Sun Sensor
Coarse + Fine Sun Sensors for Sun-Pointing
A sun sensor is an electro-optical navigation instrument combining a wide-field photodiode array with a masked quadrant detector to provide sun-vector references for solar array pointing and attitude backup. Consuming 1 W with a mass of 1 kg, the unit covers a 180-degree field of view and provides a fine-pointing accuracy of 0.05 degrees. Lunar surface operations require tracking the sun's slow apparent motion of approximately 0.5 degrees per hour across a 25-year operating life, while radiation necessitates radiation-tolerant silicon photodiodes, quartz masks, and hardened electronics to maintain a 200,000-hour mean time between failures.
Coarse (sun-presence) and fine (sub-degree) sun sensors providing sun-vector reference for solar array pointing and attitude backup.
Purpose
Coarse (sun-presence) and fine (sub-degree) sun sensors providing sun-vector reference for solar array pointing and attitude backup.
Context
Child of L2-NAV-REF within the Lunar Ark system
Principles
- ▸Coarse sun sensor: photodiode array with cosine response
- ▸Fine sun sensor: quadrant detector with mask
- ▸<0.1 degree fine accuracy
- ▸Always-on solar reference
- ▸Long-life solid-state (no moving parts)
Typical implementations
- ▸NASA standard sun sensor heritage
- ▸Adcole sun sensors (commercial)
- ▸Mars rover sun sensors
Lunar considerations
- ▸Lunar day available 50% of time (more at peaks of eternal light)
- ▸Sun motion ~0.5 deg/hr drives slow tracking
- ▸Rad-tolerant photodiodes
Specifications
Functional
| primary function | Coarse (sun-presence) and fine (sub-degree) sun sensors providing sun-vector reference for solar array pointing and attitude backup. |
| accuracy deg fine | 0.05 |
| fov deg | 180 |
Physical
| mass kg | 1 |
| materials | Silicon photodiodes, Quartz mask, Rad-tolerant electronics |
| vacuum compatibility | True |
Operational
| power consumption w | 1 |
| thermal range c | -40, 70 |
| lifetime years | 25 |
| mtbf hours | 200000 |
Interfaces
Provides
- Sun vector for solar array tracking
- Coarse attitude reference
Requires
- Sensor electronics (~1 W)
Cite this entry
Lunar Ark Codex. "Sun Sensor" (L3-NAV-REF-SUN). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-NAV-REF-SUN
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.