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HARPS User Manual

1. ES O European Southern Observatory Organisation Europ enne pour des Recherches Astronomiques dans l H misph re Austral Europ ische Organisation f r astronomische Forschung in der s dlichen Hemisph re La Silla La Silla Observatory High Accuracy Radial Velocity Planet Searcher HARPS User Manual 3P6 MAN ESO 90100 0005 Issue 2 0 Date February 21st 2010 La Silla Observatory x ESO x Chile ii February 2003 March 5 2003 March 10 2003 June 16 2003 July 8 2003 July 31 2003 Sept 17 2003 Nov 25 2003 May 25 2004 August 2005 May 2006 March 2007 February 2010 HARPS User Manual Issue 20 _3P6 MAN ESO 90100 0005 Change Record sections affected all all all all all all DRS related all all Observing HARPS characteristics amp EGGS all Add polarimetry mode Reason Remarks First version for comments first public issue for P72 CfP GRU DQU DRS end of Comm2 DQU DAU info DSo data format answer to comments DQU more information added and structure revised GLC full update GLC overheads and asteroseismology issues GLC include slow readout mode THAR3 lamp and EGGS GLC Few improvements Editor G Lo Curto ESO La Silla Contents Introduction TeV Scope a sft ur a D pere Ee Ah Lina E e del 1 2 Additional information p aep dese e i e we De a a 1 3 Contact information ue dun ia ha e AR a a ouh es LAs Acknowledgment
2. e HARPS_pol_obs_all for exposures in spectro polarimetric mode e HARPS_ech eggs_obs_all for exposures in the HAM EGGS observing modes A concise description of the observation template is given in the HARPS Template Guide 5 3 3 Calibration templates Several calibration templates are available However all calibrations necessary for a proper data reduction with the online pipeline are performed by the ready to run calibration OB named RV Standard Calibration The details of this OB are described in section 3 1 2 Only if additional calibrations are deemed necessary one needs to use one or more of the following templates e ech_cal_bias for taking bias frames e ech_cal_dark for taking dark frames e ech_cal_thoAB for taking a wavelength calibration through both fibres e ech_cal_tun for taking order location frames through fibres A and B e ech_cal_tunAB for taking spectral flat field exposures simultaneously through fibres A and B e ech_cal_tunAT2for taking spectral flat field exposures through the iodine cell using fibre A e ech_cal_tunUSER for taking user defined tungsten exposures e HARPS_pol_cal_tun_cir flat field with the circular polarimeter e HARPS_pol_cal_tun_lin flat field with the linear polarimeter If the number of exposures is set different from one in the ech_cal_tunAI2 ech_cal_tunAB or ech_cal_thoAB templates the pipeline will wait for the last exposure sum all the exposures and then process the resulting f
3. 0 0012 3 7 8 53e 03 0 0039 B 1e 03 P2 428 11 0 0012 8 5 6 92e 03 0 0035 2 5e 03 2 425 13 0 0012 8 4 6 72e 03 0 00333 2 4e 03 1 em 0 0012 9 2 Eee Las zen an kum Bi 6220608 600208 Sien 16 46 0 0011 8 6 23e 03 0 00282 2 3e 03 78 13 65 0 0011 2 9 5 82e 03 0 00268 2 1e 03 75 mum mm 25 Bite 03 0 00254 A emn 08 13 0 0011 2 6 5 17e 03 0 0024 1 9e 03 71 05 43 0 0011 2 5 4 62e 03 0 00225 1 7e 03 67 02 76 0 0011 2 4 4 41e 03 0 0021 1 6e 03 e 997 33 kum 21 Aer LOST Aids 894 97 0 00112 2 26e 03 0 00166 2e 02 46 892 44 0 0011 1 8 2 12e 03 0 00152 7 7e 02 45 369 39 mm LT Pesi 0 00139 Feroz 887 47 0 0011 1 5 1 66e 03 0 00127 6e 02 9 B85 03 0 001 1 4 fl 5e 03 0 00115 4e 02 37 852 63 0 001 1 3 927 0 00104 B 4e 02 25 360 25 mm 13 1 370403 0 000935 Bess P Figure 2 3 Table showing the spectral format of HARPS and the expected number of electrons for a 1 minute exposure on a G2V star of magnitude 6 A seeing of 0 8 airmass 1 and new moon are the values of the selected parameters In the table the spectral bin is defined as one pixel This table is obtained by the HARPS Exposure Time Calculator ETC HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 System Echelle grating Cross disperser grism Collimator mirror Camera Detector Beam focal ratio Sp
4. 590nm is about 2 5 for EGGS to be compared to 1 of HAM In table 9 1 the HAM and EGGS mode performances are compared The EGGS mode may prove particularly useful to RV programs studying faint objects where the RV accuracy is strongly limited by the photon noise Users willing to use this mode should declare it in the proposal as this requires a change in the instrument configuration HAM EGGS flux seeing 0 8 1 1 75 best RV accuracy lt 1m s 30m s diffuse light at 590nm 1 2 5 strongest ghost intensity lt 1 1 10 Table 9 1 Comparison of the HAM and EGGS performances 41 42 Efficiency HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 Night 2005 12 15 T TT T T TT T TT T TT T CH T T HARPS EGGS Seeing 0 8arcsec Star HR718 N il Il A Uh wi 5000 5500 Wavelength A 4000 6000 6500 7000 Figure 9 1 HARPS EGGS comparison Chapter 10 The HARPS polarimeter The polarimetric system of HARPS consists of two super acromatic rotatin
5. 8s each suffice to reach s SNR 1000 in the science frames taken in the HARPS instrument mode The RV Standard HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 15 Calibration acquires 5 flat exposures and reaches a Signal to Noise Ratio SNR of about SNR 400 at 450nm 500 at 550nm and SNR 900 at 650nm In case the RV Standard Calibration is not taken the DRS will use the youngest available cal ibration data This might introduce offsets and possibly have a negative effect on the achievable precision The pipeline performs quality checks on each frame In case one of the frames does not pass the quality check the youngest available calibration data will be used In this case is however advisable to contact the support astronomer on site in order to make sure the general health of the instrument is not compromised 3 1 3 Observations The necessary acquisition and observing templates are available e HARPS_ech_acq_thosimult for star acquisition and setup of simultaneous Th exposures e HARPS_ech_obs_all for taking simultaneous Th exposures When using the EGGS instrument mode the templates with the eggs prefix should be used instead than the templates with the ech prefix which are dedicated to the HARPS mode For a detailed description of the templates see section 5 3 and the HARPS Template Guide 3 1 4 Pipeline data reduction The online pipeline does spectrum extraction wavelength calibration RV ca
6. 9 2 6 Detector and read out electronics The detector is a mosaic of two 2kx4k EEV CCDs It is mounted in a ESO detector head and cooled to 148K by means of an ESO continuous flow cryostat CFC The detector is controlled by the standard ESO CCD controller FIERA The detector head is mounted on the optical bench while the CFC is fixed on the outer wall of the vacuum vessel They are linked by a specially developed mechanical interface which is damping the CFC vibration Each of the two CCDs has 50 pre scan and 50 over scan columns A 1 The two CCDs are read by two different amplifiers and a difference of up to 10 in the bias level of the two CCDs might be expected Following we present the CCD test results as they were obtained on the test bench in Garching before installation at the telescope Property Jasmin red Linda blue CTE vertical 50 kpx s 0 999992 0 9999991 CTE horizontal 50 kpx s 0 999991 0 9999990 CTE vertical 416 kpx s 0 9999997 0 99999991 CTE horizontal 416 kpx s 0 9999995 0 9999990 Non linearity not available lt 0 298 Read out noise 50 kpx sec 2 87 0 1e7 2 76 0 09e7 Read out noise 416 kpx sec 7 05 0 23e7 5 5 0 16e7 Conversion factor 50 kpx sec 0 63 0 02e7 ADU 0 62 0 02e7 ADU Conversion factor 416 kpx sec 1 42 0 04e7 ADU 1 4 0 04e7 ADU Dark current at 110C not measured not measured Quantum efficiency peak 82 at 440nm peak 85 at 460nm Cosmetics science grade
7. ASCII files not MIDAS tables For details and format description see the DRS user manual available in http www ls eso org lasilla sciops 3p6 harps manuals html 7 2 Data archiving 7 2 1 La Silla and Garching archives HARPS raw data are compliant with the requirements of ESO s Data Interface Control Board DICB They are stored locally at La Silla and in the central Garching Science Archive however see 7 2 3 Since the amount of raw data generated by HARPS can be quite substantial exceed ing 20Gb night in case of asteroseismology HARPS will use the Next Generation Archive System NGAS 7 2 2 La Silla data archiving unit For convenient archiving of raw observation data and pipeline products a dedicated Data Archiving software DAU is available at La Silla It allows the observers to write the results of their observing runs on DVDs or on their own USB disks choosing the data product they want raw data reduced data or both log files Appendix B contains the instructions on how to do this ESO will make available the necessary blank DVDs for normal observing runs e g planet search classical fibre spectroscopy to store the raw and reduced data in visitor and service mode However due to the enormous amount of raw data produced during a typical asteroseismology run gt 20Gb night the backup media will be a user s USB disk In case only the pipeline products are requested they can fit in a single DVD and the sta
8. The latest information updates about the HARPS instrument can be found on the HARPS web pages http www ls eso org lasilla sciops 3p6 harps General information about observing at La Silla is available from the La Silla web pages http www ls eso org 2 HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 1 3 Contact information In case of specific questions related to visitor mode observations please contact the La Silla High Resolution Spectroscopy Team likewise for specific questions related to Service Mode observations and proposal preparation ls harps eso org 1 4 Acknowledgments Most of the contents of this manual is based on information from the HARPS Consortium Observa toire de Gen ve Observatoire de Haute Provence Universitat Bern Service d A ronomie ESO La Silla and Garching in particular by F Pepe and D Queloz and from La Silla Science Operations G Lo Curto and T Dall Releases of this documents are based on the original version edited by Gero Rupprecht Feedback on this User Manual from users is encouraged Please email to 1s harpsCeso org Chapter 2 HARPS Characteristics 2 1 Instrument Overview HARPS High Accuracy Radial velocity Planetary Searcher is an instrument designed for the mea surement of Radial Velocities RV at highest accuracy It was built by the HARPS Consortium consisting of Observatoire de Gen ve Observatoire de Haute Provence Physikalisches Institut der Universit t Be
