Harps Upgrade 2015



Dear PIs of HARPS program,

This letter is to inform you that since June 3rd 2015 a new fiber link is installed in HARPS.
This project was recommended by the STC at its 80th meeting in April 2013.
The goal was to replace the circular fibers with octogonal ones, in order to improve the light
scrambling capabilities of the fiber-link and in this way to increase the stability of the light
injection within the spectrograph, and with it the stability of the instrumental profile and the
radial velocity precision.

During the HARPS upgrade mission, which took place from May 20th to June 3rd, we have:
- Exchanged the HAM fibres
- Exchanged the EGGS fiber
- Re-focussed the instrument (a slight de-focused had been observed after 12 years of continued operations)
- Re-commissioned all observing modes
- Verified key performances

We can already anticipate that thanks to this upgrade we have eliminated systematics due to de-centering
and de-focussing, the broken sky fiber of EGGS is now repaired and HARPS has gained in throughput by at least 10%.
As a consequence of the fiber exchange, we expect a constant offset to be introduced in the radial velocity measurements
taken after the fiber exchange (May 28th). Although the instrument and its pipeline are fully operational, we are working
on the optimization of the data-reduction and on the determination of this offset as accurately as possible with the goal
to assure best precision and long-term continuity to all programs, especially to the ones spanning pre- and post-upgrade observing time.

Be informed that we are preparing a detailed report and the main results will be published in the December edition of the ESO Messenger.

In the meantime, do not hesitate to contact us for additional information.

Best regards,
    Gaspare Lo Curto