China’s Einstein Probe, an X-ray astronomy mission, heads to orbit.

The launch of a Long March rocket from Xichang, China with the Einstein Probe. Xinhua

A Long March 2C rocket lifted of from Xichang Satellite Launch Center in China early today, with the Einstein Probe, an X-ray observatory. The launch occurred at 3:03 p.m. Beijing Time / 7:03 UT. The mission is headed towards low-Earth orbit and has a nominal operational span of three years.

The Chinese mission was conducted in collaboration with the European Space Agency and the Max Planck Institute for Extraterrestrial Physics in Germany. The country’s first X-ray mission, the Hard X-ray Modulation Telescope (HXMT), launched in 2017 and is still in operation.

Einstein carries two instruments: the Wide-field X-ray Telescope, which will use a unique lobster-eye aperture with a 60-degree field of view to hunt for X-ray sources, and the Follow-up X-ray Telescope, which will measure those same sources at much higher resolution.

Lonster Ey
The detector grating of the Wide-field X-ray Telescope (shown at top right) compares well to a lobster eye grating (top left). The bottom image shows a full view of the telescope.

China demonstrated the innovative imaging technology on the Lobster Eye Imager for Astronomy (LEIA) in 2022. The European-Canadian mission known as Solar wind Magnetosphere and Ionosphere Link Explorer (SMILE) mission, due to launch in 2025, will utilize similar technology.

Einstein's two X-ray telescopes sense X-rays with energies between 300 and 10,000 electron-volts (0.3-10 keV), similar to the XMM-Newton workhorse and the eagle-eyed (but aging) Chandra X-ray Observatory. Other X-ray telescopes work at higher energies, including NASA’s NuSTAR (which covers 3 to 79 keV) and India’s recently launched XPoSat (which covers 0.8 to 30 keV).

With its wide field of view, the Einstein Probe will focus on transient X-ray sources, including star-eating black holes, pulsars, gamma-ray bursts, and supernovae. Researchers also hope to use the wide-to-narrow field capabilities of the mission to pinpoint X-rays coming from gravitational-wave events in X-rays.

“Since black holes and gravitational waves are predictions made by Einstein’s theory of general relativity, the satellite is named after the great scientist,” said Yuan Weimin (National Astronomical Observatories of the Chinese Academy of Sciences), principal investigator of the mission, in a recent press release.

Einstein Probe
A diagram of the Einstein Probe spacecraft.

“This is the most beautiful satellite I’ve ever seen,” Yuan says. The 12 white “petals” in the diagram above belong to the wide-field telescope. The two “stamens” in the middle belong to the follow-up telescopes.

Assembling Einstein
Assembling the Einstein Probe ahead of launch. CAS

This launch kicks off a busy year for China in space in 2024. The country will attempt the first lunar farside sample return with its Chang’e 6 mission as well as launch the space telescope Xuntian later this year.


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