9. and nothing can be said at the moment about the obtainable RV accuracy with the iodine self cali bration method with HARPS For reference the iodine cell method could yield a long term 2 years accuracy of 2 65 m s with the UVES spectrograph with a S N of 66 per pixel and a resolving power of 100000 120000 similar to the HARPS one of 115000 M K rster et al A amp A 403 1077 2003 The short term RV accuracy of HARPS with the simultaneous Thorium reference method has been demonstrated during the three commissioning phases to be below 1 m s The RV accuracy can be affected by several factors external to the instrument e photon noise e telescope focus e centering errors e Thorium calibration errors As an example during the second HARPS commissioning June 2003 a 7 hours series of short exposures on a Cen B was recorded yielding a RV rms of 0 52 m s Of these 0 45 m s are due to the stellar oscillation 0 17 m s to photon noise 0 08 m s to Thorium calibration errors drift tracking and the remaining 0 18 m s to centering errors telescope focus errors and any other error source not yet identified The following systematic study is from data obtained with the simultaneous Thorium reference method only 4 1 Photon noise For a G2 star a RV rmsynoton 1 m s due to photon noise only is reached with a S N ratio of about 100 per pixel at 550nm The photon noise introduced in the RV measurement scales approximately as
10. ghosts as a percent of the flux in the order 5 Characteristic optical data of HARPS 7 Exposure meter count rates 10 Overall efficiency of the HARPS system See text 11 Fiber illumination scheme for each template 24 Execution times overheads 26 Off line overheads 26 Comparison of the HAM and EGGS performances 41 ix Chapter 1 Introduction 1 1 Scope This User Manual is intended to give all necessary information to potential users of the HARPS instru ment to help them decide on the opportunity to use the instrument for their scientific applications to be used as a reference when writing observing proposals and when preparing the observations For this purpose we give e an overall description of the HARPS instrument its performance and its observing modes e information on the preparation of the observations e information on the observing process e a description of the HARPS data and near real time pipeline data reduction The following documents are closely related to this manual and should be consulted as well e the P2PP User Manual e the HARPS Template Guide Both are available through the Information Sources section of the HARPS web pages http www ls eso org lasilla sciops 3p6 harps 1 2 Additional information
11. 100 4 1 S N550nm ES rms m s photon 21 22 HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 4 2 Telescope focus A defocus of the telescope of 30 encoder units introduces a RV offset of 1 m s In a typical focus sequence which can take from 5 to 10 minutes is reached a precision in the determination of the optimum focus of 5 10 encoder units 4 3 Centering errors A de centering of 0 5 introduces a RV offset of 3 m s The present guiding and the dynamic centering systems introduce a RV error at most of 0 2 m s rms 4 4 Thorium calibration errors An error of about 0 5 m s is given to the Thorium calibration drift tracking and zero point The zero point error is by far the dominant source 45 EGGS RV accuracy Radial velocity accuracy in the EGGS mode is still under study Preliminary measurements indicate that systematics could introduce effects as strong as 30m s Chapter 5 Preparing the observations 5 1 Introduction HARPS uses the standard ESO way of observing i e pre prepared Observing Blocks This chapter describes the philosophy behind this concept the available tools and the HARPS specific input In order to reach the full performance of HARPS with respect to the determination of accurate radial velocities the following items should be noted 1 to achieve an accurate solar system barycentric Radial velocity correction of 1 m s the target coordinates must be known to within 6 including
12. 3 G3V star 5700 K Wavelength nm Diffused stray light 90 680 116 527 160 383 Table 2 1 Level of diffuse stray light and ghosts as a percent of the flux in the order Figure 2 2 Spectral format of HARPS Blue orders are down red are up bluest orders The instrumental polarization was not detected down to a level of 1074 for zenith angles smaller than 60 degrees Closer to the horizon the instrumental polarization grows rapidly if the Atmospheric Dispersion Corrector is in the light beam Also the polarimetric data of HARPS are reduced by the online pipeline In the following is presented a brief description of the HARPS components the fibre adapter on the telescope the calibration unit and the fibre links connecting these components A sophisticated online data reduction pipeline is also part of the system section 8 The hardware part of the system is schematically illustrated in Fig 2 4 2 2 Operations overview The HARPS instrument is mounted on the Cassegrain focus of the 3 6m telescope in La Silla It shares the focus with other instruments EFOSC2 and CES TIMMI2 retired at the end of period 77 For this reason it is not always attached to the telescope Since the connection of the CES fibre into the HARPS adapter and the retirement of the TIMMI2 instrument end of P77 instru ment changes at the telescope are needed only when switching between EFOSC2 and HARPS and viceversa The instrument change is a l
13. 45 minutes If the total data size is too big for one DVD the raw files will be automatically compressed by about 50 approximately 170 gzipped FITS files fit on one DVD If the volume is still too large the user has to split the night in two e g lt date gt 1 and lt date gt _2 directories To archive both directories the complete name of the directory has to be put in the Night field Both direc tories have to be archived separately The DAU will automatically search data raw lt dir_name gt data reduced lt dir_name gt etc The Compute size button computes the total size of the data saved in the BACKUP under the lt date gt directory once the data are copied in the warch disk ol 52 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 Appendix C List of acronyms ADC AG BOB CCD CCF CES CFC CU DAU DFS DHS DICB DIMM DRS E2DS ESO ETC FIERA FITS HCFA HARPS ICS IWS ND NGAS NTT OB OG OS P2PP PSF RITZ RID RV SA SNR TBC Atmospheric Dispersion Compensator Auto Guider Broker of Observing Blocks Charge Coupled Device Cross Correlation Function Coude Echelle Spectrograph Continuous Flow Cryostat Calibration Unit Data Archiving Unit Data Flow System Data Handling System Data Interface Control Board Differential Image Motion Monitor Data Reduction Software Extracted 2 Dimensional Spectrum European Southern Observatory Exposure Time Calculator name for ESO s
14. PS Template Guide see section 1 1 In table 5 1 is shown the fibers illumination scheme as a function of the template used 5 3 1 Acquisition templates HARPS uses the acquisition template to preset the telescope and to set up the instrument configu ration for the selected observing mode The following acquisition templates are available e HARPS_ech_acq_thosimult for simultaneous Th exposures e HARPS_ech_acq_I2cell for 12 cell exposures e HARPS_ech_acq_objA for fibre spectroscopy no sky e HARPS_ech_acq_objAB for fibre spectroscopy with sky e HARPS_pol_acq_cir for circular spectro polarimetry e HARPS_pol_acq_lin for linear spectro polarimetry All the acquisition templates require an initial guess of the RV For optimum RV determination the expected radial velocity of the source should be entered with an accuracy of amp 2km s In case the RV value is not known the value 99999 will start an iterative process which will stop once the input and the output RVs differ by less than 1km s H RV computation is not desired the RV initial guess should be set to 99999 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 25 A concise description of the acquisition templates is given in the HARPS Template Guide see section 1 1 5 3 2 Observing templates HARPS uses two observation templates one for spectro polarimetry and one for all the other observing modes All instrument setup is done by the acquisition templates
15. an Iodine cell as an alternative to the standard Simultaneous Thorium Reference method In this mode fibre A is on the target fibre Bon DARK and the Iodine 16 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 cell inserted in front of the fibre A entrance to superimpose an Iodine absorption spectrum on the stellar spectrum 3 2 1 Performance The Iodine cell used in HARPS absorbs about 40 of the continuum from the source Exposure times supplied by the ETC have to be scaled accordingly The precision of HARPS using the Iodine self calibration method is still under investigation 3 2 2 Calibration A calibration sequence similar to the Simultaneous Thorium Reference method is recommended before the beginning of the night Moreover the 5 tungsten exposures series should be repeated with and without the Iodine cell However a specific sequence of observations is additionally needed during the night to later extract the Iodine information This sequence includes the observation of a star of spectral type B with and without the Iodine cell whenever a template of the target star is produced The target star template is produced by observing it without the iodine cell with a high signal to noise ratio 3 2 3 Observations The necessary acquisition and observing templates are available e HARPS_ech_acq_I2cell acquisition and setup for Iodine cell exposures e HARPS_ech_obs_all for Iodine cell exposures When using the EGGS instrument mod
