Sentinel 1

Sentinel-1A, the first component of the Copernicus Space Segment developed by the European Space Agency, was launched on 3 April 2014. It was commissioned in orbit during the following months leading to a In-Orbit Commissioning Review in September 2014. The launch of the identical Sentinel-1B is planned in April 2016, two years after Sentinel-1A with which will complete the Copernicus Sentinel-1 constellation. After launch, the LEOP Phase is expected to last three days where all subsystems and the SAR instrument will be checked. It will immediately be followed by the four-month Commissioning Phase that will include the in-orbit Calibration and Characterisation, and the verification of the satellite, in order to deliver a full functional and well performing satellite to the mission operations. This paper will present the LEOP and Commissioning activities already completed, and the status of Sentinel-1B Calibration, Characterisation and Verification activities of the Commissioning in place.

The LEOP starts with the launch of the spacecraft and include the deployment of the Solar Array Wings and of the SAR antenna.  The LEOP phase lasts three days and ends when the spacecraft has reached a stable orbit and has acquired the nominal attitude with the AOCS in the normal pointing mode. At entering the Deployment Mode the execution of the SAR and Solar Arrays deployment is as follows:

a)       SAR +X Release
b)       SAR +X Partial Deployment
c)       SAR -X Release
d)       SAW +Y Release & Deployment
e)       SAW +Y Rotation to face Sun with 30° angle with -Y
f)        SAW -Y Release & Deployment
g)       SAR -X Partial Deployment
h)       Complete SAR +X deployment
i)         Complete SAR -X deployment

Being the Ground System already commissioned during the Sentinel-1A commissioning phase and subsequent ground segment rump-up phase, the Sentinel-1B System Commissioning comprises only the commissioning of all Spacecraft components. This includes the following activities:

a)       Spacecraft in-orbit verification (i.e. Platform and Payload)
b)       SAR Calibration and System Performance verification
c)       SAR cross-calibration with Sentinel-1A
d)       Functional verification of the Sentinel-1B Basic SAR Products (i.e. L0 and L1b products w.r.t. SAR instrument performance and parameter settings
j)        Functional verification of the Optical Communication Payload (OCP) interface

The Sentinel-1B Commissioning is planned for a period of 6 repeat orbit cycles (12 days each) in the reference orbit. The Commissioning Phase will, therefore, have two sub-phases corresponding to the period determined to acquire such final reference orbit (Orbit Acquisition Phase) and once the reference orbit is acquired (Reference Orbit Phase).

Some of the Commissioning activities that do not require the final reference orbit will be executed during the Orbit Acquisition Phase, in particular those concerning the Verification of some Spacecraft Subsystems and Ground System components. Depending on the orbit injection the reference orbit acquisition may take different time and/or propellant.

Based upon the activities to be performed and considering the orbital phases, the baseline schedule for the Sentinel-1A LEOP and Commissioning phases, from launch through to its completion denoted by the In-Orbit Commissioning Review (IOCR), including the top level breakdown in terms of activities against time represented by weeks, is detailed in the following table (pls. see uploaded pdf for the table).

As part of the European Copernicus programme (formerly Global Monitoring for Environment and Security  - GMES), the Sentinel-1 mission, based on a constellation of two SAR satellites, ensures continuity of C-band SAR observations, building on ESA’s and Canada’s heritage on satellite SAR systems (ERS, ENVISAT and RADARSAT). Sentinel-1A has been launched from Kourou on a Soyuz rocket on 3^rd April 2014. The second satellite Sentinel-1B is planned for launch in April 2016. The Sentinel-1A satellite reached its nominal orbit on 7 August 2014. The In-Orbit Commissioning phase was completed on 23 September 2014, followed by an operational qualification phase (ramp-up) and the routine phase that started in June 2015. A mission ramp-up phase with the two Sentinel-1 satellites in orbit will take place in the course of 2016. Full operation capacity of the mission is planned for early 2017.

 The talk will present the overall status of the Sentinel mission, in particular the Sentinel-1A mission operations status, observation scenario and mission achievements.

The Sentinel-1 operations qualification started following the launch of Sentinel-1A launch in April 2014 and since then the Ground Segment operations have ensured the Sentinel-1 observation planning, the X-Band data acquisiton, the data processing and product calibration and validation, the data archiving and dissemination.  Following the completion of the Satellite in orbit Commissioning in September 2014, free and open data access to all users (previous self registration) was opened in October 2014 and the overall operations capacity and performance have been gradually increasing to reach the routine Sentinel-1A operations phase in June 2015. By December 2015, 1 PB of data products have been generated and archived as part of the systematic production scenario, and the whole mission production has been downloaded by users about 10 times. These outstanding operations results will be further enhanced with the launch of the Sentinel-1B unit, which will trigger the gradual qualification of the constellation operations, reaching more than twice  the current operations level by the end of 2016 and providing to users an unprecedented open and free systematic flow of high quality SAR products.

Sentinel-1 is a constellation of two polar orbiting satellites which first unit was launch on 03/04/2014. The second unit is be planned to be launched in April 2016. Both are equipped with similar C-band Synhtetic Aperture Radar (C-SAR) instrument, with electronic steering capability in elevation and azimuth allowing a high flexibility in SAR data acquisition, in terms of resolution and coverage. Four operational modes are available:

Stripmap mode: 5x5 m resolution, 80 Km swath

Interferometric Wideswath (IW) mode: 5x20 m resolution, 250 Km

Extra-Wideswath mode: 20x40 m resolution, 400 Km

Wave Mode: 5x5 m resolution, 20x20 Km imagettes

IW and EW modes are the first operational modes based on TOPSAR which provides an improved image quality compared to ScanSAR, putting on the other hand new challenges for processing, calibration and verification.

This paper will present the status of Sentinel-1A product performance and report on the Sentinel-1B product (cross-)calibration performed by the S-1 Mission Performance Center.

After 2 years in orbit, Sentinel-1A has produced an impressive amount of data, freely and openly available to all users worldwide. By end 2015, about 20,000 users have registered to access Sentinel data on the scientific data hub, 3 million products were downloaded by users (representing 3.6 Petabytes of data) and about 400,000 products were available for download. This great user uptake is also characterised by the release of very relevant mission exploitation results in various thematic areas.

The talk will present a number of application results based on Sentinel-1 data, in various application and scientific domains such as sea-ice, iceberg & lake-ice monitoring, ice sheet monitoring, ground deformation (interferometry applications related to volcanoes, earthquake, landslide, subsidence), disaster monitoring (e.g. floods), agriculture (e.g. rice monitoring), forestry, maritime surveillance (oil spill monitoring, ship detection), snow monitoring, sea state (incl. wind & wave), etc.

The objective of the presentation is not to provide an exhaustive description of Sentinel-1 based applications, but to present few results of interest in key application domains.