PROCEEDINGS OF SPIE. Status and first results of the Canarias infrared camera experiment (CIRCE) for the Gran Telescopio Canarias

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1 PROCEEDINGS OF SPIE SPIEDigitalLibrary.rg/cnference-prceedings-f-spie Status and first results f the Canarias infrared camera experiment (CIRCE) fr the Gran Telescpi Canarias Alan Garner, Richard D. Stelter, Stephen S. Eikenberry, Nestr Lass-Cabrera, Steven N. Raines, et al. Alan Garner, Richard D. Stelter, Stephen S. Eikenberry, Nestr Lass- Cabrera, Steven N. Raines, Miguel Charcs, Michelle Edwards, Antni Marín-Franch, Kendall Ackley, A. Javier Cenarr, Jhn G. Bennett, Brian Chinn, Raymnd Frmmeyer, Michael D. Herlevich, Pala Miller, Charles H. Murphey, Christpher Packham, "Status and first results f the Canarias infrared camera experiment (CIRCE) fr the Gran Telescpi Canarias," Prc. SPIE 9147, Grund-based and Airbrne Instrumentatin fr Astrnmy V, 91474A (8 July 2014); di: / Event: SPIE Astrnmical Telescpes + Instrumentatin, 2014, Mntréal, Quebec, Canada Dwnladed Frm: n 5/16/2018 Terms f Use:

2 Status and first results f the Canarias infrared camera experiment (CIRCE) fr the Gran Telescpi Canarias Garner, Alan (University f Flrida [UF]), Stelter, Richard D. (UF), Eikenberry, Stephen S.(UF), Lass-Cabrera, Nestr (Centr de Estudis de Fisica del Csms de Aragón [CEFCA]), Raines, Steven N. (UF), Charcs, Miguel (NASA Stratspheric Observatry fr Infrared Astrnmy), Edwards, Michelle (Large Bincular Telescpe Observatry), Marín-Franch, Antni (CEFCA), Ackley, Kendall (UF), Cenarr, A. Javier (CEFCA), Bennett, Jhn G. (UF), Chinn, Brian (UF), Frmmeyer, Raymnd (UF), Herlevich, Michael D. (UF), Miller, Pala (UF), Murphey, Charles H. (UF), Packham, Chris (University f Texas at San Antni) Abstract CIRCE is a near-infrared (1-2.5 micrn) imager, plarimeter and lw-reslutin spectrgraph intended as a visitr instrument fr the Gran Telescpi Canarias 10.-4m telescpe. It was built largely by graduate students and pstdcs, with help frm the UF astrnmy engineering grup, and is funded by the University f Flrida and the U.S. Natinal Science Fundatin. CIRCE is intended t help fill the gap in time between GTC first light and the arrival f EMIR, and will als prvide the fllwing scientific capabilities t cmpliment EMIR after its arrival: highreslutin imaging, narrwband imaging, high-time-reslutin phtmetry, imaging- and spectrplarimetry, lw-reslutin spectrscpy. In this pster, we review the lab testing results fr CIRCE frm 2013 and describe the instrument status (currently in shipment t GTC). 1. OVERVIEW & STATUS Figure 1: CIRCE dewar pen fr alignment testing in the labratry at the University f Flrida. The Canarias InfraRed Camera Experiment (CIRCE) is a fully reflective near-infrared (1-2.5 micrn) visitr-class instrument t be used at the Gran Telescpi Canarias (GTC). It uses a 2048x2048 engineering grade H2RG detectr, which with a reslutin f 0.1 arcsec/pixel gives it a field f view (FOV) f 3.4. CIRCE was largely built by graduate students and pstdcs, and was funded by the University f Flrida and the U.S. Natinal Science Fundatin. It was designed and built in the Astrnmy department at the University f Flrida. CIRCE cmpleted lab testing in early 2014 and cmpleted a readiness review by the GTC shrtly thereafter. CIRCE left the University f Flrida n June 5th, As f writing, it is en-rute t the GTC. Grund-based and Airbrne Instrumentatin fr Astrnmy V, edited by Suzanne K. Ramsay, Ian S. McLean, Hideki Takami, Prc. f SPIE Vl. 9147, 91474A 2014 SPIE CCC cde: X/14/$18 di: / Prc. f SPIE Vl A-1 Dwnladed Frm: n 5/16/2018 Terms f Use:

3 2. OBSERVING MODES CIRCE will initially ffer tw bserving mdes t the public, with capability t add a third mde in the future. CIRCE s imaging mde ffers 0.1 arcsec/pixel reslutin and a 3.4 FOV. It currently has three bradband filters installed and ready t use: J, H, and K-shrt. There is space fr additinal filters, including narrwband filters, t be added if desired in the future. In additin t bradband imaging, CIRCE ffers a plarimetry mde. This is accmplished with use f a half-wave plate at the fcal plane and a Wllastn prism near the pupil image. CIRCE has the capability t add a spectrscpy mde in the future. Currently there is space available fr grisms in the filter bx. It is pssible and hped that suitable grisms r funds fr such grisms will becme available in the near future, allwing us t ffer this additinal mde t the cmmunity. 3. LAB TESTING RESULTS CIRCE cmpleted lab testing during fur cldwns in late 2013 and early The earlier cldwns allwed us t verify mechanism functin, crygenic hld time/stability, and fcus adjustment. Later cldwns allwed us t measure image quality. 3.1 Image Quality, Dark Current, and Field Curvature Crrectin ti 0 a Figure 2: Fur different pinhle subimages taken frm acrss CIRCE s FOV. The pinhles in the mask are designed t be 2 pixels (0.2 ) in diameter. We measured pinhle FWHM ranging frm 2-3 pixels, fr the flat pinhle mask. Hartmann tests cnfirm that this crrespnds t n-telescpe perfrmance f <0.25-arcssec, when accunting fr the telescpe field curvature (which the CIRCE ptics crrect, but which is absent frm the test setup) - see Figure 3. In rder t measure CIRCE s inherent image quality, we installed a flat pinhle mask n the fcal plane mechanism. This mask cntained a grid f 0.2 (at the GTC fcal plane) laser-machined pinhles. This allwed us t fcus the detectr thrugh the use f tw cmplementary Hartmann masks, and als allwed us t measure image quality by measuring the pinhles full-width at half-maximum (FWHM). Crrecting fr field curvature, each pinhle image was between Thus CIRCE will be seeing-limited even during the GTC s best nights (which can reach <0.3 seeing). One interesting effect f using a flat pinhle mask at the fcal plane arises frm the fact that this is nt the field that CIRCE s ptics expect t receive. The GTC will feed a curved field t the instrument, and CIRCE was deisgned t currect this curvature in the ptics (with n need fr a separate crrectr), and prduce a flattened image at the detectr. By testing with a flat field, we intrduce anti-curvature (the GTC s curvature, but ppsite sign) at the detectr, resulting Prc. f SPIE Vl A-2 Dwnladed Frm: n 5/16/2018 Terms f Use:

4 200 CIRCE Field Curvature - 17 Dec 2013 I I a O 4 d O Psitin (pixels) 2000 Figure 3: Defcus f pinhle images acrss the field. This is a ne-dimensinal slice that ges thrugh the center. Given the flat pinhle mask used during lab testing, while the telescpe field is curved (and curvature-crrected by the CIRCE ptics), we expect this bserved anticurvature t be present. When CIRCE is n-sky these effects will cancel ut, leaving a flattened field n the detectr. in variable defcus acrss the field. This is illustrated in Figure 3, which plts the defcus f a ne-dimensinal slice f pinhles acrss the field. This curvature cmplements the GTC s curved field nicely, and n-sky CIRCE will prduce a flattened field at the detectr. During the first cldwn f final lab testing we measured higher than expected dark current. Further investigatin identified tw light leaks between the frnt f the instrument and the rear (the detectr). Additinal baffling between, added between cldwns, brught the dark current dwn by tw rders f magnitude. CIRCE demnstrates an internal dewar backgrund (including dark current) f 1.3 e-/s/pixel - mre than tw rders f magnitude less than the expected sky backgrund in its darkest bservatinal band 400 e-/s/pixel sky backgrund in J-band (H band: 1280 e-/s/pixel; K-shrt: 2700 e-/s/pixel). 3.2 Crygenic Stability CIRCE is a liquid nitrgen (LN2) cled instrument. The detectr cnsistently reached 80.5K (+/- 1K) during testing. Just as imprtant, the hld temperature was als very stable, with the detectr varying nly 0.2K acrss several hurs (Figure 5). Once fully cled, CIRCE s dual LN2 tanks hld enugh clant t keep the instrument peratinally cld fr mre than 36 hurs withut refilling. Prc. f SPIE Vl A-3 Dwnladed Frm: n 5/16/2018 Terms f Use:

5 In -dewar Backgrund (9dB) Slpe = ADU /s Gain = 8.1 e -/ADU en 2 a Expsure Time (s) Figure 4: Plt f signal versus expsure time fr dark expsures. A best-fit line, used t determine the dark current, has been verlaid. CIRCE s dark current is 1.3 e-/s/pixel. 300 CIRCE Cldwn #3 - Temperatures while cld I. I Sensrs Sensr 2 Sensr 3 Sensr 4 Sensr 5 Sensr 6 Sensr 7 ASIC Sensr Detectr Sensr Time (hurs) Figure 5: Plt f temperature versus time fr CIRCE s nine temperature sensrs. Nte that sensr tw rises and falls as the pinhle mask is inserted r retracted. When inserted, the pinhle mask bscures sensr tw s view f the entrance windw. Als nte the ASIC sensr has a binary distributin f temperatures, crrespnding t if it is pwered n r ff. Prc. f SPIE Vl A-4 Dwnladed Frm: n 5/16/2018 Terms f Use:

6 This lng hld time is due largely t the excellent vacuum CIRCE s dewar is able t achieve. Acrss the different cldwns CIRCE s bttm pressure had sme scatter, but was cnsistently belw 10 micrtrr. Our nminal bserved bttm pressure is 3-5 micrtrr. There was n nticeable degradatin f the vacuum ver the curse f the lngest f the fur cldwns, which lasted ver a mnth. 3.3 Mechanism Testing Prir t final lab testing, CIRCE s filter bx and fcal plane mechanism (the latter s purpse being t hld the half-wave plate and, in the future, slit masks) were tested exhaustively fr reliability and repeatability. Over the curse f final lab testing, we cnfirmed their functinality. The filter wheels shwed excellent repeatability and n crss-talk between ne anther was bserved. Likewise, the fcal plane mechanism als prved t be extremely reliable. The half-wave plate mechanism (fr plarimetry mde) culd nt be tested during final lab testing, as it cannt be munted simulataneusly with the pinhle mask t the fcal plane mechanism. As the pinhle mask is crucial t measure fcus and image quality, we had t test the half-wave plate mechanism separately in a test dewar. The half-wave plate mechanism passed these reliability and repeatability tests admirably. 4. FUTURE The UF CIRCE team will travel t GTC in early July 2014 t unpack the instrument (currently en rute t GTC) t prepare it fr labratry testing and telescpe deplyment n the GTC. After initial pst-shipment retesting and verificatin f the pst-ship detectr alignment, CIRCE shuld be ready fr telescpe deplyment by the end f July Figure 6: CIRCE left UF n June 5th, As f writing, it is en-rute t the GTC. Prc. f SPIE Vl A-5 Dwnladed Frm: n 5/16/2018 Terms f Use: