THE LHIRES-III SPECTROGRAPH Version 02, 02/09/2015 THE LHIRES-III SPECTROGRAPH Jean-Pierre Rivet CNRS, OCA, Dept. Lagrange jean-pierre.rivet@oca.eu © C2PU, Observatoire de la Cote d’Azur, Université de Nice Sophia-Antipolis

C2PU-Team, Observatoire de Nice The LHIRES-III LHIRES = Littrow High RESolution spectrograph 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by 1 element Incident beam assumed parallel (wavelength ) Reflecting element Collimator d Screen i ~  / d r Diffracted beam Non-reflecting substrate Maximum in the direction of geometric optics: r = - r Angular width: ~  / d 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Reflecting elements Incident beam (wavelength ) Collimator i Screen ? Non-reflecting substrate 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Incident beam (wavelength )  Collimator i Screen ? 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Diffracted beams out of phase : destructive interferences  NO LIGHT Collimator Screen NO LIGHT ! 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Diffracted beams in phase : constructive interferences  MAXIMUM LIGHT Collimator Screen LIGHT ! 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Ray 0 Ray 1 Delay of Ray 1 wrt Ray 0 = a sin(i) 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Delay of Ray 1 wrt Ray 0 = a sin(r) r Ray 0 Ray 1 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Total delay of Ray 1 wrt Ray 0 :  = a sin(i) + a sin(r) a Condition for constructive interferences:  = k .  i Ray 0 Ray 1 r Ray 0 integer; called the “order” Ray 1 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Order k = 0 a Condition for constructive interferences:  = 0, whatever  i Ray 0 Ray 1 r sin(i) + sin(r) = 0 Ray 0 ’ Snell’s law ! direction of reflection on the grating’s plane according to geometric optics NON DISPERSIVE Ray 1 ’ 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction by “n” elements Order k ≠ 0 a Condition for constructive interferences:  = k .  i Ray 0 Ray 1 r sin(i) + sin(r) = k .  / a Ray 0 ’ Ray 1 ’ DISPERSIVE 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction pattern (monochr.) Relative intensity ~  / (N.a) ~  / a Diffraction enveloppe ~  / d -3 / a -2 / a - / a  / a 2 / a 3 / a sin(i) + sin(r) 19/09/2018 C2PU-Team, Observatoire de Nice

Diffraction pattern (polychr.) Relative intensity Order 0: non dispersive Order 1: dispersive Order 2: more dispersive Order 3: even more dispersive -3 / a -2 / a - / a  / a 2 / a 3 / a sin(i) + sin(r) 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice Blazed gratings STANDARD GRATING BLAZED GRATING Diffraction envelope is maximum when: r = - i Diffraction envelope is maximum when: r = - i 0th order is maximum when: r = - i 0th order is maximum when: r = - i  (blaze angle) i i r r i r : Normal to the grating : Normal to the grooves 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice Diffraction pattern Relative intensity STANDARD GRATING Order 0: non dispersive Order 1: dispersive Order 2: more dispersive Order 3: even more dispersive -3 / a -2 / a - / a  / a 2 / a 3 / a sin(i) + sin(r) 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice Diffraction pattern Relative intensity BLAZED GRATING Maximum of diffraction curve on order k ≠ 0 Blaze angle  depends on the central wavelength 0 and order k -3 / a -2 / a - / a  / a 2 / a 3 / a sin(i) + sin(r) 19/09/2018 C2PU-Team, Observatoire de Nice

Basics on spectrographs Collimation optics Light from the telescope Collimated input beam i Entrance slit Camera optics Sensor r Dispersing element (grating) Dispersed beam 19/09/2018 C2PU-Team, Observatoire de Nice

Littrow configuration Littrow condition: r = i Collimator optics = Camera optics (cost effective configuration) i r 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice The LHIRES-III 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice The LHIRES-III F/12.5 input beam from the telescope Micrometric screw (to tilt the gating) Guiding camera Diffraction blazed grating) Bending mirror Collimator / camera optics Focuser for the guiding camera Slit environment Science camera Bending mirror 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice The LHIRES-III Guiding port F/12.5 input port Bending mirror Focuser for the guiding camera Slit environment Science port Micrometric screw (to tilt the gating) Bending mirror Diffraction blazed grating) Collimator / camera optics 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice The LHIRES-III 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice The slit environment Input beam (from telescope) Bending flat mirror Output port focusing optics Guiding output port Input slit Slit environment 19/09/2018 C2PU-Team, Observatoire de Nice

MUST HE HANDELED WITH CARE The slit environment 15 m slit Active slit 35 m slit 19 m slit 25 m slit Optically polished component: MUST HE HANDELED WITH CARE 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice The calibration lamps Spectral calibration lamp: a small glass bulb filled with low pressure gases, producing strong and well-defined emission lines when an electric current passes through. Example Neon-Argon. Goal: determine the pixel-wavelength relationship. Flat calibration lamp: A Tungsten filament bulb producing a “black body” continuous spectrum. Goal: determine the overall photometric throughput, pixel by pixel. Spectral calibration switch Flat calibration switch Power supply plug 19/09/2018 C2PU-Team, Observatoire de Nice

