Optimization of Debris Shields on the NISAR Mission’s L-Band Radar Instrument

The NASA-ISRO Synthetic Aperture Radar (NISAR)
space mission is a collaboration between NASA and the
Indian Space Research Organization (ISRO), launching
in the 2020s to a polar orbit of 747km altitude. The
mission will provide spatial and temporal measurements
of land surface changes (e.g. ice sheets, vegetation,
earthquakes). Many of the SAR electronics boxes are
mounted on the exterior of the structure. Their singlewall
box lids efficiently radiate heat for thermal control,
but are not very efficient debris shields. The initial
design showed an unacceptably high impact risk as
estimated with NASA’s ORDEM3 debris model and
Bumper impact analysis tool. Each box has a different
role in instrument functionality, and this was captured in
a reliability model used to optimize the distribution of
shield mass among the boxes: total added mass was
minimized while maintaining a threshold of
functionality and survival probability that was
acceptable to the project.