Our work since 1991 on thermal noise was well coordinated with LIGO, although on an ad hoc basis; the requirements for strict coordination were eased by the fact that our program was aimed primarily at the fundamental physics of thermal noise and at mechanisms of dissipation in representative elements of suspensions (e.g. metal wires, wire-clamp interfaces, or pieces of fused silica.)
The past year or so has seen a substantial opening of the LIGO Project to active participation by scientists outside of the Caltech and MIT groups. This fundamental reorganization of LIGO, especially the creation of the LIGO Scientific Collaboration, has made possible several new styles of LIGO-related research. In particular, the Syracuse group has participated since the January 1996 Aspen Workshop in the formation of what has become the LSC's Isolation/Suspension/Thermal Noise Development Group. This group has undertaken the design of an improved suspension (based on a double pendulum), to be ready for installation in 2004 immediately after the first two-year data run.
The responsibility to help produce this improved suspension means that our own group will have to add to its ongoing research on thermal noise and on dissipation mechanisms (described above) a program of work more directly focused on the problems of achieving good performance in a complete suspension. In part this is just an application of our previous work, and of the work of others interested in similar topics (especially the groups at GEO, Moscow, Stanford, and LIGO.) But there is an extra kind of discipline that comes from the constraint that one is not solving just a thermal noise problem (or a problem simply of vibration isolation or of sensing or of control), but instead must produce a working system that meets at the same time a complete set of specifications on all relevant parameters. Making the required trade-offs is an art in itself, familiar to those within LIGO but somewhat new to our own group.
There are also a variety of issues that don't fit neatly in any single category around which research has been typically organized, but that are nevertheless important for the search for gravitational waves. These include the class of excess noise sources sometimes referred to as ``technical'' noise. In pendulum suspensions Braginsky and his group have emphasized the possible importance of sudden large relaxations of the highly stressed wires, with excess excitation of pendulum motion as a result. Their initial reconnaissance of the problem [13] gives one cause for some optimism that the problems may not be significant, but the issue certainly bears additional careful study. Another sort of excess noise that may be important in pendulums is upconversion of low frequency pendulum motion to audio-frequency noise, for example through stick-slip events.