La Silla Paranal instrumentation – a retrospective The Messenger The VLTI roadmap The ELT’s Primary Mirror Exploring the Sun with ALMA No. 171 –March 2018 171 No. Telescopes and Instrumentation DOI: 10.18727/0722-6691/5061 40+ Years of Instrumentation for the La Silla Paranal Observatory Sandro D’Odorico1 b. a Schmidt telescope with an aperture Germany. Two instrumentation groups, of about 1.20 metres; one optical and one infrared, were set up. c. not more than three telescopes with a They were led by astronomers who 1 ESO maximum aperture of 1 metre; reported directly to the Director General. d. a meridian circle; A dedicated group of engineers was put e. the auxiliary equipment needed to to work on the procurement and testing As ESO Period 100 comes to a close, carry out research programmes with of optical and infrared detectors and I look back at the development of ESO’s the instruments listed in a., b., c. and their control systems within the Technical instrumentation programme over more d. above…”. Division. A committee of astronomers than 40 years. Instrumentation and from the member countries and from detector activities were initially started When reading this text for the first time, ESO, later called the Scientific Technical by a small group of designers, engi- I was amused to see that only the Committee, provided the guidelines and neers, technicians and astronomers telescopes and the meridian circle only general specifications for these new while ESO was still at CERN in Geneva granted the title of “research instruments” developments. During those early years, in the late 1970s. They have since led to while everything else was more modestly when ESO began to build its reputation, the development of a successful suite described as “auxiliary equipment”. The the overall structure was agile and flexible of optical and infrared instruments for first telescopes erected at the La Silla and ensured that strategic choices in the the La Silla Paranal Observatory, as site (with diameters of 50 cm, 1 m and development of instruments were driven testified by the continuous growth in the 1.52 m) were equipped with “auxiliary by the science. number of proposals for observing time equipment” supplied by institutes in the and in the publications based on data member countries: photometers for the The importance of instrumentation and from ESO telescopes. The instrumenta- smaller telescopes and high-resolution the associated detectors to observational tion programme evolved significantly spectrographs for the 1.52-metre tele- astronomy cannot be underestimated. with the VLT and most instruments were scope. These instruments mostly dupli- Instruments serve as a key interface developed by national institutes in close cated similar ones in operation at Euro- between an observatory and its scientific cooperation with ESO. This policy was a pean sites and were conceived to carry users. Along with good atmospheric cornerstone of the VLT programme from out stellar work in the southern hemi- conditions and telescopes that operate the beginning and a key to its success. sphere, reflecting the focus of European smoothly, instrumentation can determine astronomy at that time. the scientific success of an observing run. If the instruments operate well and can Instrumentation: the interface between This was in the early 1970s, when the compete with those available elsewhere, ESO and its users North American observatories were astronomers will obtain high-quality data increasingly starting to focus their scien- that ultimately gives them a more effective Most astronomers in Europe are familiar tific research on extragalactic targets, long-term impact in their field of research. with ESO as it is today, with its three spurred on by the discovery of the first This, in short, is the primary goal of an observing sites in Chile, the Extremely quasars, which changed our view observatory. Large Telescope under construction, the of the Universe. European astronomy scientific and administrative centre in needed larger telescopes and modern Santiago, headquarters in Garching, and instru mentation to compete with these 1978–1998: two decades of “fast and as the European partner in the Atacama exciting scientific developments. ESO’s furious” growth Large Millimeter/submillimeter Array founders had a vision that this was best (ALMA). However, they may not be aware achieved by joining forces, but progress The instrumentation and detector pro- of the modest goals (as compared to was initially slow. gramme started to show results at the tele- today’s achievements) set by ESO’s scopes in Chile at the end of the 1970s. founders in the ESO Convention of 1962, The 3.6-metre telescope, ESO’s main First, the Coudé Échelle Spectrograph which was signed by representatives from project, saw first light in 1976. Lodewijk (CES) with a 1D digital detector become Belgium, France, the Federal Republic of Woltjer, ESO Director General from operational in the coudé room of the 3.6- Germany, the Netherlands and Sweden. 