High performance immersed VOx Bolometer for spacecraft Earth Horizon Sensor and its reliability studies

High performance and reliable infrared detector are ever-sought in spacecraft attitude determination sensor. The most proven “Earth Horizon sensor” based on the infrared detector operating in the wavelength region of 14-16 μm (CO
₂
atmospheric emission) essentially calls for IR detector performance; high sensitivity ≥400V/W at low operating bias, fast response ≤ 2 ms, NEP~200pw/√Hz and long term durability in compliance with space specific conditions. Even though Optically Immersed Bolometer measuring Earth limb radiation budget @14-16μm wavelength region is widely adopted for the Indian Spacecraft ES applications, the sensor reliability was skeptical owing to the inherent disadvantages of materials used and conventional thick film detector technology. Novel fabrication technology for infrared detector has been developed in LEOS to overcome the issue of on-board reliability while achieving better infrared detector performance suitable for same Earth sensor configuration. Detailed design, material studies and characterization were carried out. Fabricated detectors were subjected to environmental tests according to MIL-STD-883F, MIL-STD-810F and MIL-STD-202F as per the Quality Assurance Plan, and their electro optics performance was evaluated. Finally, in house developed and Qualified Bolometer performance has been verified in the spacecraft ES. The paper provides all its details design to application and its specific performance in Earth Horizon Sensor.