NASA Landsat satellites are an invaluable remote-sensing resource for Earth observation, providing multispectral imagery at 30-meter resolution ground sampling and covering the entire Earth every 16 days.
Many scientists have recognized the potential for enhancing Landsat capabilities by incorporating an imaging spectrometer in place of the current 7-band multispectral imager to provide full, contiguous spectroscopy.
Unfortunately, many of the proposed designs have suffered from a large reduction in area coverage, making them less useful for many users.
SPIE Fellow Pantazis Mouroulis and his colleagues from the NASA Jet Propulsion Laboratory at the California Institute of Technology appear to have overcome this major limitation. In a recent Optical Engineering paper, they present a dual spectrometer design covering the 380- to 2510-nm spectral range with 6.8-nm spectral sampling, which is capable of covering the same 185-km swath as Landsat 8 with commensurate ground sampling.
Optical layout with two-mirror Schwarzschild-like telescope, proposed by JPL researchers.
The optical system employs two field-split, f/1.8 Dyson spectrometers with calcium fluoride (CaF2) and fused silica lenses fed by either a two-mirror Schwarzschild-like telescope or a tri-mirror anastigmat telescope. The two telescope designs trade off complexity and compactness.
The system uses a novel, concave, multi-blaze-grating groove design with features falling within the fabrication capabilities of electron-beam lithography. The signal-to-noise ratio of the spectrometer exceeds that of the Landsat Operational Land Imager (OLI) when aggregated spectrally for comparable spectral resolution.
The article, “Landsat swath imaging spectrometer design,” describes thorough performance, stray-light, and tolerancing analyses, solidifying the practicality of the design for potential employment on a future Landsat satellite mission.
If you have an interest in remote sensing or imaging spectrometry, you will find this work interesting and quite impressive.
Mouroulis’ coauthors include SPIE members Robert Green and Holly Bender along with Byron Van Gorp, Lori Moore, and Daniel Wilson.
40-PLUS YEARS OF LANDSAT
NASA and the US Geological Survey launched its first civilian Earth observation satellite in 1972.
Landsat 1, an unmanned, remote-sensing satellite was originally named the Earth Resources Technology Satellite (ERTS-1).
The launches of Landsats 2-8 followed, with Landsat 5 delivering high-quality global data on Earth’s land surfaces for a record 28 years and 10 months (March 1984 to January 2013).
Landsat 7 and Landsat 8, launched in 1999 and 2013, respectively, continue to provide daily global imagery for those who work in agriculture, geology, forestry, regional planning, mapping, and emergency response and disaster relief. Landsat 9 is tentatively planned to launch in 2023.
The Landsat project and the data it collects also support government, commercial, industrial, military, and educational communities throughout the world.
Read more information on Landsat.
–SPIE Fellow and Board Member Michael Eismann is chief scientist at the US Air Force Research Lab’s Sensors Directorate and editor-in-chief of Optical Engineering.