The most beautiful path: Messing with space telescopes

During working hours, the average Dutchman looks at an uninspiring industrial area. How different is it for astronauts? This satellite image of the week is the view taken by astronaut Jeffrey Hoffman during the first Hubble mission in 1993.

The Hubble telescope is a space telescope that has been hovering above the Earth’s surface for more than thirty years. Over the past decades, the telescope has been visited and/or maintained by astronauts a total of six times. The first time was in 1990 (STS-31) when Hubble was orbiting from the space shuttle. The last time was in 2009.

Hubble needs glasses
Shortly after its launch in 1990, scientists discovered a problem with the Hubble mirror. The telescope could not focus and all images were therefore of lower quality than expected. Analysis revealed that the mirror had been polished incorrectly. The deviation should be no more than ten nanometers, but in the end it turned out that the outer edge was very flat by 2,200 nanometers. Cause of the error: The debugger incorrectly adjusted the zero. The corrector blank is an optical instrument used to test large aspherical mirrors. The lens of this corrector blank was found to be fixed 1.3mm from the correct position and as a result the mirror was incorrectly grounded. costly error.

The error has been fixed
During the first service mission (ST-61) in 1993, astronauts installed two completely new instruments: the Wide Field Planetary Camera 2 (WFPC2) and the replacement coaxial optical corrective space telescope (Costar). These two devices corrected the underlying mirror problem, allowing astronomers and many amateur astronomers to finally enjoy ultra-clear images of space.

For example, a year later, the Hubble telescope captured the famous and now iconic image of the so-called Pillars of Creation, or gas plumes in the Eagle Nebula. In the decades that followed, thousands of other beautiful images followed.

Can James Webb be fixed in space?
While the Hubble Space Telescope was designed to be repaired in space, the James Webb Telescope is not. This space telescope was launched at the end of last year and will begin its scientific observations this summer. While the Hubble Space Telescope flies about 550 kilometers above the Earth’s surface, the distance to the James Webb Telescope is 1.5 million kilometers. It is impossible for astronauts to visit this telescope and fix any error. After reading this, you’ll probably understand why James Webb’s mirrors have been retested and checked so many times and why the launch has been delayed so many times in recent years.

By the way, the Hubble Space Telescope is no longer repaired. The service assignment in 2009 was also the last maintenance. More and more instruments are expected to fail in the coming years and the telescope will burn up in the atmosphere sometime between 2028 and 2040. This ends an era.