Ivair Gontijo

Model Based Systems Engineering on the Europa mission concept study

At the start of 2011, the proposed Jupiter Europa Orbiter (JEO) mission was staffing up in expectation of becoming an official project later in the year for a launch in 2020. A unique aspect of the pre-project work was a strong emphasis and investment on the foundations of Model-Based Systems Engineering (MBSE). As so often happens in this business, plans changed: NASAs budget and science priorities were released and together fundamentally changed the course of JEO. As a result, it returned to being a study task whose objective is to propose more affordable ways to accomplish the science. As part of this transition, the question arose as to whether it could continue to afford the investment in MBSE. In short, the MBSE infusion has survived and is providing clear value to the study effort. In the process, the need to remain relevant in the new environment has brought about a wave of innovation and progress. By leveraging the existing infrastructure and a modest additional investment, striking advances in the capture and analysis of designs using MBSE were achieved. The effort has reaffirmed the importance of architecting. It has successfully harnessed the synergistic relationship of architecting to system modeling. We have found that MBSE can provide greater agility than traditional methods. We have also found that a diverse ‘ecosystem’ of modeling tools and languages (SysML, Mathematica, even Excel) is not only viable, but an important enabler of agility and adaptability. This paper will describe the successful application of MBSE in the dynamic environment of early mission formulation, the significant results produced and lessons learned in the process.

Europa Clipper mission: the habitability of an icy moon

Europa, the fourth largest moon of Jupiter, is believed to be one of the best places in the solar system to look for extant life beyond Earth. The 2011 Planetary Decadal Survey, Vision and Voyages, states: “Because of this oceans potential suitability for life, Europa is one of the most important targets in all of planetary science”. Exploring Europa to investigate its habitability is the goal of the proposed Europa Clipper mission. This exploration is intimately tied to understanding the three “ingredients” for life: liquid water, chemistry, and energy. The Europa Clipper mission would investigate these ingredients by comprehensively exploring Europas ice shell and liquid ocean interface, surface geology and surface composition to glean insight into the inner workings of this fascinating moon. In addition, a lander mission is seen as a possible future step, but current data about the Jovian radiation environment and about potential landing site hazards and potential safe landing zones is insufficient. Therefore an additional goal of the mission would be to characterize the radiation environment near Europa and investigate scientifically compelling sites for hazards, to inform a potential future landed mission. The proposed Europa Clipper mission concept envisions sending a flight system, consisting of a spacecraft equipped with a payload of NASA-selected scientific instruments, to execute numerous flybys of Europa while in Jupiter orbit. A key challenge is that the flight system must survive and operate in the intense Jovian radiation environment, which is especially harsh at Europa. The innovative design of this multiple-flyby tour is an enabling feature of this mission: by minimizing the time spent in the radiation environment the spacecraft complexity and cost has been significantly reduced compared to previous mission concepts. The spacecraft would launch from Kennedy Space Center (KSC), Cape Canaveral, Florida, USA, on a NASA supplied launch vehicle, no earlier than 2022. The proposed mission would be formulated and implemented by a joint Jet Propulsion Laboratory (JPL) and Applied Physics Laboratory (APL) Project team.

Qualification and selection of flight diode lasers for the NuSTAR space mission

Reliability and lifetime of diode lasers is critical to space missions. 12Rigorous tests were conducted on diode lasers to qualify them to be deployed on the Nuclear Spectroscopic Telescope Array (NuSTAR) mission. This mission includes a metrology system that is based upon 2 laser diodes. This paper discusses the different laser diode failure mechanisms that can arise, as well as laser diode reliability requirements set forth by the NuSTAR space mission. In addition, the space qualification procedures and results on 120 laser diodes from two different vendors will be presented. Also, the results of an accelerated laser lifetime test of 20 laser diodes, along with the flight laser diode selection process will be described in this paper.

Reliability of semiconductor laser packaging in space applications

A typical set up used to perform lifetime tests of packaged, fiber pigtailed semiconductor lasers is described, as well as tests performed on a set of four pump lasers. It was found that two lasers failed after 3200 and 6100 hours under device specified bias conditions at elevated temperatures. Failure analysis of the lasers indicates imperfections and carbon contamination of the laser metallization, possibly from improperly cleaned photo resist. SEM imaging of the front facet of one of the lasers, although of poor quality due to the optical fiber charging effects, shows evidence of catastrophic damage at the facet. More stringent manufacturing controls with 100% visual inspection of laser chips are needed to prevent imperfect lasers from proceeding to packaging and ending up in space applications, where failure can result in the loss of a space flight mission.

High Speed RF Packaging Design and Fabrication for Ka-Band Radar Systems

The various choices of materials for RF packaging are reviewed and two groups of materials are used to package components for a Ka-band landing radar. A Kovar housing was designed and built for a transmit/receive module, which provides good RF performance and allows the high power semiconductor amplifiers to be mounted directly to pedestals at the bottom of the package. For the up/down converter, an Aluminum housing was designed and built with all connectors laser welded in place. Both packages are hermetic and capable of withstanding a differential pressure of over 30 psi. Environmental requirements are taken into consideration during package design, such as thermal cycling, absolute maximum temperature ratings of components and structural aspects. Details of the electrical package design to minimize radiation loss and cross talk are discussed, as well as various methods of attachment of the RF connectors to the housings.