Satoshi Furukawa, the 58-year-old astronaut who led the team, "fabricated" and "altered large amounts of data" on the psychological well-being of the experiment participants, according to the space agency.
JAXA Vice President Hiroshi Sasaki said at a press conference that despite the fact that Furukawa was not considered directly involved in the violations, he was partially responsible as he supervised the experiment, the report said.
Sasaki added that Furukawa would face disciplinary punishment, but noted that JAXA did not consider making changes to his flight to the ISS scheduled for 2023, the report read.
The JAXA vice president also apologized for the incident, saying "sloppy management of the experiment has damaged the credibility of research data, and the scientific value of research as a whole," the news agency reported.
The experiment involved eight people who were kept indoors for about two weeks to assess their stress levels and mental well-being, according to the report.