Integrating Sphere Calibration Device for CubeSat Optical Detectors
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Solution Overview
Problem
Conventional calibration methods for optical detectors, especially in harsh space environments, are expensive, complex, and prone to degradation, making them unsuitable for low-budget small satellites like CubeSats, which require a cost-effective and robust calibration solution.
Innovation Solution
A calibration device featuring a source, diffuser, integrating sphere, and thermal mechanism, with a movable arm and actuator for precise temperature control, providing a compact and durable solution for calibrating optical detectors by emitting electromagnetic radiation that can be adjusted for different wavelengths and temperatures, ensuring accurate calibration while protecting the device from ambient radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional calibration methods using reflective or emissive surfaces are used, then calibration accuracy is achieved, but the calibration surfaces degrade with time in harsh space environments and become prohibitively expensive
Solution Approach 1:
The patent replaces expensive, degradation-prone reflective/emissive surfaces with inexpensive LED light sources and diffusers that can be easily replaced. The LED-based calibration source is significantly cheaper than traditional blackbody radiators or calibrated reflective surfaces, and while LEDs have finite lifetimes, they can be replaced without requiring complex calibration surface maintenance infrastructure.
Solution Approach 2:
The patent uses LED drivers to precisely control the intensity and spectral characteristics of the calibration light source. By varying electrical parameters (current, voltage, pulse width modulation duty cycle), the system can simulate different illumination conditions without requiring physical changes to the calibration source itself, maintaining accuracy while using simple, replaceable components.
2Measurement precision
If conventional calibration equipment is used, then calibration precision is maintained, but the device size and complexity become prohibitively large for small satellites like CubeSats
Solution Approach 1:
The patent divides the calibration function into separate modular components: LED light sources, diffusers, integrating spheres, and control electronics. This segmentation allows each component to be optimized independently and enables compact integration on CubeSats, where space is at a premium. The modular design also facilitates selective deployment and replacement of individual components.
Solution Approach 2:
The patent employs integrating spheres that contain diffusers, which in turn contain or are adjacent to LED arrays. This nested arrangement maximizes the calibration functionality within minimal volume. The integrating sphere acts as a compact enclosure that distributes light uniformly throughout its interior, providing calibration illumination without requiring large external optical paths.
3Measurement precision
If reflective or emissive calibration surfaces are used, then initial calibration accuracy is achieved, but the surfaces require frequent replacement due to degradation in space environment
Solution Approach 1:
The patent accepts that LED sources have finite lifetimes but compensates by making them inexpensive and easily replaceable. Unlike degradation-prone reflective surfaces that require complex maintenance, LED modules can be swapped out as simple electronic components, and their lower cost allows for periodic replacement without significant budget impact.
Solution Approach 2:
The patent incorporates onboard control electronics that can detect LED performance degradation and automatically adjust drive parameters to maintain calibration accuracy throughout the LED's lifetime. This self-compensation extends the effective service life of the calibration source without requiring external intervention or replacement.
4Ease of manufacture
If simple calibration sources are used, then cost is reduced, but achieving precise temperature control and wavelength specificity becomes difficult
Solution Approach 1:
The patent replaces complex mechanical temperature control systems (heaters, thermal masses, active cooling) with electronic control of LED current. LED output intensity and spectral distribution are directly controlled by electrical parameters, eliminating the need for bulky thermal management hardware while achieving precise control of the calibration light source characteristics.
Solution Approach 2:
The patent uses LED driver electronics to precisely control the electrical parameters (current, voltage, frequency, PWM duty cycle) supplied to the LED, which directly determines the light output intensity and spectral characteristics. This electrical parameter control is more precise and responsive than thermal control, achieving better manufacturing precision at lower cost.
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
The solution provides efficient, low-cost, and precise calibration of optical detectors, maintaining accuracy over time and withstanding harsh space conditions, making it suitable for small satellites like CubeSats, ensuring accurate image production and reducing the need for expensive proprietary components.
Implementation Method 1
at least a first source configured to produce first electromagnetic energy EMR
Implementation Method 2
A thermal mechanism is configured to adjust and maintain the temperature of at least the first source
Data Source
AI summary
A device and method of use for the calibration of a detector. The calibration device includes a first source configured to produce first electromagnetic energy EMR. A first diffuser is connected to the first source and is configured to accept the first EMR and provide a first diffused portion of the first EMR. An integrating sphere defines an interior and is optically connected to the first diffuser, and is configured to accept the first diffused portion from the first diffuser into the interior. An exit port connected to the integrating sphere is configured to pass at least a portion of electromagnetic energy. A thermal mechanism is configured to adjust and maintain the temperature of at least the first source. The integrating sphere is configured to pass only a second portion of the first diffused portion of the first EMR from the first diffuser to the exit port. In another embodiment, the calibration device has an arm, an actuator, and a module. The module supports at least a first source that emits electromagnetic energy, a thermal mechanism, and a controller. The actuator is configured to move the arm and module to a calibration position enabling the first source to be within the line of sight of an external detector, while the controller is configured to control the thermal mechanism enabling precise temperature regulation of the source and therefore the regulation of the emitted electromagnetic energy. When the device is not in the calibration position, the actuator is configured to move the arm and module to a stowed position, protecting the device from ambient electromagnetic radiation and harm.