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HARPS-N USER MANUAL - Telescopio Nazionale Galileo

1. TNG MAN HARPN 0002 21 Figure 16 Portion of the extracted ThAr spectrum order The image quality and thus the spectral resolution varies only slightly in the cross dispersion direction seeError Reference source not found Table 7 The variation is below 10 across the whole CCD In main dispersion direction we encounter a larger spread in image quality of the order of 20 30 increasing toward the red side of the echelle order due to expected anamorphism This effect is however mostly compensated by the echelle grating dispersion which increases by about the same amount from the blue to the red side of the echelle order Table 7 Image quality of the spectrograph The FWHM of a spectral line expressed in pixels is indicated for different positions on the scientific CCD Y 0 Y 2000 Y 4000 X 0 Dispersion A E eee 29 Cross dispersion 3 8 3 1 By X 2000 Ge E is ee 1s A X 4000 e z A E 5 ZZZ 13 CS The measured optical parameters are listed in Table 8 These have been determined by means of ThAr calibration exposures The performances are all compliant with the specifications The image quality could not be measured directly thus we give here only a upper limit estimated from the FWHM values for the spectral lines given in Table 7 In order to compute the spectral resolution one has to multiply these values by the pixel size expressed in wavelength At 530 nm for exampl
2. centering of object on the fibre start of guiding 1 2 minutes depends by the user Initialization LCU 3 15 minutes AG 1 minute StartNight EndNight 22 seconds instrument configuration 8 seconds readout time included FITS headers generation 34 sec Standard calibration lt 12 minutes minimum time between successive exposures 34 sec telescope focusing at the beginning of the night or 8 10 minutes if the condition are critical DRS pipeline for thosimul without RV computation DRS pipeline for objA without RV computation DRS pipeline for objAB without RV computation DRS pipeline extra time for each RV calculation ThAr lamp pre heating once at the beginning of 5 min minimum 10 min recommended 15 the night min maximum 5 3 1 Fast time series observations asteroseismology The shortest recommended exposure time with the HARPS N shutter is 10 seconds while the shortest recommended exposure in simultaneous thorium exposure mode is 20 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 35 seconds readout mode 300 kpx sec With 20 sec exposure time on sky 55 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 left behind
3. IA2 TNG archive TNG ARCHIVE IA2 uni Image Gallery E LBT Archive EN Proprietaty data retrieval form Public data retrieval form all metadata calibration images images outside Proprietary period Powered by IA2 INAF Trieste Astronomical Observatory For any problem please contact 142 team Figure 24 TNG national Archive TNG MAN HARPN 0002 44 Appendix A Description of archived HARPS data A 1 Data naming rules The raw frames are stored in FITS format by the DFS with the ESO VLT standard naming rules HARPN YYYY MM DDTHH MM SS SSS fits with YYYY MM DD and HH MM SS SSS being respectively 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 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 HARPN 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 HARPN YYYY MM DDTHH MM SS SSS fits raw frame Tables in ASCII format are also produced by the DRS The raw data are stored in data raw and the reduced are stored in data reduced The relevant log books of the DRS is named DRS drs32 hn tng iac es Y Y Y Y MM DD It is stored with g et 2 O o FP 2 CH n Ea Kei Lo a 3 md 2 O
4. Telescopio Nazionale Galileo HARPS N USER MANUAL Version 2 1 TNG MAN HARPN 0002 Date 24 04 2012 v1 0 Prepared R Cosentino TNG MAN HARPN 0002 Change Record Issue Re Date Section Page affected Reason Remarks V V1 0 24 04 2012 First version v1 1 18 01 2013 First revision v1 2 28 01 2013 changes V2 0 14 02 2013 New sequencer V2 1 11 03 2013 V2 2 16 04 2013 Some tables and fig changed New CCD and readout TNG MAN HARPN 0002 3 1 Contents 2 3 gees ee e EE 6 2 1 NO 6 2 2 Additional information iii 6 2 3 Contact informatica REENEN EE 6 24 ee EE E 6 HARPS N Characteristics artrite ARIA AR NEREIDA RIN 7 3 1 TnStruM Ent Oyer E H 3 1 1 Instrument coupling to the telescope i 9 3 2 Ut os urca iaia a iaia 10 3 2 1 ale el niuno ila 10 3 2 2 Calibration unit C DD TEE 10 3 2 3 Front End Unit PEU eiie ee er eee ie eL eee Laser E RARE LESS ce DE e eda 11 3 3 Detector and read out electronics i 13 3 3 1 General detector chiaracterisucs eee e eee eeie ette enar etee eee ete EA Yea ee ees edes e unde ete 13 3 3 2 CCD lalla 13 3 3 3 ENEE teen ina iii pria 14 3 3 4 CED controlleti NAS 14 3 3 5 SUS RR E RR I 14 3 3 6 EXPOSULE MELEE SO 14 3 4 SIDIAVENSEnI oC 14 3 5 Data acquisition Be 15 3 5 1 Short Time Scheduler WM RE 15 3 5 2 SE UE 16 3 5 3 Front End Unit Autoguider and Calibration Unit c
5. 5 4 The HARPS N Exposure Time and Spectral Format Calculator The HARPS N Exposure Time Calculator ETC models the instrument and detector in their different configurations 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 as a function of exposure time It is available via the the Geneve University web pages at http obswww unige ch buchschn TNG MAN HARPN 0002 Extended Exposure Time Calculator Efficiency W Object counts 8i Object counts saturation 3 750 4 000 4 250 4 500 4 750 5 000 5 250 5 500 5 750 6 000 6 250 6 500 6 750 7 000 Lambda A Figure 22 Exposute Time Calculator ETC CCD Read Mode Exposure Time sec UE EELER A IO GS PIN CR a III ve C Spectral Format C Efficiency Objectc C SkyC TotalC SNR Stow Tatto Logona 35 TNG MAN HARPN 0002 36 6 Observing with HARPS More information on the startup procedures and on the use of HARPSN are reported in e HARPS N Quick Start guide TNG MAN HAN 0001 e HARPS N Operation Guide TNG MAN HAN 0003 6 1 The Observation blocks preparation From the NSTS the observer can prepare the sequence of observation blocks of the night The target can be inserted directly in the NSTS or by using a catalog file that contains the o
6. o a D P e 3 Ka go a iz O Q e o TNG MAN HARPN 0002 45 TNG MAN HARPN 0002 Appendix B List of acronyms ADC Atmospheric Dispersion Compensator AG Auto Guider CCD Charge Coupled Device CCF Cross Correlation Function CFC Continuous Flow Cryostat CU Calibration Unit DFS Data Flow System DRS Data Reduction Software E2DS Extracted 2 Dimensional Spectrum ETC Exposure Time Calculator FEU Front End Unit FITS Flexible Image Transport System FWHM Full Width at Half Maximum HARPS N High Accuracy Radial velocity Planet Searcher in the North hemisphere ND Neutral Density NSTS New Short Time Scheduler OB Observing Block RV Radial Velocity SA Support Astronomer SNR Signal to Noise Ratio TBC To Be Confirmed TBD To Be Defined ThAr Thorium Argon TNG Telescopio Nazionale Galileo TO Telescope Operator VA Visiting Astronomer 46
7. 31 4 5 4 Thorium calibration errors uil ni n 31 2 Preparing the observations aee hs dies o eee ede 31 5 1 Introduction M teeta oa Crate EE 31 5 2 Introducing Observing Blocks 20 eee i 31 321 Observing blocks gaere wh eate ei dies 31 5 2 2 Science templates tener bed e e RE Pagani 31 5 2 3 Calibration templates ea La 32 5 2 4 Technical templates de Ce ia 32 52 5 New Short Time Scheduler NSTS ii 32 5 3 Overheads EE 33 5 3 1 Fast time series observations asteroseismology esee 34 5 4 The HARPS N Exposure Time and Spectral Format Calculator 34 6 Observing WIthHARPS ue estate 36 6 1 The Observation blocks preparation conocio nono nennen entren 36 6 2 Before the m ght y a boia ila ia Aci 36 6 3 D ring the Mishit EE 36 6 3 1 Target acquisition guiding focusing iii 36 6 3 2 Pointing restEICLIOnDS nate A A ri 37 6 3 3 Night calibration EE 37 6 3 4 CARA A O 37 6 4 Observing very faint stars ii 37 6 5 Asteroselsmology imei esta 38 6 6 End of the night cess eileen He pe HE rH E Ld ER Re 38 ZG The Reduction ot HARPS N Data peut d emplea dene 39 The HARPS N data reduction pipeline irene eee einer 39 High accuracy radial velocities i 39 TNG MAN HARPN 0002 5 S Data products and archiving csi alal iaia 40 8 1 Data Pro AAA bea S 40 8 1 1 NAAA NN 40 8 1 2 Reduced
8. Moon Alpha 06h29m Zone WET MJD 56070 LT Offline LT 21 58 09 06 17 56 Delta 20d28m Offset 0 Date 23 05 2012 ST Offline ST 11 54 07 20 15 16 Vel 24 71km s ID Name Target Alpha Delta MV Start TExp Airmass Nrep v 1 OB TECHNICAL SES SS SIS e E gigi Se Y 1 HARPN_instr_Icu_init epes Gea eise AS me A RE DET DPR INS OCS mm TEL 14 HARPN_instr_ag_init 2 2 2 2 eee eee o 1 HARPN tec set lamp With I A ges Garg E A Template parameters v 24 OB TECHNICAL sie see su fig lt og 2 HARPN tec startnight Shin age Fine nes o deeem ames for S N 550nm v 349 OB_CALIBRATION NONE si 1800 10 3 HARPN_ech_cal_bias lt Sek 0 0 atta A 34 HARPN_ech_cal_tunAB 222 eee 40 gt Comment 3 HARPN_ech_cal_thoAB mimies a sms seo SAD see 1 3 HARPN_ech_cal_waveAB as ame goe cer dH wae d 3 HARPN_ech_cal_thoB Ma Et aask esa GH ani Main Keywords 3 HARPN ech cal waveB visu altalene ue MO cues 4d YWOTHS OR SCIENCE Feige 34 10h 43 0 11 18 11 5 5 0 1 07 1 4 HARPN_ech_acq_objA 10h3 43 06 11 18 11 54 TEL TARG ALPHA 10h39m36 71 47 HARPN_ech_obs_all 11 56 5 0 107 1 54 OB_TECHNICAL SSS 0 ESS ER A 11 5 0 0 0 TELTARG DELTA 43 06 10 1 ner eran unane CON Dand Moda 00h 00m 02h 00m 56078 56071 DB N 14h 00m 16h 00m 18h 00m Horizon Y Pole
9. a RV offset of 3 m s no such effect has been observed on HARPS N thanks to the use of octagonal fibers 4 5 4 Thorium calibration errors A total instrumental error of about 0 5 m s must be expected due to the Thorium simultaneous reference and calibration drift tracking and zero point The zero point error is by far the dominant source with a contribution of 0 3 to 0 4 m s 5 Preparing the observations 5 1 Introduction HARPS N uses the way of observing based on pre prepared Observing Blocks This chapter describes the philosophy behind this concept the available tools and the HARPS N specific input In order to reach the full performance of HARPS N 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 0 3 m s the target 44 coordinates must be known to within 3 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 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 onl