16. anual Issue 2 0 3P6 MAN ESO 90100 0005 x 4296 y 4096 III x 4296 y 1 RED H 4296 raws TP SO PREIS oversean SU PREIS BLUE presen SO pre x 1 y 4096 4096 columns x l y 1 Figure A 1 Raw frame format 49 50 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 Appendix B Use of the Data Archiving Unit This appendix describes the use of the Data Archiving Unit DAU This unit allows the VA to write his her data raw and reduced to DVD The disks have to be DVD R General In order to archive the data of one night the following has to be done 1 launch the Data Archiving Unit on the wharch machine as harps user the command is dau csh 2 put a writable DVD DVD R General in the burner 3 indicate the night date in the Night field the only one which is white pressing the Enter key validates the entered value 4 wait until all the sizes are calculated it takes a minute or two 5 check the check boxes for the files to be backed up 6 click the Go button to start copying the files may take up to 30 minutes 7 de select all the boxes 8 press the Compute size button to see the total size of the files 9 select the box Prepare DVD 10 press Go to start creating the image may take 15 minutes 11 de select the Prepare DVD box select the Make DVD one 12 press Go to start burning the DVD may take
17. are two calibration templates one for circular and one for linear polarization They are used for flat fielding with the respective polarimeter HARPS_pol_cal_tun_cir HARPS_pol_cal_tun_lin HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 19 3 4 3 Observations Two dedicated acquisition templates and one observation template are used to observe with the polarimeter The templates are HARPS_pol_acq_cir HARPS_pol_acq_lin HARPS_pol_obs_all The acquisition templates have the usual entry fields while the observation template contains the series of retarder wave plate angles over which to perform the polarimetric observations 3 4 4 Pipeline data reduction There are pipeline recipes to reduce both the calibrations and the spectro polarimetric science obser vations They are run online automatically from the HARPS pipeline application The data products are 5 fits files containing a one dimensional spectrum They contain the Total flux I and the U I Q I V I ratios The null spectrum containing the uncertainty on the Stokes parameters is also available 20 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 Chapter 4 RV accuracy The high RV accuracy obtainable with HARPS is a result of an extremely stable and strictly con trolled instrument and a data reduction software designed and optimized for the purpose The pipeline RV determination is optimized for data taken in the simultaneous Thorium reference method
18. before the start of the science observations are only necessary when using the Iodine self calibration method see section 3 2 2 6 4 Real time display Raw data coming from the instrument are displayed on a FIERA Real Time Display RTD Both CCDs are displayed in the same RTD fig 6 2 6 5 Observing very faint stars As explained in section 3 1 a variable neutral density filter is used to balance the intensity of the Thorium Argon calibration spectrum depending on the exposure time This works correctly for exposure times up to 2700 s For very faint stars which require even longer exposures this may lead to an overexposure of the calibration spectrum with contamination of the stellar spectrum As the ultimate accuracy of HARPS 1 m s will usually not be reached on such faint stars it is recommended not to use the simultaneous Thorium reference method but to rely on the excellent short term stability of HARPS and take separate wavelength calibration exposures immediately before and after the science exposure to interpolate and remove possible instrumental drift errors The additional time spent on this is negligible given the long science integration 6 6 Ateroseismology Asteroseismology observations are particularly demanding from the point of view of data transfer and storage Users are recommanded to use USB disks as a storage media Asteroseismology observers need to pay special attention to the guiding parameters Guiding cor rect
19. data reduction includes better corrections for instrumental effects and zero point definition wavelength calibration and it is substantially faster HARPS is a fibre fed cross dispersed echelle spectrograph located in the Coude floor of the 3 6m telescope For the sake of thermal and mechanical stability the spectrograph is enclosed in a vacuum vessel evacuated to a pressure lt 10 mbar and maintained to a temperature of 17 C constant within 0 005 C RMS No moving parts are located inside the vacuum vessel VV The spectrograph itself has only one possible mechanical configuration All necessary moving parts are located in the Harps Cassegrain Fibre Adapter HCFA with the exception of the shutter which is located just outside of the vacuum vessel The optical design shown in figure 2 1 is similar to UVES at the VLT 4 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 Figure 2 1 Optical layout of the spectrograph Its echelle grating is operated in quasi Littrow conditions off plane angle 0 721 deg blaze angle and the collimator in triple pass mode A white pupil configuration has been adopted with the cross disperser placed at the white pupil The dioptric camera images the cross dispersed spectrum on a detector mosaic of two CCDs Two fibres A and B feed the spectrograph one object fibre and one reference fibre science fibres The spectra of the light from both fibres are formed by the spectrograph side by side on t
20. e red chip Jasmin Wavelength increases from lower left to upper right HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 33 at about 6 and 9 mHz This is possibly due to a hard point in the right ascentions main gear or motor and we are trying to fix it The users however should be aware of it The amplitude of this signal can reach 30cm s This noise is only noticed in short lt 20 seconds exposures When using exposure times larger than 20 seconds the guiding is able to compensate the glitch introduced by the gear motor Observers should ask the operators proper setting of the guiding and dynamic centering parameters 6 7 End of the night No further calibrations are necessary after the end of the science observations To prolong the life of the calibration lamps HARPS is switched to the so called Dark mode All lamps still in use at the time are thereby switched off and the dust cover in the fibre adapter is put in place to protect the fibre entrance The Io cell will be left on until it is turned off manually All electronics are in stand by all internal house keeping functions temperature and pressure control logging continue to operate 34 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 Chapter 7 Data products and archiving 7 1 Data products HARPS writes FITS files with extensions containing the data of both CCDs The size of one raw data file is approximately 32Mb By default the data product
21. e the templates with the eggs prefix should be used instead than the templates with the ech prefix which are dedicated to the HARPS mode For a detailed description of the templates see section 5 3 and the HARPS Template Guide 3 2 4 Pipeline data reduction In the Iodine self calibration method the pipeline does spectrum extraction and applies the wave length calibration If TARG_RV is not set to 99999 a radial velocity is computed using the CCF technique Conversely RV calculation can be turned off by entering 99999 Considering that 12 lines pollute the spectra the radial velocity should be considered as an approximate value For more details about the pipeline Data Reduction Software DRS please refer to the DRS user manual 3 3 Classical fibre spectroscopy Classical fibre spectroscopy can be done in two different ways depending on the target and the goal of the program 1 fibre A on target and DARK on fibre B objA observation 2 fibre A on target and fibre B on the sky objAB observation HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 17 objA observation should be preferred for objects much brighter than the sky moon background where a careful CCD background correction may be needed For this type of observation the pipeline provides only the spectrum of the fibre A and uses fibre B order location to compute the CCD background objAB observation should be preferred when a sky background corr
22. ection may be needed The data reduction pipeline provides an extracted spectrum for each fibre The sky correction is left to the user The high stability of the instrument makes wavelength drifts very small If the same calibration sequence than for the simultaneous Thorium reference method is run before the beginning of the night a RV accuracy generally better than 3 m s along the whole night can be expected 3 3 1 Performance For estimates of the SNR with an accuracy of about 10 under given observing conditions the ETC available via the HARPS web pages http www 1s eso org lasilla sciops 3p6 harps can be used see section 5 5 3 3 2 Calibrations A calibration sequence similar to the Simultaneous Thorium Reference method is recommended before the beginning of the night 3 3 3 Observations The necessary acquisition and observing templates are available e HARPS_ech_acq_objA acquisition and setup for fibre spectroscopy with the object in fibre A e HARPS_ech_acq_objAB acquisition and setup for fibre spectroscopy with the object in fibre A and sky in fibre B e HARPS_ech_obs_all for fibre spectroscopy exposures When using the EGGS instrument mode the templates with the eggs prefix should be used instead than the templates with the ech prefix which are dedicated to the HARPS mode For a detailed description of the templates see section 5 3 and the HARPS Template Guide sec tion 1 1 3 3 4 Pipeline data reduct
