HARPS Laser Frequency Comb

The first commissioning run of the HARPS Laser Frequency Comb (LFC) was held from 8 – 17 April 2015. The HARPS LFC is described in a Messenger article (Lo Curto et al. 2012). During this commissioning, the emphasis was mainly on calibration but several science spectra were acquired: four asteroids and twenty stars were repeatedly observed to monitor their radial velocity variations and to compare with published data. The table lists the name of the target and the number of acquired spectra during the 10 night period.

Target No. Obs.
Ceres 9
Herculina 6
Parthenope 7
Massalia 7
HD330075 9
HD75289 10
HD76700 5
HD85512 7
HT Vir 15
FO Vir 8
V945 Cen 25
RR Cen 8
HD159656 6
HD104006 10
HD109200 11
HD123265 14
HD124292 8
HD144628 13
HD154577 8
HD183658 2
HD190248 18
HD199288 5
HD78747 6
HD97343 9

Access to the Commissioning Data

The HARPS LFC Commissiong data is available either as a single tar file (including calibration data) or as individual files for each observation or calibration exposure. By clicking on the following links, the Commissioning files can be downloaded from the Science Archive Facility:

If any of these data are used for publication, please acknowledge that the results are based on public data released from the HARPS LFC commissioning observations at the ESO 3.6-metre telescope under Programme ID 60.A-9036. See the recommended acknowledgement to be included in publications based on ESO data.


The performance of the HARPS spectrograph itself was not affected while the commission of the LFC calibration system was occurring. All listed spectra were acquired with simultaneous LFC as the reference source. Wavelength solutions and drifts are computed using the LFC. While wavelength solutions might have been recomputed using the available ThAr lamp spectra acquired at the beginning of every night, the drift can only be measured using the LFC spectra in each dataset.

The blue edge of the wavelength coverage of the LFC within the data set varies, from about 470nm to occasionally up to as high as 500nm. The red edge of the LFC spectrum is well beyond the HARPS coverage. The LFC intensity changes from one spectrum to another, mostly because of the various tests and configuration changes that were performed during the day. However these changes are not expected to affect significantly the precision of the radial velcoity measurements. LFC stability was always below 10 cm s-1 and in many cases at the level of the photon noise (down to 2 cm s-1). On the first night, 8 April 2015, another LFC with a mode spacing of 25 GHz was used, while on all the other nights the HARPS-LFC mode spacing was 18 GHz.