LDSD (Low Density Supersonic Decelerator) is a Mars EDL (entry, descent, and landing) Technology Development Project that launches three test vehicles out of the Pacific Missile Range Facility in Kauai. On the test vehicle, most mission science data can be recorded safely on land; however, high-speed and high-resolution imagery cannot be telemetered due to bandwidth constraints. Therefore, all information had to be recorded solely onboard the test vehicle; this unit is called the flight imagery recorder (FIR). A typical commercial airliner “black box” is only capable of recording on the order of gigabytes of data, whereas this work required on the order of terabytes (a few orders of magnitude larger).
As the FIR was designed to float on the top of the ocean, this allowed for the possibility of GPS-based recovery devices to be implemented. A benefit of a GPS-based recovery aid is that it allows global coverage and can give essentially pinpoint precision in the FIR’s location.
The general approach taken to ruggedize the electronics effort required a complete repackaging of the GSat Micro internal boards; the battery, antenna patch, enclosure, and associated harnessing were new additions that had to be reconfigured and required compatibility checks. Along with ruggedizing the device, the above changes led to a significant improvement in the RF performance, lower operational temperature limits, and operational life of the new GPS device referred to as the Flight Imagery Recorder Locator (FIRLo).
Due to thermal environments, there was a need to protect against the solid rocket motor plume. Early predictions showed the peak temperatures to be around 650 °C, which necessitated a radome to protect the FIRLo against extreme temperatures. The radome effectively reduces the peak temperature experienced by the FIRLo to about 80 °C. The biggest challenge with the radome was to ensure it remained RF transparent even while exposed to extended durations in the ocean. The only closed-form solution was based on a ceramic plate; however, this material is not inherently waterproof. Therefore, this material was coated through a detailed process requiring 15 coating applications with a bake-out of the material between each coating. The RF transparency of the high-temperature radome (HTR) does not, to any appreciable degree, adversely affect the FIRLo overall RF performance.
The FIRLo is an internally powered, shock-hardened, GPS tracking device that reports its location via the Iridium satellite network for global coverage. It is designed as a standalone, add-on device that relies on no power connection or signals from the system it is attached to. It is capable of providing a GPS location check every 30 minutes for over a week of operation. The radome allows for extreme thermal protection while also being waterproof and RF transparent. Furthermore, the radome is simple to manufacture and easy to modify for each specific application.