Student CubeSat SASSI2 launches today, gathers data for hard science

Today, after over three years in the making, the countdown finally begins for SASSI2—a CubeSat designed, built, and tested by undergraduate students at the University of Illinois and Purdue University. SASSI2 is bolted to the second stage of a Northrop Grumman Antares rocket that will send a Cygnus cargo spacecraft to the International Space Station from NASA’s Wallops Flight Facility on the Eastern Shore of Virginia.

The launch can be watched live today at 4:46 p.m. EDT at Ustream.tv/channel/nasa-tv-wallops.

SASSI2, which stands for Student Aerothermal Spectrometer Satellite of Illinois and Indiana, will be pushed out into space after the primary payload, the Cygus ISS resupply vehicle, separates from the second stage. SASSI2’s mission involves collecting data as it orbits the Earth—data that will be used to help scientists understand more about what happens to the flow of atmospheric gases around vehicles traveling at hypersonic speeds at very high altitudes.

When SASSI2 is first released into space, a timer onboard will tell it to wait for 45 minutes. After that, SASSI2 will boot up its computer and spend the next six hours detumbling, which is not an easy task. In space, there isn’t air to slow the vehicle down, so once it starts spinning, it stays spinning. SASSI2 uses magnetic torquers against the Earth’s magnetic field to create torques to stabilize the spinning satellite.

Sometime before 10 p.m. tonight, SASSI2 is expected to begin communicating with the team on Earth, who, at that point will breathe a collective sigh of relief.

“When we hear from it, we’ll know that it has launched successfully, deployed successfully, booted up and detumbled itself, and entered normal operations mode. At that point, we’ll have run everything except the science instruments,” said Zach Putnam, assistant professor in the Department of Aerospace Engineering at the University of Illinois at Urbana-Champaign, and principal investigator on the project.

Putnam said when SASSI2 is in orbit around the Earth, in addition to transmitting basic health and status, it is equipped with special sensors that will allow it to gather ultraviolet spectra and pressure measurements that will be used for future research projects.

“While the satellite is in the sunlight, it will charge its batteries via its solar panels and record pressure data once every three seconds using the pressure sensors developed by the team at Purdue,” Putnam said. “Once it is eclipsed in Earth’s shadow, it will begin a 35-minute cycle collecting five ultraviolet spectra using a spectrometer on board. When SASSI2 emerges from eclipse into sunlight, it will transmit the spectra and additional pressure sensor data to the science team.”

Although the CubeSat program and this SASSI2 mission is educational at its core and has involved over 30 undergraduate students actively over the past three-plus years, the data collected will be used by scientists and engineers to conduct real research in hypersonic aerothermal chemistry.

According to Putnam, this will be the first time measurements like this have been taken since the mid-1990s. And the first time in space for even longer.

“We know what the atmosphere is made of—primarily nitrogen and oxygen. SASSI2 will travel through the upper atmosphere at orbital velocity, or speeds in excess of 17,000 miles per hour, generating a shock wave in front of the vehicle. When atmospheric molecules pass through the shockwave, they get ripped apart and recombine in different ways,” Putnam said. “The spectra will tell us the number density and relative abundance of the flow in the shock layer formed in front of the CubeSat. In concert, the pressure sensors will provide important context information about the flow properties at very high altitudes.”

The experimental data from SASSI2’s 11-day mission, will be used to create better aerothermal chemistry and radiation models.  

“We’ve simulated what happens in space in terms of flow and the shock waves that are created at high altitude and hypersonic speeds, but with actual data, we’ll be able to validate our computer models,” Putnam said. “And if we can model it better, we can do a better job of designing hypersonic vehicles, heat shields, etc. We’ll have more information and not have to build in such a large margin for error. So, if we could say, cut the mass of the heat shield in half and be just as safe and reliable, that would allow us to use that mass to take other supplies to space.”

Nick Zuiker, SASSI2’s student team lead, started on the project as the payload lead when he was a sophomore. He graduated with his bachelor’s degree last May and is just finishing his first year in a master’s program.

Zuiker said working on the project this past year, in particular, has been intense. “Over the summer, I probably worked on it for about six to 10 hours every day, seven days a week. It’s been a large portion of my life so far and more than half of my time at U of I has been spent on it in some capacity.”  He and AE undergraduate Adam Newhouse drove the three-and-a-half kilogram, or about 8 pounds, satellite out to the launch site at the NASA Wallops Flight Facility in Virginia over spring break.

U of I Professor in the Dept. of Aerospace Engineering Deborah Levin is co-investigator on the project. One of Levin’s former students, Alina Alexeenko, who is now a professor at Purdue University, is also a co-investigator, and designer of the pressure sensors.

SASSI2 is funded by NASA’s Science Mission Directorate through the University Student Instrument Program.