Center Finding Algorithm for Point Source Observation of Slit - PowerPoint PPT Presentation

Center Finding Algorithm for Point Source Observation of Slit Spectrometer (IGRINS) Hye-In Lee 1 , Soojong Pak 1 , Gregory Mace 2 , Jae-Joon Lee 3 1 School of Space Research, Kyung Hee University 2 The University of Texas at Austin 3 Korea Astronomy & Space Science institute IGRINS User workshop Kyung Hee University 7/27-28, 2017

Contents 1. Introduction 2. About IGRINS 3. Observation Requirement for Slit Spectrometer - Algorithms 4. Performance Test 5. Result & Discussion 6. Summary

1. Introduction ① Identifying: Are we observing the correct target? ② Centering: Are the maximum number of photons going through the slit? ③ Guiding: Can we take long spectral exposures while guiding?

2. About Control Software for IGIRNS • IGRINS (Immersion GRating INfrared Spectro-graph) is a high spectral resolution R=45,000 near-infrared slit spectrograph. • IGRINS consists of House Keeping Package (HKP), Finding Chart Package (FCP), Slit Camera Package (SCP), Data Taking Package (DTP), Quick Look Package (QLP), Pipe Line Package (PLP). Instrument parts are HKP, SCP, DTP. • Slit Camera Package (SCP) points the target and guides the guide star through controlling the Telescope Control System (TCS).

Optical Design of IGRINS

Package Hierarchy for IGRINS

3. Observation Requirement for Slit Spectrometer • Target Centering - Reference position (Yellow dashed line) - Sending a target in the defined box (Red, Blue box) • Auto-Guiding - On-Slit Guiding: No point source besides the target - Off-Slit Guiding: General guiding method We need a “Center Fitting Algorithm” on the slit.

Target on the off-slit Target on the on-slit

Sequence for pointing Observer SCP TCS SDCS Storage Find Target Image Taking mode Setting(Single or Continuous) self.scd.send("SETFSMODE(1)") Start Single Taking Return value = self.scd.recv(1024) self.scd.send(" SETFSPARAM (…)") Return value = self.scd.recv(1024) self.scd.send("ACQUIRERAMP") Return value = self.scd.recv(1024) Save Image pyfits.open(Image Path…) Load & Display Image If Continuous mode, continue recvfrom(1024) Get Value(RA, Dec …) Show Value(RA, Dec) Select Target CalcOffset(Rotator -> RA, Dec) Calculate offset RaDecOffset(RA, Dec) GO:MoveTelescope recvfrom(1024) Get Value(RA, Dec …) Show Value(RA, Dec) SCP : Slit Camera Package DTP : Data Taking Package TCS : Telescope Control System HKP : House Keeping Package SDCS : Science Detector control Computer for Slit Camera Request : Red / Data : Green / Image Data : Orange

Sequence for auto-guiding Observer SCP TCS SDCS Storage Select A or B Position (On-slit guiding) Show A or B Position(x, y) Start Auto-guiding self.scd.send("SETFSMODE(…)") Return value = self.scd.recv(1024) self.scd.send(" SETRAMPPARAM(…)") Return value = self.scd.recv(1024) self.scd.send("ACQUIRERAMP") Return value = self.scd.recv(1024) Save Image ImageTakingProgress (road Image) pyfits.open(Image Path…) Load & Display Image calc_offset(…), CalcOffset(…) => Get Value(RA, Dec …) continue MoveTelescope RaDecOffset(RA, Dec) Stop Auto-guiding SCP : Slit Camera Package DTP : Data Taking Package TCS : Telescope Control System HKP : House Keeping Package SDCS : Science Detector control Computer for Slit Camera Request : Red / Data : Green / Image Data : Orange

Center Finding Algorithms 1. 2D-Gaussian PSF Fitting Algorithm: 2DGA 2. Center Balancing Algorithm: CBA

2D-Gaussian PSF Fitting Algorithm • Considering X line and Y line at the same time.           2 2     x x y y center center         f(x, y) Height exp Background    2  2  2   2         

Center Balancing Algorithm • Making Balance Table (B.T): - Calculating the offset from centroid of virtual slit to centroid of reference PSF. - Dividing up and down position from slit and calculate the flux ratio of up to down wings. - Making Balance Table. - Deriving the relationship between the offset and the ratio by ‘least square function’.

