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CubeRRT mission ends, its impact on Earth science continues

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November 30, 2020

For the past two and a half years, The Ohio State University’s first satellite, CubeRRT, has orbited our sphere thousands of time, while transmitting back vital data for Earth climate scientists. 

On Nov. 26, CubeRRT officially became the first of NASA’s group of shoebox-sized, constellation satellites launched in May 2018 to re-enter the Earth’s atmosphere. 

As Joel Johnson explains, an Ohio State professor of electrical and computer engineering, Sustainability Institute affiliated faculty member and principal investigator on the mission, re-entry means the CubeRRT spacecraft disintegrated in Earth's atmosphere, officially ending operations.

While the mission is over, the impact CubeRRT had on Earth science continues.

CubeRRT, an abbreviation of the CubeSat Radiometer Radio Frequency Interference Technology Validation satellite, was launched on May 21, 2018 to the International Space Station, and then deployed into orbit from there on July 13.

Much like its namesake, the 1980s popular video game “Q*bert,” the satellite was projected to fall off its proverbial pyramid at some point. All shoe-box sized satellites deployed from the International Space Station are destined for re-entry.

Johnson said that by October of 2018, CubeRRT had accomplished its mission goals of demonstrating real-time filtering of radio frequency interference aboard the satellite.

The measurements since that time have continued to demonstrate the success of the mission’s approach, he said, increasing confidence in on-board RFI filtering technologies.

CubeRRT was designed to solve a major problem for Earth-observing microwave radiometers by reducing the impact of man-made radio transmissions on measurements of Earth’s properties. 

Johnson said the Earth naturally emits microwave radiation, which scientists study with sensors called microwave radiometers. The data from these sensors helps determine important environmental information like soil moisture, sea temperature, sea ice coverage, weather, and much more.

However, humans make a lot of noise. As the need for wireless services worldwide continues to increase, he said, the growth of manmade radio transmissions is making it increasingly difficult for scientists to detect Earth’s natural microwave radiation. The unwanted man-made signals are called radio frequency interference, or RFI.

Throughout its mission, CubeRRT demonstrated a new capability of onboard RFI removal crucial for future Earth-observing microwave radiometers.

Ohio State’s ElectroScience Laboratory (ESL) led the CubeRRT project in collaboration with team members from NASA Goddard Space Flight Center, NASA Jet Propulsion Laboratory, and Blue Canyon Technologies (BCT). Ohio State ECE Research Associate Professor, Chi-Chih Chen, developed an innovative antenna design for the radiometer to allow for the satellite to perform the necessary measurements.

Ohio State ECE Research Scientist and Sustainability Institute affiliated faculty member Chris Ball said CubeRRT was originally expected to remain operable for approximately one year.

“The continued operation of CubeRRT for more than two years exceeded expectations and allowed for an extended period of data collection,” Ball said. “Because CubeRRT has no propulsion system, its altitude continuously decreased.”

He said the satellite was originally orbiting at approximately 250 miles above Earth.

According to CubeRRT operations engineer Doug Laczkowski of BCT, CubeRRT’s orbit altitude began decreasing rapidly in November.

In total, he said, the CubeRRT satellite made 13,450 trips around the Earth before re-entry.

“Not a bad run,” Laczkowski said.

To highlight Ohio State’s first satellite launch, team members spoke about the mission on NASA videos, as well as at student and public outreach events. Land Grant Brewery of Columbus also released a CubeRRT-themed “extra pale ale” beer in celebration of the Ohio State achievement. 

Some CubeRRT team members kept an unopened can in remembrance of their time on the project.

Johnson said the results of the CubeRRT mission continue to impact the design of future microwave radiometer systems for Earth observations, as indicated by the multiple presentations at the recent Microwave Radiometry 2020 conference focused on including real-time on-board interference suppressing subsystems.

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