23. ectral format Spectral resolution Sampling per spectral element Spectrum Separation Order separation Jasmin Order separation Linda Spectrograph stability 2 fibres each 1 diameter on sky distance 114 spectral range 380 690nm collimated beam diameter 208mm RA 31 6 gr mm blaze angle 75 mosaic 2x1 on Zerodur monolith 840 x 214 x 125mm efficiency gt 65 in the visible FK5 grism 257 17 gr mm blazed at 480nm 240 x 230 x 50mm T 73 average Zerodur with protected silver coating f 1560mm used di ameter 730mm triple pass all dioptric 6 elements in 3 groups f 728mm f 3 3 T gt 85 22k x 4k EEV CCDs pixel size 15 um inside the spectrograph 7 5 upper red CCD Jasmin orders 89 114 533 691nm lower blue CCD Linda orders 116 161 378 530nm RS 115 000 measured 3 4 px per FWHM 17 3 px fibres A and B order 89 1 510mm 100 7px order 114 0 940mm 62 7px order 116 0 910mm 60 7px order 161 0 513mm 34 2px 1 m s in one night under normal conditions Table 2 2 Characteristic optical data of HARPS carriage and it takes less than one minute In one night it is possible to use both HARPs and CES with minimum overheads Since the beginning of the ESO period 78 a new mode of HARPS is made available to the users EGGS Usage of this mode has to be declared in the phase 1 proposal preparation as 1t involves installation of the fibres in the HCFA In this case the CES fibre will be r
24. either by the same or independently by two different calibration sources Of the three Thorium Argon lamps the lamp dubbed THAR is the absolute reference and its use should be minimized Typically it is used for 5 minutes per day during the afternoon calibrations shining on fibre A The lamp named THAR2 is used to measure the instrument drift in parallel with the science observations THAR3 is a hot spare The lamp can be switch on at any moment It is particularly useful when one of the other lamps burns out in the course of the night Table 5 1 illustrates the fiber illumination scheme as a function of the template used 2 5 Fibre adapter All optical fibres are connected to the HCFA which forms the interface to the telescope The HCFA provides several functions 1 Illumination of the object and the reference fibres each can be separately fed by the object the sky light from a calibration source or it can be dark 2 Correction of atmospheric dispersion by means of an ADC 3 Switching between HARPS and CES from end 2004 on fibres 4 Feeding of the fibre viewer technical CCD camera for guiding 5 Introduction of the Iodine cell into the object light path 6 Attenuating the reference light beam from the ThAr lamp via a neutral density wheel to an equivalent exposure time of 40s at zero density This can be done for exposure times from 40s to 5400s HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005
25. emoved and the EGGS fibres installed instrument or mode changes during the night will be allowed depending on which fibres are mounted in the adapter 2 3 Fibre links The spectrograph is linked to the 3 6 m telescope via two optical fibres The fibre link incorporates an image scrambler which is fixed on the vacuum vessel and contributes to stabilize the input point spread function PSF of the spectrograph The scrambler serves also as vacuum feed through for the fibres and in addition houses the exposure shutter The shortest useful exposure time supported by the shutter is 0 2 seconds A second fibre link connects the Calibration Unit CU section 2 4 next to the spectrograph with the HARPS Cassegrain Fibre Adapter HCFA on the telescope see figure 2 1 2 4 Calibration unit The Calibration Unit CU contains a Tungsten flat field lamp three Thorium Argon lamps for spectral calibration and a tungsten lamp illuminating an iodine cell for tests purposes It is con nected via two optical fibres to the HCFA which redirects the light of the calibration sources into 8 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 3 6m telescope fibre adapter science fibres 2 calibration fibres 2 Calibration unit HARPS spectrograph Figure 2 4 The main components of the HARPS system the spectrograph fibres as required The two calibration fibres can be fed
26. enghty operation that takes a full day and it is scheduled at the beginning of the period when time allocation for the telescope and the instruments is defined In contrast the switch between CES and HARPS requires only the movement of the HCFA fibre 6 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 mie see n 523 22 0 0014 4 4 1 47e 04 0 00664 5 3e 03 1 2e 02 518 78 0 0014 4 4 1 34e 04 0 006458 K 9e 03 fl 2e 02 514 43 0 0014 4 4 1 39e 04 0 00631 Be 03 H 2e 02 510 14 0 0014 4 3 1 4e 04 0 00613 5 1e 03 1 2e 02 505 92 0 0014 4 3 1 41e 04 0 00595 B 1e 03 1 2e 02 501 75 0 0014 4 2 1 29e 04 0 00579 4 7e 03 Liest 97 70 0 0014 4 2 1 32e 04 0 00564 K 5e 03 Liest 93 69 0 0013 4 1 1 31e 04 0 0055 4 7e 03 L 1e 02 89 74 0 0013 4 1 1 31e 04 0 00536 4 7e 03 Lie 1455 85 0 0013 4 1 09e 04 0 00521 He 03 fle 02 82 03 0 00134 1 25e 04 0 00505 M 5e 03 1 1e 02 78 26 0 0013 3 9 1 23e 04 0 00492 A5e 03 1 1e 02 474 56 0 0013 4 1 21e 04 0 009488 4e 03 Liest 470 91 0 0013 4 H 14e 04 0 00486 Wiert Liest 467 31 0 0013 4 1 14e 04 0 0048 Mie 1 1e 02 63 77 0 0013 4 1 16e 04 0 0047 Wie Lie 460 29 0 0013 4 1 12e 04 0 00458 K 1e 03 Liest 556 55 0 0012 8 9 1 12e 04 0 00446 Wiert Liest 53 47 0 0012 3 9 P 9e 03 0 00435 B 6e 03 PI 50 14 0 0012 3 8 1 09e 04 0 00424 Weu jet 146 85 6 0012 3 8 9 75e 03 0 00415 Bier 543 61 6 0012 3 8 9 58e 03 6 0047 3 50103 97 40 42 0 0012 B S 72e 03 0 004 B 2e 03 P3 37 28
27. es of the following night Template HARPS_ech_cal_tun e A sequence of 5 Tungsten lamp exposures defined by NREP 5 where both fibres are simul taneously illuminated This sequence is used by the data reduction pipeline for producing a spectral master flat field which will be stored in the local calibration data base if it passes the quality control by the pipeline and used for the subsequent reduction of the scientific exposures of the following night Template HARPS_ech_cal_tunAB e 2 for reasons of redundancy Thorium exposures in which both fibres are simultaneously fed by light from the Thorium Argon lamps The ThArl long term reference lamp illuminates fibre A the ThAr2 lamp inlluminates fibre B During the night only the ThAr2 lamp will be used as the reference The ON time of the ThArl lamp is minimized in order to keep it as an absolute reference along the years Each exposure is used to build a wavelength solution The instrumental drift with respect to the previous calibration frames is measured expressed in m s If accepted by the built in quality control the wavelength solution is stored in the local calibration data base and used for the subsequent reduction of the scientific exposures of the following night Template HARPS_ech_cal_thoAB The user may then repeat a sequence of flat fields with more than 5 exposures if a SNR higher than 300 is aimed at in later science exposures As reference 30 flat field exposures of 2
28. g rules The raw frames are stored in FITS format by the DFS with the ESO VLT standard naming rules HARPS YYYY MM DDTHH MM SS SSS fits with YYYY MM DD and HH MM SS SSS being respec tively the date and time of the start of the observation Raw frames are written in extended fits format each CCD being on a different plane of the frame This is effective as of January 1st 2004 Pipeline products are stored in FITS format with the same generic names plus an additional suffix describing its format see next section for details and the specific fibre name A or B For example HARPS YYYY MM DDTHH MM SS SSS_E2DS_A fits is an E2DS format image of the fibre A product by the DRS derived from the HARPS YYYY MM DDTHH MM SS SSS fits raw frame Tables in ASCII format are also produced by the DRS The relevant log books of the DRS is named DRS whadrs YYYY MM DD It is stored with all the other logs in the msg directory It is automatically archived by the DAU on the DVD A 2 Data formats A 2 1 Raw frames The raw frame corresponds to a 4296 x 4096 integer 35 242 560 bytes matrix written on disk in extended FITS format see Fig A 1 each CCD being on a different plane of the frame This image includes a 4096 x 4096 sensitive zone plus 4 overscan zones of 50 pixels each The following generic descriptors are used by the DRS MJD OBS Modified Julian Day start float EXPTIME Total integration time s float DATE OBS Date and Time of observat
29. g wave plates one for linear and one for circular polarimetry The light is separated in two separate beams by a polarizing beam splitter Foster prism and imaged on the object and the sky reference fibers of HARPS After splitting by the Foster prism a second prism channels the second beam into the sky reference fiber The instrument polarization has been measured to be less than 1074 upper limit for zenith angles smaller than 60 degrees while the cross talk of the polarization signal is lower than 107 upper limit An appropriate sequence for circular polarimetry via the quarter wave plate QWP is e QWP at 45 SE 3 I V SE 5 1 V e QWP at 45 ST 5 1 V St 4 amp I V while for linear polarimetry the half wave plate HWP should be oriented e HWP at 0 9 1 1 0Q S 5 1 Q e HWP at 45 SP 4 1 Q S 4 1 Q e HWP at 22 5 SL 5 1 U S I U e HWP at 22 5 SE 1 U SF 3 1 U However the user is free to select as many angles as wanted in the polarimetric sequence template HARPS_pol_obs_all 43 44 HARPS User Manual Issue 2 0 __3P6 MAN ESO 90100 0005 Figure 10 1 Polarized line profiles of the star y Equus HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 Figure 10 2 Line profiles of a Centauri in the three Stokes parameters 45 46 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 Appendix A Description of archived HARPS data A 1 Data namin
