Civilian Earth Observation (EO) satellite sensors are normally designed to either develop or exploit a new technology, or to perform a given task. An example of the former is the Hyperion hyperpsectral sensor on NASA’s EO-1 satellite; an example of the latter is the VEGETATION sensor on SPOT-4 and -5. In both cases the planning and development of sensors is largely ad hoc. That is development occurs when a need or opportunity arises. Budget limitations also apply and hence in some cases satellites are produced but only launched after a budget-induced delay (NOAA’s SPSS satellites), or may even be cancelled after production. NASA’s Deep Space Climate Observatory (DSCOVR) was originally to be launched in 2003 but was mothballed by the Bush administration, some suspect due the that administrations opposition to climate-change related research. Indeed, EO in the United States could be considered to be in a state of crisis (Spaceref.com, 2010).
Europe, specifically the European Space Agency (ESA) has developed another concept in planning and development. The ESA EO programme has had a twin-track development process: the Earth Explorer missions which are science driven missions aimed at specific Earth Science questions, such as the Cryosat-2 satellite design to monitor the ice sheets and sea ice, and the Earth Watch programme which provides satellite data for operational users such as weather services. What is new is the ESA GMES Sentinel programme.
The Sentinels are a unified concept of next generation operational EO satellites. ESA has planned the Sentinels in collaboration with not only scientists, but also industry and crucially End Users. This latter group comprises of those who require satellite data for oeprational services: anything from sea ice mapping to oil spill monitoring. End Users might be national coastguard agencies, the European Environment Agency or even Canadian Inuit communities.
The Sentinels are not just a series of satellites, such as Landsat, that will ensure data continuity as older missions fail and are replaced by new platforms. The Sentinels are constellations of identical satellites, with each constellation delivering a different type of product. Sentinel-1 will be a series of two, or possibly three satellites, starting in 2012, which will provide synthetic aperture radar (SAR) data, over a wide swath (250 km will be standard) with interferometric capabilities. Sentinel-1 will replace the Envisat ASAR sensor. Sentinel-2 will provide high resolution visible-infrared imagery similar to the SPOT satellite series. Sentinel-2, will comprise of two satellites each capable of imaging in 13 bands and covering an impressive 290 km wide swath: the first satellite of which will be launched in 2013. Sentinel-3 is an ocean colour mission that will provide enhanced coastal and oceanographic monitoring capabilities such as algal bloom mapping from 2013. Sentinels -4 and -5 will provide atmospheric monitoring capabilities expanding the capabilities weather satellites from 2017 onwards.
The Sentinel missions therefore ensure continuity in data delivery and cover a wide range of tasks, complementing each other. The breadth of the concept, long sighted planning and in-depth consultation process is unique in Earth Observation. ESA have managed to generate the political will and drive the development of an EO concept that will provide for the needs of scientists and today’s service providers whilst delivering data for the next generation of services. The Sentinel missions are therefore an achievement of science, technology, inter-governmental planning and administration and not least [daring?] foresight. The Sentinel missions pave the way for Europe to take a leading role in space science and EO, not in competition with, but in collaboration with traditional and new partners alike.
ESA Sentinel Missions:
ESA Living Planet:
Spaceref.com (2010) on the GAO report on EO strategy in the US:
The American Institute of Physics has a similar piece here: