Daytime Infrared Satellite Imaging via Cryogenic Cooling
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Solution Overview
Problem
Current optical telescopes in the Space Surveillance Network are limited by their inability to operate effectively during daylight due to increased system noise and camera saturation, which reduces their ability to detect faint geosynchronous Earth orbit (GEO) satellites, and existing radar systems lack full global coverage and are expensive to maintain.
Innovation Solution
The development of cameras and telescopes that utilize cold traps to suppress infrared background noise and employ a shift and stare technique combined with interactive background subtraction to improve the signal-to-noise ratio, enabling continuous day and night operations and extending infrared sensor technology for enhanced space situational awareness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If optical telescopes operate during daylight to provide continuous coverage, then observation coverage is improved, but system noise increases and detection capability deteriorates
Solution Approach 1:
The patent changes the operational parameters by using infrared detection in the 3-5 micrometer wavelength range during daylight, combined with cryogenic cooling of detectors to 77K and cold stopping to reduce thermal background. This parameter change enables daytime operation by shifting from visible to infrared spectrum where the signal-to-noise ratio is improved despite daylight conditions.
Solution Approach 2:
The patent converts the harmful thermal background radiation from the daytime environment into a manageable parameter through cryogenic cooling. By cooling the detectors and optical components to 77K, the system reduces its own thermal emission to below the sky background, effectively using the cold temperature to filter out the harmful thermal noise that would otherwise prevent daytime operation.
2Measurement precision
If exposure time is increased to detect faint GEO satellites, then detection capability is improved, but camera saturation occurs during daylight
Solution Approach 1:
The patent changes the detection parameter from visible light to infrared wavelengths (3-5 micrometers) where GEO satellites have stronger thermal signatures. This wavelength shift allows longer integration times during daylight because the infrared signal from satellites is stronger relative to the background, enabling detection of faint objects without saturation.
Solution Approach 2:
The patent introduces cryogenic cooling as an intermediary mechanism between the detector and the thermal background. By cooling the detector to 77K, it creates a thermal barrier that reduces the detector's own noise contribution, allowing longer exposure times to accumulate signal from faint satellites without the camera saturating from thermal noise or daylight background.
3Measurement precision
If radar systems are used to detect GEO satellites during daylight, then detection capability is improved, but operational cost increases
Solution Approach 1:
The patent replaces the mechanical radar system with an optical/infrared detection system. Instead of using radio waves and active transmission, the system uses passive infrared detection of thermal radiation from satellites. This substitution eliminates the need for high-power transmitters and complex radar infrastructure, significantly reducing operational costs while maintaining detection capability during daylight.
Solution Approach 2:
The patent enables satellites to serve as their own signal sources by detecting their natural thermal infrared radiation in the 3-5 micrometer range. This self-service approach eliminates the need for active radar transmission and reception, allowing continuous daytime operation with minimal energy consumption and operational cost.
4Measurement precision
If cryogenic cooling is applied to reduce thermal background, then signal-to-noise ratio is improved, but system complexity increases
Solution Approach 1:
The patent uses phase transition cooling (liquid nitrogen evaporation at 77K) to cool the detectors and optical components. This phase transition provides a simple, reliable cooling mechanism that achieves the necessary temperature reduction without complex mechanical refrigeration systems. The latent heat of vaporization efficiently removes thermal energy from the system.
Solution Approach 2:
The patent uses liquid nitrogen as a disposable cooling medium that is replenished periodically. This approach is simpler and more cost-effective than installing and maintaining complex mechanical refrigeration systems. The liquid nitrogen provides reliable cryogenic cooling for extended periods before requiring replacement, reducing system complexity while maintaining the necessary low temperatures for infrared detection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides a system that is over 100 times more sensitive than current systems, enabling persistent 24/7 coverage of the GEO belt, improving detection capabilities, and reducing the need for costly radar systems while providing timely and precise data for space object tracking and surveillance.
Implementation Method 1
This invention explicitly suppresses the background infrared contribution from telescope and camera optics
Implementation Method 2
The development of cameras and telescopes that utilize cold traps to suppress infrared background noise
Implementation Method 3
extending infrared sensor technology for enhanced space situational awareness
Implementation Method 4
The invention provides cameras and telescopes that suppress through the use of cold traps infrared background from telescopes and optics, as seen by the infrared detectors
Implementation Method 5
Interactive background subtraction combined with shifting and adding to remove background noise improves the signal to noise ratio
Data Source
AI summary
GEO satellites and other space objects are studied in daylight, twilight and at night using IR cameras in clusters of no more than three with programs for pointing the instruments at known locations of the GEO objects and satellites and receiving weak near IR signals. Detection instruments have minimal optical surfaces and simple optical paths directing IR through Kshort and combined Kshort and H near IR band filters in cryogenic assemblies. Large focal ratios and large apertures reduce the effect of sky brightness, lower noise and improve the target signal, increasing the noise to signal ratio. Sky background noise is reduced by co-adding hundreds of pixels, allowing for the faint IR signal integration of one second or more. Results are read after integration.