10. a sequence of flat fields with more than 5 exposures if a SNR higher than 300 is aimed at in later science exposures The RV Standard 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 calibration 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 TNG MAN HARPN 0002 28 4 1 3 Observations The necessary acquisition and observing templates are available HARPN_ech_acq_thosimult for star acquisition and setup of simultaneous Th exposures HARDN ech obs all for taking spectroscopy exposures For a detailed description of the templates see section 1 1 1 and the HARPS N Template Reference Guide 4 1 4 Pipeline data reduction The online pipeline does spectrum extraction wavelength calibration RV calculation 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 o
11. can be accessed at any time by the DRS recipes which always choose the best available calibration dataset TNG MAN HARPN 0002 20 tkTrig the HARPS N trigger GUI online mode version 5 11 Partial logging mode Trigger controlled plots Eile Configure Help Reduction Information Window Information returned by Reduction Recipes On fiber A estimated RV accuracy on spectrum 8 31 m s On fiber A estimated RV accuracy on CCF 19 00 m s Number of Cosmic corrected 71 on fiber B Barycentric Earth RV correction 11 01835 km s Template used for CCF computation K5 Guessed RV is at 82 5 km s Correlation fiber B C 86 8 RV 82 33580 km s FWHM 1 0424 km s maxcpp 2 1 On fiber B estimated RV accuracy on spectrum 13 67 m s On fiber B estimated RV accuracy on CCF 139 87 m s Recipe obj TWO harpn is terminated VI Raw Frames Reduction Log Window idata raw 2012 05 24 Messages returned by Reduction Recipes On fiber B S N 450nm 0 4 S N 550nn 0 0 S N 650nm 0 04t 1727 cosmic removed 02 40 34 5 Instrument response correction is disabled hadgtVISU megaplotfic tmp plotA 1337913622 hadgtVISU megaplotfic tmp plotB 1337913622 overplot 1 xtitl Number of Cosmic corrected 42 on fiber A Barycentric Earth RV correction 11 01835 km s Template used for CCF computation K5 Guessed RV is at 12 5 km s Correlation fiber A C 36 4 4 RV 13 01243 km s FWHM 6 2345
12. coating parallel to the readout direction for enhanced response from 385nm to 691nm from left to right as shown in Figure The CCD is read by two different amplifiers and a difference of several 100 ADUs in the bias level of the two CCDs might be expected Following we present the CCD Quantum efficiency curve as provided by the supplier Astro QE 100C 16 um silicon CCD231 models Readout Split se Amplifier H Amplifier G re i 4112 rows 04 Amplifier E Amplifier F Wavelength nm midband Broadband maxge graded 2048 active pixels 50 blank pixels Figure 8 The CCD coating and quantum efficiency TNG MAN HARPN 0002 14 3 3 3 Cryostat An ESO supplied continuous liquid nitrogen flow cryostat houses the CCD and a preamplifier board A dedicated controller regulates the LN flow control to maintain the temperature of the base plate inside the cryostat at a suitable temperature The CCD mount stage will have a separate temperature control system using a Lakeshore controller to maintain the CCD temperature at its operating value 3 3 4 CCD controller The HARPS N Camera control and data acquisition system UCam uses the controller hardware from Astronomy Research Cameras Inc USA ARC Controllers The ARC controller provides all the bias voltages and clocks required to operate the detector and process the CCD video signal 3 3 5 Shutter A 45mm c
13. computation K5 Guessed RV is at 82 5 km s Correlation fiber B C 86 8 RV 82 33580 km s FWHM 1 0424 km s maxcpp 2 1 On fiber B estimated RV accuracy on spectrum 13 67 m s On fiber B estimated RV accuracy on CCF 3 139 87 n s hadgtVISU mesaplotfic tmp plotA 1337913622 xmin 103 xmax 61 umin 0 25 ymax 1 05 hadgtVISU negaplotfic tmp plotB 1337913622 xmin 103 xmax 61 uminz0 25 umax 1 05 o0ver Recipe ob j THO harpn is terminated 4 E a E m Scroll Unlock Scroll Lock 9 ei rs bi KE Figure 15 Screenshot of the data reduction trigger 3 7 HARPS N performances 3 7 1 Spectral format and resolution The recorded spectral format corresponds well to the calculated values Table 6 gives the order number central wavelength and the total spectral range covered by the respective echelle order at the top center and bottom of the CCD All the orders up to 158 could be localized and extracted using a tungsten flat field lamp while the wavelength calibration was done using the ThAr spectral lamp Figure 16 shows a part of the corresponding extracted and wavelength calibrated spectrum Table 6 Central wavelength and spectral range of the echelle orders Pipeline Echelle Central wavelength A Total spectral range AA A order nr order nr 69 89 6880 8 75 9 68 90 6804 4 75 1 67 91 6729 7 74 3 2 156 3951 6 43 4 1 157 3926 3 43 1 0 158 3901 3 42 8
14. in April and the first scientific observation started on May 21 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 N is based on the experience acquired with HARPS installed at 3 6m telescope in La Silla The basic design of HARPS N is therefore very similar to this instrument The efforts to increase the HARPS N performance compared to HARPS address mainly three issues e Increase of the input beam stability To send the light from the FEU to the spectrograph we use a 26 m octagonal fiber link This new geometry increases the light scrambling effect and guarantees a very high precision in radial velocity measurement since they minimize spectrograph illumination changes due to the positioning error of the star in the fiber entrance e Increase the reference precision Two external high precision references are included The first is already available and consists of an ultra stable Fabry Perot interferometer The second one a stabilized laser frequency comb is currently under development and will become available in 2013 e Improvement of the image quality and quantum efficiency The CCD is a 4Kx4K back illuminated e2v CCD231 with 15 um square pixels It is a device processed from standard silicon process and coated with graded AR coating parallel to t
15. km s maxcpp 43 5 On fiber A estimated RV accuracy on spectrum 8 31 m s On Fiber A estimated RV accuracy on CCF 19 00 n s hadgtVISU megaplotfic tmp plotA 1337913622 xmin 33 xmax S ymin 0 25 umax 1 05 hadgtVISU megaplotfic tmp plotB 1337913622 xmin 33 xmax 8 uminz0 25 umax 1 05 o0verplo Number of Cosmic corrected 71 on fiber B N 2012 05 24T22 21 46 000 fits NONE WAVE WAVE FP D N 2012 05 24T22 22 51 000 fits NONE WAVE WAVE FP N 2012 05 24T22 23 55 000 fits NONE WAVE WAVE FP N 2012 05 24T22 25 00 000 fits NONE WAVE WAVE FP N 2012 05 24T22 26 04 000 fits NONE WAVE WAVE FP N 2012 05 24T22 27 09 000 fits NONE WAVE WAVE FP N 2012 05 24T22 28 13 000 fits NONE WAVE WAVE FP N 2012 05 24T22 20 18 000 fits NONE WAVE WAVE FP N 2012 05 24T22 30 22 000 fits NONE WAVE WAVE FP N 2012 05 24T23 51 50 000 fits HD127334 STAR WAVE N 2012 05 24T23 54 22 000 fits HD127334 STAR WAVE N 2012 05 25T00 15 07 000 fits NONE WAVE WAVE FP N 2012 05 25T00 16 12 000 fits NONE WAVE WAVE FP N 2012 05 25T00 24 53 000 fits K00141 STAR SKY N 2012 05 25T00 59 14 000 fits K00141 STAR SKY N 2012 05 25T01 31 58 000 fits K00356 STAR SKY N 2012 05 25T02 04 18 000 fits NONE WAVE WAVE FP N 2012 05 25T02 05 23 000 fits NONE WAVE WAVE FP N 2012 05 25T02 09 49 000 fits K00356 STAR SKY Barycentric Earth RV correction 11 01835 km s Template used for CCF
16. noted that this means that the spectrum did not move in absolute terms by more than 0 001 pixels or 15 nm on the scientific CCD This is actually the typical stability obtained with HARPS N during a night despite the fact that the thermal control system of HARPS N has not yet been fully implemented The dispersion on the drift measurements over this same 1 hour period is of the order of 30 cm s This noise has a typical period of 10 minutes It is observed also on HARPS N south and it is possibly due to tiny but periodic temperature variations of the CCD or its dewar It is important to note however that on the differential value one obtains a dispersion of 8 cm s which is almost identical with the combined photon noise precision of the ThAr and FP spectral sources This demonstrates without any doubt that the simultaneous reference technique is able to correct for drifts at the level of 10 cm s and below This statement is strengthened by the fact that over the whole test duration the differential drift never exceeded the 40 cm s level despite the fact that the instrument had been exposed to extreme stress conditions never occurring during standard operations Furthermore the differential drift appears to be compatible with zero after 5 hours which not only confirms the power of the used technique but also demonstrates that our FP based reference source is stable within 10 cm s during an observation night However the FP does not yet
17. number of exposures is set different from one in the 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 frame A description of the observation template is given in the HARPS N Template Guide 5 2 4 Technical templates HARPN instr lcu init for the initialization of the calibration and Front End units HARPN instr ag init for the initialization of the auto guider HARPN tec set lamp to set the power of the lamps HARPN tec startnight to set the instrument for observation HARPN tec endnight to set the instrument in rest position 5 25 New Short Time Scheduler NSTS NSTS is the standard tool for the building of observing blocks from the instrument specific templates A comprehensive description including the user manual is available from the Geneve University web pages at http obswww unige ch buchschn Observers using HARPS N in Visitor Mode should prepare their OBs in advance using the HARPS N Instrument Package which is automatically downloaded once NSTS is started and the Offline Mode is selected from the menu OBs prepared at the observer s home institution can be quickly imported in the NSTS running at telescope console and be ready for execution TNG MAN HARPN 0002 33 C 2 sl ll Sj e 5008 005 A UN 0000 O ks om Place LaPalma Unix Time Offline UT Offline Night Nautical UT 20 58 09 05 17 56
18. observing standard stars since the sky conditions telescope focus etc are not known with sufficient accuracy Therefore we prefer just to compare real measurements with calculated count rates This procedure allows us to identify possible discrepancy without focusing on the detailed efficiency curve which depends on too many observational parameters Figure 19 shows the measured SNR as a function of wavelength obtained during one of the first GTO nights on May 24 2012 The used star was HD127334 a GSV star with m 6 36 The exposure time was of T p 120 sec and the observation were taken at an airmass of 1 03 and with a seeing of about 0 9 arcsec The best measurement of this night is shown since one has to be sure that efficiency losses due to effects not considered in the exposure time calculator ETC e g varying atmospheric extinction or telescope defocus are minimized The calculated curve was derived for a seeing of 1 arcsec which actually has been chosen to take into account for the 0 4 arcsec image quality losses discussed above The measured signal to noise ratio SNR is in excellent agreement with the calculated curve The curve may slightly differ mainly because a a KO spectrum was used for the computation and b the theoretical values of some sub components may be affected by small errors On the other hand and as mentioned above other aspects such as seeing variations extinction image quality etc cannot be controlled in de
19. pipeline uses different reduction recipes Results of the reduction are e Extracted spectrum all modes 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 3 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 chapter 8 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 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 spectrograph 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
20. provide the full stability on longer time scales e g from day to day probably because of a thermal instability of the temperature regulation As long as this problem has not TNG MAN HARPN 0002 25 been solved we recommend to observe in the standard simultaneous thorium mode or without simultaneous reference in case of faint objects with m gt 12 Fiber A ThAr measured drift Fiber B FP measured drift Fiber B Fiber A differential drift Drift and differential drift m s a un UJ N e o Fa N UJ gt un n N oo of exposure 1 per minute Figure 20 Short term stability of the spectrograph and quality of the FP and ThAr tracking technique 3 7 4 On sky precision HARPS N makes use of octagonal optical fibers and a double scrambler which when combined are supposed to perfectly scramble the light illuminating the spectrograph and thus remove any potential guiding effect on the measured radial velocity On HARPS N south an effect of the order of 3 to 4 m s was measured when moving the star from the center of the fiber to the edge This effect was observed to be symmetric with respect to the fiber center and fully understood as a consequence of differential pupil illumination of the spectrograph due to non perfect scrambling by circular fibers This experience led us to use octagonal fibers for HARPS N Tests in the laboratory had already shown that we could expect an excellent performance but tests on the sky and
21. than 10 m sec The TO 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 disagreement the dome should first be closed and subsequently the VA may take up the issue with the support astronomer and finally the TNG director 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 TO will further confirm that the condensation on the dome has completely evaporated 6 3 3 Night calibrations Night calibrations in addition to the calibration observations taken before the start of the science observations are only necessary when using the template without simultaneous reference 6 3 4 Real time display Raw data coming from the instrument are displayed on a DS9 Display 6 4 Observing very faint stars As explained in section 4 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 6000 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 N 1 m s wi
22. the RV initial guess should be set to 99999 The focus template is included in the science OB because the procedure moves the telescope and uses the guiding camera to calculate the optimum focus HARPN_focus is used to focusing the telescope Note In the focus OB the HARPN_ech_obs_all must be removed A description of the fofus procedure is given in the HARPS N Operation Guide A description of the acquisition templates is given in the HARPS N Template Reference Guide 5 2 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 OB Standard Calibration The details of this OB are described in section 4 1 2 Only if additional calibrations are deemed necessary one needs to use one or more of the following templates HARPN ech cal bias for taking bias frames HARPN ech cal dark for taking dark frames HARPN ech cal tunA B for taking order location frames through fibres A or B HARPN ech cal tunAB for taking spectral flat field frames through fibres A and B HARPN ech cal thoA B for taking a wavelength calibration through fibres A or B HARPN ech cal thoAB for taking a wavelength calibration through both fibres HARPN ech cal waveA B for taking a wavelength calibration through fibres A or B HARPN ech cal waveAB for taking a wavelength calibration through fibres A and B If the
23. user to optimize the exposure time depending on the SNR and vice versa The STS GUI is shown on Figure 10 TNG MAN HARPN 0002 16 c D a ER HEA en II iij SOOO O tet Morne Place LaPalma Unix Time Offline UT Offline Night Nautical UT 20 58 09 05 17 56 Moon Alpha 06h29m MJD 56070 LT Offline LT 21 58 09 06 17 56 Delta 20d28m Zone WET Offset 0 Date 23 05 2012 ST Offline ST 11 54 07 20 15 16 Vel 24 71km s ID Name Target Alpha Delta MV Start TExp Airmass Nrep S viv OB_TECHNICAL 00 0 ITE i ENEE seg ora mes ep ses RES ep RSR MESES DET DPR INS OCS TPL TEL 14 HARPN instr ag init 2 2 222 2 2 1 HARPN tec set lamp mosey meat GG as a Gole Son Template parameters v Ze OB_TECHNICAL 00 0 2 HARPN tec startnight eem ML pime come mieie nese cime S N 550nm v 34 OB_CALIBRATION NONE SS sia See see TIBUS 10 3 HARPN_ech_cal_bias mea lara s ae 10 0 maso d 3 HARPN ech cal tun B 40 5 Comment 34 HARPN_ech_cal_thoAB 40 0 1 3 HARPN_ech_cal_waveAB 40 0 1 34 HARPN_ech_cal_thoB aa e ent suns SD Eodem g Main Keywords 3 HARPN ech cal waveB 400 1 id 3 OB SCIENCE Feige 34 10h 43 0 11 18 11 5 5 0 1 07 1 4 HARPN ech acq obj 10h3 43 06 11 18 11 54
24. 1 to achieve an accurate solar system barycentric Radial velocity correction of 1 m s the target n 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 TNG MAN HARPN 0002 40 8 Data products and archiving 8 1 Data products HARPS N writes FITS files with extensions containing the data of both CCDs The size of one raw data file is approximately 32Mb Data naming rules are summarized in A 1 Data naming rules pag 44 By default the data products of the online pipeline are archived as well Following is an example of the files that are included in the archiving of one exposure 8 1 1 Raw data file HARPN YYYY MM DDTHH MM SS SSS fits raw spectra data Full image with header A HARPN YYYY MM DDTHH MM SS SSS fits Autoguide full image E HARPN YYY Y MM DDTHH MM SS SSS fits autoguide integrated box image G HARPN YYYY MM DDTHH MM SS SSS tbl exposure meter data ascii file 8 1 2 Reduced data file Cross correlation function summary table with extracted RV for each order for M mask HARPN YYYY MM DDTHH MM SS SSS ccf M A tbl Cross correlation function matrix in fits format for mask M HARPN YYYY MM DDTHH MM SS SSS ccf M A fits 2D extracted spectrum one row per order HARPN YY Y Y MM DDTHH MM SS SSS e2ds A fits 1D extracted full spectrum wavelength calibrated in the sol
25. 1 4 but 1t 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 4 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 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 correction 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 4 3 1 Performance For estimates of the SNR with an accuracy of about 10 under given observing conditions the ETC ava
26. Diffused stray light Ghosts order nr order nr 68 90 680 0 2 lt 0 2 42 116 527 0 3 0 2 0 158 390 lt 1 lt 2 In the following is presented a brief description of the HARPS N 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 3 1 1 Instrument coupling to the telescope The instrument comprises two parts the spectrograph which is located in the ground floor of the telescope and the Front End and Calibration unit which it is mounted on the telescope Nasmyth B fork An optical fiber link sends the light from the Front End Unit to the spectrograph Figure 3 show the schematic view TNG MAN HARPN 0002 10 Nasmyth B derotator Ground floor Figure 3 HARPS N general schematic view 3 2 Operational overview The HARPS N instrument is mounted on the Nasmyth B focus of the TNG telescope in La Palma It shares the focus with other instruments Dolores and SARG Theswitch between the three instruments requires only the movement of M4 mirror entrance slider 3 2 Fiberlink To send the light from the FEU to the spectrograph we use a 26 m octagonal fiber link This new geometry increases the light scrambling effect and guarantees a very high precision in radial velocity measurement since they minimize spectrograph illumination changes due to the positioning erro
27. ELENC RA DEC 0 1 Ti 197 jo 99 1 217 fo sse Figure 14 LCU Device Monitor 3 6 Data Reduction Software An automatic data reduction system DRS is included with HARPS N to reduce shortly after the exposure observations for classical spectroscopy and high precision Doppler measurements with simultaneous wavelength reference For science exposures the DRS outcomes are flat fielded wavelength calibrated spectra and when possible and requested barycentric radial velocity of the target Calibration exposures are used by the DRS to calibrate the instrument for best quality scientific reduction The DRS is designed to run automatically like a batch process on the archived frames All relevant parameters required by the DRS are passed to the DRS through the FITS headers of the archived frames Results of the DRS are stored in the FITS keywords of reduced frames The top level of the DRS is represented by a set of programs recipes performing the various calibration and science tasks They take as inputs the raw data produced by the instrument and are executed online TNG MAN HARPN 0002 19 Each raw product has its associated DRS recipe which performs the required reduction tasks An additional top layer application Trigger acts as an automatic on line recipe launcher The role of the Data Reduction Software DRS is to transform the raw data produced by the instrument into reduced data of scientific quality These represent the ba
28. ET 20 20 03 Finished 5 A I e Y Coordinate 0 0 20 20 04 Execute CAL_setlamp PWM Turn ON Turn OFF OFF 20 20 04 OK ASA see MX 9 0 20 20 04 Finished FWHM Y 0 0 THAR2 Lamp 20 20 09 Execute CAL_setlamp Peak 0 0 Tumon Tumorr OFF 20 20 09 OK 8 ui 20 20 09 Finished Automatic Acquisition Background 0 0 File Edit View Frane Zoom Scale Color Region WCS Analysis Help File 201302137211048 Fitslagaca Ob ject PEPE Value 1473 WCS NON baya Physical K 220 000 i 270 000 Image hi 220 000 n 270 000 Frame 1 Zoom 1 000 Angle 0 000 nnt file edit view frame zoom scale color region wes help about open save image header page setup print exit TNG MAN HARPN 0002 13 Z AG_GuidingSimple vi Ele Edit view Project Operate Tools Window Help FI AG_GidUpdateTask vi Ele Edit view Project Operate Tools Window Help gt Y gt o fe Tox Le s Center 212 5 L T Ss 8 Hole Position p A SR bx center 1216 0 x center 1218 Reset to Restart Averaging SE Figure 13 Autoguider LCU_DEYMon vi Pila Ea File Edit Operate Tools Window Help Hare LAE HARPS N LCU Device Monitor Device Status pp er e Tes e PIE IR CA Eee a a ro rr eos una TC a pae JE ESC CEA ECO CEI CECI ETA Telemetry Status CCD Shutter State THRES PARALL
29. TEL TARG ALPHA 10h39m36 71 4 HARPN ech obs all 11 56 5 0 1 07 1 gt Se OB_TECHNICAL See 2 eo SSS 11 5 0 0 See 9 TELTARG DELTA 43 06 10 1 ner eran MODE a CCD Dand Moda 00h 00m 02h 00m TUE f 12h 00m LA 56078 56071 ate Horizon s Pole Y Meridian Zenith Y Start Night End Night Moon Position Moon Velocity Airmass f Figure 10 Short Time Scheduler screenshot 3 5 2 Sequencer The sequencer is the HARPS N observation control software It gets the observation blocks from the STS and executes them according to several XML template files Sequencer templates files define the commands statements and variables to run an Observing Block Moreover the sequencer is able to emulate HARPS N units and display through a GUI the execution status for each of the commands defined in the command template file Figure 11 The sequencer interacts with a DS9 application that visualizes the image coming from the Auto guider camera 3 5 3 Front End Unit Autoguider and Calibration Unit control instrument software The FEU and CU software are LabView modules which controls the movements and settings of the instrument and the autoguider This software can also control the units in stand alone mode as an engineering interface or by the HARPS N sequencer using an XML RPC interface 3 5 4 Telescope Control System HARPS N has an interface to the TCS This interface enables the instrume
30. Y Meridian Zenith Y Start Night End Night 4 Figure 21 Short Term Scheduler o4poom PON 12h 00m EIA 1 6 um Moon Position Y v Airmass f Moon Velocity Fora description of all HARPS N templates and the parameters selectable with NSTS consult the HARPS N Template Reference Guide In the fibers illumination scheme as a function of the template used is shown Table 9 Fiber illumination scheme as a function of the template used HARPN ech acq objA Star Dark HARPN ech acq objAB Star Sky HARPN ech acq thosimulth Star ThAr lamp 2 HARPN_ech_acq_ wavesimulth Star FB HARPN_ech_cal_ thoAB ThAr lamp 1 ThAr lamp 2 HARPN_ech_cal_ thoA ThAr lamp 1 Dark HARPN ech cal thoB Dark ThAr lamp 2 HARPN_ech_cal_ tun A Tungsten Dark HARPN_ech_cal_ tun B Dark Tungsten HARPN_ech_cal_ tunAB Tungsten Tungsten HARPN_ech_cal_ waveA Wave A Dark HARPN_ech_cal_ waveB Dark Wave B HARPN_ech_cal_ waveAB Wave A Wave B 5 3 Overheads The pipeline overheads are for reference only observations can proceed without the need for waiting the pipeline results Thorium lamps pre heating overhead have to be considered before the start of the afternoon calibrations TNG MAN HARPN 0002 34 telescope preset included dome rotation 8 min upper limit for large more than 180deg dome rotation 2 min typical for new pointing within a few degrees from the previous position
31. ar system baricentric frame HARPN YY Y Y MM DDTHH MM SS SSS sld A fits Bisector from the cross correlation computed with a MASK mask HARPN YYYY MM DDTHH MM SS SSS bis MASK A Dt Geometry of the order This fits file contains the FWHM of each order for each row HARPN Y Y YY MM DDTHH MM SS SSS fwhm order A fits Geometry of the order This fits file contains the x position of the center of the order HARPN YY Y Y MM DDTHH MM SS SSS loco A fits Flat Field measurement this fits file contains the blaze for each order HARPN YYYY MM DDTHH MM SS SSS blaze A fits Flat Field measurement this fits file contains the flat for each order HARPN YYYY MM DDTHH MM SS SSS flat A fits Wavelength Calibration fits file with the wavelength solution wavelength of each order for each pixel HARPN YYY Y MM DDTHH MM SS SSS wave A fits TNG MAN HARPN 0002 41 Wavelength Calibration ascii file with a list of all thorium lines detected with information about FWHM sig etc HARPN YYYY MM DDTHH MM SS SSS_lines_A rdb Wavelength Calibration Ascii file with a sample of Th lines intensities and FWHM only for TH calibration frames HARPN YYYY MM DDTHH MM SS SSS_spot_thAB tbl Fits file with the Reduced tungsten data file Full image Flat Field HARPN YYYY MM DDTHH MM SS SSS_order_profile fits Fits file with the extracted tungsten data file Flat Field HARPN YYYY MM DDTHH MM SS SSS_lamp_A fits Other summary tables are produced at the end of ea
32. bjects information The format of the catalog file is an ascii file and the fields separator is a TAB ascii code 9 The fields of the catalog are shown in Table 1Error Reference source not found the mandatory fields are shown in bold format An example of catalog file is shown in the HARPS N webpage http www tng iac es instruments harps data SpStdHARPSN cat Table 10 Catalog file entries name object code alpha right ascension nn nn nn nn delta Declination nn nn nn nn mualpha proper motion alpha arcsec year mudelta proper motion delta arcsec year mv magnitude V bv bv TypSp spectral type radvel mean radial velocity KM sec or 99999 sn Signal Noise 550nm spectr spectral type for the mask two chars only remarks remarks tpltype template es HARPN_ech_acq_objA equinox equinox progid program identificator es TAC_xx piname PI name 6 2 Before the night Depending on the observing method applied simultaneous Thorium reference 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 Thorium because they are needed for the pipeline to produce optimum results A calibration OB OB Standard Calibration is available in the NSTS and ready for execution to take these exposures 6 3 During the night 6 3 1 Target acquis
33. bration 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 2 bias exposure The CCD bias is very stable only one bias is therefore needed by the pipeline Template HARPN ech cal bias 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 TNG MAN HARPN 0002 27 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 exposures of the following night Template HARPN ech cal tun A sequence of 5 Tungsten lamp exposures defined by NREP 5 where both fibres are simultaneously 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 HARPN ech cal tunAB 2 for reasons of redundancy Thorium exposures in which both fibres are simultaneously fed by light from the Thorium Ar
34. ch night Calibration Ascii file with Bias table cal BIAS result tbl Bias table Flat Field measurement this ascii file contains parameter of 4 orders cal FF result HARPN tbl Wavelength Calibration ascii file with the parameters of the thorium wavelength calibration cal TH result HARPN tbl Wavelength Calibration ascii file with the parameters of the FP wavelength calibration cal WAVE result HARPN tbl Fabry perot table for wavelength calibrations RV measurement Ascii file with the Th lines drift in m s measured on fiber B filled only in the simultaneous Thorium reference mode drift result tbl RV measurement Ascii file with results of the CCF with measured RV and RV sigma filled only when the RADVEL field in the template is different by 99999 CCF results tbl 8 2 Data archiving 8 2 1 TNGand Trieste archives HARPS N raw data are stored locally at TNG and in the central Trieste Science Archive 8 2 2 TNG data logging The user can look up locally the logbook of the observation through the TNG archive logbook see Figure 23 http alexandria tng iac es logbook TNG MAN HARPN 0002 42 Archive Logbook EM Fil 2012 09 09 SARO Instrument Operation is very simple download the program run it on a directory and it will create YYYY MM DD Gi Datetime a file which you use to submit on this form and you ll get a HTML output table a la OIG Show Today Logbook Here you can see the manual of gen
35. data file anena eee n e lia 40 8 2 Data rchiyin iia cti a laca ii 41 8 2 1 TING and Trieste archives teorie rie ia 41 5 2 2 ING data loBgilg serat eter ii ala 41 8 2 3 Use of archived HARPS N data 42 E 43 A Datanammp rules ennemi dati ees etc utei 44 TNG MAN HARPN 0002 6 2 Introduction 2 1 Scope This User Manual is intended to give all necessary information to potential users of the HARPS N instrument 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 An overall description of the HARPS N instrument its performance and its observing modes Information on the preparation of the observations Information on the observing process A description of the HARPS N data and near real time pipeline data reduction The following documents are closely related to this manual and should be consulted as well The HARPS N Startup Manual TNG MAN HARPN 0001 The HARPS N Operation Guide TNG MAN HARPN 0003 The New Short Term Scheduler User Manual NSTS The DRS User Manual OG MAN HAN 13 0004 These manuals are available through the TNG web page http www tng iac es instruments harps 2 2 Additional information The latest information updates about the HARPS N instrument can be found on the HARPS N web pages https plone2 unige ch HARPS N harps n
36. e in the center of the CCD the scale is 0 001415 nm pixel and the spectral resolution taking into account the measured spotsize is computed to about R 124 000 Because of the changing dispersion and image quality along the orders the spectral resolution is not perfectly constant Nowhere on the CCD the spectral resolution decreases below R 1007000 however Table 8 Measured spectrograph parameters Wavelength range on the CCD 390 1 691 5 nm Spectral resolution at center 115000 Order width FWHM at center 3 2 pixels Sampling at CCD center 0 0014 nm pixel Separation of fibers 16 8 pixels TNG MAN HARPN 0002 22 Figure 17 Raw of a spectrum recorded by HARPS in the wave mode Two spectra can be distinguished each one corresponding to one spectrograph fiber illuminated by A the star lower fiber and B the simultaneous FP upper fiber 3 7 2 Efficiency of the spectrograph The total calculated HARPS N efficiency obtained at the center of the echelle order blaze condition is shown in Figure 18 The efficiency of various subsystems is also shown in the figure The instrument efficiency has been computed using the efficiency data for each single optical component measured in the laboratory The shape of the instrument efficiency follows the blaze response of the cross disperser grism the rapid cut off below 380 nm is however accentuated by the band pass filter which has been installed in order to
37. el Table 1 Harps Main Characteristics Spectrograph type Fiber fed cross dispersed echelle spectrograph Spectral resolution R 115 000 Fiber field FOV 1 Wavelength range 385 nm 691 nm Total efficiency e 8 550 nm incl telescope and atmosphere 0 8 seeing Sampling s 3 3 px per FWHM Calibration ThAr Simultaneous reference feed by 2 fibers CCD Back illuminated CCD 4k4 E2V chips graded coating Pixel size 15 um Environment Vacuum operation 0 001 K temperature stability Global short term precision 0 3 m s 10E 9 Global long term precision better than 0 6 m s 2x10E 9 Observational efficiency SNR 50 per extracted pixel on a Mv 8 TExp 60 sec wavelength accuracy 60 m s 2x10E 7 on a single line All necessary moving parts are located in the HARPS N Front End Unit FEU with the exception of the shutter which is located just outside of the vacuum vessel The optical design shown in Figure 2 is similar to HARPS S ML IN Figure 2 Optical layout of the spectrograph Its echelle grating is operated in quasi Littrow conditions off plane angle 0 721 deg blaze angle TNG MAN HARPN 0002 9 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 Two fibres A and B feed the spectr
38. f the following spectral type others are in preparation templates G2 K5 M2 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 N 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 subtractionRadial velocity and Julian date correction are calculated in the solar system barycenter reference based on the Bretagnon amp Francou 1988 VSOP87E 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 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 4 2 Simultaneous Fabry Perot reference method The Simultaneous Fabry Perot mode is the base line observation mode to get the best short term accuracy in radial velocity determination from the instrument In this mode fibre B is fed by the Fabry Perot while fibre A is on the stellar target A variable neutral density ND filter
39. fitinput Image Observ Type Program Object UT Date Coord PA Expo Time Air Mass HARPN 2012 09 10T06 15 20 295 FITS CALIB CALIB 2012 09 10T06 15 20 295 06 15 20 02 10 25 29 48 35 20 0 0 0 0 0 HARPN 2012 09 10T06 03 47 451 FITS SCIENCE GAPS 2012 09 10T06 03 47 451 06 03 47 02 10 26 29 48 31 600 0 0 0 1 13 HARPN 2012 09 10T05 47 45 089 FITS SCIENCE GAPS 2012 09 10T05 47 45 089 05 47 45 01 58 13 37 32 40 800 0 0 0 1 13 HARPN 2012 09 10T05 25 23 462 FITS SCIENCE GAPS 2012 09 10T05 25 23 462 05 25 23 01 57 23 37 36 23 1200 0 0 0 1 11 HARPN 2012 09 10T05 00 00 176 FITS SCIENCE GAPS 2012 09 10T05 00 00 176 05 00 00 01 58 14 37 15 17 1200 0 0 0 1 07 HARPN 2012 09 10T04 40 42 952 FITS SCIENCE GAPS 2012 09 10T04 40 42 952 04 40 42 01 44 31 44 27 33 900 0 0 0 1 08 HARPN 2012 09 10T04 17 56 745 FITS SCIENCE GAPS 2012 09 10T04 17 56 745 04 17 56 01 57 53 37 27 28 1200 0 0 0 1 03 HARPN 2012 09 10T03 53 58 335 FITS SCIENCE GAPS 2012 09 10T03 53 58 335 03 53 58 01 56 23 37 37 37 1200 0 0 0 1 02 HARPN 2012 09 10T03 27 45 982 FITS SCIENCE GAPS 2012 09 10T03 27 45 982 03 27 45 01 55 58 37 40 18 1400 0 0 0 1 01 HARPN 2012 09 10T03 14 47 195 FITS CALIB CALIB 2012 09 10T03 14 47 195 03 14 47 00 16 21 16 39 08 20 0 0 0 1 06 Figure 23 TNG archive loogbook 8 2 3 Use of archived HARPS N data For convenient archiving of raw observation data and pipeline products dedicated Data A
40. gon lamps The THARI 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 THARI 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 HARPN ech cal thoAB 2 for reasons of redundancy Fabry Perot exposures in which both fibres are simultaneously fed by light from the Fabry Perot interferometer The Fabry Perot interferometer illuminates fibre A and fibre B 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 HARPN ech cal waveAB 1 Thorium exposures in which fibres B is fed by light from the ThAr2 lamp Template HARPN ech cal thob Fabry perot exposures in which fibres B is fed by light from the Fabry Perot reference Template HARPN ech cal waveB The user may then repeat
41. he moment of writing no long term radial velocity performances can be reported given the fact that HARPS N was installed in April 2012 and that the first GTO run took place from May 21 to 25 2012 The radial velocity dispersion over 2 5 hours and 41 exposures is of only 1 08 m s most probably this is completely dominated by the stellar p modes The same star was observed although at much lower frequency during all the four half nights of the first GTO run The obtained dispersion is of the order of 1 5 m s We are convinced that this value will be improved further by optimizing the instrument and the data reduction software We expect that a long term instrumental precision of the about 0 5 m s can and will be attained after the first semester of operations TNG MAN HARPN 0002 26 4 Observing modes HARPS N offers the following observing modes e Simultaneous Thorium Reference observation e Simultaneous Fabry Perot Reference observation e Classical fibre spectroscopy with and without sky 4 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 fibre B is fed by the Thorium lamp 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
42. he readout direction for enhanced response from 385nm to 691nm from left to right HARPS N is a fiber fed cross dispersed echelle spectrograph based on the design of its predecessor working at ESO 3 6m This successful spectrograph already has proven its capability to achieve a precision better than 1 meter per second and revealed several super earth planets in the habitable zone Two fibers an object and a reference fiber of 1 arcsec aperture pick up the light at the Nasmyth B focus of the telescope and feed the spectrograph either with calibration or stellar light The fiber entrance is re imaged by the spectrograph optics onto a 4kx4k CCD where echelle spectra of 69 orders are formed for each fiber The covered spectral domain ranges from 385nm to 691 nm The resolution of the spectrograph is given by the fiber diameter and reaches an average value of R 115000 At this resolution each spectral element is still sampled by 3 3 CCD pixels The spectrograph is mounted on a nickel plated stainless steel mount and contains no moving parts Furthermore in order to avoid spectral drifts due to temperature and air pressure variations it is accurately controlled in pressure and temperature In Figure 1 the mechanical mount on the left and the installation inside the vacuum vessel on the right are shown A summary of the main HARPS N characteristics is given in Table 1 TNG MAN HARPN 0002 8 Figure 1 HARPS N mechanical design and vacuum vess
