lunes, 14 de agosto de 2017

NASA's smartest satellite is gone. Can private space replace it?

It follows one article published on August 9th on WIRED website, highlighting the success of Satellogic at providing scientists its hyperspectral data for free.


LOOK DOWN ON Buenos Aires from the sky, and you can learn a fair bit about the city. It's got a lot of concrete. Also a lot of trees. There's a bright green river delta to the north, which probably explains the ruddy-brown bay to the east. But with the right camera—a hyperspectral one—you can pick up a whole lot more. New colors emerge, hidden hues your eyes and mine aren't wired to see. And these colors reflect even more detail about the scene: the gases coming out of the city, the health of the plants surrounding it, the species of algae coloring the water offshore.

Scientists love pointing hyperspectral cameras at the Earth to analyze things like crop health, or the mineral content of exposed soil. But there aren't many spectroscopic satellites in orbit: The US decommissioned one of the best, called Hyperion, earlier this year. So a private company called Satellogic wants to give scientists its data for free—the company plans to have 300 spectroscopic satellites in orbit by the early 2020s.

Hyperspectral imagery lets scientists see the world for what it is: molecules. Every rock, every crop, every building, and every one of you is made out of them, and every molecule reflects a different brand of photons. Pick up the signals from enough different kinds of light—Satellogic's orbiting imagers use 30 kinds, with wavelengths from 450 to 850 nanometers—and you can get a pretty good idea of a landscape's molecular composition.

Let's say you point your imager at field of corn. The light hitting the nitrogen, magnesium, carbon, hydrogen, and other molecules in their leaves can reveal the species, its health, and whether it's getting enough water. "This has many interesting use cases in agriculture," says Emiliano Kargieman, Satellogic's founder. "It can help monitor and identify crops, show levels of herbicide use, whether disease is spreading, water quality, and overall biomass."

That kind of data is super valuable for megafarmers. And hyperspectral data can even read the gas content in the air—important if you're a pipeline company keen to track possible gas leaks. Kargieman won't name any specific customers, but he says Satellogic serves ag and oil pretty heavily.

Obviously, that sort of information would also come in handy if you're a scientists trying to make sense of the Earth's capacity for sustaining life. But why would Satellogic give it away for free? "Well, for one, we see some trends in defunding Earth science research in the public sector, so we have a certain sense of responsibility to open up our data," says Kargieman. And then there's the fact that Satellogic's dataset is fairly new—they only have three birds in the air at the moment, with two more set to launch in September. The more people they have looking at their data, playing with it, and inventing new applications for it, the better it is for their overall business.

Buenos Aires province as seen from Space through Satellogic's
hipersprectral cameras.

The competition in this area is heating up. Last year Planetary Resources announced $21.7 million in Series A funding to launch 10 hyperspectral imagers aboard the company's low Earth-orbiting Arkyd satellites.

Satellogic's operation has several advantages. First, its satellites are already in orbit. Second, the company has strength in numbers. The satellite constellation—collectively called Aleph, after a spacetime vortex in a Jorge Luis Borges story—will remap the same areas in shorter and shorter intervals, as more satellites join its fleet. "By this time next year we will have better than daily remaps of the planet with the hyperspectral camera," says Kargieman.

That's if the company can keep to its ambitious launch schedule. Next year it plans to launch 12 to 18 satellites, and another 60 in 2019. Each satellite has a nickname: The first two were Fresco and Batata, after a popular Argentinian dessert, and the third was Milanesat—another food reference. Numbers four and five are named after famous mathematicians Ada Lovelace and recently deceased Fields Medal laureate Maryam Mirzakhani.

But no matter how dense that constellation gets, it won't be enough for Earth scientists tracking some of the planet's most critical changes. "At their coverage range, they will be missing the spectral signatures of the absorption of snow and ice," says Robert Green, an Earth scientist at NASA's Jet Propulsion Laboratory. That's pretty important these days, as scientists are scrambling to figure out how polar feedback contributes to climate change. Melting ice and warming water both emit energy in the near infrared spectrum, which extends from about 700 to 2,500 nanometers.

Green points to the late, great Hyperion as a model for space-based, science-oriented imaging spectrometer: a souped-up hyperspectral imager. Hyperion collected more than 200 spectral bands, in wavelengths ranging from 400 to 2,500 nanometers—that's all of the visible light spectrum, and a nice chunk of infrared. Hyperion was recently decommissioned after 17 years of service (it was only supposed to last 12 months). It will spend the next 40 or so years slowly spiraling into the upper atmosphere, where friction will set it aflame in a brief, but colorful, spectral display of its own.

To shift Hyperion's scientific responsibilities to a private company, scientists like Green will need to know the data is good. When it was operational, Hyperion would recalibrate once a month by shooting images of the moon—with no atmosphere, its reflectance values stay pretty much the same—and comparing those to pre-launch calibration data. "We found that the far blue, and some of the other bands were changing at a rate of over 5 percent over the life of the mission," says Betsy Middleton, a mission scientist at NASA's Goddard Space Flight Center. Most of the other bands varied a bit less, about 2 percent. But nonetheless, that's an important thing to know for anyone relying on the data.

For any scientists who are intrigued, Satellogic invites them to reach out via their website.

Source: Wired

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