• Applying to on-slit image - Selecting the real on-slit image. - Calculating the ratio of up to down. - Getting an offset through the previous calculated relationship To get the A, B for calculation of ‘ least square ’ from the array of ‘offset - ratio’, 𝑧 = 𝐵 + 𝐶𝑦 𝐵 = Σ𝑦 2 Σ𝑧 − Σ𝑦Σ𝑦𝑧 𝐶 = 𝑂Σ𝑦𝑧 − Σ𝑦Σ𝑧 Δ Δ ( 𝑧 : boxsize/2+offset, 𝑦 : log 10 Ratio) It can just calculate 𝑧 from this formula : 𝑝𝑔𝑔𝑡𝑓𝑢 = 𝐵 + 𝐶log 10 Ratio

4. Performance Test • Performance Simulation - Selecting a point target with a guiding star within the slit camera FOV. - When the target is on the reference position, measure the relative distance between the target and the guide star.

• Translation of Reference Frames

• Expected Position VS (Expected Position – Positions by each of algorithms) - 𝑴𝒇𝒐𝒉𝒖𝒊 𝑭 VS ( 𝑴𝒇𝒐𝒉𝒖𝒊 𝑭 - 𝑴𝒇𝒐𝒉𝒖𝒊 𝑩𝒎𝒉𝒑𝒔𝒋𝒖𝒊𝒏 ) 8 6 4 2 0 -50 -40 -30 -20 -10 0 10 20 30 40 50 -2 -4 2DG -6 CB -8 𝑴𝒇𝒐𝒉𝒖𝒊 𝑭 (𝒒𝒋𝒚𝒇𝒎)

• Expected Position VS (Expected Position – Positions by each of algorithms) - 𝑿𝒋𝒆𝒖𝒊 𝑭 VS ( 𝑿𝒋𝒆𝒖𝒊 𝑭 - 𝑿𝒋𝒆𝒖𝒊 𝑩𝒎𝒉𝒑𝒔𝒋𝒖𝒊𝒏 ) 8 6 4 2 0 -8 -6 -4 -2 0 2 4 6 8 -2 -4 2DG -6 CB -8 𝑿𝒋𝒆𝒖𝒊 𝑭 (𝒒𝒋𝒚𝒇𝒎)

5. Result & Discussion • Results of 16 samples analysis – Considering “Slit Width” - Full graph of 16 samples for comparison - Table & Graph: Mag – RMS - Table & Graph: FWHM - RMS

• Results of 16 samples analysis – Considering “Slit Width” [ Relationship w T - ∆w 2DG, CB ] • Date Index / Mag (K) / FWHM • RMS of Residual • Green Color Background Graph: Those match with algorithms. • Yellow Color Background Graph: Those do not match with algorithms. • Purple star and box: Same Target of different days. • The blue circles (2DGA) of the yellow graphs show jumping parts between upper and lower wings (about 5 pixels).

• Results of 16 samples analysis – Considering “Slit Width” Mag - RMS Reference Position RMS of Residual No Index Date Target Mag(K) Background Peak FWHM LOG_flux 2DG CB 12 02-Jul 20140708 HIP5131 5.3 208.14 22351.28 14.69 -13.5 1.16 1.09 13 03-Jul 20140709a HIP93580 5.3 195.89 15642.35 18.21 -13.4 1.86 2.09 7 04-May 20140525b 24 Oph 5.5 207.80 20795.50 15.10 -13.5 2.53 1.34 14 04-Jul 20140709b HIP95560 5.6 160.69 14340.58 17.85 -13.3 1.03 1.77 15 05-Jul 20140709c HIP97376 6.0 162.30 14427.29 14.81 -13.1 1.16 0.85 20 10-Jul 20140713 HD155379 6.5 217.20 20336.74 9.58 -13.0 2.13 0.74 19 09-Jul 20140712b HD155379 6.5 188.05 20983.42 9.65 -13.0 3.88 1.90 17 07-Jul 20140711b HD155379 6.5 262.36 18917.52 10.22 -13.0 3.07 1.31 8 05-May 20140525c 2MASS J18331755 6.8 169.65 17616.99 8.06 -12.6 2.40 0.55 4 01-May 20140524a Serpens15 7.0 211.59 12697.75 9.24 -12.4 2.50 0.22 18 08-Jul 20140712a GSS32 7.3 207.20 10709.17 9.74 -12.3 2.11 1.00 9 06-May 20140526a GSS32 7.3 154.75 5137.68 14.07 -11.9 2.53 1.80 16 06-Jul 20140711a SR4(V* V2058 Oph) 7.5 229.51 6571.84 9.36 -11.7 1.81 1.53 6 03-May 20140525a Oph Ttau 7.6 442.84 8050.78 10.78 -12.1 2.58 0.75 5 02-May 20140524b SS433 8.2 143.47 5608.74 9.59 -11.6 3.00 0.66 10 07-May 20140526b Serpens2 8.6 137.01 3590.78 8.40 -10.9 2.95 0.51

[ Relationship Mag (K) – RMS (pixel) ] • For fainter targets, CBA shows better performance than 2DGA. • The blue circles (2DGA) and red triangle (CBA) have similar results on the green circle. • The stars on the purple box mean same target of different days which show different RMSs.