Standard snapshots of space do not quite show the Earth in all its splendor. There is so much more to see.
To reveal details that can not be seen by the naked eye, the engineers at Rice University are building a portable spectrometer that can be mounted on a small satellite, flown in a plane or drone, or even held in a plane. hand one day.
Bioengineer Tomasz Tkaczyk and his colleagues at the Brown School of Engineering and Rice's Wiess School of Natural Sciences have released the first results of a NASA-funded project to develop a small, sophisticated spectrometer with high performance spectroscopy. unusual versatility. Their paper appears in Optics Express.
A spectrometer is an instrument that captures the light of an object or scene, separates the colors and quantifies them to determine the chemical content or other characteristics of what he sees.
The Rice device, called Tunable Image Processing (Light-Guide) snapshot spectrometer (TuLIPSS), will allow researchers to instantly capture data in the visible spectrum and in the near-infrared, unlike current systems that scan a scene line by line for later reassembly.
Each pixel of hyperspectral images produced by TuLIPSS contains spectral or spatial information. The "pixels" in this case are thousands of optical fibers, flexible light guides that transmit the image components to a detector. Because they can reposition fibers, researchers can customize the balance of image and spectral data sent to the detector.
The device, for example, can be set to measure the chemistry of a tree to determine whether it is healthy or sick. It can do the same thing for a cell, a single leaf, a neighborhood, a farm or a planet. In continuous capture mode, similar to the motorization of a camera, it can show how the spectral "fingerprints" of a motionless scene change over time or capture the spectral signature of a lightning-in-time real.
Tkaczyk said that TuLIPSS is unique because it works like any camera and captures all hyperspectral data – what researchers call a data cube – in an instant. This means that a plane or satellite in orbit can take an image of the ground fast enough to avoid motion blur that would distort the data. The integrated processing will filter the data and send only what is needed on Earth, thus saving time and energy.
"It would be an interesting tool in the event of an event like Hurricane Harvey," Tkaczyk said. "In case of flooding and potential contamination, a device capable of flying over a tank could indicate if this water is drinkable, it would be more effective than sending someone on a hard to reach site. "
In a normal camera, a lens focuses the incoming light onto a sensor chip and converts the data into an image. In TuLIPSS, the lens focuses this light on an intermediate: the optical fiber bundle.
In the current prototype, these fibers collect more than 30,000 space samples and 61 spectral channels in the 450 to 750 nanometer range, essentially hundreds of thousands of data points, divided by prisms in their component bands and transmitted to a detector . The detector then transmits these data points to software that recombines them into the desired images or spectra.
The fiber network is tightly congested at the entrance and reorganized into individually addressable lines at the output, with spaces between them to avoid overlap. Line spacing allows researchers to adjust spatial and spectral sampling for specific applications, Tkaczyk said.
The first author, Ye Wang, who earned her doctorate this year at Rice, and her colleagues painstakingly built the prototype, assembling and positioning fiber bundles by hand. They used scenes in and around Rice to test it, reconstructing images of buildings to refine TuLIPSS, and taking spectral images of campus trees to "detect" their species. They have also successfully analyzed the health of various plants with only spectral data.
Continuous images of moving traffic in Houston have shown the ability of the system to see which spectra evolve over time (such as moving vehicles and changing traffic lights) and which are stable (everything else). The experiment was a useful proof of concept to show how well the spectrometer could filter motion blur in dynamic situations.
The co-author, David Alexander, professor of physics and astronomy and director of the Rice Space Institute, said the researchers had begun discussions with the city of Houston and Rice's Kinder Institute for Urban Research on the test. TuLIPSS in the city's aerial survey.
"Since we have to test TuLIPSS anyway, we want to do something useful," he said, suggesting that a hyperspectral map of the city could reveal the evolution urban landscape, distinguish buildings from parks or map sources of pollen. "In principle, regular flights over the city will allow us to map changing conditions and identify areas that need special attention."
Tkaczyk suggested that future versions of TuLIPSS would be useful for agricultural and atmospheric analysis, the proliferation of algae and other environmental conditions in which rapid data acquisition would be useful.
"The real challenge was deciding what to focus on first," said Alexander. "In the end, we want to be successful enough so that the next phase of development brings us closer to the TuLIPSS plane in the space."
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Ye Wang et al., Light guide imaging spectrometer for remote sensing applications, Optics Express (2019). DOI: 10.1364 / OE.27.015701
Hyperspectral camera captures a wealth of data in an instant (May 20, 2019)
recovered on May 20, 2019
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