Europe’s planet-gazing telescope opens eyes to the universe

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The Characterising ExOPlanets Satellite (CHEOPS) mission blasted off from Kourou, French Guiana on 18 December 2019.

The launch came 24 hours after a first attempt was delayed shortly before liftoff because of a software problem in the upper stage of the rocket.

Now, scientists say the space telescope has shed its cover, opening its eyes to the universe.

In the next two months, astronomers will test the telescope’s measurement accuracy. They hope to publish the first images in “one to two” weeks. Science operations will begin in earnest by late March.

The European Space Agency says the satellite is the first mission dedicated to studying bright nearby stars that are already known to have planets and will focus on “planets in the super-Earth to Neptune size range.”

The agency hopes that the data sent by the mission will enable the bulk density of those planets to be calculated, a first step toward understanding them better.

Its telescope will focus on bright stars to determine the size of planets as they pass in front of their host star.

The mission will focus on 100 of the more than 4,000 exoplanets – ones beyond our own solar system – discovered so far, partly to determine if there’s a possibility of an Earth-like planet capable of sustaining life.

The mission is a partnership between the European Space Agency (ESA) and Switzerland, with contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the UK.

Here at the Geneva Observatory in Versoix in Switzerland, home to the 2019 Nobel Physics Prize laureates Didier Queloz and Michel Mayor, who discovered the first exoplanet in 1995, researchers hope a treasure trove of data is about to be discovered.

“We are expecting to start the scientific operation in late March, early April 2020, and from this point on we will collect, really, scientific data,” explains CHEOPS mission scientist David Ehrenreich.

“And so, depending on how nature is generous to us, we hope to publish the first results, the first discoveries of CHEOPS, just shortly before next summer.”

Ehrenreich says CHEOPS is particularly interested in planets he describes as being located in Earth’s “close neighborhood” because they are easiest to study.

“We don’t want to discover more planet(s) with CHEOPS, instead we want to learn more about the planets that we discovered in the past, he says.

“And we will not be able to say that this planet or that planet is habitable or not, what we are going to say is that these planets are made of, essentially, rocks, ice or gas.”

Once the data that CHEOPS collects has been sent back to Earth, Ehrenreich says researchers at other facilities like that at the James Webb Space Telescope, which is due to be launched by NASA in 2021, will be able to do follow-ups.

He says CHEOPS will be peering far into space, examining the light of stars with known planets in their orbit.

“The idea is to observe a star before the planet passes in front of it, (and) during the passage of the planet, and compare the amount of light we receive from the star between these two epochs,” he says.

“The difference is going to tell us how much of the starlight is missing, hence how much is hidden by the planet, thus, how big is the planet in front of the star.”

The key to collecting meaningful data about exoplanets is to carry out repeat observations, Ehrenreich adds.

ESA says, CHEOPS will make repeated observations of several hundred exoplanets over the life of its mission.

For planets around the size of Earth, the decrease in light from a sun-like star might be minute, ESA says – perhaps 0.01 percent of its normal brightness.

“In the past, we have had other space telescopes that were observing in the field of exoplanets,” says Matthias Beck, CHEOPS Ground Segment Manager.

“Most of the time, they were more generic instruments to look at the white field, to observe many stars at the same time, CHEOPS is the first instrument that is really dedicated to the follow-up of exoplanets that are known to exist – so we have other instruments that have detected these exoplanets, and we do the follow up, to measure the size of the exoplanets, then to combine it with the measurements from other instruments.”

CHEOPS will operate in a low-Earth orbit, about 700 kilometres above us.

Its camera will always point towards the night side, meaning sunlight won’t disturb its sensitive measurements.

The data CHEOPS collects will be sent first to the Mission Operations Centre in Madrid, before being passed through to the CHEOPS Science Operations Center in Geneva.

That’s where Beck’s team comes in.

“We receive all the data that is recorded onboard of CHEOPS, we receive this via the Mission Operations Center, and this is basically the first look on the data that we receive twice a day, usually early in the morning around six o’clock, and the second time in the evening, around six o’clock again,” explains Beck.

ESA says the mission paves the way for the next generation of exoplanet satellites – Plato and Ariel – planned for the next decade.

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