Pleiades (optics)

Pleiades (optics)
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Name	Pleiades
Caption	Artist's impression of the Pleiades constellation in orbit.
Organization	Centre National d'Études Spatiales, European Space Agency
Location	Low Earth orbit
Wavelength	Visible spectrum, Panchromatic
Built	2009–2011
First light	2011
Website	https://www.cnes.fr/en/pleiades

Pleiades (optics). The Pleiades constellation is a pair of high-resolution Earth observation satellites operated as part of a French-led international partnership. Developed by Airbus Defence and Space for the Centre National d’Études Spatiales (CNES) with contributions from Austria, Belgium, Spain, and Sweden, the system provides optical imagery for both civilian and defense applications. Launched in 2011 and 2012, the twin satellites, Pleiades-1 and Pleiades-2, offer a rapid revisit capability and form a core component of the European Copernicus Programme.

Overview

The Pleiades program was initiated to meet the growing demand for high-resolution, agile Earth observation data across Europe. It succeeded earlier French systems like SPOT and was designed to be interoperable with the Italian COSMO-SkyMed radar satellite constellation under a joint Franco-Italian agreement. The system is managed from the Toulouse Space Centre in France, with ground stations located globally, including in French Guiana and Sweden. Data from Pleiades is used by a wide range of entities, from the French Armed Forces and the European Union Satellite Centre to commercial entities and scientific researchers, supporting applications from mapping to disaster response.

Design and construction

The satellites were built by Airbus Defence and Space at its facilities in Toulouse, with key optical components supplied by Thales Alenia Space. Each spacecraft is based on the Astrobus platform and features a large, innovative three-mirror anastigmat telescope with a primary mirror diameter of 65 cm. This design, coupled with CCD detectors using Time delay and integration technology, allows for high image quality across a wide field of view. The agility of the satellites is provided by control moment gyroscopes, enabling rapid retargeting and stereo imaging during a single pass. Critical subsystems were contributed by partner nations, such as the Swedish Space Corporation and the Austrian Space Agency.

Scientific applications

Pleiades imagery supports diverse scientific investigations, particularly in geology, environmental monitoring, and cartography. Researchers utilize its data for detailed topographic mapping, monitoring glacier retreat in regions like the Alps and Himalayas, and assessing damage from natural disasters such as the 2011 Tōhoku earthquake and tsunami and Hurricane Sandy. Its role in the Copernicus Programme enhances pan-European efforts in land cover classification and emergency management. The data also contributes to archaeology, helping to identify and map historical sites, and supports urban planning studies for major cities like Paris and Rome.

Performance and specifications

Each Pleiades satellite delivers panchromatic imagery at a ground sampling distance of 0.70 meters and multispectral data (Blue, Green, Red, Near-infrared) at 2.80 meters. The swath width is 20 km at nadir, and the satellites can tilt up to 47 degrees off-nadir, providing a daily revisit capability anywhere on the globe. They operate in a Sun-synchronous orbit at an altitude of approximately 695 km, with a local time of descending node at 10:30 AM. The onboard storage capacity is 600 Gbit, with a downlink rate of 450 Mbit/s via X-band to ground stations like Kiruna Station.

Operational history

Pleiades-1 was launched on December 17, 2011, aboard a Soyuz-2 rocket from the Guiana Space Centre. Its twin, Pleiades-2, followed on December 2, 2012, also launched by a Soyuz-2 from the same site. Both launches were conducted by Arianespace. The system achieved full operational capability in 2013. Throughout their service, the satellites have been pivotal in numerous international events, providing imagery during the Russo-Ukrainian War, the 2015 Nepal earthquake, and the Notre-Dame de Paris fire. The satellites continue to operate beyond their designed lifespan, with successor systems like Pleiades Neo now augmenting the constellation.

Category:Earth observation satellites Category:Satellites of France Category:Spacecraft launched in 2011 Category:Spacecraft launched in 2012