Euclid is a European Space Agency mission dedicated to the mapping of the dark Universe launched the 1st of July 2023. The mission will investigate the distance-redshift relationship and the evolution of cosmic structures. This is achieved by measuring shapes and redshifts of galaxies and clusters of galaxies up to 10 billion years away. Euclid makes use of two cosmological probes, in a wide survey over the full extragalactic sky: the Weak Gravitational Lensing (WL) and the Baryonic Acoustic Oscillations (BAOs). The WL is a method to map the dark matter and measure dark energy by measuring the apparent distortion of galaxy images by mass inhomogeneities along the line-of-sight. This probe requires extreme image quality thus constraining the optical system imaging quality and its characterization both on-ground and in-flight. The BAOs are wiggle patterns, imprinted in the clustering of galaxies, which provide a standard ruler to measure dark energy and the expansion in the Universe. The first images were released on the 7th of November 2023 showcasing the capabilities of the space segment. To achieve the stunning first images and the scientific objectives of the mission, the space segment (i.e. the spacecraft) underwent a thorough and extensive test campaign on-ground. These tests demonstrated the excellent image quality and the overall stability of both the payload and the spacecraft in a representative operational environment. In complement, further tests were performed during the commissioning phase, just after launch, to validate the spacecraft pointing stability.
Developed by ADS under CNES responsibility in partnership with Eumetsat, IASI-NG payload on board of METOP-SG satellite will deliver data for operational meteorology, climate monitoring, and atmospheric chemistry in the next decades. In order to improve by a factor two compared to IASI the spectral resolution and radiometric error, the instrument is designed around a Mertz compensated interferometer, whose good spectral performances have been checked at subassembly level in 2020. The PFM is now fully integrated and will go through functional tests, performance tests at ambient and in TVAC through 2022. The aim of this paper is to give an overview on these activities.
Euclid, an ESA mission designed to characterise dark energy and dark matter, passed its Mission Critical Design Review in November 2018. It was demonstrated that the project is ready to start integration and test of the main systems, and that it has the ability to fulfil its top-level mission requirements. In addition, based on the performances at M-CDR, the scientific community has verified that the science requirements can be achieved for the Weak Lensing and Galaxy Clustering dark energy probes, namely a dark energy Figure of Merit of 400 and a 2% accuracy in the growth factor exponent gamma. We present the status of the main elements of the Euclid mission in the light of the demanding high optical performance which is the essential design driver is the to meet the scientific requirements. We include the space segment comprising of a service module and payload module hosting the telescope and its two scientific instruments, and the ground segment, which encompasses the operational and science ground segment. The elements for the scientific success of the mission for a timely release of the data are shortly presented: the processing and calibration of the data, and the design of the sky survey. Euclid is presently on schedule for a launch in September 2022.
KEYWORDS: Telescopes, Space telescopes, Modulation transfer functions, Mirrors, Synthetic apertures, Satellites, Space operations, Wavefront sensors, Tolerancing, Imaging systems
For very large telescope diameters, typically above 4 meters, monolithic telescopes can hardly be envisaged for space applications. Optical aperture synthesis can be envisaged in the future for improving the image resolution from high altitude orbits by co-phasing several individual telescopes of smaller size and reconstituting an aperture of large surface. The telescopes can be deployed on a single spacecraft or distributed on several spacecrafts in free flying formation. Several future projects are based on optical aperture synthesis for science or earth observation. This paper specifically discusses the limitations and interest of aperture synthesis technique for Earth observation from high altitude orbits, in particular geostationary orbit. Classical Fizeau and Michelson configurations are recalled, and system design aspects are investigated: synthesis of the Modulation Transfer Function (MTF), integration time and imaging procedure are first discussed then co-phasing strategies and instrument metrology are developed. The discussion is supported by specific designs made at EADS Astrium. As example, a telescope design is presented with a surface of only 6.6 m2 for the primary mirror for an external diameter of 10.6 m allowing a theoretical resolution of 1.2 m from geostationary orbit with a surface lower than 10% of the overall surface. The impact is that the integration time is increasing leading to stringent satellite attitude requirements. Image simulation results are presented. The practical implementation of the concept is evaluated in terms of system impacts in particular spacecraft attitude control, spacecraft operations and imaging capability limitations.
Astrium has developed a product line of compact and versatile instruments for HR and VHR missions in Earth Observation.
These cameras consist on a Silicon Carbide Korsch-type telescope, a focal plane with one or several retina modules - including five lines CCD, optical filters and front end electronics - and the instrument main electronics.
Several versions have been developed with a telescope pupil diameter from 200 mm up to 650 mm, covering a large range of GSD (from 2.5 m down to sub-metric) and swath (from 10km up to 30 km) and compatible with different types of platform.
Nine cameras have already been manufactured for five different programs: ALSAT2 (Algeria), SSOT (Chile), SPOT6 & SPOT7 (France), KRS (Kazakhstan) and VNREDSat (Vietnam). Two of them have already been launched and are delivering high quality images.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.