Seeking to burnish its prestige in the world, China is portraying its Tiangong orbital outpost as a space station that is available for scientists everywhere, not just for those who happen to live in other countries with established space programmes.
“We stand ready to conduct more international cooperation and exchanges with countries and regions committed to the peaceful use of outer space,” said Wang Wenbin, a spokesperson for the Chinese foreign ministry.
For the International Space Station — a partnership amongst Nasa, Russia, Canada, the European Space Agency and Japan that has been in orbit for more than two decades — the laboratory resources are split among the partner nations, which then offer their scientists opportunities to send experiments to the space station.
But scientists living in countries that are outside of the partnership are generally shut out of the ISS.
Through a United Nations programme called Access to Space for All, China has offered opportunities for scientists from any country to get their experiments carried to the Tiangong space station.
The UN announced the first round of nine awards in 2019, which included projects from India, Japan, Peru, Mexico as well as Saudi Arabia.
One of the selected experiments, POLAR-2, is an international effort led by the University of Geneva, Switzerland, to study distant gamma-ray bursts.
Gamma-ray bursts are some of the most violent explosions in the universe, caused by exploding stars or merging neutron stars. The explosions send short, intense jets of ultra-high-energy photons known as gamma rays travelling across the universe.
As its name suggests, POLAR-2 is a follow-up to POLAR, a smaller detector that flew to an earlier, smaller Chinese prototype space laboratory.
“Historically, the University of Geneva had a strong connection to Chinese research groups,” said Merlin Kole, project manager for POLAR-2, which is scheduled to be launched in Tiangong in 2025.
The experiment examines whether gamma rays from a gamma-ray burst line up in a particular way. More than a decade ago, measurements by an instrument on a Japanese spacecraft suggested that gamma rays were often linearly polarised — that is, the oscillating electric fields of the gamma rays were parallel to each other like a squadron of airplanes flying level instead of with their wings skewed in every direction.
The Long March rocket carrying Shenzhou
But the data from POLAR, which flew in 2016, suggested that the gamma rays were unpolarised.
The POLAR scientists considered how they could get a larger, follow-up detector launched to space. They decided not to seek to build a dedicated satellite of their own. “That would be much more complex on the whole,” said Agnieszka Pollo, an astrophysicist at the National Center for Nuclear Research in Poland and the principal investigator for the Polish part of the POLAR-2 collaboration.
And the ISS was also not considered viable because “there is a big competition for that,” Pollo said, “and this is also not exactly so cheap and easy.”
So when the research opportunity for Tiangong was announced, “relatively quickly we were able to submit something, and we got acceptance in the first round,” Kole said.
Tiangong’s high-speed communications system will allow tens of gigabytes of data to be sent to the ground each day. That will allow scientists to analyse all of the data that may contain nuggets of discovery such as very weak gamma-ray bursts or other astrophysical events that might otherwise be discarded as noise
There is also a supercomputer on the space station to analyse the data while it is still in space. That will allow quick calculation of where a gamma-ray burst originated. That information could then be shared with astronomers on the ground for rapid follow-up observations using other telescopes, Kole said.
So far, the collaboration with Chinese space officials has gone well, Kole said, although that can involve wading through the Chinese bureaucracy.
“There are several agencies involved, and we don’t talk to all of them directly,” he said. “So that makes it a bit tricky at times. But when we really need to know something, we figure it out.”
Because the $2 million instrument is largely being built in Europe and then shipped to China, the project involves bureaucracy and paperwork with European officials, too.
“We’re not giving secrets, of course,” Kole said. “All of the components are relatively easy, and nothing is secretive. It’s a scientific instrument. But, yeah, there’s no very clear bureaucratic channel to do this properly.”