1975 to 1987, writes in his book (Woltjer, metre telescope, fed by the newly erected An excerpt from the English version of the 2006), “When I came to ESO in 1975, it 1.4-metre Coudé Auxiliary Telescope document states1, “The purpose of the was evident that there was no real plan (CAT) and, a few years later, by an optical Organisation shall be to build, fit out and to effectively use the 3.6 m telescope for fibre from the 3.6-metre. An off-the-shelf operate an astronomical observatory situ- contemporary science. There also would instrument, the Boller and Chivens grat- ated in the southern hemisphere. The be no suitable instrumentation to attach ing spectrograph, was acquired to offer initial programme of the Organisation to the telescope.” An instrumentation the possibility to observe faint objects at shall comprise the construction, installa- development programme was started the 3.6-metre. It initially used a 1D Image tion and operation of an observatory in while ESO was still at CERN in Geneva Dissector Scanner (IDS) detector. the southern hemisphere, consisting of: (between 1972 and 1980). This was further a. a telescope with an aperture of about expanded when the Organisation moved Two instruments designed and built by 3 metres; to its new Headquarters in Garching, ESO then become operational in 1984 2 The Messenger 171 – March 2018 Figure 1. Below is the hand-drawn map of the La Silla Observatory from the beginning of the 1980s, before the installation of the 2.2-metre telescope and the NTT. A photo from the same epoch was taken from the plane that was used to commute staff from Santiago to the Pelicano airstrip close to La Silla. The small plane was in use until the early 1990s. definition of several instruments (EMMI, FORS, UVES, X-shooter), which was always a gratifying experience. On receiv- ing a set of requirements, such as wave- length range, spectroscopic resolution, image scale and the likely properties of the detector, he would create a prelimi- nary, often original, design in just a few days. A robust discussion with the pro- ject team would follow, about perfor- mance, feasibility and cost, and would eventually lead to a final configuration that formed part of an instrument proposal. Table 1 lists the most-demanded instru- ments at the three most powerful La Silla telescopes, along with their period of operation and the number of publications that have used their data. The years from 1978 to 1998 saw a spectacular growth in ESO facilities, with the arrival of new instruments at the 3.6-metre telescope, the installation of the 2.2-metre Max- Planck-Gesellschaft (MPG)/ESO tele- scope and the completion of the New Technology Telescope (NTT) with three fixed instruments at its two Nasmyth foci. All of this was during the construction of the VLT. The growing interest and con- fidence of the community in the use of ESO’s facilities was reflected in the num- ber of observing proposals, which went from about 150 in 1978 to over 550 in and 1985: CASPEC, an efficient cross- EFOSC deserves a special mention. This 1995 (Patat et al., 2017). dispersed échelle spectrograph and the innovative transmission optics instrument ESO Faint Object Spectrograph & Cam- was the first major work by the ESO The use of near-infrared (NIR) instruments era (EFOSC). Both used silicon charge- designer Bernard Delabre, who recently was initially limited by the lack of suitable coupled device (CCD) detectors — the retired. It was followed by an upgraded detectors. In the first part of this period, first to operate at the 3.6-metre tele- version, EFOSC2, which served as the the first NIR spectrograph, IRSPEC, scope. The high efficiency of the optics, prototype for the very successful FORS started operating at the 3.6-metre tele- coupled with the high quantum sensitivity instruments at the Very Large Telescope scope with just a 32-diode linear detector, of the CCDs, boosted the performance (VLT). As noted by de Zeeuw et al. (2017), which was upgraded to a 58 × 62 pixel of these instruments and, for the first EFOSC clones or derivatives have been InSb array when the instrument was time, gave European astronomers the built for telescopes distributed across moved to the NTT in 1991. A few years possibility of competing on crucial observ- almost all continents. Delabre put for - later when the 1k × 1k pixel HgCdTe ing modes with their colleagues at other ward many other original ideas over his infrared arrays become available, ESO 4-metre-class telescopes worldwide. 40 years at ESO, with the consistent aim quickly put them into operation using two In the mid-1980s these two instruments of designing more efficient instruments new instruments, SOFI at the NTT and regularly used around 60 % of the tele- using affordable optics.