The Messenger No. 124 – June 2006 Telescopes and Instrumentation CRIRES: Commissioning of the MACAO Adaptive Optics Module and General Status Report Hans Ulrich Käufl, Raul Esteves, veloped for the interferometry feed of the ment. This approach is also very much in Enrico Fedrigo, Domingo Gojak, VLT UTs, but were later also used for the line with the reintegration process at Jean-Louis Lizon, Enrico Marchetti, VLT instruments SINFONI and CRIRES the VLT. The integration, alignment and Sylvain Oberti, Jerome Paufique, (see Arsenault et al. 004, Bonnet et al. testing of the AO part require special Eszter Pozna, Sebastien Tordo (ESO) 004 or Paufique et al. 004; alternatively tools and a special test camera which in one can consult the ESO AO webpage turn require a sequential integration at the http://www.eso.org/projects/aot/ which telescope. The CRIRES warm-optics The installation and commissioning of contains detailed information). acceptance review took place at ESO on CRIRES, the Cryogenic Infrared Echelle 4 February 006, and thereafter packing Spectrograph, marks the completion In mid-005 the assembly and integration and shipment of the units could start, of the original plan for the first genera- activities of CRIRES had progressed such subject to few additional checks. Packing tion of VLT instrumentation. Here we that the in-depth verification of the per- of the ‘warm optics’ finally started on report on the commissioning of the cur- formance could be started. As the re- 8 February 006 and the crates left ESO vature sensing adaptive optics part quirements on stability and reproducibility Headquarters on 8 March 006. All (MACAO) of CRIRES in April 2006. This are relatively demanding this test phase boxes of this first batch arrived in good activity also brings the quasi-series pro- resulted in requests for a variety of modi- order on Paranal on 17 March and duction of the MACAO systems to an fications which did not allow keeping the were met by a joint team of the ESO In- end. All four UTs are now equipped with original schedule. strumentation and Telescope Systems one MACAO system each to feed inter- Divisions. Reintegration and installation of ferometry while UT1 and UT4 have one However, in February 006 CRIRES ulti- the components progressed rapidly with additional dedicated system each inte- mately passed the last fundamental mile- hardly any problem. grated into instruments. A summary of stone on its way to the VLT: the success- the overall status of CRIRES is given as ful completion of an ‘end-to-end’ test In the meantime, the CRIRES cold part well. of the system. Using a simulated cool star underwent further improvements and (black-body source and a gas cell with testing in Garching. By the time of writing CO mimicking a COmosphere1) and a tur- of this article the PAE for the complete CRIRES is a cryogenic, pre-dispersed, bulence generator to generate ‘seeing’, instrument had been granted and the infrared echelle spectrograph designed the overall stability of the system, that is spectrograph arrived in good order on to provide a resolving power l/Δl of the Adaptive Optics System and the Paranal on 5 May. The commissioning of 105 between 1 and 5 μm at the Nasmyth cryogenic spectrograph, was checked by the complete instrument will be reported focus A of the 8-m VLT Unit Telescope 1 recording spectra over many hours. in the next issue of The Messenger. (Antu). A curvature sensing adaptive op- The result of this test was that vibrations tics system feed is used to minimise slit and other instabilities are generally at losses and to provide diffraction-limited a level of the equivalent of 1/0th of a Testing the adaptive optics at the spatial resolution along the slit. The nomi- pixel (75 m/s Doppler shift equivalent) or telescope nal slit width of CRIRES is 0.2 arcsec. less and thus in line with the specifica- tions reflecting the astrophysical require- The commissioning of the warm-optics A mosaic of four Aladdin III InSb-arrays ments. part ran in parallel with the final pre- packaged on custom-fabricated ceramics paration for the second part of the PAE. boards has been developed. This pro- Thanks to the joint efforts of the team vides for an effective 4096 × 51 pixel How to move CRIRES from Garching and of Paranal staff, the integration and focal plane array, to maximise the free to the VLT realignment of the warm part in Paranal spectral range covered in each exposure. were successful: the MACAO system is Insertion of gas cells to measure high- Like any other VLT instrument, CRIRES now functional at full performance level. precision radial velocities is foreseen. had to pass the scrutiny