The Neon-Argon spectrum 19/09/2018 C2PU-Team, Observatoire de Nice

The diffraction ratings Protection frame Active grating surface Tilt axis Available gratings: 150 gr/mm 300 gr/mm 2400 gr/mm Housing High precision optical component: MUST HE HANDELED WITH EXTREME CARE NO FINGER PRINTS ! 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice The micrometric screw How to read the micrometric screw : Micrometric screw Value = 23.5+0.34 = 23.84 Drum tick mark in front of the fixed index : 34 45 40 35 30 25 Last visible mark: 23.5 20 Fixed index 15 Active grating surface 10 Half-integer tick marks Integer tick marks 5 Fixed tilt axis 19/09/2018 C2PU-Team, Observatoire de Nice

C2PU-Team, Observatoire de Nice Configurations Available gratings: 150 gr/mm 300 gr/mm 2400 gr/mm Available slits: 15 microns 19 microns 23 microns 35 microns Spectral resolution @ 589nm 15 m 19 m 23 m 35 m 150 gr/mm 1179 931 769 505 300 gr/mm 2365 1867 1543 1014 2400 gr/mm 26644 21034 17376 11419 Slit Grating 19/09/2018 C2PU-Team, Observatoire de Nice

Spectral range, spectral scale Spectral range accessible around 589 nm on a single image, and spectral scale. Science camera: SBIG ST402 Grating Spectral range Spectral scale 150 gr/mm 230 nm 0.30 nm/pix 300 gr/mm 110 nm 0.15 nm/pix 2400 gr/mm 10 nm 0.013 nm/pix 19/09/2018 C2PU-Team, Observatoire de Nice

The Hydrogen H line in the solar spectrum (LHIRES-III + 2400 gr/mm) Sample spectra The Hydrogen H line in the solar spectrum (LHIRES-III + 2400 gr/mm) 19/09/2018

Sample spectra The Sodium D1 and D2 lines in the solar spectrum (LHIRES-III + 2400 gr/mm) 19/09/2018

The Magnesium triplet in the solar spectrum (LHIRES-III + 2400 gr/mm) Sample spectra The Magnesium triplet in the solar spectrum (LHIRES-III + 2400 gr/mm) 19/09/2018

Sample spectra The Hydrogen H line in Saturn’s spectrum (LHIRES-III + 2400 gr/mm) The lines are tilted by the planet’s surface rotation (Doppler effect) 19/09/2018

Methodology Observing session = Observing run = + observing run 1 + ... + bias images + dark images Observing run = A self-contained set of spectral images with THE SAME CONFIGURATION and THE SAME SCIENCE TARGET. It should include: + Flat field spectral images (Tungsten bulb) + Calibration spectral images (Ne-Ar discharge tube) + Reference star spectral images (with known spectrum) + Science star spectral images (with known spectrum) + 19/09/2018

Methodology Rules for a good observing sessions: Organize the session so as to minimize the grating changes. Maintain the log file (see template) accurately, including UT timestamps before and after any group of similar frames, and before and after any hardware change (grating, micrometer). Minimal working group: two persons (one person for log file and one for telescope/camera operation). Do flat field and spectral calibration frames before any group of science frames (reference star or target). Do reference star spectra only if absolute spectro-photometric calibration is needed. Groups of science frames should not last more than 10 minutes. Don’t forget to specify the type of frame (Flat, Callib, Science) to the acquisition software (it can’t guess). 19/09/2018

Observing log FILE HEADER: 19/09/2018 LHIRES-III OBSERVING LOG Date : 2017/02/15 Observers : Jean DUPONT, Michel DUPOND. Telescope : Epsilon@C2PU (OCA) Instrument : LHIRES-IIIa Science camera: SBIG ST402 FW Guiding camera: iNova PLB-Mx OBSERVING RUN NUMBER 01 --------------------------------------- . --------------------------------------------------------------- OBSERVING RUN NUMBER 02 --------------------------------------- 19/09/2018

Observing log OBSERVING RUNS: 19/09/2018 OBSERVING RUN NUMBER 01 --------------------------------------- Target : Jupiter Reference star : Vega Grating : 150 tr/mm Micrometer : 03.16mm Central wavelength : 656.3nm Telescope on target: 22:30:00 UT 22:30:30 UT 05 Tungsten flat frames. Exp=0001s000 22:30:50 UT 05 Argon-Neon calibration frames. Exp=0000s100 22:31:00 UT 10 science frames on Ref. star Exp=0000s500 22:32:00 UT 22:32:30 UT 22:33:10 UT 10 science frames on target. Exp=0000s500 . 22:35:50 UT --------------------------------------------------------------- 19/09/2018