Space Grant Consortium - University of Wisconsin - Green Bay

A. Abstract
For hardware to be flight certified; it’s verification must either be by test, a
precise analysis, significant heritage (history of similar hardware) or a combination of
these to infer that the hardware will perform in its intended environment. In general, of
the three methods of certification; testing of the hardware is the preferred over analysis
and heritage. The infrared detectors of the JWST are part of a larger Sensor Chip
Assembly (SCA) which in turn is a part of a larger Focal Plane Assembly (FPA). The
FPA structure is the hardware that needs to be shock qualified to be certified for space
missions. Shock certification for the FPA involves more risk than for other hardware.
The qualification methods do not provide complete assurance because the shock
environment is difficult to quantify. Furthermore these efforts do not always simulate an
accurate shock response environment. This results in the margin between the acceptance
and qualification level to be large. In many cases the qualification level is twice the
acceptance. These levels have also been known to change in the course of a mission.
Shock testing the FPAs is costly because it involves replicating high frequency
environments. This testing involves tailored setups that require significant effort to tune.
Avoiding the risk of testing is preferred because of the testing setup and the uncertainty
in shock levels. Precise structural analysis of the FPA involves risk as well because it
relies on the same uncertainty in shock. As far as heritage, prior to this document,
detailed FPA heritage has not been compiled.
56