NASA’s ER-2 Aircraft Captures Moonlight to Calibrate Space Sensors

A NASA instrument designed to measure the Moon’s brightness to help satellite sensors make more accurate measurements completed a three-week mission on a high-flying plane on Feb. 5.

NASA uses the Moon as a natural calibration source to improve the accuracy of space-based sensors. These sensors provide critical data to observe weather patterns, survey agriculture, and study the Earth’s ecosystems – supporting decisions that affect everyday life. By measuring the Moon’s brightness from near-space, scientists can ensure satellite instruments remain precise without adding costly onboard calibration equipment.

The Airborne Lunar Spectral Irradiance, or air-LUSI, instrument flew over the West Coast on NASA’s high-altitude ER-2 aircraft, based at NASA’s Armstrong Flight Research Center in Edwards, California, transforming the plane into an airborne lunar observatory. The instrument was carried to an altitude of about 70,000 feet, above 95% of the Earth’s atmosphere. The air-LUSI team has been operating missions to measure moonlight since 2022.

Because the Moon’s surface reflects light consistently and is unaffected by Earth’s changing environment, moonlight is a good reference point for calibration. Unlike the Sun, the Moon’s brightness is similar to Earth’s, making it a better match for how satellite sensors are designed to operate.

The air-LUSI project is a collaboration between NASA, the National Institute of Standards and Technology, the U.S. Geological Survey, the University of Maryland, Baltimore County, and McMaster University in Ontario.

~Jay Levine