On this day, 27 years ago, on February 21, 1998 (January 25, 1998 in the lunar calendar), American astronauts successfully modified the Hubble Space Telescope and returned to the ground. In the early morning of February 11, 1998, seven American astronauts took off on the space shuttle Discovery to transform the Hubble Space Telescope, which had been flying in space for seven years. Since its launch in 1990, the Hubble Telescope has traveled nearly 1.6 billion kilometers in space and conducted as many as 110,000 astronomical observations for more than 2000 scientists from more than 20 countries. "Hubble" has made great achievements, but it is riddled with holes and needs maintenance. In the early morning of February 13, American astronauts "picked" the Hubble telescope from space and placed it on the platform of the space shuttle's cargo bay. From the late night of the 13th to the early morning of the 18th, the astronauts conducted five spacewalks and replaced 11 new equipment for the Hubble telescope, including the near-infrared camera, the multi-target spectrometer and the space telescope image spectrograph, and repaired part of the peeling insulation layer on the telescope. In the early morning of February 19, astronauts released the newly modified "Hubble" telescope into space. This "space eye" with better "vision" will help humans understand more about the secrets of the universe. In the early morning of February 21, the American astronauts who successfully completed the maintenance of the Hubble telescope successfully returned to the ground.