ARCSTONE: Calibration of Lunar Spectral Radiance from Space

Overview

Lunar calibration helps researchers improve data quality of spaceborne hyperspectral instruments in the reflected solar wavelength range for Earth systems like weather and climate. Current lunar calibration techniques, however, are not accurate enough to serve the increasingly complex needs of Earth-monitoring instrumentation. ARCSTONE could potentially enable high-accuracy on-orbit calibration using lunar spectral reflectance as an SI-traceable reference, increasing the scientific utility of this lunar calibration approach significantly and allowing future missions and constellations of small satellites to calibrate themselves using light reflected off the Moon as an absolute reference.

Science Area

Lunar calibration has long been considered a potential technique for calibrating Earth-monitoring instruments in the  reflected solar wavelength range. But ground-based methods for measuring lunar reflectance are vulnerable to interference from Earth’s atmosphere, limiting their accuracy. For example, estimated accuracy of current Robotic Lunar Model (ROLO, USGS) is limited to 5 – 10%. By measuring lunar reflectance from LEO instead, ARCSTONE would eliminate atmospheric interference altogether and establish an approach for collecting extensive data sampling required for establishing the Moon as high-accuracy calibration reference.

Technology

ARCSTONE features a spectrometer with single 0.7˚ field-of-view integrated into a 6U CubeSat platform. From Low Earth Orbit (LEO), this instrument will directly measure both lunar and solar spectral irradiances within the visible to shortwave infrared (VSWIR) wavelength range (350nm – 2300nm). ARCSTONE will demonstrate the feasibility of measuring solar and lunar irradiances with a single set of optics, having dynamic range greater than 106 – thereby minimizing the impact of long-term optical degradation via a rationing method for lunar reflectance. The ARCSTONE instrument also provides researchers with spectral sampling better than 4nm and a combined uncertainty smaller than 0.5% (k=1), increasing the overall accuracy of lunar calibration by an order of magnitude. During its 6-months space-flight, ARCSTONE will cover multiple lunar geometries (phase angles and librations) to complete a full demonstration of the measurement concept.

Advancements

  • Novel approach of high-accuracy measurements of lunar spectral reflectance from space would enable reliable on-orbit calibration using the Moon, increasing the reliability of Earth-monitoring, spaceborne remote sensors operating in the reflected solar wavelength range.
  • Compact spectrometer measures both lunar and solar irradiance from a 6U CubeSat for deriving lunar spectral reflectance, demonstrating cost-efficient approach for implementing complex and accurate measurements from a CubeSat platforms.
  • Instrument dynamic range  greater than 106 achieved by only changing integration time, allowing ARCSTONE to collect solar and lunar data by direct views using the same optical path. This approach will minimize expected impact of long-term degradation of front optics.

Principal Investigator

Constantine Lukashin is a Physical Research Scientist at NASA Langley Research Center (LaRC), where he leads the development of approach, methodology and algorithms for reference inter-calibration in reflected solar for CLARREO Pathfinder and and serves as the Principal Investigator for ARCSTONE. He has extensive experience in remote sensing data calibration and validation, data merging and analysis, scientific algorithm development, analytical and Monte Carlo modeling. Constantine also served as PI of the NASA Information And Data System (NAIADS) project, funded by ESTO’s AIST program in 2015. Currently, he is PI of the ARCSTONE project for establishing the Moon as accurate calibration reference for spaceborne sensors in reflected solar wavelength range.

Lukashin’s co-investigators include Cindy Young and Trever Jackson, both at LaRC; Rand Swanson, Resonon, Inc.; and Gregg Kopp, University of Colorado.