Prepping a satellite instrument for its journey into space can feel like getting ready to lift off yourself. The sensors on board are vulnerable to the slightest speck of contamination—so to get close, you have to suit up. Required clean room attire includes a hair net, face mask, paper suit, disposable boots, and surgical gloves. No notebooks allowed—only paper that doesn’t release fluff if you tear it—and no clicky ballpoint pens. They spit out tiny balls of ink.
In the wee hours of Saturday, a fastidiously clean scanning machine named VIIRS launched into orbit on a Delta II rocket from Vandenberg Air Force Base in California, just one instrument outfitting a next-generation weather satellite. The Visible Infrared Radiometer Suite is a washing machine-sized sensor, built to capture light and other waves that bounce off the surface of Earth. It collects those reflections, turning them into data about our planet, the oceans, land and vegetation cover, ice caps, volcanic plumes, and global temperatures—allowing accurate weather forecasts, wildfire and fishing fleet tracking, and climate monitoring.
If an Enterprise-like starship were above us now, scanning our Class M planet for life, this sophisticated camera-telescope hybrid is the instrument it’d be using. Instead, the lookie-loos are NASA and the National Oceanic and Atmospheric Administration.
A week ago I witnessed another VIIRS undergoing pre-launch testing at the headquarters of space and defense company, Raytheon, in Los Angeles. This was the identical sibling to the one that launched on the Joint Polar Satellite System-1 orbiter this morning, the third VIIRS instrument that Raytheon has built. (The first is in orbit, launched on the Suomi NPP satellite in 2011.) Ultimately, five of these sensors will orbit Earth—on four JPSS satellites and the S-NPP—spinning around the planet in vertical, polar orbits, scanning the surface below, and beaming that data back down to scientists.
More Weather Sats
VIIRS may be just one instrument on board JPSS-1, but it’s a particularly powerful one. With a resolution of 2,500 feet, enough to make out roads and cities, its counterpart on S-NPP can see exactly where Hurricane Maria wiped out electric power in Puerto Rico, for example, even if people there don’t have communications to ask for help. By looking in the green spectrum at light reflected from leaves containing chlorophyll, researchers can create a “normalized vegetation index” for drought-prone areas. “That’s important in trying to predict where areas are drying out, and where you need more or less irrigation,” says Robert Curbeam, Raytheon’s vice president for space systems. Military customers, alternately, can use VIIRS data to figure out ocean visibility and temperature, which impacts how well sonar works.
More VIIRS in orbit will mean even more of that valuable data. So in the clean room for VIIRS trois, engineers carefully unplug a ponytail of cables as they slide the instrument out of a 15 feet wide, very black, stainless steel chamber. When the door is sealed on the end, and the pumps run, testers can check VIIRS out in a near vacuum, in a cryogenically cooled environment. “It feels like it’s going to feel in space,” says Brian Fellers, manager for systems engineering at Raytheon. If something on board is going to fail, better that it happens here. This is just one stage of five months of verification tests.
The optics are hidden behind a horizontal slot door. When that opens in space, incoming photons bounce off primary, secondary, and tertiary mirrors before they split off toward the sensors—one for infrared, one for visible light, and a more sensitive sensor for night time scanning. That entire assembly of mirrors spins in a housing the size of two coffee cans, taking just 1.78 seconds for a full rotation. That means the optics sweep across the Earth below horizontally, scanning a panoramic 1,864 mile swath, line by line, building up a picture of our world.
Because nobody knows exactly how it could be used, the JPSS satellites are designed to beam that data back in a raw form. “The scientific community is finding ways to take the data and get more information out of it every week,” says Mark Sargent, Raytheon’s JPSS Programs director. And getting the data to researchers is another exercise in technical precision.
JPSS is a polar orbiter, meaning it will pass over two points on the ground—the north and south poles—every 45 minutes. So Raytheon is upgrading its ground stations nearby in Norway, Alaska, and Antarctica, adding white domes to grab the five gigabytes of data that beam down during the 11 minutes the satellite is within range. In a single day, Suomi NPP sends down a total of 126GB. JPSS-1 will double that when it comes online soon.
As more of the JPSS constellation launches, satellites will pass over the poles more frequently, meaning the data they send to forecasters on the ground will be even more real-time. “This year’s hurricane season was a real stress test for the system,” says Sargent. But it all worked as designed; Suomi NPP monitored the storms tracking across the Atlantic, helping forecasters give more accurate warnings of their paths. The scope and application of that data will grow as NASA and NOAA launch more of these next-gen satellites and their super-sensitive instruments, making the months of ball-point-pen-free clean-room testing all worthwhile.