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15 May 2018
'3B' satellite completes first batch of orbiting Earth observation units launched by the European Space Agency.
The European Space Agency (ESA) says that its latest Earth observation satellite, the Copernicus Sentinel-3B, has relayed its first images back to ground stations.
Launched from Russia in late April, the latest payload is the seventh in the Copernicus constellation, and joins its Sentinel-3A “twin” in a low-Earth orbit, to measure sea surface topography, sea and land surface temperature, and ocean and land surface color with high accuracy.
ESA chiefs say that Sentinel-3B completes the first “batch” of payloads in the Copernicus mission, the European Union’s ambitious project to provide round-the-clock, high-resolution imagery for a variety of scientific, land management, and humanitarian applications.
Instrumentation
Like the 3A satellite, which was launched in early 2016, the 3B carries four main instruments for observation – including a high-resolution multispectral imager, and a sea and land surface temperature radiometer (SLSTR).
Over oceans, the equipment measures the temperature, color and height of the sea’s surface, as well as the thickness of sea ice. These measurements can then be used to monitor changes in Earth’s climate, and for what the ESA describes as a more “hands-on” applications including monitoring marine pollution.
When orbiting over land, the Sentinel-3B is able to monitor wildfires, map the way that land is used, check the health of vegetation, and measure the height of rivers and lakes with a laser retro-reflector instrument.
Elzbieta Bienkowska, the European Commissioner responsible for industry, entrepreneurship and SMEs, highlighted the commercial potential of the data and imagery received, saying in an ESA release: “This new satellite will deliver valuable images of how our oceans and land are changing. This will not only speed up the response to natural disasters, but also create new business opportunities.
“Earth observation is a larger market than you would think - a driver for research discoveries, a provider of highly skilled jobs, and a developer of innovative services and applications.”
Enabling technology
In part, those commercial opportunities are enabled by the state-of-the-art photonics technology on board. That includes the multi-spectral Ocean and Land Colour Instrument (OCLI), which collects images across 21 different wavelength bands in the visible-near infrared spectrum, between 400 and 1020 nm.
Tuned to specific ocean color, vegetation, and atmospheric correction measurement requirements, OCLI has a spatial resolution of 300 m for all measurements and features a swath width of 1270 km, overlapping the SLSTR instrument’s swath.
“OLCI’s new eyes on Earth will allow ocean ecosystems to be monitored, support crop management and agriculture and provide estimates of atmospheric aerosol and clouds – all of which bring significant societal benefits through more informed decision-making,” states ESA.
Based on the opto-mechanical and imaging design of the MERIS instrument deployed on board Europe’s earlier Envisat payload, the OLCI kit includes a push-broom imaging spectrometer with five camera modules arranged in the form of a fan, to share the field of view.
Although the 3B satellite has already sent back initial imagery showing sunset over Antarctica, sea ice in the Arctic Ocean, and a clear view of northern Europe, its instruments will not be handed over to routine operations until a five-month period of commissioning and calibration is completed.
Monitoring Kilauea eruption
In recent days, the earlier Sentinel launches have shown their value by helping to monitor the eruption of the Kilauea volcano on Hawaii’s Big Island.
Both the Sentinel-1A and Sentinel-1B satellites have generated interferometric radar imagery indicating how the local land has been displaced by seismic activity associated with the eruption, and have used laser terminals to return large data sets to ground stations much more rapidly than was possible previously.
“The pattern of fringes near the summit of the volcano indicate withdrawal of magma from the subsurface to feed the eruption, which is occurring about 40 km away along the volcano's lower East Rift Zone,” explained the Copernicus team.
Additional high-resolution imagery has been provided by Sentinel-2 satellites, showing the temperature of the Kilauea crater. In a Copernicus release, the US Geological Survey (USGS) geophysicist Michael Poland was quoted saying:
“Sentinel-1 data have proven invaluable for tracking the highly dynamic current volcanic and earthquake activity at Kīlauea Volcano in Hawaii. That the data are accessible very soon after acquisition and cover the entire island have allowed for rapidly available and synoptic views of surface deformation that might not otherwise be available.”
Subsequent Sentinel payloads are set to include optical instrumentation for monitoring aerosols and air quality, and to provide more detailed information for climate and weather modeling.
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