World calibration expert ready for a new focus

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BROOKINGS – Young faculty member Dennis Helder visited the office of fellow electrical engineering instructor Bob Finch in 1986 and saw the book, “Digital Image Processing.”

Helder browsed it, was captured by figures showing how blurry images could be corrected, and the spark to ignite a career-shaping fire had been lit. Helder, who grew up on a Canton farm, had only been on the South Dakota State University faculty three years after earning degrees in animal science (1979) and electrical engineering (1980), working as a cellphone designer, giving farming a try and earning a master’s degree (1985).

His first role on the faculty was as a graduate assistant working on an electrical tractor. 

“I asked Dr. (Virgil) Ellerbruch, (head of electrical engineering), if I could teach a class to see if I liked it.” He was assigned EE211, the foundation circuits class, not as a lab instructor but as classroom teacher. “I found I really liked teaching,” said Helder, who retired from his duties at South Dakota State University Friday.

Counting time spent as a graduate assistant, the distinguished professor and associate dean of research retired after 35 years as a South Dakota State employee.

His teaching impact was profound.

Cory Mettler, who has been lecturing in the electronic engineering program for 16 years, recalls taking Helder’s signals class in 2000, which motivated him to take Helder’s digital imaging class the next year, which sent him on to graduate school and his current position.

“It’s immediately apparent he is passionate about the material and he cares about the students learning the material – and he’s fun,” Mettler said. He added that Helder’s most important influence on him as a teacher is “showing the students that you care that they succeed.”

A book that changed his life

Back in 1987, Helder realized if he was going to make education a career, he needed to have a doctorate. South Dakota State didn’t offer a doctorate in electrical engineering then. Helder was commuting to campus from De Smet, where he continued to farm part time. Going to graduate school in those pre-internet days made location the primary criteria.

“I went somewhere close because I still had a soybean field that needed harvesting,” Helder said of his selection of North Dakota State University.

In fall 1988, when he was in need of a dissertation topic, digital image restoration was still on his mind. Engineering research associate Mary DeVries O’Neill gave him the name of a person at EROS (Earth Resources Observation and Science Center) who might be of help.

A lady that changed his career

That person, June Thormodsgaard, was the image mapping and research development section leader. She gave Helder a problem that neither NASA nor EROS could fix.

She recalls their first meeting:

“I’m sitting at my desk. All of sudden there’s this lanky body that fills up my entire door. He said he is from Canton, which is my hometown and that he was looking for a dissertation topic. It was just then that the Landsat Thematic Mapper had started dropping scan lines. We were looking for a fix. There were people around the world that hadn’t been able to correct it.

“Dennis was definitely an electrical engineer … Gee, I thought maybe he could find an approach to fill in these missing lines.”

She introduced him to her staff and checked on Helder with a university research leader, but she didn’t thoroughly investigate this stranger. “He just struck me as somebody I could trust,” Thormodsgard said.

Helder proved himself not only trustworthy but also bright. Using a university computer, he figured out an algorithm to remove lines, or bands, from satellite images of the Earth that were created by the camera. A bound copy of “Debanding Thematic Mapper Imagery,” Helder’s dissertation, is still on his bookshelf as is Finch’s copy of “Digital Image Processing.”

So happy was Thormodsgard with Helder’s work that she sent another assignment his way in about 1990. An unspecified client needed an algorithm to fix satellite images of Saudi Arabia. When the first Gulf War broke out, Helder realized his work had helped the Department of Defense.

“I owe most of my career to that lady,” Helder said.

15 minutes that netted 15 years

Meanwhile, the now-retired Thormodsgard said, “It’s a small, narrow group of people that have the expertise Dennis has. He didn’t need anybody. He just needed his hard work and his mathematical brain.”

In 1992, Helder did a summer fellowship for NASA in Washington, D.C. The assistant professor from the overlooked college on the Great Plains explained his research to a skeptical, popcorn-munching supervisor. John Barker spent 15 minutes telling Helder why his project wouldn’t work. Helder listened and went back to his cubicle.

He returned with a project that could successfully calibrate satellite images and made Barker a believer in Helder’s work.

“I did 10 years’ worth of work based on one afternoon’s discussion.” When Barker retired, the bureaucrat’s supervisor assigned all of Barker’s research funds to Helder. “I’ve been running my lab, in part, on John Barker’s money for 15 years. EROS and NASA have funded our research for decades,” Helder said of the image processing lab’s primary funders.

‘One of top guys in the world’

Through the years, Helder has been the primary investigator on dozens of research projects. He has received grant funding of more than $25 million. The topics include development of ethanol-based aviation gas, alternative power technologies and aviation electronics. But his favorite roots back to what he saw in Bob Finch’s book in 1986 – image restoration.

It’s called radiometry. As Helder explains it, “Radiometric calibration turns pretty pictures into quantitative data sets.”

“I’m one of the top guys in the world” in radiometry, he asserts. The humble scientist quickly adds, “There’s a whole 12 of us.”

