HOW IS EUCLID MADE? /
THE SPACECRAFT
EUCLID
THE SPACECRAFT
Euclid, an ESA telescope, will observe billions of galaxies to study dark matter and dark energy, which make up 95% of the Universe.
HOW IS EUCLID MADE?
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SGS
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Payload
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Korsch
SCIENCE GROUND SEGMENT OFÂ Â EUCLID MISSION
In all space missions, the essential component for analyzing data is the Science Ground Segment: the hardware and software infrastructure that processes the data acquired by the instrument in “flight” in space.
Euclid’s SGS will analyze and catalogue over a billion luminous sources by collecting more than 100 PetaBytes of data in 5 years of observations: the equivalent of more than 1 million new-generation video games!
To manage all this data, the SGS will leverage resources distributed across a network of 11 data centres across Europe and the US. One of these is located in Italy, at the Trieste Astronomical Observatory where a team of researchers prepares and tests the analysis algorithms using the supercomputer of the Altec company in Turin.
Euclid has two highly accurate cameras that will capture images of tens of millions of galaxies to extract parameters verifying the equations of cosmology describing the evolution of the Universe.
The transition from images to numbers for use in equations is the key element of the scientific analysis of the mission. For each galaxy within each image, it is necessary to measure the position, brightness and distribution of light with extreme precision, both spatially and in the various light frequencies, i.e. measure its spectrum. First of all, the images must be cleaned of noise and instrumental effects: like all cameras, Euclid’s tools are not perfect and must be taken into account.
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PAYLOAD MODULE
The part of the Euclid satellite called Payload consists of the telescope, the eye of the mission, and the signal receptors: the two scientific instruments VIS and NISP. The telescope’s primary mirror – which has a diameter of 1.2 m – provides razor-sharp images of a region of the sky the size of the full moon in a single photograph.
The telescope, formed by the primary mirror, the secondary mirror and the support structure, is built in Silicon Carbide (SiC): an innovative ceramic material that is not very sensitive to temperature variations.
The Euclid telescope uses the off-axis Korsch optical scheme, which has low aberrations and a wide field of view. It is housed in a white cylindrical radiation shield to prevent interferences from other parts of the sky.
The tenuous light of the galaxies, collected by the telescope, is then sent, through a system of return optics, to a special mirror, the dichroic, which reflects the visible light (the one that the eyes perceive) towards the VIS instrument and is allowed to pass through by the infrared radiation reaching the NISP instrument.
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KORSCH TELESCOPE
The Euclid telescope is equipped with three silicon carbide mirrors, with the primary mirror measuring 1.2m and having a focal length of 24.5m. The telescope offers a wide field of view, covering an area of 1.25×0.73 square degrees.
The telescope directs light to two instruments through a dichroic filter, with the reflected light going to the visible light measuring instrument (VIS), and the transmitted light reaching the near-infrared measuring instrument (NISP). NISP has a slitless spectrometer and a three-band photometer.
Both instruments cover a large common field of view, measuring approximately 0.54 square degrees.
VISIBLE IMAGER (VIS)
VIS is equipped with 36 CCDs. It measures galaxy shapes with a resolution better than 0.2 arcsec with 0.1 arcsec pixels in a broad band of visible light.
NEAR INFRARED SPECTRUM (NISP)
The NISP photometer contains three near-infrared (NIR) bands, employing 16 HgCdTe NIR detectors with 0.3 arcsec pixels. The NISP spectroscope operates in the 1.1-2.0 micron wavelength range with an average spectral resolution λ/Δλ ~ 250, employing 0.3 arcsec pixels. Service Module (SVM)
The Service Module is essential for the proper functioning of the spacecraft as it hosts all the vital service functions. It is made of a rigid mechanical structure in carbon fibre, which includes a central cone that houses the gas tanks for propulsion and lateral niches closed by carbon fibre panels.
