Moon Shot to Pluto – and Beyond
The following blog post is by Steve Saxe of the Optical Security and Performance Products division, Viavi Solutions.
You hear the term “moon shot” thrown around a lot – you know, that euphemism referring to far-out ideas that may just be crazy enough to work.
Karen Hendrix uses the term a tad more literally. Well, maybe more like “Pluto shot.”
A full thirteen years after Hendrix, Viavi Solutions’ principal filter design engineer in the Optical Security and Performance Products division in Santa Rosa, CA, first started creating new technology for NASA’s New Horizons spacecraft, she – and the rest of the world – have begun seeing the fruits of her and other engineers’ labors.
Karen Hendrix, Viavi Solutions’ principal filter design engineer in the Optical Security and Performance Products division
In 2002, Hendrix and her colleagues undertook an ambitious NASA project: Design the optical filter for a compact, lightweight spectrometer that could be sent three billion miles across the solar system to Pluto to gather and send back information about the chemical make-up of that remote body.
“It is so cool to see the data coming in,” Hendrix said from her Santa Rosa office, in her typically understated way. “It’s just amazing to learn what Pluto is made of.”
Spectrometers, instruments that measure the intensity of different wavelengths of light, at the turn of the century were generally bulky, benchtop instruments unfit for launching into deep space aboard a lightweight, high speed spacecraft. The unique filter technology Karen’s group developed allowed the spectrometer to shrink to about the size of a golf ball, but it had never been proven in space before. On top of that, NASA’s project leader wanted this particular spectrometer to perform better than any Karen’s team had designed before. In other words, NASA wanted something that had yet to exist.
“It was quite a challenge in many ways,” Karen quipped with a smile.
So for two years, from 2002 to 2004, Karen co-led a team of colleagues and, along with partners at NASA, designed, fabricated, tested, redesigned and re-tested multiple iterations of filters before getting it just right. They designed a “linear variable filter,” or LVF, that turned NASA’s miniature optical sensor into a spectrometer. This filter was actually an assembly of two high-precision LVFs to enable NASA scientists unprecedented sensitivity in analyzing the chemistry of dwarf planet Pluto. In 2004, the team shipped the final parts to NASA and began the long wait.
On Jan. 19, 2006, New Horizons took to the sky from Cape Canaveral, FL. NASA and partners had spent the two-year interval integrating and testing all of the spacecraft systems. Two years of testing is actually quite common when performance and reliability are critical – after all, there’s really no service call for a broken spacecraft on its way to the edge of the solar system.
Hendrix’s team’s filters were tucked inside the Linear Etalon Imaging Spectral Array (LEISA) near-infrared imaging spectrometer inside the Ralph telescope, one of seven major instrument packages aboard the spacecraft. Karen and her colleagues had been invited to the launch, but with nothing more precise than a two-week launch window and pressing family obligations, Karen was not able to attend. She watched the launch on TV.
New Horizons was scheduled to rendezvous with distant Pluto nine and a half years later, on July 14, 2015. “Rendezvous” in this case means screaming by Pluto at 30,000 miles an hour, furiously snapping pictures and gathering data with the powerful scientific instruments on board. Almost miraculously, that’s exactly what happened just last month. The Ralph telescope and the LEISA spectrometer performed flawlessly, and New Horizons sped on to continue its scientific mission in the Kuiper Belt beyond little Pluto.
So, what is far-flung Pluto made of? More than one substance, to the surprise of planetary scientists worldwide (see NASA press release below). Methane ice, as expected, covers most of the surface, but large areas of the planet, including the north polar cap, are coated with nitrogen ice – without any obvious explanation. This is a puzzle scientists will be working on for years to come, thanks to the LEISA instrument and the unique spectral filters developed by Karen and her colleagues.
And Hendrix – what puzzles will she be working on?
“We’re still working a lot with NASA and JPL,” she said. “In fact, we just shipped a similar – and even more sophisticated – filter for the OSIRIS-REx mission to asteroid 101955 Bennu. That will launch next year, arrive at the asteroid and gather up samples in 2019, and return to earth in 2023.
“Our filters are key to finding the right place to land on the asteroid in 2019 – only four years away – so that will seem pretty quick!”
Hendrix is also quick to point out that these filters are good for more than space exploration.
“The same types of filters go into our new MicroNIR™ Spectrometer, which our customers are using right here on earth to ensure the quality of food, feed, and pharmaceuticals.”
Those are worthy missions, indeed, and no need to wait.
Pluto: The Ice Plot Thickens – 15 July 2015
http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Planets&IM_ID=20257 The latest spectra from New Horizons Ralph instrument reveal an abundance of methane ice, but with striking differences from place to place across the frozen surface of Pluto. “We just learned that in the north polar cap, methane ice is diluted in a thick, transparent slab of nitrogen ice resulting in strong absorption of infrared light,” said New Horizons co-investigator Will Grundy, Lowell Observatory, Flagstaff, Arizona. In one of the visually dark equatorial patches, the methane ice has shallower infrared absorptions indicative of a very different texture. “The spectrum appears as if the ice is less diluted in nitrogen,” Grundy speculated “or that it has a different texture in that area.” An Earthly example of different textures of a frozen substance: a fluffy bank of clean snow is bright white, but compacted polar ice looks blue. New Horizons’ surface composition team, led by Grundy, has begun the intricate process of analyzing Ralph data to determine the detailed compositions of the distinct regions on Pluto. This is the first detailed image of Pluto from the Linear Etalon Imaging Spectral Array, part of the Ralph instrument on New Horizons. The observations were made at three wavelengths of infrared light, which are invisible to the human eye. In this picture, blue corresponds to light of wavelengths 1.62 to 1.70 micrometers, a channel covering a medium-strong absorption band of methane ice, green (1.97 to 2.05 micrometers) represents a channel where methane ice does not absorb light, and red (2.30 to 2.33 micrometers) is a channel where the light is very heavily absorbed by methane ice. The two areas outlined on Pluto show where Ralph observations obtained the spectral traces at the right. Note that the methane absorptions (notable dips) in the spectrum from the northern region are much deeper than the dips in the spectrum from the dark patch. The Ralph data were obtained by New Horizons on July 12, 2015