43. ilable via the HARPS N web pages http obswww unige ch buchschn can be used see section 1 1 1 4 3 2 Calibrations A calibration sequence similar to the Simultaneous Thorium Reference method is recommended before the beginning of the night 4 3 3 Observations The necessary acquisition and observing templates are available e HARPN_ech_acq_objA acquisition and setup for fibre spectroscopy with the object in fibre A e HARPN_ech_acq__ objAB acquisition and setup for fibre spectroscopy with the object in fibre A and sky in fibre B TNG MAN HARPN 0002 30 e HARPN_ech_obs_all for taking spectroscopy exposures 4 3 4 Pipeline data reduction The pipeline performs the same reduction as for the simultaneous Thorium reference method section 4 1 4 but 1t 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 4 4 Focusing of the telescope A telescope focusing procedure can be done with the focus template The template points the selected star set the spectrograph executes the focus procedure and move the telescope M2 mirror 4 4 1 Performance The focus template reaches the optimum focuses of the telescope if the seeing conditions are stable The procedure takes 8 minutes to execute For more details about the fofus pr
44. is used to keep the Fabry Perot spectrum at a flux level equivalent to a 40 seconds exposure with zero density Since the density to which the ND filter is set 1s computed by the instrument software from the exposure time as defined in the template The Fabry Perot 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 Fabry Perot spectra For the simultaneous reference method the Fabry Perot in fiber B is used 4 2 1 Performance For estimates of the SNR with an accuracy of about 10 under given observing conditions the ETC available via the HARPS N web pages http obswww unige ch buchschn can be used see section 1 1 1 4 2 2 Calibrations A calibration sequence similar to the Simultaneous Thorium Reference method is recommended TNG MAN HARPN 0002 29 before the beginning of the night 4 2 3 Observations The necessary acquisition and observing templates are available e HARPN ech acq wavesimult for star acquisition and setup of simultaneous fabry perot exposures HARPN_ech__ obs all for taking spectroscopy exposures For a detailed description of the templates see section 1 1 1 and the HARPS N Template Reference Guide 4 2 4 Pipeline data reduction The pipeline performs the same reduction as for the simultaneous Thorium reference method section 4
45. ition guiding focusing Target acquisition is done by the FEU The object is centered on the entrance of the science fibre and kept there by an automatic dynamic centering algorithm The guiding accuracy may introduce radial velocity errors but considered the use of octagonal fibers the expected errors are well below TNG MAN HARPN 0002 37 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 15 5 seeing 1 0 arcsec TBC 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 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 focus template when the image quality observed on the guiding camera deteriorates significantly or whenever there is a significant temperature change few C 6 3 2 Pointing restrictions The telescope dome shall be closed when any of the following weather conditions occur on the TNG Weather Panel webpage http tngweb tng iac es weather e Wind speed gt 15 m sec e Humidity gt 85 Temperature within 2 of dew point The telescope shall not be pointed into the wind when the wind speed is more
46. lear aperture bi stable Uniblitz shutter is mounted just outside the spectrograph vessel to get the timed science exposures The shutter is controlled by its own controller and is located in the detector electronics rack close to the spectrograph The control input to the shutter controller is derived from the ARC controller 3 3 6 Exposure meter The spectrograph possesses an exposure meter which serves to measure the stellar flux and to accurately measure the mid time of the exposure flux weighted mean of the time This exposure meter consists of two photomultipliers one for each of the two fibres entering the spectrograph from the FEU 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 FIT S 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 Add the table Mv counts error time RV error The number of dark counts per second fluctuates between 10 and 15 However the data reduction pipeline is currently not using this value to correct for possible departures from the nominal 0 5 value centered exposure 3 4 Software architecture HARPS N SW is organized in modules chained together by the Data Flow System First the chosen targets are scheduled for obser
47. ll 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 N 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 TNG MAN HARPN 0002 38 6 5 Asteroseismology Asteroseismology observers need to pay special attention to the guiding behavior continuous control by the observer Also it is recommend to use the NSEQ parameter to produce exposure multiplication instead of duplicating OBs This method will save useless re acquisition of the star and thus produce a considerable gain of time 6 6 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 N 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 All electronics are in stand by all internal house keeping functions temperature and pressure control logging continue to operate TNG MAN HARPN 0002 39 7 The Reduction of HARPS N Data The HARPS N data reduction pipeline Every HARPS N frame is processed by the online pipeline Depending on the observation the
48. ller The software can be run remotely with a network connection to the host computer The UCam software runs on three HTTP server processes Camera Control File Save and Data De multiplexer servers The Camera Control server initializes configures downloads and executes applications The File Save server handles the image data and writes to disk a meta data file It also contains instructions to sample and de multiplex the raw data image The De multiplexer server processes the saved data and saves it in FITS file format A GUI client application is used for controlling the UCam server application 3 5 1 Short Time Scheduler STS STS is the application which allows the user to prepare the observations It helps the astronomer to choose and schedule the targets for the observing night as well as to calibrate the instrument Within the STS the exposures are organized in blocks called the Observation Blocks of three types science calibration and technical Science OBs contain the parameters for the target acquisition the instrument and the detector set up Calibration OBs describe the calibration exposures Technical OBs define the instrument initialization and the start and end procedures of the observing night STS controls the feasibility of the scheduled exposures with respect to the observational conditions and constraints like the limit airmass out of the night placement etc The Exposure Time Calculator which is part of the STS helps the
49. nt to send commands to the telescope via the TNG library Currently HARPS N is able to send three commands Pointing AG offsets and M2 offsets to calculate and correct the focus via an automatic procedure The connections between both systems are completely asynchronous but when the command finishes successfully the TCS returns an Ok status When an error condition has arisen the TCS also returns a message back to the sequencer flagging that condition TNG MAN HARPN 0002 17 Sequence amp Instrument Control Commande Simulation Observations Execution logs 64 47 90 MNEU H Sequence Control Instrument Control 3 E gt Next OB Start End Night 20 19 40 Execute CAL_setlam SES E 20 19 41 OK P Single OB Queue Mode Start Night End Night STARTED 20 19 41 Finished Current OB Status Auto Guiding 20 19 42 Execute CAL_setlamp Exposure n 20 19 42 OK 20 19 42 Finished OE Block ID 1 SL BERO OB Block name Technical 20 19 45 Execute CAL_setlamp ME LCU 20 19 45 OK KA 20 19 45 Finished Template name HARPN_tec_set_lamp LCU Init READY 20 19 46 Execute CAL_setlamp SR i Dust Cover 20 19 46 OK Status FINISHED 20 19 46 Finished ces m OPEN 20 19 59 Execute CAL setlamp 20 19 59 OK TUN Lamp 20 19 59 Finished e Turn ON Turn OFF OFF 20 20 02 Execute CAL setlamp EM 20 20 03 OK Add Magnitude Dal X Coordinate 0 0 TORR
50. ocedure Please refer to the HARPS N operation guide manual 4 4 2 Template The necessary focusing template is available e HARPN focus focusing of the telescope 4 5 RV accuracy The high RV accuracy obtainable with HARPS N is a result of an extremely stable and strictly controlled instrument and data reduction software designed and optimized for the purpose The pipeline RV determination is optimized for data taken in the simultaneous Thorium reference method The short term RV accuracy of HARPS N 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 Photon noise Telescope focus Centering errors Thorium calibration errors 4 5 1 Photon noise For a G8 star a RV rmsphoton m s due to photon noise only is reached with a S N ratio of about 67 per pixel at 550nm The photon noise introduced in the RV measurement scales with the SNR in the continuum as long as one stays in the photon limited and not detector limited domain i e at SNR gt 5 4 5 2 Telescope focus Opposite to HARPS ESO a defocus of the telescope does not introduce any RV offset thanks to the use of octagonal fibers Good focus is however extremely important for efficiency reasons TNG MAN HARPN 0002 31 4 5 3 Centering errors Opposite to HARPS ESO for which a de centering of 0 5 introduces
51. ograph 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 the 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 Ghosts seem to be due to third order reflections in the grism see Table 1 and 2 for some characteristic values However the dominant effect is cross contamination between the two fibers In the worst case at physical echelle order nr 92 the contamination is of the level of 1 5 after extraction In average however the cross contamination between the two fibers is of the order of 0 5 and in 68 of 70 echelles order lower than 1 The instrument is coupled to the telescope through an adapter the HARPS N Front End Unit FEU Two calibration fibers transmit the light from the calibration unit located in the Nasmyth B Focus and inject it in the two science fibers for calibration Table 2 Halogen lamp 3000k Level of diffuse stray light and ghosts as a percent of the flux in the order Pipeline Echelle Wavelength nm Diffused stray light Ghosts order nr order nr 68 90 680 0 2 0 05 42 116 527 0 4 0 5 0 158 390 1 1 Table 3 G3V star 5700 K Level of diffuse stray light and ghosts as a percent of the flux in the order Pipeline Echelle Wavelength nm
