This is a continuation of a series of papers on the integrated modeling activities for the James Webb Space Telescope (JWST). Starting with the linear optical model discussed in part one, and using the optical sensitivities developed in part two, we now assess the optical image motion and wavefront errors from the structural dynamics. This is often referred to as "jitter" analysis. The optical model is combined with the structural model and the control models to create a linear structurdopticalicontrol model. The largest jitter is due to spacecraft reaction wheel assembly disturbances which are harmonic in nature and will excite spacecraft and telescope structural. The structuralioptic response causes image quality degradation due to image motion (centroid error) as well as dynamic wavefront error. Jitter analysis results are used to predict imaging performance, improve the structural design, and evaluate the operational impact of the disturbance sources.

A 19 degree-of-freedom (DOF) dynamics and controls model of a laser interferometer space antenna (LISA) spacecraft has been developed. This model is used to evaluate the feasibility of the dynamic pointing and positioning requirements of a typical LISA spacecraft. These requirements must be met for LISA to be able to successfully detect gravitational waves in the frequency band of interest (0.1–100 mHz). The 19-DOF model includes all rigid-body degrees of freedom. A number of disturbance sources, both internal and external, are included. Preliminary designs for the four control systems that comprise the LISA disturbance reduction system (DRS) have been completed and are included in the model. Simulation studies are performed to demonstrate that the LISA pointing and positioning requirements are feasible and can be met.

The laser interferometer space antenna (LISA) mission, a space-based gravitational wave detector, uses laser metrology to measure distance fluctuations between proof masses aboard three spacecraft. Each spacecraft has two incoming and two outgoing laser beams for a total of six laser links. These links are established sequentially at the start of the mission, and the spacecraft control systems must aim their lasers at each other with pointing motions less than 8 nrad Hz−1/2 in the frequency band 1–100 mHz. The process for acquiring the laser links as well as the simulated performance is described.

The Laser Interferometer Space Antenna mission is a planned gravitational wave detector consisting of three spacecraft in heliocentric orbit. Laser interferometry is used to measure distance fluctuations between test masses aboard each spacecraft to the picometre level over a 5 million km separation. The disturbance reduction system comprises the pointing and positioning control of the spacecraft, electrostatic suspension control of the test masses and point-ahead and acquisition control. This paper presents an approach for the acquisition control of the LISA formation. The approach establishes one link at a time. For each link, it defocuses the incoming beams to make its light detectable by the receiving spacecraft. Simulations are performed to demonstrate the feasibility of the proposed approach.

Ultimately, after the Single Aperture Far-IR (SAFIR) telescope, astrophysicists will need a far-IR observatory that provides angular resolution comparable to that of the Hubble Space Telescope. At such resolution galaxies at high redshift, protostars, and nascent planetary systems will be resolved, and theoretical models for galaxy, star, and planet formation and evolution can be subjected to important observational tests. This paper updates information provided in a 2000 SPIE paper on the scientific motivation and design concepts for interferometric missions SPIRIT (the Space Infrared Interferometric Telescope) and SPECS (the Submillimeter Probe of the Evolution of Cosmic Structure). SPECS is a kilometer baseline far-IR/submillimeter imaging and spectral interferometer that depends on formation flying, and SPIRIT is a highly-capable pathfinder interferometer on a boom with a maximum baseline in the 30 -50 m range. We describe recent community planning activities, remind readers of the scientific rationale for space-based far-infrared imaging interferometry, present updated design concepts for the SPIRIT and SPECS missions, and describe the main issues currently under study. The engineering and technology requirements for SPIRIT and SPECS, additional design details, recent technology developments, and technology roadmaps are given in a companion paper in the Proceedings of the conference on New Frontiers in Stellar Interferometry. Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.