30. grade 1 science grade grade 1 Readout time 4296x4096 px 50 kpx s 180s 416 kpx s 23 s Mosaic flatness peak to peak 15um CCD parallelism 12 Chip to chip gap 1215 45um The two CCDs are nicknamed Jasmin the red CCD and Linda the blue one Their quantum efficiencies are given in figures 2 5 and 2 6 respectively The read out mode of 50kpix s has shown to be more noisy than expected when measured at the telescope This mode has therefore been decommissioned and a new high gain low noise mode with a readout speed of 104kpix s has been made available The characteristics of the two modes available for scientific purposes are spelled out in the following table Property Jasmin red 78 Linda blue 77 Read out noise 104kpix s e7 3 0 2 8 Read out noise 416kpix s e 4 5 4 8 Gain 104kpix s ADU e 2 04 2 04 Gain 416kpix s ADU e 0 74 0 76 Bias 104kpix s ADU 198 196 Bias 416kpix s ADU 186 248 The read out time 4296x4096 pixels is of 87s and 23s for the 104kpix s and the 416kpix s modes respectively The 104kpix s read out mode or slow mode is particularly useful when observing faint objects 10 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 Stellar magnitude total count rate error on mean time worst case De cps of exposure eure sec RV error m sec saturated 2 850 000 456 000 12 000 120 19 8 Table 2 3 Expected count rate of the expo
31. he detector Although all care has been taken to avoid stray light and ghosts both are present at some level most noticeably in the blue part of the spectrum table 2 1 Ghosts seems to be due to third order reflections in the grism The instrument is coupled to the telescope through an adapter the HARPS Cassegrain Fiber Adapter HCFA Two calibration fibers transmit the light from the calibration unit located in the Coude floor to the HCFA and inject it in the two science fibers for calibration The characteristic optical data are given in table 2 2 The spectral format is shown in Fig 2 2 Since the beginning of Period 78 a new mode is offered for HARPS In the new mode the photon collecting efficiency is increased by a factor up to two dependent on the seeing at the expense of Radial Velocity accuracy The new mode could be useful for faint objects for which a radial velocity accuracy of no better than 30m s is required The characteristics of the new mode and its operation are described in section 9 Starting from period 86 a polarimeter is available on HARPS The unit is able to perform both circular and linear polarimetry Preliminary measurements of the throughput indicate a light loss with respect to the base mode of HARPS in the range of 20 to 30 increasing to 40 in the HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 5 Halogen lamp 3000 K Wavelength nm Diffused stray light 90 680 116 527 160 38
32. ibre hole image on the guide camera changes when the iodine cell is inserted in the light path In addition the focus position of both the auto guider and the telescope change and have to be re adjusted This takes about 5 10 min once during the night If more changes cell on cell off are required during the night the previously defined optimum values of the guide camera and telescope focus as well as the fiber position can be re set very quickly overhead 30 s For a proper reduction of the data taken with the Iodine cell it is necessary to obtain the following spectra e target through the iodine cell S Napprox200 e target without iodine cell template S N 400 e B star with and without the iodine cell S N 400 The spectra of the B star are only needed when the template spectra is obtained In this case they must be taken in the same night during which the template spectra are recorded Sufficient time for obtaining these spectra must be foreseen 5 5 The HARPS Exposure Time and Spectral Format Calculator The HARPS Exposure Time Calculator ETC models the instrument and detector in their different configurations the EGGS mode is not included yet but take as a reference a gain of 2 in flux with a seeing of 1 4 It can be used to compute the detailed spectral format wavelength and order number as function of position on the detector and the expected SNR for the specified target under given atmospheric conditions a
33. ion The pipeline performs the same reduction as for the simultaneous Thorium reference method sec tion 3 1 4 but it does not correct for the instrumental drift this one not being traced by the Thorium lamp as in the simultaneous Thorium reference method It does not perform sky subtraction For more details about the pipeline Data Reduction Software DRS please refer to the DRS user manual For pipeline execution times see section 5 4 1 18 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 Throughput using HAM fibers 10 HARPS HARPSpol circular fiber A B HARPSpol linear fiber A B HARPSpol circular fiber A Bir s HARPSpol linear fiber A HARPSpol circular fiber B HARPSpol linear fiber B e 6 gt D DEEM CELA i ee e 2 202300 iS PINS E CH res fi OL 400 450 500 550 600 650 Wavelength nm Figure 3 1 Throughput of HARPS with and without the polarimeter for both the linear and the circular polarimeter 3 4 Polarimetry The HARPS polarimeter allows to perform both linear and circular polarization The retarder wave plate is located in the HCFA above the fiber head Only the HAM fibers can be used in conjunction with the polarimeter 3 4 1 Performance Preliminary measurements of the throughput indicate a light loss with respect to the base mode of HARPS in the range of 20 to 30 increasing to 40 in the bluest orders see figure 3 1 3 4 2 Calibrations There
34. ion string RA RA of the target float DEC DEC of the target float EQUINOX Equinox of observation float The DRS needs as well the following HIERARCH ESO descriptors 47 48 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 DET1 READ SPEED CCD Readout mode speed port and gain string DET OUTi GAIN Conversion from electrons to ADUs of port i float DET OUTi RON Readout noise of port i e float DET WIN1 DIT1 Actual sub integration time s float DET WIN1 DKTM Dark current time s float DET DPR CATG Observation category string DET DPR TYPE Observation type string INS DET1 TMMEAN Normalized mean exposure time on fibre A float INS DET2 TMMEAN Normalized mean exposure time on fibre B float INS OPTI5 NAME Lamp name on fibre A string INS OPTI6 NAME Lamp name on fibre B string OBS NAME OB Name string OBS START OB Start Date and time string TPL ID Template signature ID string OBJECT TYPE What is on fibre A and B string OBJECT SP Object spectral type string OBJECT RV Object expected RV string TEL TARG RADVEL Object expected RV string 1 the use of this keyword made by the DRS is wrong the keyword shall be later replaced by OBJECT TYPE not yet implemented by the DICB shall replace some of the DPR TYPE current function not implemented yet in the DICB 3 not implemented yet but needed for optimum RV computation 4 this keyword shall be later replaced by OBJECT RV HARPS User M
35. ion 70 sec DRS pipeline extra time for each RV calculation 30 sec spectrum ThAr lamp pre heating once at the beginning of the night 2 min minimum 10 min rec ommended 15 min maximum Iodine cell pre heating once at the beginning of the night 2 hours Table 5 3 Off line overheads 5 4 3 Fast time series observations asteroseismology The shortest exposure time possible with the HARPS shutter is 0 2 seconds while the shortest exposure in simultaneous thorium exposure mode is 15 seconds minimum exposure time to achieve a 15 cm sec instrument drift tracking For each CCD frame there is an overhead readout attachment of fits header etc of 32 seconds in the fast readout mode 416 kpx sec With 15 sec exposure time on sky 50 seconds cycles have been achieved The pipeline presently implemented is able to reduce this flood of data in nearly real time Reduction of one frame lasts about 24 seconds the pipeline no frames will be eft behind 5 4 4 Iodine cell out of service since May 2004 The Iodine cell needs to be in a thermally stable state before it can be safely used This means that it has to be switched on at least two hours before the first exposure through the cell should be done HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 27 This constraint holds both for science and for calibration exposures Target acquisition with the Iodine cell is done through the cell This makes that the position of the f
36. ions should be faster if the exposure time is short For example if the exposure time is less than 5 seconds guiding correction time should be no more than 2 seconds this is also the maximum correction frequency we can use for guiding due to the telescope reaction time The dynamic fibre centering correction time should be set to 10 15 minutes maximum 30 minutes however a quite long time interval which shall not be the same nor a fraction of the period of the star s oscillations which are being measured The rationale behind this choice is to diminish the low frequency noise in the RV power spectrum The minimum correction time for the dynamic fibre centering algorithm is 30s As from June 2004 a periodic signal is detected in the RV power spectrum at 2 8mHz and aliased 32 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 XA Rtd Real Time Display version 2 59 Moka File View Graphics Real time Help harps 2105 0 4509 0 23 57 39 733 01 15 06 00 2000 Min 210 Max 302 3 1 16 Low aro High foz Auto Set Cut Levels scale vex Z ziS am Camera harps E image select object scroll image measure WCS Control JH select region Figure 6 2 The Real Time Display of a HARPS spectrum taken with the tungsten lamp illuminating both fibers The lower part is the blue chip Linda the upper one is th
37. ith the average La Silla seeing of 0 9 The instrument efficiency includes the fibre link scrambler and spectrograph collimator in triple pass echelle cross disperser grism and camera Instrument and CCD efficiencies are measured in the laboratory Wavelength 350 400 450 500 550 600 650 690 nm Table 2 4 Overall efficiency of the HARPS system See text 12 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 DE efficiency w a H e I e n g t h Figure 2 5 Quantum efficiency of Jasmin the red CCD Quantum efficiency Wavelength nm Figure 2 6 Quantum efficiency of Linda the blue CCD Chapter 3 Observing modes HARPS both in its high RV accuracy mode and in its high efficiency mode EGGS offers the following observing modes 1 Simultaneous Thorium Reference observation 2 Iodine self calibration observation de commissioned 3 Classical fibre spectroscopy with and without sky From the point of view operations the EGGS mode is identical to the HARPS one Only the templates with the eggs prefix should be used instead than the templates with the ech prefix which are dedicated to the HARPS mode 3 1 Simultaneous Thorium reference method The Simultaneous Thorium Reference mode is the base line observation mode to get the best short term accuracy in radial velocity determination from the instrument In this mode fib
