ESA Releases First Euclid Space Telescope Test Images

The first images have arrived from the European Space Agency’s Euclid telescope, and they are stunning. Released by the European Space Agency (ESA) on July 31, 2023, test photos shot using the spacecraft’s VISible instrument (VIS camera, for visible light imagery used to measure shapes) and Near-Infrared Spectrometer and Photometer (NISP camera, for infrared shots that also measure the light being emitted by celestial objects in various bandwidths) are clear and detailed.

Euclid’s pristine images are great news for the ESA, which has spent more than 11 years on this project. The space telescope was launched on July 1, 2023 aboard a SpaceX Falcon 9 rocket, and is now parked at the Sun-Earth Lagrange point 2 (L2), at an average distance of 1.5 million km beyond Earth’s orbit. L2 provides a stable location that balances out the gravitational pulls of the Earth and the Sun.

The ESA’s space telescope platform consists of a payload module and a service module. The payload module contains a 1.2-meter-diameter telescope plus the VIS and NSIP cameras. The service module houses the spacecraft’s attitude control, data processing electronics, electric power generation and distribution, propulsion, telecommand and telemetry equipment, and thermal control.

“For astronomers who have developed a new instrument, seeing the first data or ‘first light’ is a very important event because they hope to see the sky in a way nobody has seen it before,” René Laureijs, an ESA Euclid Project Scientist told SpaceRef over email. “It is also an emotional event for them, it is the confirmation of many years of hard work. The Euclid scientists really wanted to share the excitement with the world, showing that Euclid’s capabilities are real and not a promise anymore.”

As for the photos that are wowing the astronomy world? “The Euclid images that we released are the first images of the sky after we had focused the telescope,” Laureijs explained. “We were amazed by the quality of the raw images!”

It is accurate to refer to Euclid’s first images as raw data. “We did not apply any image processing to highlight the good quality of the raw data,” said Laureijs. “You still can see the many cosmic rays causing streaks, but these artifacts will be removed routinely when we are fully operational. We also witnessed for the first time the panoramic view provided by Euclid. Each Euclid image covers an area of the sky of more than two full moons. We already see numerous galaxies and other objects and we are looking forward to collecting thousands more of these images.”

Processed or not, the test images were also an important step in the process of getting Euclid operational.

“The images gave immediate confirmation that the main science enabling components are working: the two instruments, the telescope, and the fine tracking system of the satellite,” Laureijs added. “Quick inspection showed that the image quality is excellent, that the instrument sensors are all performing, and that the tracking performance is better than expected because no image degradation could be spotted. We see very sharp and deep images, giving us confidence that we have the essential elements in place for a successful mission.”

It will now take two months for the ESA to assess the overall performance of Euclid’s systems. “We are going to test the survey and imaging performances in very [high] detail, and we will finish the instrument calibrations that can only be done in space against astronomical standards,” Laureijs told SpaceRef. “After an accurate point source characterization for different thermal conditions of the telescope, we will start the nominal Euclid sky survey in December. The survey will last for about six years.”

During that time, Euclid is expected to image and map an area far greater than that previous space telescopes have achieved.

“The total area of sky mapped by Hubble over its entire lifetime can be achieved by Euclid in about one week,” he added. “Euclid will survey an area of about one-third of the sky; this could never be done with Hubble or JWST.

However, that doesn’t mean that other space telescopes have outlived their usefulness. Quite the opposite, Laureijs said.

“The Euclid survey will provide a unique atlas of the extragalactic sky in the visible and infrared leaving a great opportunity for new discoveries,” Laureijs told SpaceRef. These can be followed up with Hubble or JWST, since they can observe much deeper than Euclid in a small sky area and using different wavelengths.”