of a review Spectro-polarimetry (circular and linear before shipment, termed PAE (Preliminary Figure 1a shows the adaptive-optics part polarisation) will be added in the course Acceptance Europe) in ‘ESO-speak’. of CRIRES after reintegration. For test of the project. To that end a cryogenic CRIRES consists of two relatively inde- purposes an infrared test camera with Wollaston prism in combination with re- pendent subunits: the adaptive optics a spatial sampling of 17 mas/pix (milli-arc- tarders for magnetic Doppler imaging part with the derotator, also carrying the seconds per pixel) was additionally in- is foreseen. CRIRES is part of the initial calibration facilities and the cryostat stalled to characterise the AO perform- first-generation instrumentation com- with the cryogenic optical bench. Hence ance (to be compared with the diffraction plement and is an in-house project done it was decided to split the PAE process limit: e.g. 1. l/D = 45 mas at 1.45 μm). by ESO (for an in-depth description of in two, and to have the ‘warm optics’ part In fact, once CRIRES is installed with its CRIRES see e.g. Moorwood 003 or reviewed ahead of the rest of the instru- infrared slit viewer, the sampling – Käufl et al. 004). The CRIRES MACAO system carries series number 6 of the 1 COmosphere is a term coined by Tom Ayres to highly successful ESO curvature sensor account for the very special chromospheres of cool AO systems which were originally de- stars dominated by the CO-molecule. The Messenger 124 – June 006 Figure 1a: A view of the CRIRES ‘warm optics’ near- Figure 1b: A team member, trying to sort out and re- ly completely installed on the Nasmyth A platform of connect the fibre bundle connecting the wave-front Antu (aka VLT UT1). The left electronics rack houses sensor lenslet array with the 60 avalanche photo di- most of the entire AO related electronics, that is the odes (APDs) contained in a special cabinet. The real-time computer, the local control unit (LCU), the APDs are solid-state photon-counting detectors. As adaptive mirror control and the power supplies for all curvature wavefront sensing systems basically need motors. Moreover the warm optics part comprises only one fast photometric channel per sub-pupil, the calibration unit with continuum sources, spectral APDs were given preference over CCD-detectors, lamps and the gas-cell slide, which allows to port due to their extremely low noise level (typically the ‘Iodine-cell-method’ for high-precision radial-ve- 0.4 counts per loop cycle). APDs, however, are very locity measurements into the infrared. The electron- sensitive and fragile devices, and the prevention of ics rack in the centre is an auxiliary rack for the in- accidental (and catastrophic) overexposures is a key frared test camera (which can be seen on the right issue. side in preparation: the shiny cryostat cylinder on a blue table). At this point a normal CCD camera is still used for alignment. For the reflection in the centre, see Figure 1b. 45 mas/pix – is no longer well suited to showing up as a ‘hot spot’. The system 4–13 August 006. In mid-June there will explore the AO-image quality (this cam- has proven its stability by observing in all be a first call for proposals for science era scale was chosen to be able to ex- typical seeing conditions from 0.5 up to verification programmes and at this point plore a larger field for offset-guiding). 1.5 arcsec. For bright stars with mR < 11, CRIRES will most likely be included in Figure 1b shows part of the integration. Strehl ratios in K-band above 55 % are the next call for proposals (P79). More obtained for median seeing conditions science verification is planned for P78 Figure (next page) shows details inside (0.8?, t0 between 3 and 4 ms at 0.5 μm), (1 October 006 to 31 March 007) and the MACAO box. The commissioning at the level of performance of the other potentially also an early start of opera- culminated within a few minutes of twi- MACAO units. tions of CRIRES for normal programmes light on 3 April to check the derotator selected by ESO’s OPC through the nor- algorithm. Official first light for the adap- mal selection process. tive optics part with the infrared test Outlook camera was on 6 April when the AO con- trol loop was closed at 3h4 UT on the The commissioning of the complete sys- References 5th-magnitude B-star Muscae. The tem is ongoing and everything is pre- h Arsenault R. et al. 004, The Messenger 117, 5 following commissioning tasks could be pared for first light on 4 June. A second Bonnet H. et al. 004, SPIE proc. 5490, 130 finished so smoothly that the team gave commissioning run and potentially some Käufl H.