38. lculation using a template spectrum of ideally the same spectral type as the target star A comprehensive library of stellar spectral templates is being built up Currently it contains templates of the following spectral type others are in preparation e G2V The pipeline applies the following corrections detector bias dark flatfield cosmic ray removal and rebins the spectrum according to the wavelength calibration obtained in the afternoon or in the closest succeful HARPS_ech_cal_thoAB exposures The drift correction is not done At present the drift is measured and inserted in the fits header but is not applied to the RV value The user can do tha if he she wishes by simple subtraction Radial velocity and Julian date correction are calculated in the solar system barycenter reference based on the Bretagnon amp Francou 1988 VSOPSTE planetary theory Radial velocity computation is automatically done for all exposure types when a radial velocity value different from 99999 is provided by the TARG_RV parameter Conversely RV calculation can be turned off by entering 99999 The RV must be provided with an accuracy better than 1 2 km s in order to reach the expected performance For more details about the pipeline Data Reduction Software DRS please refer to the DRS user manual For pipeline execution times see section 5 4 1 3 2 Iodine self calibration method out of service since May 2004 HARPS offers the possibility to use
39. ndard procedure will be used to back up the data 7 2 3 Use of archived HARPS data HARPS data can be requested from the Garching Science Archive Data taken by observers in Visitor or Service Mode are subject to the usual proprietary period of 1 year According to the Agreement between ESO and the HARPS Consortium the data taken by the Consortium during their Guaranteed Time are subject to special protection e Raw data and reduced spectra I f A in the Earth reference frame at the time of the obser vation will be made public one year after observations e All raw data and radial velocity measurements obtained by the Consortium will be made public one year after the end of the 5 year Guaranteed Time period In practice this means that data obtained by the Consortium can be requested from the Garching Science Archive as usual one year after the observations However in order to make recovery of precise radial velocities impossible the keywords containing information about the exact time of the HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 37 observations will be filtered from all file headers raw and reduced by the Archive during the de archiving process This filtering will be applied until one year after the end of the 5 year Guaranteed Time period 38 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 Chapter 8 The Reduction of HARPS Data 8 1 The HARPS data reduction pipeline Every HARPS frame is processed by
40. nual is available from the ESO web pages at 23 24 HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 HARPS_ech eggs_acq_thosimult Star ThAr lamp 2 3 HARPS_ech_acq_I2cell Star Dark HARPS_ech eggs_acq_objA Star Dark HARPS_ech eggs_acq_objAB Star Sky HARPS_ech eggs_cal_thoAB ThAr lamp 1 ThAr lamp 2 3 HARPS_ech eggs_cal_tun exposure 1 Tungsten Dark HARPS_ech eggs_cal_tun exposure 2 Dark Tungsten HARPS_ech eggs_cal_tunAB Tungsten Tungsten HARPS_ech_cal_tunAI2 HCFA 12 cell Dark HARPS_ech_cal_tunI2AB CU 12 cell CU 12 cell HARPS_pol_acq_cir Circular pol Circular pol HARPS_pol_acq_lin Linear pol Linear pol HARPS_pol_obs_all Polarimeter Polarimeter Table 5 1 Fiber illumination scheme for each template http www eso org observing p2pp Observers using HARPS in Visitor Mode should prepare their OBs in advance using the HARPS Instrument Package which is automatically downloaded once P2PP is started and the HARPS program is selected from the list of the user s approved programs OBs prepared at the observer s home institution can be quickly imported after having ftp ed them in the proper machine in La Silla in the P2PP running at the telescope console and be ready for execution Service Mode observers need to check in their OBs with ESO see the La Silla web pages http www 1s eso org lasilla sciops for details For a concise description of all HARPS templates and the parameters selectable with P2PP consult the HAR
41. ograph for accurate radial velocity measurements by Baranne Queloz Mayor et al A amp AS 119 373 1996 In order to get the full performance of the pipeline with respect to the determination of accurate radial velocities the following items should be noted 1 to achieve an accurate solar system barycentric Radial velocity correction of 1 m s the target coordinates must be known to within 6 including proper motion 2 the RV of a star needs to be known to within 1 2 km s to give the pipeline a reasonable starting point for the RV computation 39 40 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 8 3 Iodine cell data On I2 cell data the DRS provides to the user a wavelength calibrated spectrum For further analysis the observer should consider the following input data 1 high SNR template spectrum of the science object without I gt cell 2 high SNR spectrum of a B star taken through and without the I gt cell during the same night as the template spectrum of the science object 3 Fourier transform spectrum of the Iodine cell For the HARPS Iodine cell this FTS is available from the HARPS web site http www ls eso org lasilla sciops 3p6 harps The extraction of the I2 information itself is left to the observer The description of one method to model the data is given in the paper The planet search program at the ESO Coud Echelle Spectrometer I Data modeling technique and radial velocity precision
42. or and S N is given by the following formula 100 S Ns50nm As a rule of thumb an photon noise error of 1 m s or S N 100 can be achieved for a 6th magnitude G dwarf in 60 seconds in the HARPS mode Note that due to the small fiber aperture on the sky 1 the performances are critically seeing dependent 3 1 rms m s In the EGGS mode the efficiency increases by up to a factor of 2 with respect to what indicated by the exposure meter with a seeing of 1 4 but the RV accuracy of this mode is hampered by systematics to 30m s 3 1 2 Calibrations The Simultaneous Thorium Reference Method needs a sequence of calibration exposures to be taken before the beginning of the night No further calibration exposures are required during the night In order to produce the correct calibration sequence the available observing block RV Standard Calibration should be executed without changes before the beginning of the night It includes e 1 bias exposure The CCD bias is very stable only one bias is therefore needed by the pipeline Template HARPS_ech_cal_bias e 2 Tungsten lamp exposures where respectively fibre A and fibre B are successively fed by the Tungsten lamp These exposures are used for order location which is done automatically by the pipeline The processed products are stored in the calibration database if they pass the quality control of the pipeline and used for the subsequent reduction of the scientific exposur
43. ormance ad ug en ua D Le ee a Be ae ee 342 Calibrations we eA rain ana pa ee aria Bas 34 3 Observations ss sr aa aaa ae ae ee 3 4 4 Pipeline data reduction a ee ii iv 9 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 RV accuracy AT PHOLONANOIS diario re i a e n Bae Gages ek 42 Telescope foc s etse Da ein eee el ana A MO ele 4 3 Centering errors ves sea da a EE DE a 4 4 Thorium calibration errors 4 5 EGGS RV accuracy estudi ela De net Ape e a en ue Aa Preparing the observations DL Introduction 24 ag Aura pena tir nie Binks wed Las rie Boe dm re 5 2 Introducing Observing Blocks 5 3 PIPPI Wa a ina A tn LR teste Late nine EE 5 3 1 Acquisition templates ee 5 8 2 Observing templates 5 3 3 Calibration templates DA Overheads acs poneva do e dee SE na a Da is nee 5 4 1 Execution time overheads 5 4 2 Off line overheads 5 4 3 Fast time series observations asteroseismology 5 4 4 Iodine cell out of service since May 2004 5 5 The HARPS Exposure Time and Spectral Format Calculator Observing with HARPS 6 1 Bef resthe nicht is 2 244 2 LE Br MR ar aaa 6 2 Duringtheinisht ciano ee i A ee ae 6 2 1 Target acquisi
44. proper motion 2 the RV of a star needs to be known to within 1 2 km s to give the pipeline a reasonable starting point for the RV computation From the point of view preparation of the observations the EGGS mode is identical to the HARPS one Only the templates with the eggs prefix should be used instead than the templates with the ech prefix which are dedicated to the HARPS mode 5 2 Introducing Observing Blocks An Observing Block OB is a logical unit specifying the telescope instrument and detector parameters and the actions needed to obtain a single observation It is the smallest schedulable entity which means that the execution of an OB is normally not interrupted as soon as the target has been acquired and centered on the fibre An OB is executed only once when identical observation sequences are required e g repeated observations using the same instrument setting but different targets a series of OBs must be built Usually one OB consists of two separate entities the acquisition template and the observation template s For normal science observations HARPS uses four different acquisition templates dif ferent for the various observing modes and one common observing template They are described in section 5 3 and the HARPS Template Guide 5 3 P2PP P2PP is the standard tool for the building of observing blocks from the instrument specific templates A comprehensive description including the user ma
