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Airborne Lunar Spectral Irradiance (air-LUSI) Instrument

ER-2 taking off
NASA’s ER-2 taking off with the air-LUSI moonlight collection equipment on board.
Credit: NASA photo/Ken Ulbrich

Telescope Details



Flown on NASA’s ER-2 aircraft, a high-altitude aircraft based at NASA Armstrong Flight Research Center in Palmdale, California 


The Airborne Lunar Spectral Irradiance (air-LUSI) instrument will help characterize the Moon as a reference standard for calibrating satellite instruments used to study and monitor the Earth’s environment and climate. The uncertainty of measurements of the Moon’s brightness must be improved from a few percent to below 0.5% to calibrate instruments at the level needed for climate monitoring. 

NIST’s role:

Primary developer of Air-LUSI instrument, which includes a telescope, and responsible for calibration. The automatic pointing system to lock the telescope on the Moon was developed by University of Guelph.    

Significant discoveries:

Air-LUSI has completed seven engineering and demonstration ER-2 flights, successfully recording lunar observations on six flights. It is scheduled to start official operation with more lunar observation flights in March 2022.

Other interesting facts:

The “near-space airplane” operates as high as 21 kilometers (about 13 miles) above sea level, to enable measurements above most of Earth’s interfering atmosphere. Air-LUSI flies at night to observe the Moon with the telescope mounted inside a wing pod. A robotic mount keeps the telescope tracking the Moon, compensating for aircraft motion.

Supported by:

NIST, University of Maryland Baltimore County, NASA Headquarters, NASA Goddard, University of Guelph and U.S. Geological Survey 

Operated by:

NIST, University of Maryland Baltimore County, NASA Goddard, NASA Armstrong, University of Guelph and US Geological Survey 


air-LUSI telescope
Air-LUSI telescope being calibrated by artificial moon in the ER-2 hangar.
Credit: NASA photo/Ken Ulbrich
Created January 4, 2022, Updated January 7, 2022