Overview

• The Visible Tunable Filter (VTF), a key instrument of the Daniel K. Inouye Solar Telescope, achieved technical first light in April 2025 by capturing a high-resolution image of a planet-sized sunspot.
• The sunspot cluster spans 241 million square miles of the Sun’s surface, with each pixel in the image corresponding to just 10 kilometers (6.2 miles), offering unprecedented detail.
• Developed over 15 years by the Institute for Solar Physics in Freiburg, Germany, the VTF is designed to map solar phenomena such as magnetic fields, plasma flows, and solar flares with exceptional spatial, spectral, and temporal resolution.
• This milestone aligns with the Sun's peak activity during its 11-year solar cycle, providing critical insights into geomagnetic disturbances that can disrupt Earth's infrastructure.
• Routine scientific use of the VTF is planned for early 2026, paving the way for improved predictions of solar storms and their potential effects on satellites, communications, and power grids.