ASU Research E-Magazine: Homework in the Sky

ASU students learn the gritty details of the space program as they design, build, and launch ASUSat 1, a tiny, ten pound satellite.

Astronaut William Gregory may have surprised a group of Arizona State University students when he told them about his on-board duties once he piloted the space shuttle Endeavour into orbit last March.

“My most important job was to keep the toilet working,” Gregory said. He also maneuvered the shuttle about 200 times, tended to two secondary payloads, made the meals for the group on his shift, and cleaned the windows.

Gregory’s comments during a visit to main campus last April reflect the gritty details of real-life experience. The students he talked with are designing and building a satellite to be called ASUSat 1. More than 150 students are participating in the project. Each of them is learning something about gritty details, as well.

“It’s not just a paper design project. It’s actually going to be launched,” says ASUSat 1 program manager Joel Rademacher.

Most satellites weigh thousands of pounds and cost millions of dollars. At 10 pounds, ASUSat 1 will be the world’s smallest satellite to do meaningful science. The device will carry a price tag to match: about $300,000, including launch costs.

Orbital Sciences Corporation of Chandler, Ariz., will launch the minisatellite as a secondary payload in March 1997. The completed ASUSat 1 will be loaded into an OSC Pegasus rocket ahead of the primary payload.

The ASU mission was the brainchild of Scott Webster, OSC’s co-founder and president of its Space Data Division in Chandler. Webster proposed the idea in the fall 1993 semester after Rademacher and Helen Reed, director of ASU’s Aerospace Research Center, asked him to collaborate on a project relevant to his company.

Since then, more than a dozen other Phoenix-area companies have added their assistance, including Honeywell, Motorola, and Intel. Additional support comes from the NASA Space Grant Program, the National Science Foundation, the AMSAT Organization, and the Jet Propulsion Laboratory.

The companies have donated their time to the project, along with equipment and test facilities. The engineers at Honeywell’s Satellite Systems Operation in Glendale have been especially generous with their time. Six Honeywell engineers, for example, attended the half-day design review on campus in May 1994. Honeywell engineers have also spent hours meeting privately with ASUSat 1 students to discuss design issues.

“They have an ambitious list of experiments using some advanced technology that hasn’t, to my knowledge, been used before on satellites,” says Richard Van Riper, a Honeywell engineering manager.

The commercial interests of Honeywell’s Satellite Systems Operation cover all 11 of ASUSat 1’s subsystems to some extent.

“We’re always interested in new things for satellites and the trend toward smaller satellites. This is going to the extreme of small satellites,” Van Riper adds.

The idea of putting a 10-pound working satellite into space is so extreme, Honeywell’s engineers laughed the first time they heard it. But they soon became intrigued.

“The engineers at these companies are puzzled by this problem,” says Jordi Puig-Suari, an ASUSat 1 faculty adviser. Engineers usually start with a well-defined mission and then design a satellite to support it. But ASU was told, “Here’s 10 pounds. Do as much as you can.”

About 30 local industry engineers showed up to trouble-shoot at each of ASUSat 1’s four formal design reviews over the past 18 months. Each review lasted from four to eight hours as program manager Rademacher and the subsystems team leaders presented their designs.

The industry group’s advice and criticisms have guided the satellite’s development nearly every step of the way. “We couldn’t do it without your experience,” Rademacher told the group after one of the design reviews.

The students actually have designed two satellites since the project’s first meeting on Oct. 13, 1993. At the first design review, the students ambitiously proposed two experiments for their tiny satellite. They envisioned collecting data for two years on atmospheric ultraviolet radiation that interferes with radio communications, and recording the amount of space debris the satellite encountered.

But the early designs called for heavy instruments that would require a lot of power. The team quickly jettisoned the ultraviolet radiation experiment. The move saved at least 2 pounds.

The satellite’s exact orbit remained to be determined, but the students knew it would fly lower than most satellites. Telstar 1, an American communication satellite launched in 1962, orbits at an altitude of 600 miles, for example. The Hubble Space Telescope circles the Earth about 380 miles high.

The original plans assumed that ASUSat 1 would achieve an orbital altitude of about 280 miles. OSC dropped the orbital altitude to about 200 miles in early April.

The new altitude led to some design changes. Oxygen atoms would have destroyed the satellite’s space-debris detectors at the lower altitude. The main goal then was to study the ionosphere, the part of Earth’s atmosphere composed largely of plasma, an electrically charged gas.

The latest plans call for an orbital altitude of 341 miles. The goals now are to prove several innovative student-designed attitude determination sensors and use a commercial Global Positioning System to determine the satellite’s orbital lifetime. The satellite also will carry two cameras to take pictures of the Earth from orbit.

“I think the science is very impressive,” says Jan King, the former vice president of OSC’s Boulder, Colo., operations. “The kind of science/engineering experiments that the students are trying to do are very useful.”

King says that low-altitude and low-cost spacecraft technology has been little explored.

“To be able to use the plasma to do various engineering functions on board is a novel idea,” he explains. “It does have to be proven, but I think there are some sound things going on there. I think the ASU students will have a lot of fun with this.”

As a founder of AMSAT, King also has an interest in ASUSat 1’s voice-repeater capability. As long as power is available, the satellite will provide nearly continuous service to the amateur radio community throughout its projected 2-year lifetime.

“We’re hoping we only have to turn that off during the short periods while we’re communicating with the ground station here at ASU,” says deputy program manager David Staggers, a graduate student in mechanical and aerospace engineering.

The students have packed everything from the exotic to the mundane into their design. A $58,000 gallium-arsenide solar array will help power the satellite, while segments of carpenter’s measuring tape will service as on-board antennas.

“We’re using commercial components as much as possible because space-rated components are typically very expensive,” Staggers says.

The satellite itself will be a 14-sided structure measuring 9 inches tall by a foot in diameter with solar panels mounted on the side. Constructed of a carbon fiber and epoxy resin composite, the device will be extremely thin—just three hundredths of an inch thick.

“It’s very thin, but the strength is extremely high,” says Chris Michaelis, formerly the structures subsystem team leader. “It’s one of the best materials you can use right now for space structures.”

Most satellites are made of aluminum, but aluminum would have been too heavy for ASUSat 1. “With our 10-pound weight budget, we realized we could not build an aluminum structure no matter how thin," Michaelis says.

The challenges of building ASUSat 1 sounded quite familiar to Wesley Huntress, NASA’s associate administrator for space science. Huntress visited ASU the same day as astronaut William Gregory in connection with a conference on NASA-funded undergraduate research.

Huntress learned that ASU students were given 26 months and a budget of $300,000 to deliver a 10-pound satellite. In recent years, NASA has unveiled a new class of smaller, faster, cheaper planetary probes.

The goal of the program was to reduce development time to less than three years, and mission costs to less than $150 million. NASA’s planetary programs normally require at least a decade and hundreds of millions of dollars for development.

Huntress visited the main campus on April 7, the day after the ASUSat 1 team learned they would need to deliver the product in August—five months earlier than previously scheduled. All the design reviews were over. Construction was ready to begin.

“So you’re going to build this baby in six months?” Huntress asked.

“Three months,” replied Joel Rademacher.

Huntress: “I’m impressed.”—Steve Koppes