Comet ISON Provides Look at Origins of Solar System
Ray Russell is an astronomer.
As a seven year old in 1957, Russell was awestruck by the launch of Sputnik. The pioneering Soviet satellite captured the young boy’s imagination and led him to dream — like many other children of the era — that he would one day become an astronaut. Within that same year, the seven-year-old Russell discovered that his eyesight was 20/400, as opposed to the 20/20 required of pilots and astronauts. With a pragmatism belying his age, Russell immediately decided that he would devote himself to astronomy, figuring that if he couldn’t travel into space, the next best thing would be to study it.
With renewed purpose and dedication to his education, the precocious Russell diligently carried a briefcase to his elementary school classes and took on extracurricular, astronomy-focused science projects in his rural hometowns of Heuvelton and Westville — located close to the Canadian border, deep in the wilds of upstate New York. Though he lived far from New York’s cultural centers, Russell made the most of his towns’ limited resources and continued to progress as a student and as an amateur astronomer. His passion for space and scientific exploration only grew from there, eventually leading him to the State University of New York at Stony Brook, where he earned an undergraduate degree in astronomy. Upon completion of his degree, Russell was accepted into a graduate program at the University of California, San Diego. Then, things got a little bit more difficult.
“I should have taken physics,” says Russell. “I had taken all of the astronomy classes that I could, thinking that it was a good way to prepare for astronomy … bad idea. If you take physics, you can pick up the astronomy, but if you take astronomy it’s tough to pick up the physics.”
At the time, U.C. San Diego didn’t offer a Ph.D. program in astronomy or astrophysics, so Russell was forced to pursue a Ph.D. in physics — a subject he had unintentionally neglected during his years of undergraduate studies. “When I took the first departmental physics exam my first year at UCSD, I failed miserably,” says Russell. “I didn’t have anywhere near the background that I needed. So I booked it. Seven days a week for that whole year, learning everything I possibly could about physics.” Russell devoted himself to physics and performed well in his courses, allowing him to secure valuable time working in observatories and gathering astronomical data.
Arrival at Aerospace and the Comet ISON
After six years in the program, Russell received his Ph.D. and went to work as a postdoctoral fellow at Cornell University where he put five instruments on two NASA airborne observatories in three years. This hardware experience led to his being hired to work at Aerospace in 1981. “My first question to Aerospace was: ‘will I get to do any astronomy when I come here?’” recalls Russell. “And they said: ‘you’ll get to do some and how much you do will depend on how clever you are at finding things that are applicable to both the astronomy and the applied world.’”
Ray Russell has now worked at Aerospace for more than 32 years, and in that time he has consistently explored the intersections of scientific discovery and customer-serving pragmatism. His work is always geared toward the needs of Aerospace customers, but the techniques and technology that he uses are often equally relevant to the scientific community. One of Russell’s most recent projects is a NASA-sponsored effort that involves the compositional analysis of Comet ISON — an unprocessed comet (a comet that has not been heated and cooled by passing close to a star) that emerged from deep space and disintegrated as it passed the sun late last year. ISON is an acronym for International Scientific Optical Network, the facility from which researchers discovered the comet.
For years, Russell and his Aerospace colleagues have been accumulating sets of data on the composition and properties of stars and their dust shells, which are primarily used for the calibration of infrared sensors. By consistently obtaining high-accuracy measurements of the brightness of stars, Aerospace is able to offer its customers a consistently high-quality set of data that can be used to calibrate and characterize the accuracy of their space-based sensors. Russell started working specifically on star measurements for calibration in the early 1990s. In the intervening decades, Russell’s Aerospace team has made significant improvements in the accuracy and reliability of its data sets. The calibration set that Aerospace currently maintains provides data for close to ninety stars and it represents the most comprehensive effort of its kind.
