SPEQS: Electronics

The SPEQS instrument is a compact device that combines not only the optical module carrying the photon source and detectors, but also an optimized electronics platform that supports the experiment and provides a mechanical interface to the rest of the satellite. The electronics platform is a critical part of the entire endeavor - the platform must perform well for high quality data to be captured.

The most important aspect of the electronics platform is to fit all the necessary functions into the size requirement of a CubeSat. The front and back view of the electronics platform is shown below. The front view (a) has the optical unit mounted on it. You can also see the black cradles holding the Matsusada high voltage in place. These high voltage supplies are bulky, but necessary as they are a proven method of supplying low-noise high voltage supplies to the Si GM-APD modules. Each GM-APD is supplied with each own voltage supply to avoid electronic cross-talk. The back side of the electronics platform contains a large number of circuits for controlling different opto-electronics elements such as the pump laser, the polarization rotators and the operation of the GM-APDs, as well as data recording. The largest element on the backside is the PSoC3 micro-controller that works very well as the glue for the different circuits. A PSoC type system is really useful for controlling the SPEQS instrument because not only does it have a micro-controller but also additional logic elements such as DACs that reduce the final number of parts in the Bill of Materials (always an important consideration when fabrication costs are included).

The electronics platform has passed numerous environmental tests including radiation exposure to highly damaging low-energy proton beams. We are sufficiently satisfied with its performance and plan to use it on a series of upcoming CubeSat missions. Below we show how the SPEQS electronics platform fits into a 2U CubeSat.

Full details of the electronics platform can be found in the IEEE Journal of Lightwave Technology.