Space certification and qualification programs for laser diode modules on the NASA ICESat-2 Mission

A laser diode module (LDM) space certification and qualification program was developed for NASA's Ice, Cloud and Land Elevation Satellite-2, ICESat-2 mission. The ICESat-2 laser transmitter is a high performance diode-pumped solid state laser that requires high reliability, high efficiency and high brightness fiber coupled LDMs, capable of supporting a 27,000 hour mission life. The test centric LDM space certification and qualification programs consisted of several key phases including a technology plausibility study, laser diode and LDM pedigree reviews, environmental acceptance and qualification testing, and extensive life testing. The intent of the plausibility study was to analytically and experimentally demonstrate that a commercial-off-the-shelf (COTS) LDM design was capable of being space-certified. A pedigree review of the laser diode population was conducted to reject out-of-family laser diodes from the population. The laser diode pedigree review was a statistical analysis of several laser diode performance metrics (efficiency, operating current, etc.) with outliers being rejected. All LDMs underwent environmental acceptance testing including vibration, thermal cycling and an extended burn-in. The primary purpose of the acceptance testing was to highlight internal workmanship issues. The pedigree review of the acceptance tested LDMs was conducted to reject out-of-family LDMs in statistical analysis of several performance metrics (operating current, coupling efficiency, etc.). A sub-set of the flight-certified LDMs will be exposed to environmental qualification testing and will subsequently be tested to failure to determine the LDM capability. Multiple LDMs are being life tested under flight-like conditions and show no signs of degradation with run times of 22,000 hours, which is over 80% of the mission life. Details of the LDMs space certification and qualification programs are presented.