How NASA turned the Hubble telescope into an innovative UV camera cleaner

Sunday 19 January 2025 - 11:15

By: Dakir Madiha

How NASA turned the Hubble telescope into an innovative UV camera cleaner

The world of astronomy has a golden rule: never look directly at the sun. This warning echoes through public lectures and stargazing events, as unfiltered sunlight can permanently damage human retinas and optical equipment. Yet, in a remarkable departure from this principle, NASA once deliberately pointed the Hubble Space Telescope toward our nearest star.

The story begins in the late 1980s when engineers encountered a significant challenge with Hubble's Wide-Field/Planetary Camera (WF/PC). The camera suffered from quantum efficiency hysteresis (QEH), a condition where bright objects left persistent afterimages that compromised subsequent observations.

Engineers discovered that ultraviolet (UV) light could reset the camera's detectors. Rather than constructing a specialized UV light source, they devised an innovative solution: harness the sun's natural UV radiation directly from space.

The execution required precise planning and careful engineering. Instead of pointing Hubble directly at the sun, which would have destroyed its sensitive instruments, the team aimed the telescope at the "antisun" - a point exactly opposite the sun's position. They then used a specially designed reflector, similar to a periscope, to capture and redirect filtered sunlight into the WF/PC.

In December 1990, shortly after Hubble's launch, NASA implemented this daring plan. The telescope performed a series of carefully choreographed movements, creating a mosaic of split-second exposures across the sun's surface. While some attempts missed their mark, the successful scans achieved two significant outcomes: they successfully cleaned the camera's detectors and produced the first-ever far-UV images of the sun.

Despite the images' imperfections and artifacts, this unprecedented observation predated specialized solar observatories like the Solar and Heliospheric Observatory (SOHO). The mission also provided valuable data about light reflection within the telescope, improving future observations and calibration procedures.

This creative solution to a technical problem demonstrates the innovative thinking behind space exploration. While astronomers continue to warn against unprotected solar observation, this calculated risk showcases how careful engineering can transform a potentially destructive force into a useful tool.

The success of this unconventional approach not only solved the immediate technical challenge but also contributed to our understanding of solar observation techniques, proving that sometimes the most effective solutions come from thinking outside traditional boundaries.