter

Transcription

1 Sentinels and Waves GMES Sentinel-1 SAR GMES Sentinel-3 Altimeter Simon Pinnock, ESA-ESRIN, Frascati, Italy with help from Craig Donlon (ESTEC) & Nuno Miranda (ESRIN) et al.

2 GMES Space Component: dedicated missions Sentinel-1 (A/B) SAR imaging All weather, day/night applications, interferometry Sentinel-2 (A/B) Multi-spectral imaging Land applications: urban, forest, agriculture, Continuity of Landsat, SPOT Sentinel-3 (A/B) Ocean and global land monitoring Wide-swath ocean color, vegetation, sea/land surface temperature, altimetry Sentinel-4 (A/B) Geostationary atmospheric Atmospheric composition monitoring, transboundary pollution Sentinel-5 precursor/ Sentinel-5 (A/B) Low-orbit atmospheric Atmospheric composition monitoring 2013 / / / / /2020/2027

3 Sentinel-3: Continuity of ENVISAT Ocean Observation Main satellite characteristics 1250 kg maximal mass Volume in 3.89 m x m x m Average power consumption of 1100 W 7.5 years lifetime (fuel for 5 add. years) Large cold face for optical instruments thermal control Modular accommodation for a simplified management of industrial interfaces Launch S3A April 2014 Launch S3B mths later Sea and Land Surface Temperature Radiometer GPS Microwave Radiometer Ocean and Land Colour Instrument X-band Antenna DORIS Antenna Observation Data Management: Gb (170 Gbit) of observation data per orbit Space to ground data rate 2 x 280 Mbps X-Band 1 ground contact per orbit 3h delivery timeliness (from satellite sensing) Laser retroreflector S-band Antenna SAR Radar Altimeter

4 Sentinel-3: Instrument Swath and Satellite Orbit Instrument Swath Patterns Ground Track Patterns S3-A S3-B SRAL (>2 km) and MWR (20 km) nadir track 2 days 1400 km SLSTR (nadir) 740 km SLSTR (oblique) 1270 km OLCI Orbit type Repeat cycle LTDN Average altitude Inclination Repeating frozen SSO 27 days (14 + 7/27 orbits/day) 10: km deg 1 Repeat Cycle (27 days)

5 S3: Topography Mission Objectives: - Sea Surface Height - Significant Wave Height - Sea Ice Thickness - Wind speed - Ice Sheet Margins - Inland Water heights - Atmospheric Water Content [cm] ENVISAT S-3 Altimeter noise Sea state bias 2 2 Ionosphere Dry troposphere Wet troposphere Total range error Radial orbit error contributor SRAL SRAL SRAL SRAL MWR POD Topography package includes 1. Dual frequency Synthetic Aperture Radar Altimeter (SRAL) 2. Microwave Radiometer (MWR) 3. Precise Orbit Determination (POD) Key Improvements: Improved range and SSH errors 2 RADAR modes (SAR and LRM) Two Tracking modes (open and closed loop) Better POD

6 S3 SAR RADAR Altimeter Dual frequency Ku/C band Radar Altimeter CryoSat and Jason heritage High horizontal resolution (~300m in SAR mode) SRAL Radar features: Ku-Band ( GHz) : main frequency C-Band (5.41 GHz) : ionosphere corrections Fully redundant electronics Measurement modes: 2 radar modes: Low Resolution Mode (LRM) and High Resolution SAR mode 2 tracking modes: Closed-loop (traditional) and Open-loop tracking modes over rough surfaces using an on-board DEM Any radar mode can be combined to any tracking mode Objective: To retrieve orbit altitude information with an end-to-end accuracy of 3 cm (Ocean) Supported by MWR, GPS, LRR and DORIS

7 Sentinel-3 SRAL Mode Mask Operational Baseline Mission Scenario LRM over open ocean (Closed Loop) SAR mode in coastal zones and EU Inland Seas (Closed Loop) SAR over sea-ice regions (Closed loop) SAR mode over land/ice interiors (Open Loop) Leave the SAR on over land to limit mode switching 100% compliant with Mission Requirements. SAR Closed Loop tracking SAR Open Loop tracking (uses on-board DEM) LRM Closed Loop tracking LRM Open Loop tracking

8 S-3 Altimetry Products SRAL Waveforms Altimeter backscatter (Sigma-0) 1 Hz and 20 Hz Ku and C band parameters (LRM/SAR), the waveforms and the associated parameters necessary to reprocess the data. Access to lower level (e.g. so called SGDR product containing the full radar-echo waveforms/l1b) data on request for regional RLH and coastal altimetry applications. SRAL sigma-0 backscatter ~ 300 m along track (SAR) > 2 km along track (LRM), NRT ~ 300 m along for coastal waters >2 km along track (LRM) for open ocean, NRT Sea Surface Height Anomaly (SSHA) Significant wave height (Hs) Surface wind speed over ocean Variations of the SSH with respect to a mean sea surface. The average wave height (trough to crest) of the one-third largest waves in a given sample period SRAL derived surface wind speed modulus ~ 300 m along track (SAR) for coastal waters >2 km along track (LRM) for open ocean, NRT ~ 300 m along track (SAR) for coastal waters >2 km along track (LRM) for open ocean, NRT ~ 300 m along track (SAR) for coastal waters >2 km along track (LRM), NRT

