In October 2020, the European Space Agency (ESA) unexpectedly cancelled the ESA Medium Class M5 mission candidate SPICA (SPace Infrared telescope for Cosmology and Astrophysics) (press release):

The European Space Agency (ESA) and the Japanese Aerospace Exploration Agency’s Institute of Space and Astronautical Science (ISAS/JAXA) have announced their decision to no longer consider the infrared space observatory, SPICA, as a candidate for the upcoming selection as ESA’s 5th medium-class mission in its Cosmic Vision Programme (M5).

An open letter with nearly 300 signatures was sent to the Director of Science at ESA, calling for more transparency in decision-making processes at ESA. An abridged version of the letter has been submitted to Nature.

On 24/11/2020) Nature has published this correspondence: