Closed-Loop Laser Relay Pointing for Moving Satellites
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Solution Overview
Problem
Laser communications with non-stationary satellites face challenges due to atmospheric interference and the need for precise alignment, as atmospheric conditions like turbulence change the path of laser beams, leading to high bit error rates and missed transmissions.
Innovation Solution
A satellite communication system with a relay system positioned at a selected distance based on the satellite's speed, using closed-loop pointing to maintain alignment and reduce bit error rates by relaying information through a reflector or relay satellite, avoiding the need for complex calculations to predict satellite positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If laser beam is transmitted directly from terrestrial location to fast-moving satellite, then communication speed is high, but alignment precision deteriorates due to atmospheric turbulence and satellite motion
Solution Approach 1:
A relay system comprising a relay satellite and reflector is introduced as an intermediary between the terrestrial location and the fast-moving satellite. The relay satellite receives laser beams from the ground station and reflects them to the target satellite, enabling communication without requiring direct precise alignment over long distances. This mediator approach resolves the contradiction by breaking the direct transmission path into segments, each with more manageable alignment requirements.
Solution Approach 2:
The communication path is segmented into multiple hops: terrestrial location to relay satellite, then relay satellite to target satellite. Each segment has shorter duration and distance, allowing the relay system to maintain alignment precision despite satellite motion and atmospheric turbulence. The segmentation transforms a single high-speed direct link into multiple lower-speed sequential links with better alignment characteristics.
2Loss of time
If relay system is positioned closer to satellite, then alignment time is reduced, but communication reliability deteriorates due to increased bit error rates
Solution Approach 1:
The relay satellite is positioned in a trailing orbit behind the fast-moving satellite, creating a dynamic configuration where the relay continuously adjusts its position to maintain optimal communication geometry. This dynamic positioning allows the relay to stay within the laser beam's path without requiring precise real-time alignment calculations, reducing alignment time while maintaining communication reliability through continuous orbital adjustment.
Solution Approach 2:
The relay satellite is pre-positioned in a trailing orbit ahead of the target satellite's position, anticipating where the satellite will be when the laser beam arrives. This preliminary positioning action allows the relay to intercept the laser beam without requiring complex real-time predictive calculations, reducing alignment time while maintaining reliable communication through pre-established geometric relationships.
3Productivity
If direct laser communication is used with non-geosynchronous satellite, then data rate is high, but communication stability deteriorates due to atmospheric interference
Solution Approach 1:
The relay satellite acts as an intermediary that receives laser beams from the terrestrial location and forwards them to the non-geosynchronous satellite. By breaking the direct atmospheric path into two separate paths (ground to relay, then relay to satellite), the system reduces the impact of atmospheric turbulence on any single transmission, improving communication stability while maintaining high data rates through the laser links.
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
Enables reliable laser communications with fast-moving satellites by maintaining alignment and reducing bit error rates, even in the presence of atmospheric turbulence, without relying on complex predictive calculations.
Implementation Method 1
The relay system is configured to receive a laser beam encoding information from a terrestrial location and relay the information to the satellite
Implementation Method 2
Laser communications involves using a laser to send communications between a satellite and terrestrial location such as a ground station
Implementation Method 3
Using infrared light can allow a laser beam to penetrate the atmosphere of the earth with reduced interference
Data Source
AI summary
A satellite communications system comprising a satellite traveling in an orbit and a relay system. The relay system is configured to receive a laser beam encoding information from a terrestrial location and relay the information to the satellite. The relay system is positioned at a selected distance from the satellite and the selected distance is set based on a speed of the satellite.