9 Sentinel-3: Status summary Sentinel-3 A & B units are under development Sentinel-3 CDR review process completed, with release of CDR Close-out Report to the Board mid of Jan SLSTR and OLCI development driving S3A schedule SLSTR STM and EM test campaigns completed successfully, providing confirmation of instrument thermo-mechanical and architectural design Several anomalies affecting parts and processes of SLSTR and OLCI S/S s introduced significant delays in the Instrument PFM AIT programme Mitigations at SATELLITE level required for minimizing Sentinel-3 launch date impacts Phase C/D activities progressing nominally: All Flight Hardware released for manufacturing and some equipment already delivered S3A AIT very advanced Platform integration completed; IST planned in Oct/Nov 2012 Platform PFM delivery to Prime planned end of Nov. 2012, for completion of Platform testing and start of Satellite AIT Instrument delivery and integration starting from March 2013, with the environmental test campaign planned in the second half of 2013

10 Sentinel-3: Status summary Ground Segment development proceeding GS CDR, involving both FOS and PDGS an including EUM elements planned in the first quarter of 2013 ESA coordinating with EUMETSAT the development of the ground segment Cal/Val and in-orbit verification plans for commissioning phase defined and under consolidation An S3 Validation team international call has been issued (closes initially in December 2012) Launch of the Sentinel-3A currently foreseen for Apr 2014 Launch of the Sentinel-3B expected ~18 months later Sentinel operation will be funded by the European Commission (not yet established) EUMETSAT in charge of the Sentinel operations and of the marine Mission ESA will be the operator of the land Mission

11 GMES Sentinel-1 Launch: Oct 2013,... Constellation of two satellites C-Band Synthetic Aperture Radar Nominal lifetime in orbit of 7 years (max. 12 yrs) Systematic acquisition in 4 modes Document title Author Name Place Data doc Programme Pag. 11

12 S-1 acquisition modes 19 o 46 o 30 o 45 o S-1 can be operated in 4 exclusive acquisition modes High Bit Rate Modes: Stripmap (SM) Interferometric Wide Swath (IW) Extra Wide Swath (EW) IW and EW are operated under the TOPS acquisition mode 46 o 19 o Low bit Rate Mode Wave Mode (WV) 23 o 36 o HBR are single or dual polarisation, LBR is single polarisation only

13 Sentinel-1 Wave Mode WV2 WV1 S-1 WV mode is the default mode over open ocean where no other mode is requested by a GMES/national services 36 o S-1 WV is the direct continuation of ERS and ASAR WV mission with several differences: 23 o swath Sentinel-1 Alternating (leap-frog): WV1: 23 equivalent to SM/S2 WV2: 36.5 equivalent to SM/S4 ASAR Single IS2 : 23 equivalent to IM/IS2 Imagette size 20x20 Km (gd rg x azi) 10x20 Km Imagette sampling 100 Km 100 Km Polarisation 1 Single (HH or VV) Single (HH or VV) Resolution WV1: 74.5MHz WV2: 48.2MHz 16MHz 1) For WV, the default polarisation is VV for continuity purposes. Recommendations are welcome!

14 L2 OCN: OSW component OSW component provides continuity measurement of SAR swell spectra at C-band: 2D ocean surface swell spectra estimated from inversion of the corresponding cross- spectra at spacing of 20x20km (i.e. one per imagette) Available for WV (global) and SM (local) acquisition modes Not available for TOPS Algorithm scheme: Spectra derivation: Derivation of co and cross-spectra by computed by performing inter-looking (3 looks) in azimuth Spectra inversion: OSW obtained by inversion of the corresponding image cross-spectra using a refined MTF followed by spectra partitioning* Generated from the co-polarisation channel For coastal area a bathymetry model is used for wave dispersion in finite depth ASAR WV azimuth cut-off (03/2012) OSW partition in 2 wave systems Final OSW spectra

15 L2 OCN: OWI component OWI component is new wrt to ERS/ASAR. OWI provides wind fields (Speed and direction) at 10m: SM/TOPS : resolution 1x1km WV: 20x20km (One estimate per imagette) Available for all acquisition modes: Over open ocean with WV mode Over coastal areas with TOPS modes Algorithm: Bayesian scheme (Kerbaol and al., 2007) using a priori ECMWF winds and CMOD-IFR GMF Estimation based on the co-pol channel (no inversion combining co and cross-pol). The Mouche polarisation ratio model is used (Mouche and al. 2006) 1 Limitation: Low wind speed estimates are limited by the NESZ (<-22dB) Under-estimation at winds > 25 m/s Current can affect the estimation (Mouche, Seasar 2010) Product performance Wind speed (U10)<2 m/s RMSe, for winds within [0, 25] m/s Wind direction(degn) < 30 RMSe 1) As per SEASAR 2010 recommendation Courtesy of CLS

16 For more information: Today and tomorrow: best to ask the GlobWave experts! "GMES Sentinel-1 Mission", R. Torres et al., Rem. Sens. Env., 120 (2012) 9-24 doi: /j.rse "GMES Sentinel-3 Mission", C. Donlon et al., Rem. Sens. Env., 120 (2012) doi: /j.rse