SOS: CubeSat Solar Sensor

In Brief

A group at the University of Maryland Baltimore County (UMBC) and NASA's Goddard SFC are developing a cloud-imaging CubeSat would like to investigate the feasibility of multiple types of sun sensors for maintaining the orientation of the satellite.

The CubeSat

Cloud CubeSat Illustration
The Cloud CubeSat
Image courtesty Goddard SFC.
A CubeSat is a small (30x30x10 cm - about the size of a loaf of bread) satellite designed to be modular and relatively inexpensive to launch. The CubeSat in development by a team at the NASA Goddard SFC Climate and Radiation Branch is designed to produce images of cloud structure from space. By comparing the reflectance of two wavelengths of light, information can be obtained about the ratio of water to ice in various regions of the cloud. These profiles can be important in studying the behaviors of clouds and their interactions with aerosols and pollutants.

The Sun Sensor

In order to generate side profiles of clouds, the Cloud CubeSat must be oriented between a 45 and 70 degree angle to the Earth's normal. Therefore, accurate alignment and determination of angular position is important for analyzing the images produced by the Cloud CubeSat. One of the most accurate methods for determining a spacecraft's orentation involves use of a sun sensor, which finds a satellite's orientation with respect to the sun.

The majority of satellites launched into Earth orbit have some type of sun sensor system installed. Multiple sun sensor technologies exist, though recent systems have tended toward use of digital pinhole cameras. By using an algorithm to detect an image of the sun on the CMOS sensor, an orientation can be calculated. The Olin-NASA team evaluated other sun sensor technologies to determine feasibility and effectiveness for application in the Cloud CubeSat. In conjunction with the Attitude Control System on board the satellite, the Cloud CubeSat could be oriented towards the Earth at a desired angle.