China to launch Einstein Probe in 2023 to observe violent cosmic events

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HELSINKI — A Chinese wide-field x-ray space observatory has passed a major review and is expected to launch next year to detect flashes from cataclysmic cosmic events.

The Einstein Probe is expected to launch around mid-to-late 2023 to observe distant, violent interactions such as tidal disruption events—in which stars are pulled apart by supermassive black holes—supernovae, and detect and localize the high-energy, electromagnetic counterparts to gravitational wave events.

A March 25 review session organized by the National Space Science Center (NSSC) under the Chinese Academy of Sciences (CAS) approved the mission to proceed to the spacecraft assembly, integration and testing phase, ahead of an expected launch next year.

The roughly 1,400-kilogram spacecraft will be launched into a 600-kilometer altitude, low inclination orbit. From there it will observe the sky with a Wide-field X-ray Telescope (WXT) with a field of view of 3,600 square degrees, using cutting edge “lobster eye” optics to allow the probe to view X-ray events more deeply and widely than previously possible. 

The spacecraft will feature onboard data processing and autonomous followup capabilities, meaning the probe’s Follow-up X-ray Telescope (FXT), developed in collaboration with Europe, can be quickly brought to bear after WXT detects an X-ray event.

The Einstein Probe team hopes to detect violent extra-galactic events which have so far been only sparsely explored, with so far relatively few confirmed observations of tidal disruption events (TDEs).

By picking up soft band X-ray emissions from stars being ripped apart by massive black holes, the probe could provide new insights into how stellar matter falls into black holes and the complex and rare phenomena of formations of jets of ionized matter emitted by the events.

Mission Principal Investigator Yuan Weimin of the National Astronomical Observatories (NAOC) noted in a 2021 conference presentation that the probe could potentially detect up to one hundred TDEs per year.

The probe’s surveying of the sky for transient X-ray events the probe could also provide insight into other phenomena including black holes, magentars, active galactic nuclei, red shifted gamma-ray bursts, and the interactions between comets and solar wind ions.

The mission will utilize the Beidou navigation satellite constellation to allow rapid relay of alert data to the ground.  Alerts will be publicly shared to allow rapid followup observations by other teams and telescopes. There have also been discussions on utilizing the VHF network belonging to France space agency CNES.

CNES’s VHF network will support the China-France SVOM astronomical X-ray space telescope, with which the Einstein Probe will have synergies. SVOM could also launch in 2023.

The Einstein Probe mission is being managed by the NSSC, with involvement of CAS’s NAOC, the Institute of High Energy Physics (IHEP), the Shanghai Institute of Technical Physics (SITP) and the Innovation Academy for Microsatellites, the spacecraft maker, which has previously manufactured space science and Beidou navigation spacecraft.

The ­European Space Agency is contributing to the mission by providing a mirror module for the FXT instrument as well as ground station and science management support. Germany’s Max Planck Institute for Extraterrestrial Physics is also involved in the FXT instrument.

The Einstein Probe was proposed in 2013 and approved in 2017 as part of a second phase of the Chinese Academy of Sciences’ Strategic Priority Program (SPP) on Space Science.

The SPP first phase consisted of four missions—the Dark Matter Particle Explorer (DAMPE), ShiJian-10 (SJ-10), Quantum Experiments at Space Scale (QUESS) and Hard X-ray Modulation Telescope (HXMT)—launched across 2016-17. 

Other missions in the second phase are the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM), the Advanced space-based Solar Observatory (ASO-S) due to launch this year, and the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE), for which ESA recently shipped a module to China. The missions are part of China’s major space plans for the next five years.

Proposals are being studied and reviewed for a further phase of Chinese space science missions, according to the NSSC.

Image and article updated at 11:59 p.m. Eastern, March 31.