Russell and his Aerospace colleague George Rossano started working with NASA on a very longwave infrared project on the NASA Learjet in the early ’80s. Their work with NASA expanded to the first use of 2D infrared arrays on aircraft for the Army as part of the Kuiper Infrared Technology Experiment (KITE) from 1985 through 1987. Russell and the rest of the Aerospace team later moved on to working with NASA on a project that involved the characterization of Leonid meteors. In 1998, the group flew to Okinawa, Japan, bringing along a midwave infrared imager and a broadband array spectrograph system for measuring the thermal spectrum of the meteors.
“NASA sponsored the trips for the meteor study, which got us into the business of saying that we could make measurements in the field that could help characterize threats to the satellites and thus help protect the satellite constellation,” says Russell. The ability of the Aerospace team to characterize the composition of meteors, stars, and a litany of other objects in space — both manmade and naturally occurring — is incredibly useful for both research scientists and organizations with valuable spacecraft on orbit.
How it Works
Russell and his Aerospace colleagues use a number of techniques to measure and characterize the composition of stars and other objects in space. In the case of Comet ISON, the Broadband Array Spectrograph System (BASS – created by John Hackwell and David Warren in the late ’80s) was used to gather the infrared data. The BASS is a metal cylinder with two cans inside— one holding liquid nitrogen and one holding liquid helium. The helium is incredibly cold— around 4.7 degrees Kelvin— and the nitrogen serves to protect and increase the lifespan of the helium. There are two prisms contained within the BASS, one made of table salt and one made of calcium fluoride. While pointing at the object of interest, the BASS uses its two prisms to spread the infrared spectrum onto two lines of detectors. The detectors are connected to a set of small cooled amplifiers that produce a signal proportional to the amount of light to which a given detector element is exposed. The detectors are each connected to an individual amplifier and the voltages put out by these signal chains are sampled 200 times per second and converted into digital signals in the analog electronics rack. Thus, the raw data are produced.
In early November of 2013, Russell and Daryl Kim traveled to NASA’s Infrared Telescope Facility located atop the dormant Mauna Kea volcano on the island of Hawaii. The Comet ISON had been tracked since its discovery in September of 2012, and the Aerospace team had timed its observational trip to coincide with ISON’s near approach of the sun. ISON provided a unique opportunity for the Aerospace team to observe and study an object from deep space that may be about 4 billion years old and had been traveling on its lonely course since the earliest days of the solar system.
The composition of a distant comet like ISON has the potential to reveal a great deal about the makeup of the materials that contributed to the formation of the solar system and the process by which comets are formed. Using the BASS, the Aerospace team was able to collect a large amount of data on ISON. Plans had been made to track the comet after it had passed by the sun, but unfortunately, the sun’s heat overwhelmed the comet and ISON had fully disintegrated by Dec. 2.
Though ISON is gone, Aerospace’s November observational trip to Mauna Kea produced unique spectroscopic data, and at first glance, it appears there will be some interesting and unexpected results in the months to come.
“We were actually able to get the shape of the comet’s spectrum and we were able to see a silicate emission feature, but it wasn’t a very strong emission feature,” says Russell. “The weird thing is, although we need to do more analysis on the data, at first blush, quick-look reductions say there was actually some crystalline material there.” The finding of crystalline material in a first-time comet would lend credibility to the notion that there was an unknown process of particle flow and mixing in the early solar system that brought amorphous grains from the outer reaches of the solar system closer to the sun, which resulted in some of the grains being converted to a crystalline form — which requires a fairly high temperature and thus usually only occurs near stars. This mix of grains then travelled back into cold, deep space where comets like ISON were formed.
ISON’s data will live on, well past the life of the actual comet, and the record it left behind might very well increase our understanding about the nature and mechanics of our solar system. Russell will continue to hone his processes and utilize the infrared to glean more information about the composition of planets, stars, comets, and other celestial bodies. His work lies not just in the acquisition of new information, but in the understanding of age-old properties that govern the vast expanses of space.
ISON may have traveled for an eternity, only to appear to us as an ephemeral streak of light in the night’s sky, but its disintegration merely represents the end of its physical journey. After a multi-billion year voyage through deep space, ISON’s next phase of life is just beginning — among the scientists and astronomers here on planet Earth.