System analysis for the near-infrared camera and multiobject spectrometer cryogenic and structural design

The requirements for a second generation Hubble Space Telescope (HST) Science Instrument (SI) are similar to those of other space-borne instruments: the shuttle launch loads must be survived; the instrument must have specific dynamic characteristics; mass, size envelope, and electrical power constraints are imposed; thermal interfaces are defined; and a minimum on- orbit lifetime is required. The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) differs from first generation and other second generation HST SIs in that it is an infrared instrument. The NICMOS detectors must be cooled to 58 K. This leads to a demanding instrument design that includes as an integral part of the optical bench design, a solid nitrogen (SN2) cryogen dewar with a five year minimum lifetime goal. The dewar requires over 50% of the total instrument weight budget and occupies a significant portion of the available size envelope. Designing for five year cryogen lifetime while achieving a structural design that will meet launch loads and optical stability led to many design conflicts. The system level trades along with the structural and cryogenic lifetime analyses used to resolve these conflicts and arrive at the innovative NICMOS design will be discussed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.