45. r Manual Issue 20 3P6 MAN ESO 90100 0005 List of Figures 2 1 Optical layout of the spectrograph 4 2 2 Spectral format of HARPS Blue orders are down red are up 5 2 3 Table showing the spectral format of HARPS and the expected number of electrons for a 1 minute exposure on a G2V star of magnitude 6 A seeing of 0 8 airmass 1 and new moon are the values of the selected parameters In the table the spectral bin is defined as one pixel This table is obtained by the HARPS Exposure Time Calculator ETO de a Lei De e sa 6 2 4 The main components of the HARPS system 8 2 5 Quantum efficiency of Jasmin 12 2 6 Quantum efficiency of Linda 12 3 1 Throughput of HARPS with and without the polarimeter for both the linear and the circular polarimeter al ra ES le ai e N n 18 6 1 The sky area accessible for HARPS 30 6 2 HARPS spectrum in the RIDD a 32 9 1 HARPS EGGS comparison 42 10 1 Polarized line profiles of the star y Equus 44 10 2 Line profiles of a Centauri in the three Stokes parameters 45 AT Raw frame format lara tica SE AE OR Ae A 49 vil vili HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 List of Tables 2 1 2 2 2 3 2 4 5 1 5 2 5 3 9 1 Level of diffuse stray light and
46. r of 20 cm s and is therefore negligible within the accuracy attainable with HARPS Users with crowded fields close binaries faint objects etc should prepare finding charts The guide camera can guide on stars of magnitude up to 17 In the fibre AB spectroscopy mode object sky the observer should verify that the sky fibre is not contaminated by light from other sky objects This should in the first place be done by checking on the Digital Sky Survey At the telescope it can be verified by e offsetting the telescope the sky fibre entrance is exactly 114 west of the target fibre e watching the count rate of the exposure meter photometer B It is important that the telescope is well focused at all times It is recommended to have a through focus sequence performed using the guiding camera and the exposure meter two to three times per 29 30 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 3 6m polnting limits DEC dag Figure 6 1 The sky area accessible for HARPS night or whenever the image quality observed on the guiding camera deteriorates significantly or whenever there is a significant temperature change few C A defocusing of 30 encoder units introduces an RV error of 1m s The accuracy of the telescope focus determination is within 10 encoder units 6 2 2 Pointing restrictions The usual pointing limit restrictions of the 3 6m telescope apply see Fig 6 1 The telescope dome shall be closed
47. rame A concise description of the observation template is given in the HARPS Template Guide 5 4 Overheads 5 4 1 Execution time overheads 5 4 2 Off line overheads The pipeline overheads are for reference only observations can proceed without the need for waiting the pipeline results ThAr lamp and iodine cell pre heating overhead have to be considered before the start of the afternoon calibrations 26 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 telescope preset incl dome rotation 5 min upper limit for large more than 180deg dome ro tation 2 min typical for new point ing within a few degrees from the previous position Fibre automatic redefinition and centering of object on the 1 min fibre start of guiding Instrument configuration readout time incl writing of FITS headers and transfer to 23s with 416kpx s readout IWS speed 87s with 104kpx s readout speed minimum time between successive exposures 32 sec 416kpx s switching between ThAr and lodine modes telescope focusing at the beginning of the night to be re 10 min peated 4 5 times during the night HARPS EGGS or HARPS CES instrument change Polarimeter insertion 15s circ 30s lin 15s switch lin circ Polarimeter full rotation Table 5 2 Execution times overheads Tom DRS pipeline for thosimul without RV computation 110 sec DRS pipeline for objA without RV computation 50 sec DRS pipeline for objAB without RV computat
48. re B is fed by the Thorium lamp located in the calibration unit see figure 2 4 while fibre A is on the stellar target A variable neutral density ND filter is used to keep the Thorium spectrum at a flux level equivalent to a 40 seconds exposure with zero density Since the density to which the ND filter is set is computed by the instrument software from the exposure time as defined in the template the exposure time should not be modified from within BOB Broker for Observing Blocks Otherwise the flux levels of both fibres will not be balanced The Thorium spectrum which is recorded simultaneously with the stellar spectrum is used to compute the instrument drift from the last wavelength calibration usually done at the beginning of the night The calibration unit contains two identical ThAr lamps For the simultaneous reference method only the lamp ThAr2 can be used The lamp ThArl should be used as a reference only for the afternoon calibrations and switch off afterwards Ideally this should prolong the life time of this reference lamp 3 1 1 Performance For estimates of the SNR in the HARPS mode under given observing conditions the Exposure Time Calculator ETC available via the HARPS web page http www ls eso org lasilla sciops harps 13 14 HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 can be used with an accuracy of about 10 see section 5 5 The relationship between photon noise induced radial velocity err
49. rn Service d A ronomie du CNRS and with substantial contribution from ESO La Silla and ESO Garching Its purpose is to reach a long term radial velocity accuracy of 1 m s for slowly rotating G dwarfs Such precision enables the detection of low mass Saturn like extra solar planets and low amplitude stellar oscillations The design of HARPS is based on the experience acquired with ELODIE installed at the 1 93m telescope at OHP and CORALIE at the 1 2m Swiss Euler telescope at La Silla during the past 10 years by the members of the HARPS Consortium The basic design of HARPS is therefore very similar to these instruments The efforts to increase the HARPS performance compared to its predecessors address mainly three issues e Increase of the instrumental stability The spectrograph is installed in an evacuated and temperature controlled vacuum enclosure This allows to remove to a very large extent all RV drifts which would be produced by temperature variations or changes in ambient air pressure and humidity e Increase of the signal to noise ratio SNR on single RV measurements The improvement is attained through different steps First HARPS is installed on the ESO 3 6 m telescope Second the spectral resolution is increased by a factor of about two The higher spectral resolution helps also to reduce instrumental errors Third the spectrograph optics which is very similar to that of UVES is very efficient e Improvement of the online
50. s 0 20 2 ae ie ete a ec A A HARPS Characteristics 2 1 Instrument Overview 44444040 2 2 Oper tionsioverViewn fog ich ox Rai bas then ie dee a 2 3 BARE aR 22 3 2 Ne A Ac ie feet le hais es EEN 2A Calibration unit susa e ah dan na mena LE n 2 9 Fibresadapter s a 2 2 Da re ee ae nergie des 2 6 Detector and read out electronics 2 7 EXposure meet oa perde un A Abe AAA E ES 2 8 Data reduction software 2 9 System efhiclency i pi ilo es ia ee ea ee a ea Observing modes 3 1 Simultaneous Thorium reference method 3 1 1 Performante gt lt ic cnet Mat salade Ru it nm tale ga 3402 Calibrations gt fa 2 8 Lama den oe JLS Observations ve 2 24 eta BER ee Br le 3 1 4 Pipeline data reduction 3 2 Iodine self calibration method out of service since May 2004 320 Performance e usa ah eee en AA a ks ls 31222 Galibrabion 5 2 5 4 0222 AS AN ee BG ae A Se wine 3 23 ODSerVELIONS 2 4 Be eni ee ala Ba Se Sa BOO A AE ee e 3 2 4 Pipeline data reduction a 3 3 Classical fibre spectroscopy 3 31 Performance lt 2 ati ous a RL ee i 3 32 Calibrations z B Si ee er se dd E E EENEG 3 3 4 Pipeline data reduction a 34 Polarimetry planare Farai a aa lt Da das Do SAN Perf
51. s a function of exposure time It is available via the HARPS web pages http www ls eso org lasilla sciops 3p6 harps 28 HARPS User Manual Issue 20 3P6 MAN ESO 90100 0005 Chapter 6 Observing with HARPS 6 1 Before the night Depending on the observing method applied simultaneous Thorium reference Iodine self calibration classical fibre spectroscopy different sets of calibration exposures need to be taken before the start of the science observations For all three methods it is necessary to take a series of calibration exposures Bias Tungsten Tho rium because they are needed for the pipeline to produce optimum results A calibration OB RV Standard Calibration is available at La Silla and ready for execution to take these exposures De tails are described in section 3 1 2 More calibration exposures are necessary during the night when using the Iodine self calibration method see section 3 2 2 6 2 During the night Observations are performed in the standard VLT way i e OBs are selected by the Visiting As tronomer VA with P2PP and fetched by the Telescope and Instrument Operator TIO into BOB 6 2 1 Target acquisition guiding focusing Target acquisition is done by the TIO The object is centered on the entrance of the science fibre and kept there by an automatic dynamic centering algorithm with an accuracy of better than 0 2 pixels 0 05 This guiding accuracy introduces radial velocity errors of the orde