52. ontrol instrument software 16 3 5 4 Telescope Control System culinari fai 16 3 6 Data Reduction Software 18 3 7 SE ue Le 20 3 7 1 Spectral format and resolution i 20 3 7 2 Efficiency or the spectrograph ertet ree tias ii 22 3 7 3 Instrumental stability and simultaneous reference 24 3 7 4 Of sky precisiOD xui taria Eugene P eU ET rase HE PUDE letus esp E Bo eta dea EE 25 ODSer vine Modes s 26 4 1 Simultaneous Thorium reference method ii 26 4 1 1 Se reg 26 4 1 2 NS 26 4 1 3 ecu RI IE ERA PARROT i air 28 4 1 4 Pipeline data reduction urinaria 28 4 2 Simultaneous Fabry Perot reference method 28 4 2 1 Performance MERE 28 TNG MAN HARPN 0002 4 4 2 2 Calibrations gege deet ad 28 4 2 3 le e Ge ET 29 4 2 4 Pipeline data reduction nee a 29 4 3 Classical fibre spectroscopy i 29 4 3 1 Performance tilda i o eR te iege pie etie ed i Re eL see Re d 29 4 3 2 Calibrations A nia 29 4 3 3 ODSEPVAtIONS EE 29 4 3 4 Pipeline data reduction eee eem gebe e e ees 30 4 4 Focusing of the telescopes E 30 4 4 1 Performance ito tina todas Aes sath ee Seege dd 30 4 4 2 Template it ie och hte Mentone cl ists eats hese ae eae 30 4 5 RV AccUracya tl Do ee e Ee EE ee li e ie 30 4 5 1 Photon noise lilla De eere be eee teen en ic ees 30 4 5 2 Telescope TO CU ii eere Pede eet beer nep ara aan 30 4 5 3 Centerin errOES 23 eere etit aa
53. operations and observations 2 3 Contact information 2 4 Acknowledgments Most of the contents of this manual is based on information from the HARPS N Consortium Astronomical Observatory of the Geneva University lead the Harvard Smithsonian Center for Astrophysics in Cambridge USA the Universities of St Andrews and Edinburgh the Queens University of Belfast and the TNG INAF Observatory Releases of this document are based on the ESO HARPS User Manual edited by G Lo Curto Feedback on this User Manual from users is encouraged Please email to cosentino tng iac es TNG MAN HARPN 0002 7 3 HARPS N Characteristics 3 1 Instrument Overview HARPS N High Accuracy Radial velocity Planetary Searcher is an instrument designed for the measurement of Radial Velocities RV at highest accuracy The HARPS N Project is collaboration between the Astronomical Observatory of the Geneva University lead the Harvard Smithsonian Center for Astrophysics in Cambridge USA the Universities of St Andrews and Edinburgh the Queens University of Belfast and the TNG INAF Observatory The project started in 2006 but suffered a two year delay due to financial problems After a re organization of the project in 2010 it was successfully completed in less than two years In March and April 2012 HARPS N was installed at the Nasmyth B Focus of the 3 6m TNG at the Observatory of the Roque de los Muchachos La Palma Island The first commissioning took place
54. prevent the second grism order below 360 nm to be imaged on the CCD For the CCD we indicate the QE values measured in laboratory by E2V Telescope and atmosphere efficiency have been estimated from experience values The slit efficiency indicates an average value computed at an airmass Z 1 03 and for an effective seeing of 0 9 arcsec In practice we estimate that 0 4 arcsec must be added quadratically to the seeing value to account for additional telescope effects due to image quality and possible defocus TNG MAN HARPN 0002 23 100 8 90 A A 7 80 6 70 60 50 Efficiency 40 Y w gt x x Total efficiency Atmosphere Telescope Front End Slit efficiency 0 9 arcsec seeing 2 7 7 Fiber link Spectrograph CD 1 30 20 10 Atmosphere 0 350 400 450 500 550 600 650 700 Wavelength um Figure 18 Total efficiency of HARPS N black plain curve right hand scale and efficiency of subsystems left hand scale The values have been calculated for each echelle order at its blaze wavelength The fast drop below 380 nm is produced by a band pass filter installed in the fiber link to remove 2 order of the grism The grey area shows HARPS N spectral range An interesting aspect is to measure the on sky performances and derive the instrument efficiency It is however almost impossible to calculate precisely the effective efficiency of the instrument by
55. r it can be dark 2 Correction of atmospheric dispersion by means of an ADC TNG MAN HARPN 0002 13 3 House the technical CCD camera for guiding 4 Guide the star in the fibre thanks to the tip tilt mirror acting together with the autoguider system 6 Attenuating the reference light beam from the ThAr lamp via a neutral density wheel to an equivalent exposure time of 20s at zero density This can be done for exposure times from 20s to 5400s 3 3 Detector and read out electronics 3 3 1 General detector characteristics The HARPS N scientific camera is based on an e2v CCD231 scientific grade CCD detector and an ARC generation III CCD controller The detector has been integrated in a continuous flow cryostat CFC supplied by ESO The CCD controller allows different readout modes 1 2 and 4 output readout and different binnings but to optimize the automatic data reduction pipeline and the operations we chose only two fixed configurations of the acquisition mode The detector is configured without binning and the readout is using two outputs The readout speeds is 500 kHz per channel and the readout noise is lt Se The electronic conversion factor is about 1 6 e ADU The HARPS N science detector system is summarized in Figure 7 Figure 7 Detector control system scheme 3 3 2 CCD The CCD is a 4Kx4K back illuminated e2v CCD231 with 15um square pixels It is a device processed from standard silicon process and coated with graded AR
56. r linear mechanism with 4 fixed positions Dust Cover linear mechanism with two positions open close Guide camera FLI PL47 20 TBC Connection to the LCU in the control rack is via USB Guide camera ND filter Two rotating wheels with three filters and a transparent glass each producing attenuation density from 0 to 6 factor 1 to 1 000 000 Calibration ND filter Two rotating wheels with unconstrained motion can be set to any position in 360 deg Attenuation range of 1 to 300 ADC prism Two atmospheric density compensation prisms with unconstrained motion Tip tilt mirror Precision piezo motor and strain gauge position sensors CU y tT T9 ai EC 2 arr SPARE SPARE LAMP 1 LAMP 2 TH CABINET COOLING SYSTEM TBD 4 FEU HIGH CAL THORIUM cem VOLTAGE FOLD MP 1 POWER MIRROR Dus Flat fetd SUPPLY 1 IVER LED t c1 RELAY 1 t A n T1 GUIDE x m LAT A EF Ve RELAY 2 PRIEM r3 FERT TS AERA ILTER 2 4 amp t f at og T SCH A m m t et A Figure 4 Calibration and Front End Units TNG MAN HARPN 0002 12 Calibration Fibres Figure 5 FEU optical scheme Figure 6 The Front End Unit All optical fibres are connected to the FEU which forms the interface to the telescope The FEU 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 o
57. r of the star in the fiber entrance These fibers have shown excellent laboratory performances and demonstrated excellent results on sky A second fibre link connects the Fabry Perot reference next to the spectrograph with the HARPS N Calibration Unit CU 3 2 2 Calibration unit CU The calibration unit contains the lamps and the power supply and provides the reference source thorium tungsten for the FEU Two external high precision references are included The first is already available and consists of a Fabry Perot interferometer The second one a stabilized laser frequency comb is currently under development and will become available in 2013 The CU is connected via two optical fibres to the FEU which redirects the light of the calibration sources into the spectrograph fibres as required The two calibration fibres can be fed either by the same or independently by two different calibration sources Of the two Thorium Argon lamps the lamp THARI 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 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 The HARPS N Calibration Unit has two linear mechanisms to move the reference fibers between 5 posi
58. rchiving software is available at Trieste Science Archive It allows the observers to get the observations data choosing the data product they want raw data reduced data or both log files HARPS N data can be requested from the Trieste Science Archive http Aa2 oats inaf it index php tngarchive tng Data taken by observers in Visitor or Service Mode are subject to the usual proprietary period of 1 year According to the Agreement between GTO consortium and the HARPS N Consortium the data taken by the Consortium during their Guaranteed Time are subject to special protection e Raw data and reduced spectra I f 1 in the Earth reference frame at the time of the observation 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 TNG 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 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 TNG MAN HARPN 0002 43 INAF O CENTRO ITALIANO ARCHIVI ASTRONOMICI
