A shake before spaceflight
Rough-and-tumble testing makes for an orbit-ready satellite sensor
If you really want to shake things up, stick 'em on a rocket.
A rocket launch generates lots of noise, heat and especially, vibration. Systems that are carried into space have to be properly prepared to survive all the way into orbit.
That's why Raytheon tested its spacefaring Visible Infrared Imaging Radiometer Suite for Joint Polar Satellite System-2 by shaking it up. A lot.
The result: In its pre-environmental review with NASA, the high-flying sensor received the highest possible rating.
That review "was the first time the electronics and optical mechanical modules were mated together to perform as a single instrument,” said Roger Cole, director, JPSS Programs at Raytheon. “Passing this review with flying colors puts us on track to deliver the instrument well ahead of schedule.”
Launches are hard on complex equipment, and the stresses don't end when the last rocket engine has fired.
“We’re talking upwards of 3,200 degrees Fahrenheit of heat, vibration you can feel from miles away, and sound that reaches incredible decibels: 100,000 times louder than a sports car,” said Robert Curbeam, a vice president at Raytheon Space Systems, who adds that space conditions are also extreme. “To get into space, there’s a lot to survive, and it’s unforgiving.”
Although the worst of the shaking ends once the sensor is in orbit, it still has components like reaction wheels and solar arrays – big wings that bow, flex, and cause vibration that cannot be allowed to affect instrument performance.
VIIRS goes through three separate vibration tests simulating the worst-case environments of launch and orbit.
“Vibration tests are just what they sound like,” said Cole. “VIIRS is placed on a shaker table – a big flat platform. We use single axis shakers, which are designed to shake in only one direction, so we perform three shakes to test the different angles.”
The team recently wrapped up vibration test verification. The VIIRS functioned exactly as it should.
VIIRS is in electromagnetic interference and compatibility testing. Next up is preparation for thermal vacuum testing.
Those tests are performed in one of Raytheon's space-qualified, thermal vacuum chambers, which replicate the extreme heat and freezing cold cycles that spacecraft and sensors experience in space. This third and final stage of testing will be completed in March.
The first Raytheon-built VIIRS instrument is currently flying on the NOAA/NASA Suomi National Polar-orbiting Partnership satellite launched in 2011. The company delivered a second VIIRS sensor for NOAA’s JPSS-1, scheduled for launch in 2017.
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