Sentinel-1 is the first of the Copernicus Programme satellite constellation conducted by the European Space Agency. This mission is composed of a constellation of two satellites, Sentinel-1A and Sentinel-1B, which share the same orbital plane. They carry a C-bandsynthetic-aperture radar instrument which provides a collection of data in all-weather, day or night. This instrument has a spatial resolution of down to 5 m and a swath of up to 400 km. The constellation is on a sun synchronous, near-polar orbit. The orbit has a 12-day repeat cycle and completes 175 orbits per cycle. The first satellite, Sentinel-1A, launched on 3 April 2014, and Sentinel-1B was launched on 25 April 2016. Both satellites lifted off from the same location in Kourou, French Guiana, and each on a Soyuz rocket. Sentinel-1C and 1D are in development with launch dates to be determined. There are a wide range of applications for the data collected via the Sentinel-1 mission. A few of these uses include sea and land monitoring, emergency response due to environmental disasters, and economic applications. A major goal of the mission was to provide C-Band SAR data. Recently, Sentinel-1 has worked in conjunction with SMAP to help achieve a more accurate measure of soil moisture estimates. Observations from both instruments show to be complementary of each other as they combine data of soil moisture contents. The ESA and European Commission's policies makes Sentinel-1's data easily accessible. Various users can acquire the data and use it for public, scientific, or commercial purposes for free.
Instruments
Sentinel-1 spacecraft are designed to carry the following instruments:
A single C-band synthetic-aperture radar with its electronics. This instrument provides 1 dB radiometric accuracy with a central frequency at 5.405 GHz. The data collected in C-SAR was made to be continuous after the termination of a previous mission.
An SDRAM-based Data Storage and Handling Assembly, with an active data storage capacity of about 1,443 Gbit, receiving data streams from SAR-SES over two independent links gathering SAR_H and SAR_V polarization, with a variable data rate up to 640 Mbit/s on each link, and providing 520 Mbit/s X-band fixed-user data-downlink capability over two independent channels towards ground.
Strip Map Mode features spatial resolution and an swath.
* The sole uses of SM are to monitor small islands as well as emergency management for extraordinary events upon request
* Offers data products in single or double polarization
Interferometric Wide Swath Mode features spatial resolution and a swath.
* IW is the main operational mode over land
* IW accomplishes interferometry through burst synchronization
* Offers data products in single or double polarization
Extra Wide Swath Mode features spatial resolution and a swath.
* EW is used mainly to monitor wide coastal areas for phenomena such as shipping traffic and potential environmental hazards like oil spills or changes in sea ice.
* Offers data products in single or double polarization
Wave Mode features resolution and a low data rate. It produces sample images along the orbit at intervals of.
* This is the main operational mode over open ocean.
* Offers data products only in single polarization
* Complex images with phase and amplitude of specified areas
Ground Range Detected Level 1 data:
* Only systematically distributed multi-looked intensity
Level 2 Ocean data:
* Systematically distributed data of ocean's geophysical parameters
All data levels are publicly available for free online within 24 hours of observation.
Applications
Sentinel-1 will provide continuity of data from the ERS and Envisat missions, with further enhancements in terms of revisit, coverage, timeliness and reliability of service. A summary of the main applications of Sentinel-1 include:
Marine monitoring
* Sea-ice levels and conditions
* Ocean oil spills
* Ship activity
* Marine winds
Land monitoring
* Agriculture
* Forestry
*Subsidence
**The C-SAR instrument is capable of measuring land subsidence through the creation of interferometric synthetic-aperture radar images. The analysis of phase changes between two or more synthetic aperture radar images taken at different times is able to create maps of the digital elevation and measure the land surface deformation of an area. High spatial and temporal resolutions allow S1 to improve on current InSAR techniques and provide systematic continuity to the data.
Emergency response
* Flooding
* Landslide and volcanic
* Earthquakes
** Shortly after the August 2014 South Napa earthquake, data collected by Sentinel-1A was used to develop an interferometric synthetic-aperture radar, or InSAR, image of the affected region. The Sentinel-1 satellites are expected to make analysis of earthquakes using InSAR techniques quicker and simpler.
Industrial
The prime contractor of the mission is Thales Alenia Space Italy, with whole system integration and also with production of platform Spacecraft Management Unit and payload Data Storage and Handling Assembly. Sentinel-1A was constructed in Rome, Italy. Other technologies such as the T/R modules, the C-band synthetic-aperture radar antenna, the advanced data management and transmission subsystems, and the on-board computer, were developed in L'Aquila and Milan. The C-SAR instrument is the responsibility of Astrium Gmbh. The ground segment prime contractor is Astrium with subcontractors Telespazio, WERUM, Advanced Computer Systems and Aresys. Final test verification of the satellite was completed at Thales Alenia Space's clean rooms in Rome and Cannes.
