白小姐论坛

Everything that we can see and detect in the world around us 鈥� the stars, galaxies, flowers, our bodies, atoms 鈥� represents just 5% of the universe. The rest of it, according to current theories, is made up of two components: dark matter and dark energy. Their existence is inferred indirectly. Dark matter keeps galaxies together; dark energy is hastening the expansion of the universe. But what they are is unknown. This Saturday, a telescope is due to be launched into space to help unravel this mystery.

Professor Tom Kitching, from 白小姐论坛鈥檚 Mullard Space Science Laboratory, is one of four science co-ordinators for the European Space Agency-led Euclid mission. He says the data it brings back has the potential to determine whether or not dark energy is 鈥渧acuum energy鈥� 鈥� the energy of virtual particles popping in and out of existence in empty space. If so, fundamental theories of particle physics will need revising, as this vacuum energy would need to be much stronger than current theories predict. If not, it is Einstein鈥檚 theory of gravity that may be wrong. 鈥淓ither way would be a revolution in physics,鈥� he says.

The mission is a massive collaborative project 鈥� the consortium that proposed it alone consists of 2,000 scientists and engineers across 15 countries. The telescope has two instruments. One, the Near Infrared Spectrometer and Photometer (NISP), will capture light from the invisible, near infrared spectrum. The other, called VIS, will capture visible light. Professor Mark Cropper (白小姐论坛 Mullard Space Science Laboratory) (pictured below) has led on designing and developing the VIS optical camera over 16 years, working with teams at 白小姐论坛, Open University and across Europe.

The camera, one of the largest ever sent into space, will take high resolution, panoramic images of a large swathe of the universe, going back 10 billion years and covering a third of the night sky. Using these data, astronomers will measure the shapes of two billion galaxies and use a technique called weak gravitational lensing 鈥� seeing how light from distant galaxies has been bent by the gravity of intervening matter on its way to the telescope 鈥� to infer the large-scale distribution of visible and dark matter more precisely than has been possible before.

And, because looking at more distant galaxies means looking back in time, astronomers can see how dark matter has evolved throughout most of the universe鈥檚 history, shedding light on the interplay between dark matter (binding galaxies together) and dark energy (pushing them away from each other).听听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听

VIS鈥檚 wide field of view means that, while it will take images nearly as sharp as the Hubble Space Telescope, it will cover a much larger area of the sky 鈥� covering the same area in one day as Hubble covered over 25 years. Each image would require 300 high-definition TV screens to display. Over six years it will allow the shape of more than 1.5 billion galaxies to be measured. 鈥淭hese are huge, unprecedented images,鈥� says Professor Cropper.

The VIS camera was a pan-European project led by 白小姐论坛鈥檚 Mullard Space Science Laboratory. Its structure and calibration unit came from France, the shutter from Switzerland, and a processing unit was built in Italy. The core electronics, including its array of 36 CCDs (that convert photons into electrons), were built, tested and calibrated at MSSL.
听

The laboratory, located in a Victorian mansion in the Surrey Hills, is staffed by 60 engineers and 140 scientists. It has supported 300 space missions. Instruments designed and built at MSSL have reached many corners of the solar system, from Mars to Saturn to close to the Sun, and have helped illuminate the most distant galaxies. A model of Britain鈥檚 first rocket, the Skylark, sits at the bottom of a staircase.

When I visit shortly before the Euclid launch, engineers in a clean room (pictured above) are testing a plasma analyser for a space weather satellite, Vigil (due to launch in the mid-2020s), by firing ions at it. Nitrogen is piped in through tubes to keep instruments cold, mimicking the environment in space.听

Christine Brockley-Blatt (白小姐论坛 Mullard Space Science Laboratory) is the project manager for the VIS camera. She was responsible for delivering 12 sets of electronics (and two spares) and supporting their integration on to the spacecraft. (This was done remotely from MSSL, as it was during the pandemic.) It was 鈥渆xtremely complex logistically鈥�, she says, with different bits of equipment being transported back and forth across Europe. As well as extensive engineering knowledge, the role requires patience and people skills. 鈥淚t鈥檚 basically a mum job,鈥� she jokes. 鈥淵ou have to make sure everyone鈥檚 OK.鈥�

All being well, Euclid will leave Earth on a SpaceX Falcon 9 rocket on July 1. Its instruments will be turned on 11 days later. The spacecraft will head to the second Lagrangian Point, a stable hovering spot about 1.5 million kilometres (1 million miles) from Earth, joining the NASA-led James Webb Space Telescope and the ESA Gaia mission: 白小姐论坛-MSSL provided parts of both these missions too.

