Sun Sensor Design Project


My name is Anna Cruz and I am Mechanical Engineering major and rising sophomore at The College of New Jersey (TCNJ). This summer I was given the opportunity to work at Princeton Satellite Systems (PSS) as their engineering intern. The most recent project I have been working on is the mechanical design and 3D model of the sun sensor that will be made using a 3D printer. All the models I have created were done using SolidWorks. I have been working alongside my coworker Gary, and manager of the project Mike that have done a wonderful job in giving me helpful tips when I needed it the most.

Figure 1.1

This sun sensor will fly on a CubeSat or small spacecraft in low earth orbit. The main body of the sensor has a pyramid shape with a solar cell on each side. I had already been given a drawing and STEP file of the circuit board that will be attached to the sun sensor so the dimensions for the sensor I am making were based on that single part. To start, I did some research on different sun sensor models to get a sense of how they work. I first needed to figure out how these parts would be assembled. To make it simple, I decided to use 4 screws on each corner to attach the sensor to the circuit board. The base is rectangular with dimensions a bit larger than the circuit board to allow space for the screw clearance holes and room for the screw head as shown in figure 1.1.

Then it was time to design the pyramid itself. I created a pyramid with a flat top and placed it at the center leaving space from each edge of the pyramid to the edge of the rectangular base adjusting the dimensions as needed. The pyramid holds one solar cell on each side. To make sure that the cells fit nice and snug, I added a placeholder feature deep enough to hold the chip. However, after discovering that the solar cell did not have a flat surface and that there was a wire attached to the back and front of the chip, my original design had to change completely! After a few days of trying out new designs and working with Gary to find the best solution, we liked the idea of creating a trench like feature in the middle of the placeholder extruding a bit further into the pyramid. This will accommodate the wire from the back of the solar cell as well as increase the tolerance regarding the location of the wire for each chip. As for the wire coming out the front of the chip, I added a rectangular slot feature next to the placeholder which channels all the way down the pyramid shown in figure 1.2. This will help gather and guide both wires all the way down one channel to the circuit board. There is one channel on each side of the pyramid, a total of 4. Aside from these hollow channels, the entire pyramid is a solid piece.

Figure 1.2

The placeholder for the solar cell is deep enough so that nothing sticks out of the pyramidal faces. This will aid in the application of the glass window on top of each solar cell using a space qualified adhesive. The same adhesive will be used to attach the solar cells to their placeholders.

Because the sun sensor is attached to a spacecraft, there is a high change of reflective light bouncing off the spacecraft and onto the sensors. To prevent this, a lip feature around the pyramid needed to be added. I went along and added an extruded frame like feature surrounding the pyramid leaving a gap between the end of the frame and the end of the pyramid. The outside edge of this feature is perpendicular to the base surface. The inside edge is at about a 50 degree angle from the base surface as shown in the section view in figure 1.3.

Figure 1.3

Since this sun sensor will be used in space, the plan is to do a vacuum test of this part. As of right now, I am currently waiting on the entire part to be printed so that it could be tested. I am very excited to see the final product!