TY  - JOUR
A1  - Ellis, S. C.
A1  - Bland-Hawthorn, Joss
A1  - Lawrence, J.
A1  - Horton, A. J.
A1  - Trinh, C.
A1  - Leon-Saval, S. G.
A1  - Shortridge, K.
A1  - Bryant, J.
A1  - Case, S.
A1  - Colless, M.
A1  - Couch, W.
A1  - Freeman, K.
A1  - Gers, L.
A1  - Glazebrook, K.
A1  - Haynes, R.
A1  - Lee, S.
A1  - Löhmannsröben, Hans-Gerd
A1  - O'Byrne, J.
A1  - Miziarski, S.
A1  - Roth, M.
A1  - Schmidt, B.
A1  - Tinney, C. G.
A1  - Zheng, J.
T1  - Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results
JF  - Monthly notices of the Royal Astronomical Society
N2  - The background noise between 1 and 1.8 ?mu m in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, the Gemini Near-infrared OH Suppression Integral Field Unit (IFU) System (GNOSIS), which suppresses 103 OH doublets between 1.47 and 1.7?mu m by a factor of 1000 with a resolving power of 10?000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the Anglo-Australian Telescope. We present measurements of sensitivity, background and throughput. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is 36?per cent, but this could be improved to 46?per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low-resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 mu m is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low-resolution OH-suppressed spectroscopy is illustrated with example observations of Seyfert galaxies and a low-mass star. The GNOSIS background is dominated by detector dark current below 1.67 mu m and by thermal emission above 1.67 mu m. After subtracting these, we detect an unidentified residual interline component of 860 +/- 210 photons s-1 m-2?arcsec-2?mu m-1, comparable to previous measurements. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artefact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimized OH suppression spectrographs. The next-generation OH suppression spectrograph will be focused on resolving the source of the interline component, taking advantage of better optimization for a fibre Bragg grating feed incorporating refinements of design based on our findings from GNOSIS. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.
KW  - atmospheric effects
KW  - instrumentation: miscellaneous
KW  - infrared: general
Y1  - 2012
U6  - https://doi.org/10.1111/j.1365-2966.2012.21602.x
SN  - 0035-8711
VL  - 425
IS  - 3
SP  - 1682
EP  - 1695
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - GEN
A1  - Ellis, S. C.
A1  - Bauer, S.
A1  - Bacigalupo, C.
A1  - Bland-Hawthorn, J.
A1  - Bryant, J. J.
A1  - Case, S.
A1  - Content, R.
A1  - Fechner, T.
A1  - Giannone, D.
A1  - Haynes, R.
A1  - Hernandez, E.
A1  - Horton, A. J.
A1  - Klauser, U.
A1  - Lawrence, J. S.
A1  - Leon-Saval, S. G.
A1  - Lindley, E.
A1  - Löhmannsröben, Hans-Gerd
A1  - Min, S. -S.
A1  - Pai, N.
A1  - Roth, M.
A1  - Shortridge, K.
A1  - Waller, L.
A1  - Xavier, Pascal
A1  - Zhelem, Ross
T1  - PRAXIS: an OH suppression optimised near infrared spectrograph
T2  - Ground-based and Airborne Instrumentation for Astronomy VII
N2  - The problem of atmospheric emission from OH molecules is a long standing problem for near-infrared astronomy. PRAXIS is a unique spectrograph which is fed by fibres that remove the OH background and is optimised specifically to benefit from OH-Suppression. The OH suppression is achieved with fibre Bragg gratings, which were tested successfully on the GNOSIS instrument. PRAXIS uses the same fibre Bragg gratings as GNOSIS in its first implementation, and will exploit new, cheaper and more efficient, multicore fibre Bragg gratings in the second implementation. The OH lines are suppressed by a factor of similar to 1000, and the expected increase in the signal-to-noise in the interline regions compared to GNOSIS is a factor of similar to 9 with the GNOSIS gratings and a factor of similar to 17 with the new gratings. PRAXIS will enable the full exploitation of OH suppression for the first time, which was not achieved by GNOSIS (a retrofit to an existing instrument that was not OH-Suppression optimised) due to high thermal emission, low spectrograph transmission and detector noise. PRAXIS has extremely low thermal emission, through the cooling of all significantly emitting parts, including the fore-optics, the fibre Bragg gratings, a long length of fibre, and the fibre slit, and an optical design that minimises leaks of thermal emission from outside the spectrograph. PRAXIS has low detector noise through the use of a Hawaii-2RG detector, and a high throughput through a efficient VPH based spectrograph. PRAXIS will determine the absolute level of the interline continuum and enable observations of individual objects via an IFU. In this paper we give a status update and report on acceptance tests.
KW  - Near infrared
KW  - spectroscopy
KW  - OH suppression
KW  - astrophotonics
KW  - fibre Bragg gratings
Y1  - 2018
SN  - 978-1-5106-1958-6
U6  - https://doi.org/10.1117/12.2311898
SN  - 0277-786X
SN  - 1996-756X
VL  - 10702
PB  - SPIE-INT Soc Optical Engineering
CY  - Bellingham
ER  - 
TY  - JOUR
A1  - Bland-Hawthorn, Joss
A1  - Ellis, S. C.
A1  - Leon-Saval, S. G.
A1  - Haynes, R.
A1  - Roth, Martin M.
A1  - Löhmannsröben, Hans-Gerd
A1  - Horton, A. J.
A1  - Cuby, J. -G.
A1  - Birks, T. A.
A1  - Lawrence, J. S.
A1  - Gillingham, P.
A1  - Ryder, S. D.
A1  - Trinh, C.
T1  - A complex multi-notch astronomical filter to suppress the bright infrared sky
JF  - Nature Communications
N2  - A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come.
Y1  - 2011
U6  - https://doi.org/10.1038/ncomms1584
SN  - 2041-1723
VL  - 2
IS  - 50
PB  - Nature Publ. Group
CY  - London
ER  -