Europe's new exoplanet-spotting space telescope has observed its first alien worlds.

The probe, called the Characterizing Exoplanet Satellite (CHEOPS), launched into Earth's orbit last December and has just completed a three-month commissioning phase. During that time, the European Space Agency (ESA) tested out CHEOPS' instruments and even used the telescope to observe a few exoplanets, or planets that orbit stars beyond our solar system. The space observatory is now ready to begin routine science observations, which should begin at the end of April, ESA officials said in a statement.

While other exoplanet missions like NASA's Kepler Space Telescope and the Transiting Exoplanet Survey Satellite (TESS) were designed to search for planets around other stars, CHEOPS will spend its time honing in on known exoplanets to measure their sizes with unprecedented accuracy and precision. Combined with data on each exoplanet's mass, which can be calculated from their orbits, the size measurements will allow astronomers to determine each exoplanet's density, thus revealing more clues about the composition of these worlds — and whether they could sustain life.

Video: Europe's new exoplanet hunter begins star observations

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An image of the star HD 88111, taken by the European Space Agency's Characterizing Exoplanet Satellite (CHEOPS) during its in-orbit commissioning in early 2020. The star is located 175 light-years away from Earth in the Hydra constellation. Cheops took an image of this star every 30 seconds for 47 consecutive hours to demonstrate the stability of its instruments. (Image credit: ESA/Airbus/CHEOPS Mission Consortium)

CHEOPS performed a series of in-flight tests between January and February to make sure its instruments were functioning and calibrated properly. The spacecraft took its first images in February, featuring blurry views of star systems. Those fuzzy images were no accident.

"The deliberate defocusing is at the core of the mission's observing strategy, which improves the measurement precision by spreading the light coming from distant stars over many pixels of its detector," ESA said in the statement.

In March, the new space telescope began looking at well-known star systems. CHEOPS "first needed to observe stars whose properties are well known, stars that are well-behaved — hand-picked to be very stable, with no signs of activity," CHEOPS project scientist Kate Isaak said in the statement. This allowed the CHEOPS team on Earth to verify that the satellite's instruments are precise and stable enough for observations.

"We were thrilled when we realised that all the systems worked as expected or even better than expected," CHEOPS instrument scientist Andrea Fortier said in the same statement.

Artist's impression of the star HD 93396 and its hot Jupiter planet, KELT-11b. (Image credit: ESA)

CHEOPS spent the last two weeks of in-orbit commissioning observing two stars that are known to host exoplanets. Specifically, the telescope practiced watching as exoplanets transited their stars. During a transit, an exoplanet crosses in front of the star, blocking a tiny bit of starlight and causing the star to dim slightly. While TESS uses the "transit method" to search for alien worlds, CHEOPS will use transits to take precise measurements of exoplanets.

One of the exoplanets that CHEOPS observed during this practice one is a puffy, gaseous world known as KELT-11b. The exoplanet orbits a subgiant star called HD 93396, which is located 320 light-years away from Earth. HD 93396 is three times larger than our sun, and KELT-11b is about 30% larger than Jupiter, but the gas giant orbits closer to its host star than Mercury is to the sun.

Using data CHEOPS gathered during that transit, scientists measured that KELT-11b is 112,800 miles (181,600 kilometers) wide. This measurement is five times more accurate than what can be done using Earth-based telescopes, ESA officials said in the statement.

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This infographic shows the light curve that ESA's CHEOPS mission measured as it observed the transit of exoplanet KELT-11b in front of its host star, HD 93396. (Image credit: ESA/Airbus/CHEOPS Mission Consortium)

ESA held a formal review of the satellite's performance and ground operations on March 25, and CHEOPS passed it with flying colors. "The in-orbit commissioning phase was an exciting period, and we are pleased we were able to meet all requirements," said Nicola Rando, CHEOPS project manager at ESA. "The satellite platform and instrument performed remarkably, and both the Mission and Science Operation Centres supported operations impeccably."

While the mission's science phase has not yet officially begun, CHEOPS is already taking a peek at some of its early targets, which include the exoplanets 55 Cancri e (a hot 'super-Earth' with a lava ocean) and GJ 436b, a so-called 'warm Neptune' that is losing its atmosphere.

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us on Twitter @Spacedotcom and on Facebook.