Introduction
Sun sensors are used to determine the direction of the sun from the spacecraft. These can be used for fault detection and recovery.
Key Criteria
- Field of view
- Angular resolution
- Accuracy and stability
- Mass and volume
- Input voltage and power
- Output characteristics
- Durability
Types
There are many types of sun sensors. Some detect whether or not the sun is within the field of view. Others detect the intensity and direction as well. Two of the most common for CubeSats are cosine detectors and quadrant detectors:
Cosine Detectors (Coarse)
- Photocells
- Current is measured and is (roughly) proportional to the cosine of the angle between the sensor boresight and the Sun
- At least 2 in different directions are needed and 4 is ideal
Quadrant Detectors (Fine)
- Sun shines through a window onto photodiodes (2x2 array)
- Current is function of the direction of the sun relative to the sensor
- Can then be used to extrapolate the angle to the sun
Pros
- Sun is easily identifiable
- Cosine detectors are inexpensive, lightweight, simple and reliable
Cons
- Must differentiate sun from moon, sensitive to other reflections
- Sun sensors alone are not sufficient to determine a 3D attitude estimate; another source of attitude information is needed
- Accuracy is typically limited to a few degrees
- Require analog-to-digital converters
Environmental Considerations
- May need temperature corrections
- Radiation hardening
- Tolerance to vibration
- Tolerance to thermal cycling
Component Options
- ISSDX/TX/AX SUN SENSOR (Digital/Coarse sensor)
- MASS SENSOR
- Includes one accelerometer, one magnetometer, and one sun sensor to measure angle of sun-ray, DNI solar radiation and azimuth and elevation position of the device
- Contact for quote
- http://www.solar-mems.com/solar-tracking/
- FINE SUN SENSOR (±50°)
- DIGITAL SUN SENSOR (±64°)
- Lens R&D (Various)
- Coarse/Fine/Cosine Sun Sensors
- NanoSense FSS
- SS200
- FSS-1-G2
- COARSE SUN SENSOR PYRAMID
- Nano-SSOC-A60 analog sun sensor
Links