52. s of the online pipeline are archived as well Following is an example of the files that are included in the archiving of one exposure e Raw data file HARPS 2003 11 01T02 40 09 824 fits e Cross correlation function summary table with extracted RV per each order HARPS 2003 11 01T02 40 09 824_ccfG2_A tbl e Cross correlation function matrix in fits format for mask G2 HARPS 2003 11 01T02 40 09 824_ccf_G2_A fits e 2D extracted spectrum one row per order HARPS 2003 11 01T02 40 09 824_e2ds_A fits e 1D extracted full spectrum wavelength calibrated in the solar system baricentric frame HARPS 2003 11 01T02 40 09 824_s1d_A fits e Bisector from the cross correlation computed with a G2 mask HARPS 2003 11 01T02 40 09 824_bis_G2_A fits e Sample of Th lines intensities and FWHM only for TH calibration frames HARPS 2007 02 11T20 21 01 144_spot_th AB tbl Other summary tables are produced at the end of each night e cal_loc_ONE_result tbl order localization table e cal_FF result tbl flat field table e cal_TH result tbl Thorium table for wavelength calibrations 39 36 HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 e drift_result tbl Th lines drift in m s measured on fiber B filled only in the simultaneous Thorium reference mode e CCF_results tbl results of the CCF with measured RV and RV sigma filled only when the RADVEL field in the template is different by 99999 All files with extension tbl are
53. standard CCD controller Flexible Image Transport System HARPS Cassegrain Fibre Adapter High Accuracy Radial velocity Planet Searcher Instrument Control Software Instrument WorkStation Neutral Density Next Generation Archive System New Technology Telescope Observing Block Observatoire de Geneve Observation Software Phase 2 Proposal Preparation Point Spread Function Remote Integrated Telescope Zentrum Real Time Display Radial Velocity Support Astronomer Signal to Noise Ratio To Be Confirmed 53 54 TBD ThAr TIO UVES VA VLT XTC HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 To Be Determined Thorium Argon Telescope and Instrument Operator Ultraviolet Visible Echelle Spectrograph Visiting Astronomer Very Large Telescope eXtended exposure Time Calculator HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 59
54. sure meter as a function of stellar magnitude and estimated errors associated with the error on the photometric mean time of the exposure Count rates are indicative depend heavily on atmospheric conditions and slightly on stellar spectral type Calculated 2 7 Exposure meter The spectrograph possesses an exposure meter which serves to measure the stellar flux and to accu ratly measure the mid time of the exposure flux weighted mean of the time The mean time of the exposure delivered by the exposure meter is not used yet to correct the RV value This exposure meter consists of two photomultipliers one for each of the two fibres entering the spectrograph from the HCFA which use the light picked up at the gap between the two sub gratings of the echelle mosaic no light is lost due to this design The flux in both photomultipliers can be read at the instrument console It is also recorded in the FITS header cumulative average and center of gravity The expected count rates as a function of stellar magnitude and the estimated errors in RV are given in table 2 3 The number of dark counts per second fluctuates between 10 and 15 2 8 Data reduction software A sophisticated Data Reduction Software DRS is an integral part of the HARPS system It allows the complete reduction of all spectra obtained in all three observing modes in near real time in about 30 seconds Once the triggger software is started the start of the pipeline reduc
55. tests Endl M K rster M Els S 2000 A amp A 362 585 also available from the web http aa springer de bibs 0362002 2300585 small htm Chapter 9 HARPS high efficiency mode EGGS Since October 2006 the high efficiency mode of HARPS dubbed EGGS has been made available to the users This new mode uses a set of fibres with a projected aperture on the sky of 1 4 arcsec and a diameter of 100um while the standard HARPS fibres used for optimum radial velocity accuracy have an aperture of 1 arcsec and a diameter of 70um The light injection mechanism is via image injection for the High Accuracy Mode HAM and pupil injection for the high efficiency mode Moreover in order to minimize light losses the EGGS mode does not use the image scrambler The EGGS mode gains a factor of 1 75 in flux with respect to the base HARPS mode with a seeing of 0 8 arcsec see fig 9 The best RV accuracy reachable with the EGGS mode is of 30m s due both to the different injection mechanism and the absence of the image scrambler The ghost contamination is higher in EGGS than in HAM In particular the reflected order which crosses the detector perpendicularly to the main dispersion direction has an intensity in EGGS ranging from 10 to 1 of the flux of the regular echelle orders the higher value being in the blue side The same reflected order in HAM has an intensity generally below 1 of the flux of the regular echelle orders The diffuse light at
56. the online pipeline Depending on the observation the pipeline uses different reduction recipes Results of the reduction are e extracted spectrum all modes e precise radial velocity only if parameter TARG_RV is defined and different from 99999 e cross correlation function CCF only if parameter TARG_RV is defined and different from 99999 If the parameter TARG_RV is defined equal to 99999 the software will compute the radial velocity in an iterative manner This is useful when the RV of the object is not known a priori with an accuracy of 2km s The pipeline output is available immediately after the processing is finished see section 5 4 1 It can then be transferred to the offline workstation for further analysis It can also be saved to disk and CD DVD using the Data Archiving Unit see 7 2 2 available with HARPS This is typically done next morning by the telescope operator or the Data Handler Administrator The visitor is not requested to produce a backup of the raw data and of the pipeline products such a backup will be delivered to the user on the day of departure from La Silla However results of analysis made outside of the scope of the HARPS pipeline should be back ed up separately by the visitor 8 2 High accuracy radial velocities The reduction concept applied by the pipeline for the calculation of high accuracy radial velocities using the Thorium reference method is described in the paper ELODIE A spectr
57. tion guiding focusing 6 2 27 Pointing restrictions s v4 5 4 op Wer ae Senn anche n 6 30 Nisht calibrationist oriali ana a paio e mt RSR Ea 6 4 Real time display sita PID ALI i a OR e LA 6 5 Observing Very faint Stars i ao en i e a ne A e e T 6 6 Ateroseismology 6 7 End f the night i BE E a a les er un au metre ee Data products and archiving Tel Data products ia ara a ER ai NIT e rs 1 2 Dat rarchiving si custa ein ASS Pala e Sete BAe Ben 7 2 1 La Silla and Garching archives 7 2 2 La Silla data archiving unit ee 7 2 3 Use of archived HARPS data The Reduction of HARPS Data 8 1 The HARPS data reduction pipeline 8 2 High accuracy radial velocities 8 3 Jodine cell dat s ii srpa Bas aa na dena rin eh E HARPS high efficiency mode EGGS 10 The HARPS polarimeter A Description of archived HARPS data AL Data naming rules orto ae ER era ee Bs A2 Data tformats ua salta ila Boch Bad aa a Vote IN ne ee A2 b Raw frames meule na allea ta e 21 21 22 22 22 22 23 23 23 23 24 25 25 25 25 25 26 26 27 29 29 29 29 30 31 31 31 31 33 35 39 36 36 36 36 39 39 39 40 41 43 HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 B Use of the Data Archiving Unit C List of acronyms 51 53 vi HARPS Use
58. tion is automatically trig gered as soon as a new raw data file appears on the data reduction workstation whaldrs in the data raw night directory where night is the name of the subdirectory named after the day on which the observing night started e g 2004 02 11 The output of the pipeline is archived together with the raw data in data reduced night For a description of the reduction performed by the pipeline in the different observing modes see sec tions 3 1 4 3 2 4 and 3 3 4 Pipeline execution times are given in section 5 4 1 For each frame that processes the pipeline performs basic quality checks When a problem is en countered an error message is displayed to warn the user Calibration frames are also processed by the pipeline If they pass the quality check then the cali bration database is updated Otherwise an error message will be displayed and the latest entry in the calibration database will be used The manual of the DRS can be found online http www ls eso org lasilla sciops 3p6 harps manuals html HARPS User Manual Issue 2 0 _3P6 MAN ESO 90100 0005 11 2 9 System efficiency The overall efficiency of the HARPS system over the complete wavelength range is given in table 2 4 In this table the atmosphere telescope transmission is standard atmospheric transmission plus alu minum reflectivity The slit efficiency indicates an average value corresponding to z 1 and is calculated from the HARPS 1 fibre together w
59. when any of the following weather conditions occur e Wind speed gt 20 m sec on the 3 6m monitor e Humidity gt 90 on the 3 6m monitor e Temperature within 2 of dew point on the MeteoMonitor e Dew on the dome the TIO will check the dome in person when there is reason to believe that condensation may occur The telescope shall not be pointed into the wind when the wind speed is more than 14 m sec 3 6m monitor Note Weather conditions at the 3 6m telescope may be significantly different from those near the RITZ In particular the wind speed is a few meters per second higher and the humidity lower The TIO will make the decision to close the dome as necessary VAs should accept the decision since the reason is exclusively the protection of the telescope from damage At any rate in case of a HARPS User Manual Issue 2 0 3P6 MAN ESO 90100 0005 31 disagreement the dome should first be closed and subsequently the VA may take up the issue with the support astronomer and finally the La Silla shift leader though it is highly unlikely that the decision will be altered The dome may be re opened if weather conditions improve and stay below the operating limits for at least 30 minutes This waiting period is particularly important in case of humidity The TIO will further confirm that the condensation on the dome has completely evaporated 6 3 Night calibrations Night calibrations in addition to the calibration observations taken

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