NASA Explores Photophoretic Sensors to Map the 'Ignorosphere'

• NASA's NIAC program is funding research into sensors that float in the "ignorosphere," an atmospheric layer between 30 and 100 km that is too thin for balloons but too dense for long-term satellite orbits.
• The sensors utilize the photophoretic effect, where sunlight creates a temperature differential on the device, generating thrust via gas particle kinetic energy.
• This technology enables low-cost, long-term atmospheric monitoring without the need for heavy batteries or active propulsion.

The Technology

• The sensors are engineered to be transparent on top and dark on the bottom, creating a thermal gradient when exposed to sunlight.
• Gas molecules hitting the warmer bottom surface bounce off with higher kinetic energy, providing the thrust necessary to maintain altitude.
• Designed for intentional degradation in UV light to prevent them from becoming long-term space debris.

Mission Logistics

• Deployment: Sensors are carried to 30 km by balloons or rockets, then autonomously rise to their 90-100 km equilibrium altitude.
• Tracking: To minimize weight and cost, sensors do not carry transmission equipment; instead, orbiting satellites track them by reflecting LIDAR light off the sensors.

Challenges and Future Outlook

• Nighttime: Lack of sunlight causes a drop in altitude during the night, leading to orbital variability.
• Data Processing: Managing LIDAR tracking and data output for thousands of sensors remains a technical hurdle.
• Funding: Currently in Phase I of NIAC development, with potential for future scaling.