Radial velocity stability

It has been proposed to provide octagonal fibers and a double scrambler in order to improve the radial-velocity stability of FIES. A first step is to define the requirements of all the users to see how best to serve all of their the needs. A questionnaire was sent around to the community.

The conclusion was that what we currently offer is what the community wants. In order to meet the radial-velocity stability requirements and the communities wish we can retain the low-resolution and two medium-resolution fibers, and upgrade the high-resolution fiber for superior radial-velocity stability. The medium-resolution fibers can be made octagonal as well.

To come to a final design, the physical constraints on the design of the fiber bundle should be defined. The relevant info was presented on a web page, see

http://www.not.iac.es/instruments/fies/staff/fiber-bundle-constraints.html

and the link was sent to the various people involved. This page describes in full what are the technical and optical constraints for a new fiber bundle. A new fiber bundle will decrease the RV scatter, that is now at best at 8m/s, by a factor 2-3.

Very recently, a regular user of FIES in OPTICON time doing observations of planetary systems, Davide Gandolfi from the University of Heidelberg, Germany, has show interest in improving the radial-velocity stability of FIES, indicating he could both provide some funds and manpower.

It seems timely that the next step of making a first design is taken soon.