Athermal Cassegrain Telescope for Lasercom Alignment
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Solution Overview
Problem
Current wireless radio communication technologies face challenges such as signal dispersion, attenuation, and security issues due to geographic overlap and interference, while laser communication offers high-speed and secure alternatives but requires precise alignment and identification of communicating nodes, which is difficult, especially in satellite communications.
Innovation Solution
An athermal two-mirror Cassegrain lasercom telescope device with a thermally-matched silicon carbide structure and silicon optics, incorporating a solar rejection coating and a precision star tracker function, to maintain optical alignment and reject unwanted light, enabling low-SWAP and cost-effective manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional wireless radio communication is used, then communication coverage and accessibility are improved, but signal attenuation and interference increase with distance
Solution Approach 1:
The patent replaces radio frequency electromagnetic wave transmission with optical laser beam transmission. This substitution fundamentally changes the communication medium from RF waves that disperse broadly to laser beams that maintain tight focus, thereby reducing signal attenuation over distance while enabling high-data-rate communication between satellite and ground station
Solution Approach 2:
The patent changes the wavelength parameter from radio frequency to optical frequency, and controls the beam divergence angle to be extremely small (10-20 micro-radians). This parameter change allows the communication signal to remain tightly focused over long distances, maintaining energy concentration and reducing attenuation while achieving both wide coverage and low loss
2Adaptability or versatility
If radio frequency communication is used, then communication accessibility is improved, but security against interception and jamming deteriorates
Solution Approach 1:
The patent substitutes optical laser communication for radio frequency communication, utilizing the inherent properties of laser beams including tight directional focus and high energy concentration. This substitution provides intrinsic security because intercepting or jamming the communication requires precise alignment with the narrow beam path, making eavesdropping and interference significantly more difficult compared to dispersed RF signals
Solution Approach 2:
The patent changes the operating wavelength to optical frequencies and controls beam divergence to 10-20 micro-radians, creating a highly directional communication channel. This parameter change inherently improves security by limiting the spatial region where interception or jamming can occur, while maintaining full communication accessibility between the satellite and ground station
3Productivity
If laser communication is used, then data transmission speed and security are improved, but alignment precision requirements increase
Solution Approach 1:
The patent integrates multiple functions into the telescope system: the same optical telescope serves both as the communication beam receiver and as the platform for the star tracker. The star tracker provides precise attitude determination and alignment verification, enabling the system to achieve the required alignment precision while maintaining high data transmission speeds through the narrow laser beam
Solution Approach 2:
The patent employs a star tracker that continuously monitors stellar positions to provide feedback on the satellite's attitude and orientation. This feedback enables real-time adjustment and verification of the alignment between the laser communication beam and the ground station, ensuring precise tracking and maintaining high data transmission rates despite the stringent alignment requirements
4Volume of moving object
If telescope aperture is reduced, then device size and cost are improved, but beam focusing capability and communication distance deteriorate
Solution Approach 1:
The patent changes the beam divergence parameter to be extremely small (10-20 micro-radians) through precise optical design and control. This parameter change compensates for the reduced aperture size by maintaining tight beam focus over long distances, enabling effective laser communication with a compact 4-8 inch telescope rather than requiring large apertures
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 robust, high-speed, and secure laser communication by maintaining alignment and rejecting unwanted light, overcoming the challenges of signal dispersion and interference, while reducing manufacturing complexity and costs.
Implementation Method 1
a solar rejection coating on the window passes a spectral region comprising 1300-1600 nm, to allow star energy to be used for sensing
Implementation Method 2
the window comprises silicon wherein its transmission characteristic absorbs optical energy from UV about 250 nm up to near infrared about 1150 nm whereby solar energy warms the window with absorption of this solar flux
Implementation Method 3
An athermal two-mirror Cassegrain lasercom telescope device with a thermally-matched silicon carbide structure and silicon optics
Data Source
AI summary
A Cassegrain telescope design consists of a silicon primary mirror bonded into a silicon-carbide (SiC) telescope metering tube. A secondary mirror is bonded directly to the telescope window. The window sits in a SiC bezel that is bonded to the SiC telescope tube. A graphite snout is bonded to the rear of the primary mirror and extends forward into the telescope. The snout incorporates a field stop that blocks stray light and sources outside the acquisition field of view (FOV). A lens cell threads into the snout and holds two lenses that collimate the light exiting that end of the telescope.