Redesign and test of cryogenic mechanism for improved stiffness

The near infrared camera (NIRCam) instrument for NASA is one of four science instruments installed into the integrated science instrument module (ISIM) of the James Webb space telescope (JWST) intended to conduct scientific observations over a five year mission lifetime. The NIRCam instrument will have a pupil imaging lens actuator assembly (PIL) to provide a means of imaging the primary mirror for ground testing, instrument commissioning, and diagnostics which must operate from 293 - 37 Kelvin and be in support of the usual launch environments. More refined optic prescriptions and initial PIL vibration test data led to the redesign of the PIL. This paper discusses the redesign of the lens mounts to accommodate a new optic prescription. This paper also details the analysis of vibration test data that led to the redesign of a stiffer bearing mount for the PIL flight mechanism that would ultimately be tested to show appropriate margins for meeting program vibration test requirements.