a-LASE-ing
Thank you to our sponsors, Professor Al Gasiewski and the Center for Environmental Technology (CET)!
Modern day satellite communication is heavily limited by the bottleneck in bandwidth from space to ground stations. The amount of useful science many satellites can perform is limited by the amount of downlink bandwidth they have available. For CubeSats in particular, their orbit limits their downlink time to only a few minutes per pass, meaning the total amount of data we can collect from them is relatively small. Team a-LASE-ing’s project is to build a scaled model of a laser communication system to test the possibility of putting the system into space. This system would greatly increase the data rate, at least tenfold, and would allow more science data to be collected and received. In order to accomplish this goal our product will consist of three main systems, the transmitter, receiver, and tracking system. Scientists operating CubeSats or other small satellites will benefit from this increased data rate by being able to do more useful science in orbit.
Transmitter
The transmitter system takes an Ethernet input and sends it to a visible light laser output. A user interfaces with this end of the system through an Ethernet cable. A wire backlink will be used to ensure that packets can be sent over TCP. The transmit side computer should be set up like a file or web server if intending to use TCP, that way a user can thus use standard Unix tools, like wget, to transmit files across the link.
Receiver
The receiver system will receive the pulsed laser signal and send feedback to both the transmit system (via the TCP backlink) and the tracking system (via an analog backlink). As with the transmitter system, the receiver will interface with a computer via Ethernet. The receiver is responsible for sending back the data the tracking system needs to operate.
Tracking
The tracking system is responsible for ensuring that the laser beam remains pointed at the active region of the receiver’s photodiode. To do this, it uses a high precision galvanometer and an algorithm known as conical scanning, originally developed for radar. This algorithm allows the tracking system to make minute corrections to stay on target, even while that target is moving. The tracking system scans, and then locks on to a target.