A Low-Cost Photodiode Sun Sensor for CubeSat and Planetary Microrover

This paper presents the development of low-cost methodologies to determine the attitude of a small, CubeSat-class satellite and a microrover relative to the sun's direction. The use of commercial hardware and simple embedded designs has become an effective path for university programs to put experimental payloads in space for minimal cost, and the development of sensors for attitude and heading determination is often a critical part. The development of two compact and efficient but simple coarse sun sensor methodologies is presented in this research. A direct measurement of the solar angle uses a photodiode array sensor and slit mask. Another estimation of the solar angle uses current measurements from orthogonal arrays of solar cells. The two methodologies are tested and compared on ground hardware. Testing results show that coarse sun sensing is efficient even with minimal processing and complexity of design for satellite attitude determination systems and rover navigation systems. 1. Introduction One of the key problems in the development of attitude determination and control systems (ADCS) for small satellites is the use of attitude sensors small enough and efficient enough to fit within mass and power budgets. One of the simplest and most common sensors for attitude determination is the sun sensor [1], which measures the angle of incident light from the sun with respect to an inertial body frame. Both single-axis and dual-axis sensors are available, though a dual-axis sensor can be constructed from two compact single-axis sensors, resulting in lower component costs and processing requirements [2, 3]. In other sun sensor applications, both CCD and CMOS technology have been used to achieve fine pointing accuracy [4, 5], and software methods can be used to increase the accuracy of a sensor [6]. Although several embedded sun sensors for nanosatellite ADCS hardware are now available, it is desirable in many nanosatellite development programs to develop the sun sensors in-house using commercial off-the-shelf (COTS) hardware [7], both for reasons of cost and to increase the potential for further research within their own program. Sun sensors are also used on planetary rovers when other sensors such as magnetometers or GPS receivers are not sufficient. Measuring solar angles with a sun sensor is a good way of estimating absolute orientation [8–10]. Typical requirements include an accuracy on the order of 1 degree and a field of view of 30 degrees or 60 degrees [11]. Wide-field-of-view sun sensors [12] suitable for use on CubeSat and microrover platforms