History of EquiSat’s Beacon
Originally, EQUiSat planned to use a xenon flash tube (XFT) often used in photographic strobes as the light source for an optical beacon. We have since transitioned to an LED array. LEDs are considerably more durable than an XFT making them much more likely to survive the launch environment. Additionally, the LEDs will not require the large aluminum reflector necessary for the XFT to reach desired brightness and maintain structural support of the glass bulb. This will significantly reduce the mass of the payload and increase feasibility of meeting CoG specifications. The resulting circuit will no longer require the use of a flyback transformer for Xenon gas ionization. This greatly simplifies and increases the reliability of the payload’s circuitry. Finally, LEDs also offer a much more predictable flash in both duration and magnitude, making them much easier to manipulate and therefore easier to test. Increased testing reliability will result in greater confidence in sighting opportunities and predicted brightness.
The original LED array would have consisted of between 9 and 15 Luminus SST-90s. These LEDs met all of our goals and additionally they had the advantage of redundancy; if one or more failed it would not greatly diminish the brightness of our satellite. However, in order to reduce electronic complexity, we decided to wire them 3S3-5P, meaning that if one fails, you lose the entire row. Additionally, testing determined that we did not have enough room for the number of LEDs that it would take to accomplish our brightness goals. We briefly considered using reflectors again, however the manufacturing complexity of adding all of those reflectors made it time to choose a different LEDs.
To minimize the total number of LEDs and complexity in our circuitry, we switched to Luminus CXM-27s. These LEDs were much simpler to work with for both manufacturing and electronics. Not long after we selected these LEDs, Luminus released the CHM-27, which provides a more luminous output for the same power requirements and package.