59. sic products from which the user will start in order to perform the desired specific analysis Therefore the endpoint of the DRS processing is defined as the furthest stage at which the data products are still sufficiently generic to be used as inputs for all main HARPS N science cases The main steps of the scientific data reduction are e Bias and dark subtraction e Bad pixels correction e Background subtraction e Order extraction with cosmic rejection e Hat fielding e Wavelength calibration e Merging and rebinning of the spectral orders e Sky subtraction if applicable e Instrumental drift correction if applicable e Flux calibration Cross correlation with a numerical template e Radial velocity computation For HARPS N the final products of the DRS process have been found to be the extracted background subtracted cosmic corrected flat fielded and wavelength calibrated spectra with and without merging of the spectral orders The possibility to flux calibrate the spectra is also available These products are provided also for the reference fiber sky or simultaneous wavelength calibration if applicable In addition to these reduction products cross correlation functions of the spectra are also computed to provide high precision radial velocities One important feature of the DRS environment is the calibration database in which all calibration products needed to reduce science data are stored The complete calibration database
60. ssible to a track possible instrumental drifts and b estimate the power of the simultaneous reference technique This technique is employed in HARPS N to remove possible instrumental drifts from the stellar radial velocity While calibrating the instrument or observing the star the second spectrograph fiber B is always illuminated by a spectral reference source in this case a Fabry P rot FP etalon illuminated in white light The stable FP records potential drifts of the instrument occurred between calibration and observation Once expressed in terms of radial velocity the recorded value can be subtracted from the measured stellar radial velocity to correct for these drifts We have done laboratory tests to measure the performances of the simultaneous reference technique An example is shown in Figure 20 which shows the radial velocity of the ThAr fiber A and FP fiber B spectral sources as a function of exposure number Since one exposure was taken every minute the series represents a time span of about 5 hours During this time we have made a stress test of the instrument by pumping on the vacuum chamber and by changing the temperature of the detector dewar both producing absolute radial velocity changes of several meters per second The obtained results are very satisfactory During the first hour during which the instrument was not touched the radial velocity remains stable well within the 1 m s level It must be
61. tail We conclude therefore that at a level of about 20 precision the expected efficiency matches the actual efficiency of the instrument The radial velocity precision obtained on a given star depends on many factors not the least being the stellar intrinsic noise or jitter Nevertheless even for a quiet star the obtained precision depends on the spectral line width depths and density which all depend partially on the spectral type In order to provide a bench mark for the transformation between SNR and expected radial velocity precision we focus on a quiet non rotating KO dwarf In this case a SNR per extracted pixel of about 50 is obtained on a star with m 8 in 60s At this SNR value a radial velocity photon noise limited precision of the order of 1 3 m s can be expected TNG MAN HARPN 0002 24 250 200 150 SNR computed 100 SNR measured SNR per extracted pixel 50 3800 4300 4800 5300 5800 6300 6800 Wavelength Angstroem Figure 19 Measured signal to noise ratio SNR of HARPS N red curve compared with the values computed by the exposure time calculator of the STS blue dcurve The efficiency tests have be carried out on HD 127334 a mv 6 36 G5 star The exposure time was of 120 seconds 3 7 3 Instrumental stability and simultaneous reference When observing in wave mode it is possible to feed fiber A with a ThAr spectrum and fiber B with the FP spectrum By doing so it is po
62. tions Three of the positions have lamps two of which are Thorium Argon hollow cathode lamps while the other one is a filament halogen lamp The others two positions are used for ultra stable external references which can be fed through an optical fiber connection At the moment one of these positions hosts the Fabry Perot interferometer located in the HARPS N cabinet close to the spectrograph TNG MAN HARPN 0002 Table 4 CU components 11 Movement component Description Thorium lamps 1 and 2 The Thorium Argon lamps are type 4160AHP from S amp J Juniper amp Co Halogen lamp The halogen lamp is a type 6337 TBC Quartz Tungsten Halogen bulb from Newport Fabry Perot The FP interferometer is located close to the spectrograph 3 2 3 Front End Unit FEU The FEU is the first part of the spectrograph where the incoming light from the telescope and from the calibration unit is conditioned and collimated in the fibers In this stage the incoming beam from the telescope is corrected by the atmosphere dispersion corrector ADC The star is maintained in the fiber thanks to the tip tilt mirror acting together with the autoguider system The folding mirror selects which object reference configuration has to be put into the fibers The optical scheme in Figure 3 shows the optical path inside the FEU and the main components Table 5 FEU components Movement component Description Calibration fold mirro
63. to which the ND filter is set is computed by the instrument software from the exposure time as defined in the template 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 THAR1 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 4 1 1 Performance For estimates of the SNR in the HARPS N mode under given observing conditions the Exposure Time Calculator ETC included in the New Short Term Scheduler NSTS available via the HARPS N web page http obswww unige ch buchschn can be used with an accuracy of about 10 The relationship between photon noise induced radial velocity error and S N is given by the following formula 100 rms m s S N sso As a rule of thumb an photon noise error of 1 3 m s or S N 50 can be achieved for a 8th magnitude K0 dwarf in 60 seconds in the HARPS N mode Note that due to the small fiber aperture on the sky 1 the performances assume a seeing better than 1 and critically depend on seeing 4 1 2 Calibrations The Simultaneous Thorium Reference Method needs a sequence of cali
64. using a real star had to be performed Summarizes the results of this test During a night with good atmospheric seeing conditions always below 1 arcsec we have measured the radial velocity of the star HD 89269 During this sequence we have alternatively centered and de centered the star at the entrance of the optical fiber The de centering was of 0 5 arcsec which means that the star was placed on the edge of the fiber in the identical way we had done this on HARPS N south in 2003 The first remarkable aspect is that the p modes of the star pulsation of about 2 m s semi amplitude are directly visible in the temporal series The second aspect concerns the excellent scrambling and is represented by the fact that no discontinuity is observed in the radial velocities when switching from centered to de centered observations In order to estimate the off guiding effect on the radial velocity we have averaged all centered exposures and compared them to all de centered exposures The difference in radial velocity is of the order of 0 5 m s which is in turn small compared to results obtained on HARPS N south We consider this value to be actually an upper limit of the effect since the measurement noise is dominated by the stellar pulsation This result is thus fully consistent with the laboratory measurement which had indicated an improvement of about a factor 10 on the scrambling efficiency of octagonal fibers compared to circular fibers At t
65. vation with the new short time scheduler N STS where their parameters are organized in Observation Blocks The prepared OBs are sent on request to the Observation Control System the Sequencer When an OB is get into the OCS all the instrument subsystems are set up according to its definition the telescope the spectrograph and the detector Once the observation has been executed the raw image with the FITS keywords gathered from all the subsystems is registered Then the appropriate data reduction recipe is automatically triggered by the Trigger software and the raw data are reduced TNG MAN HARPN 0002 15 package HARPS ICS au Software Architecture 1 Short Time Scheduler GUI component GI NTCS Command STS ff Broker AXML RPC d SEQ UCAM Pd ActiveMQ PA gt NTCS Broker athe p E Server sEQISTS P E Pod _ 77 xMc component E component GL SEQ AG u OCSLib k Sequencer ActiveMQ SS a a e FEU SEQ OCS lt N S XML RPC N w p SEQ FEU X P Ae CU Qu Q besen pero XMI PC gt SEQFGUI x SEQ CU component El Sequencer GUI Z N Sequencer GUI Y Figure 9 The HARPS N software architecture 3 5 Data acquisition software The camera control and data acquisition system UCam operates under PC control running RTLinux interfaced to a Generation III ARC Contro
66. y once when identical observation sequences are required e g repeated observations using the same instrument setting but different target 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 N uses four different acquisition templates different for the various observing modes and one common observing template 521 Observing blocks There are three different observing blocks defined OB SCIENCE OB CALIBRATION OB TECHICAL 5 2 2 Science templates HARPS N uses the science template to preset the telescope and to set up the instrument configuration for the selected observing mode The following acquisition templates are available HARPS N ech acq thosimult for simultaneous Th exposures HARPN ech acq wavesimult for simultaneous Fabry Perot exposures HARPN ech acq objA for fibre spectroscopy no sky HARPN ech acq objAB for fibre spectroscopy with sky HARPN ech acq eff for fibre spectroscopy sky in both fibers TNG MAN HARPN 0002 32 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 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 If RV computation is not desired

HARPS-N USER MANUAL - Telescopio Nazionale Galileo

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