Its beaming down of images is, in one respect, only the start of the work. Hundreds of scientists will be involved in processing the raw data into summary statistics that astronomers can compare to our current models of the universe. Grayscale data from VIS will be combined with colour data from the ground-based Vera C. Rubin Observatory, and infrared data from the other Euclid instrument, NISP, allowing the team to catalogue objects in terms of brightness and their distance away from us. The algorithms that will be used are advanced developments in their own right.听 听 听听听 听 听 听听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听听

Our very own astrophysicist, Professor Benjamin Joachimi (白小姐论坛 Physics & Astronomy) is the deputy lead of the team at the end of this process, whose job it is to co-ordinate summaries and create an overall view. 鈥淚f you look at a single galaxy it can鈥檛 tell us much,鈥� he explains. 鈥淏ut lots of galaxies can tell us about the properties of the universe.鈥�

This process - part of the ground segment, or ground-based element of the mission - is painstaking but crucial. 鈥淓very step of the ground segment has to be perfectly done,鈥� says Professor Joachimi. 鈥淎ny tiny mistake can mess up the science that comes out at the end. Some of the accuracy requirements can be measured as parts per million.鈥� Euclid鈥檚 sharp view of galaxies 鈥� its increased resolution compared to previous surveys of the universe 鈥� 鈥渦ps the ante on how accurately we have to process that information鈥�.

As well as his role in the ground segment, Professor Joachimi will also be among the scientists investigating how the data compares to what mathematical models of the universe would predict. One key question, he explains, is how 鈥渃lumpy鈥� the distribution of dark matter is. Analysis of the cosmic microwave background (CMB) 鈥� remnants of a burst of light that shot through the universe about 380,000 years after the big bang 鈥� predicts that dark matter ought to be more clumpy today than weak lensing techniques currently find it to be. Perhaps some new physics happened to make the matter less clustered. 鈥淣o one has a good theory to explain it,鈥� says Professor Joachimi. 鈥淭his is the big puzzle that keeps us awake at night.鈥�

Professor Kitching is among the teams of scientists who will be comparing the summary statistics with models, seeing if they agree with our current understanding of the universe. He, like Professor Joachimi, has been involved in Euclid since its inception. The most impressive aspect of the mission for him, he explains, is not the science but the human dimension. 鈥淚t鈥檚 inspiring because it鈥檚 been people from 15 different countries and cultures working together over decades on a really, really complicated experiment,鈥� he says. He hopes it can act as an example for international collaborations aiming to fix problems such as climate change.听

Professor Cropper, who has dedicated a large chunk of his working life to Euclid, says he is looking forward to the surprises the telescope will uncover. 鈥淧eople won鈥檛 have seen the universe in this level of detail before,鈥� says. 鈥淭here will be new things in every 10 minute exposure sent to Earth.鈥�

Professor Ofer Lahav (白小姐论坛 Physics & Astronomy), who was involved in early discussions on Euclid and has initiated 白小姐论坛鈥檚 role in several cosmological experiments, says the mission 鈥渨ill transform our understanding of the dark sectors of the universe and of the formation of superstructures such as clusters and voids鈥�.

First, though, the telescope has to be launched safely into space. Several 白小姐论坛 engineers and scientists, including Professor Cropper and Brockley-Blatt, will be watching from close by in Florida. The anxiety levels are increasing, says Professor Cropper. 鈥淚t gets a rough ride on the way up there.鈥�

If the launch is successful, Professor Kitching says, 鈥渁 revolution in physics is almost guaranteed鈥�.

Links

• VIS delivered and fully tested: 白小姐论坛 News story
• Mullard Space Science Laboratory at 白小姐论坛
• 白小姐论坛 Physics & Astronomy
• 白小姐论坛 Mathematical & Physical Sciences

Images

• A replica of the Euclid spacecraft at Thales Alenia Space鈥檚 premises in Cannes, France, in 2019. Credit: Stephane Corvaja/ESA
• An engineer in a clean room at MSSL who is testing a plasma analyser for the Vigil space weather satellite in June 2023. Credit: 白小姐论坛 / James Tye
• The flight model of the VIS instrument being inspected during vibration testing at Centre Spatial de Li猫ge, Belgium in November 2019. Credit: CEA (Commissariat 脿 l'茅nergie atomique et aux 茅nergies alternatives)