The on-board subsystems are mounted on these panels. The main ones include
- solid-state mass storage, which can collect up to 2.6 Tbit of data. The on-board computer receives commands and controls all of Euclid’s electronic units, including the telecommunications system. This system can transmit scientific data collected by the instruments to the ground, which is located 1.5 million kilometres away, at a speed of 55 Mbit/s through a satellite dish mounted outside the SVM. Sky images are compressed, and in the case of NISP, pre-analyzed on board.
- The attitude control system must control the satellite’s pointing with great stability to collect the faint light of the galaxies and have very sharp details. Individual images are collected with exposures of over 10 minutes, during which the telescope must practically neither move nor vibrate. Therefore, a mechanical compensation system for the movements of the on-board elements has also been installed.
Another panel of the SVM houses the four electronic control and data analysis units of VIS and NISP, which constitute the brain of the two instruments. They command and receive images from the detectors and communicate with the scientists at the ground control centre.
How does the spacecraft move?
To achieve large rotations, a reaction wheel system is activated, causing the satellite to rotate in the opposite direction of the wheels. For precise movements and translations, thrusters are installed outside the SVM. These actuators are positioned in various directions, enabling the satellite to move by emitting gas at high velocity, facilitating both large movements required for maintaining the orbit and fine pointing.
The satellite is equipped with two different antennas:
CONTROL ANTENNA
Responsible for managing operational data and commands.
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TRANSMISSION ANTENNA
Will send scientific data to the SGS for storage and processing.
Common field of view: ~0,54 deg²
Data amount: 100 Petabytes
N. of mirrors: 3 in silicon carbide
Telescope diameter: 1,2m
Field of view: ~1,25x0,73 deg²
Focal length: ~24,5m
N. of VIS CCDs: 36
Total mass: 2020 kg
Power consumption: 1920 W
VIS CCD resolution: 0,2 arcsec
CCD pixel: 0,1 arcsec
N.of NIR bands: 3
N.of NIR detectors: 16 HgCdTe a 0,3 arcsec px
Wavelength: 1,1-2,0 µm a 0,3 arcsec px
Wavelength resolution:λ/Δλ ~ 250 a 0,3 arcsec px
Extragalactic sky observed:15.000 deg²
Data rate:850 Gbit/day
Mission duration:6,25 years
A Surveyor of Galaxies
Equipped with cutting-edge technology and sensors, Euclid will scan one-third of the sky in just 6 years, observing distant galaxies whose light has traveled up to 10 million years before reaching us.
While Hubble would take 900 years to scan the same portion of sky that Euclid will observe in just 6 years, both telescopes offer equivalent image quality.
1/3
OF THE SKY
10
BLN LIGHT YEARS
3D
MAP OF THE UNIVERSE
What are the reasons for using SpaceX?
The Euclid satellite was launched on July 1st from Cape Canaveral, aboard a SpaceX Falcon 9 rocket. Why is a rocket needed for this mission?
Satellites are transported by rockets, which are equipped with enough fuel to propel them to the desired distance from Earth.
Rockets are launched into space using a scientific principle established by Isaac Newton over 300 years ago: for every action, there is an equal and opposite reaction.
In launch images and videos, you can see the exhaust stream coming out of the back of the rocket. This stream, composed of flames, high-temperature gases, and fumes generated by the combustion of the fuel, is expelled downwards by the rocket engine.
This in turn produces a reaction and exerts an upward acceleration that is maintained for the time necessary to impart an acceleration greater than the Earth's gravitational pull, which becomes weaker and weaker.
Heavier payloads require more fuel and, consequently, larger rockets.
Euclid will lift off on board a Falcon 9 rocket and will be transported to the second Lagrangian point, known as L2, about 1.5 million kilometers from Earth, on the opposite side from the Sun.
Here, Euclid will be placed in a stable orbit where, apart from small occasional corrections, it will exploit the balance between the initial thrust provided by the rocket and the gravitational pull of the Earth and the Sun.
IL NOME DEL PADRE DELLA GEOMETRIA PER TRACCIARNE QUELLA DELL'UNIVERSO
Euclid ha il compito di mappare la geometria dell’universo attraverso l’osservazione di oltre un miliardo di galassie, del loro redshift e di materia ed energia oscure
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