Tarps changed how we see the world

Another major advancement in the image processing lab’s stature came following a 1998 visit by Helder to NASA’s Stennis Space Center in Mississippi. Soon afterward, he got a call from Lockheed Martin, a company contracting research work with NASA, to develop techniques to measure the amount of blurring in satellite images. “They hired us to do that,” he said.

To calculate the modulation transfer function (MTF), a measurement of blur in satellite images, Helder’s lab developed ways to measure that based on test images.

“We became world leaders in this,” Helder said. It involved a crew of 12 students staking black, white and blue tarps as well as 20 convex, 1-meter mirrors laid out on the open field at the south end of Brookings. After passing satellites captured the image, the crew would tear down the odd sight off 22ndAvenue.

The mirrors allowed the researchers to produce a two-dimensional measurement. “We perfected the tarp method. We came up with methods of perfecting the edge reconstruction,” Helder said.

One claim to fame for the lab is that it calibrated the images taken by the QuickBird and Worldview satellites, which was operated by DigitalGlobe. The firms’ images are used extensively in Google Earth.

Created world-renowned lab

Larry Leigh, who succeeded Helder as director of the image processing lab, was a graduate research assistant in 2001, when he started doing vicarious calibration field work for the lab. He was brought on as a full-time staff member of the image processing lab in 2005 and has been the day-to-day leader in the lab since 2016.

Because of the image processing lab’s worldwide standing in vicarious calibration, he has traipsed through a salt lake in central Turkey and the Algodones Dunes Desert to take reflectance measurements used for calibration.

Leigh said, “Dennis had a big influence on me, and as a mechanical engineer, he brought me into a career path I would have never thought possible. Through Dr. Helder, the IP Lab is world-renowned for its capability to perform on-orbit calibration. To think, it all started with Dr. Helder in the late ’90s, that a little lab in the middle of South Dakota, has calibrated satellites not only locally with USGS, but nationally and internationally as well.  

“This is due to the vision and the leadership Dr. Helder brought to the table, and thanks to his mentoring, it provided me an opportunity to work in aerospace in a very challenging and ever-changing field, while being able to stay local in South Dakota.”

The kings of calibration

Helder said there are three major image processing labs that work in the field of satellite radiometric calibration – the University of Arizona, Rochester Institute of Technology and SDSU, which specializes in calibration using vegetative surfaces.

“Our guys are experts at it. People who use the data want to see calibration over vegetation because the most interesting areas of the Earth are vegetated,” Helder said.

“We’ve also become the world leader in PICS (pseudo and invariant calibration sites) based calibration of satellite imagery that uses invariant desert sites throughout the world to convert each pixel in a satellite image to a physical unit of energy. We’ve been working closely with the French government calibration group to set the standards for PICS calibration. 

“Morakot Kaewmanee (SDSU imaging engineer) has clearly become the leading person in the world on what you can do with PICS these days,” Helder said.

Guiding hand behind Daktronics Engineering Hall

The lab is located on the top floor of Daktronics Engineering Hall, its home for the last 10 years and light years better than when it was in Harding Hall, a former dormitory. 

Helder, then head of the Department of Electrical Engineering and Computer Science, remembers attending a meeting June 19, 2006, with the SDSU Foundation, then-Dean Lew Brown and university benefactors Al Kurtenbach, Van Fishback and Jerry Lohr, who would become the namesake of the college. After the meeting, Brown and Helder asked one another, “Did we just get a new building?”

They had. Faculty moved into what was initially called the Electrical Engineering and Computer Science Building during a sleet storm March 6, 2009, and dedicated it on sunny May 1. It was the first new instructional building erected on campus since 1993.

The June 19, 2006, and March 6, 2009, dates are on a simple, framed sheet of paper in Helder’s office. Between those dates Helder put in seemingly endless hours in overseeing planning and construction.

“My job was to make sure the building worked for the department. I had to work with architects, engineers, the construction team, campus administration, Dean Kattelmann (campus facilities director), state engineers. I worked with everybody day after day after day. It had to be right,” Helder said.

Only director of Office of Engineering Research

Helder estimates he spent 50 percent of his time in his role as associate dean of research, a position he has held since the Office of Engineering Research was founded May 22, 2010.

During nearly a decade in operation, “We have provided a capability for the faculty that they never had before for getting proposals out the door. Since this office has started, we’ve never missed a deadline for grant proposals.

“Jessica Andrews – she does more of the tactical stuff. I do more of the strategic stuff. Tammy (Loban) does a terrific job keeping the office running and all the budgets in order,” Helder said of the three-person office.

The associate dean for research is being filled on an acting basis by Steve Gent, an associate professor in mechanical engineering. 

What does the future hold?

As for Helder, who turns 62 July 15, he will be camping at Custer State Park June 24 as he has scheduled a week of hiking with his 15-year-old grandson. He also enjoys shooting, hunting, portrait photography and is an amateur magician for his 10 grandchildren. He also is considering working part time in the calibration field.

In addition, Helder is committed through August on an elite team that is crafting what the next version of NASA’s Landsat satellite should be like.

“I’ve really been blessed to work at SDSU for 35 years doing what I enjoy and being surrounded by great people who also are passionate about what they do.”