Three UH Engineering undergraduate students are improving NASA’s CubeSat missions by programming the small satellites to orient and stabilize themselves based on the position of the sun.
The code developed by mechanical engineering student Abby Zinecker and electrical and computer engineering students Julia London and Tiffany Yao will solve one of the biggest obstacles to successfully completing CubeSat missions: the inability to stabilize a small satellite after it’s launched into space.
“When CubeSats are launched, at first they’re just tumbling and spinning in space,” said London. “They need to stabilize before they can take readings and collect data.”
With standard-sized satellites, the angular velocity, or the direction and speed of the spinning satellite, is often calculated using a device called an accelerometer. But the added weight and power requirements of these devices render them impractical for use in CubeSats.
The size, weight and power constraints of CubeSats drove the innovation process for Zinecker, London and Yao. Their goal was to develop an alternative method for calculating angular velocity in CubeSats without increasing its size, weight or power consumption. To achieve their mission, the undergrads had to find cost-effective ways to use and repurpose the components of a standard CubeSat to execute tasks more efficiently and perform altogether new functions.
CubeSats are made up of 4x4x4 inch cubes called units and can be as small as one unit (1U) or as large as six units (6U). Each unit weighs approximately 3 pounds and is covered in solar panels for energy collection. Once the solar energy is collected, it is stored in batteries inside the satellite. The entire process is managed by a microprocessor, which serves as the “brain” of the satellite.
Under the guidance of Len Trombetta, the associate chair of the Cullen College’s electrical and computer engineering (ECE) department, and Steve Provence, a NASA engineer and alumnus of the Cullen College’s ECE department, the team wrote code that employs a CubeSat’s built-in solar panels and microprocessor to orient the satellite according to a light source, such as the sun, and stabilize the satellite in space by determining its angular velocity.
The model simulated the CubeSat’s rotation using servomotors – a small, energy-efficient motor often used in robotic and industrial applications – and was lined with clear acrylic walls to make the internal wiring and microprocessor visible. The students said that being able to see the internal components proved invaluable throughout the design process.
“We could see how everything connected, which was really helpful for debugging and testing,” said Zinecker.
With the team’s code, CubeSats can be stabilized after launch by using the sun as a reference point to determine its location and calculating the satellite’s angular velocity.
“Calculating the angular velocity is important because we have to find out how fast the satellite is going to be able to accurately reverse the spin and slow it down,” said Yao.
The team built the CubeSat model during the fall 2015 semester and spent the following spring semester fine-tuning the algorithms and formulas used in the code. While many engineering projects can have clearly defined solutions, Zinecker, London and Yao said they encountered several challenges during this project unique to the complex and creative process of coding.
“Coding is a lot like painting or drawing, because it’s never quite done,” said London. “It’s always evolving.”
But the project also provided unique rewards. The ability to determine angular velocity in a CubeSat is a challenge currently faced by NASA and others interested in the small satellites. With their code, the team provided a novel and practical solution to a current, real world challenge.
“My favorite part of this project is knowing that we were able to accomplish something new,” said Zinecker.
To further the potential application of their code, the team created a user interface designed so that both engineers and non-engineers could interpret the data.
“We wanted to make something with a very user-friendly display, so that anyone with a computer could open the interface and easily read the data collected from satellites,” said Yao.
The team presented the CubeSat model, code and user interface at the Graduate Research and Capstone Design Conference, hosted by the ECE department on April 29, 2016.