This manuscript presents the improvements implemented on the future Sentinel-1C/D spacecraft, which will eventually replace the current in-orbit Sentinel-1A/B satellites. Changes are based on the Sentinel-1A/B lessons learnt and on the addition of new functionalities to improve the system performance. More specifically, the modifications that will be covered in this paper are those that will enhance the performance of the mission. The addition of an Automatic Identification System (AIS) will provide ship position and identification while operating the SAR instrument. The Attitude and Orbit Control System (AOCS) will be upgraded to improve the pointing stability and to be compatible with the new Galileo signals. A novel mechanical bracket interfacing the SAR central panel and the platform has been designed to facilitate the disintegration during the re-entry. The propulsion system has also been modified to allow a faster orbit acquisition. The upgrades done on the SAR instrument to improve the radiometric stability will be also detailed.
The ESA Sentinels constitute the first series of operational satellites responding to the Earth Observation needs of the
EU-ESA Global Monitoring for Environment and Security (GMES) programme. The GMES space component relies on
existing and planned space assets as well as on new complementary developments by ESA. In contrast to SAR systems
already existing in C-band like ASAR/ENVISAT or RADARSAT-2, high demands on the radiometric stability and
accuracy are made for Sentinel-1. The mission depends on the method of calibrating the entire Sentinel-1 system in an
efficient way. This paper describes the strategy and provides a plan of all activities required for in-flight calibration of
The paper provides an overview of the GMES Sentinel-1 system characteristics including the SAR imaging modes and
their key performance parameters, the SAR interferometry capabilities, and the specifics of related attitude and orbit
control modes (i.e., roll steering mode and zero-Doppler steering mode). Furthermore, the paper outlines the planned
Sentinel-1 System Commissioning Phase activities related to the in-orbit SAR system end-to-end performance
verification and calibration.
The ESA Sentinels constitute the first series of operational satellites responding to the Earth
Observation needs of the EU-ESA Global Monitoring for Environment and Security programme. The GMES
space component relies on existing and planned space assets as well as on new complementary developments by
ESA. In particular, as part of the GMES space component, ESA is currently undertaking the development of 3
Sentinels mission families. Each Sentinel is based on a constellation of 2 satellites in the same orbital plane. This
configuration allows to fulfil the revisit and coverage requirements and to provide a robust and affordable
operational service. The launch of the 2nd satellite is scheduled 18 months after the launch of the 1st spacecraft of
the constellation. The lifetime of the individual satellite is specified as 7 years, with consumables allowing mission
extension up to 12 years. The lifecycle of the space segment is planned to be in the order of 15-20 years. The
strategy for Sentinel procurement and replacement over this period is being elaborated, but will likely result in a
need for 4-5 satellites of each type if the desired robustness for the service that GMES will provide is to be
This paper will describe the operational and observational capabilities of the Sentinel-1 mission based on the user
requirements, including potential emergency requests. An example of a pre-defined mission timeline for each and
every cycle will be given.
Repeat-pass interferometry data have been acquired during the first and second SIR-C/X-SAR missions in April and October 1994. This paper presents the first results from X-SAR interferometry on four different sites. The temporal separations were one day and six months. At two sites the coherence requirements were met, resulting in high quality interferograms. A digital elevation model has been derived. The limitations of the X-SAR interferometry are discussed.