The Mid Infrared Instrument (MIRI), one of the four instruments on the Integrated Science Instrument Module (ISIM) of
the James Webb Space Telescope (JWST), supports all of the science objectives of the observatory. MIRI optical
alignment is an important step in the verification process, directly affecting mission success. The MIRI optical alignment
is verified on the ground at the integrated ISIM level using an element in the MIRI Filter Wheel, the pupil alignment
reference (PAR), developed by NASA GSFC and provided to MIRI. It is a ~2.3g aluminum piece that has a flat,
specularly reflective, 3mm diameter surface in its center, with laser-etched fiducials within its aperture. The PAR is
illuminated via an optical stimulus (ground support equipment) and imaged using a pupil imaging camera, during the
ISIM test program in order to determine absolute and relative changes in the alignment that impact pupil shear and roll.
Here we describe the MIRI PAR; its physical properties and challenges during its design, manufacturing, and testing.
KEYWORDS: Interfaces, James Webb Space Telescope, Observatories, Space operations, Electronics, Space telescopes, Systems engineering, Simulation of CCA and DLA aggregates, Switches, Cooling systems
On the James Webb Space Telescope (JWST), the Mid-Infrared Instrument (MIRI) is unique among the four science
instruments in that it operates around 7K as opposed to 40K like the other three near infrared instruments. Remote
cooling of the MIRI is achieved through the use of a Joule-Thomson (J-T) Cooler, which is precooled by a multistage
Pulse Tube Cooler. The MIRI Cooler systems engineering is elaborate because the Cooler spans a multitude of regions
in the observatory that are thermally and mechanically unique with interfaces that encompass a number of different
organizations. This paper will discuss how a significant change to the MIRI Cooling System from a solid hydrogen
Dewar to a Cooler was achieved after the instrument Preliminary Design Review (PDR), and it will examine any system
compromises or impacts that resulted from this change so late in the instrument design. A general overview of the Dewar
and the Cooler systems management, the roles of the systems teams in the different organizations, how the requirements
are managed in such an elaborate environment, and the distinct design and Integration and Test (I&T) challenges will
also be provided.
The Integrated Science Instrument Module (ISIM) for the James Webb Space Telescope (JWST) provides the critical
functions and the environment for the four science instruments on JWST. This complex system development across
many international organizations presents unique challenges and unique solutions. Here we describe how the
requirement flow has been coordinated through the documentation system, how the tools and processes are used to
minimize impact to the development of the affected interfaces, how the system design has matured, how the design
review process operates, and how the system implementation is managed through reporting to ensure a truly world class
scientific instrument compliment is created as the final product.
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