PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~ 1.6-2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project recently started undertaking the commissioning process of a subsystem at the Subaru Telescope side, with the integration and test processes of the other subsystems ongoing in parallel. We are aiming to start engineering night-sky operations in 2019, and observations for scientific use in 2021. This article gives an overview of the instrument, current project status and future paths forward.
FOCCoS, "Fiber Optical Cable and Connector System", is a part of subsystem of Prime Focus Spectrograph”, for Subaru telescope. FOCCoS are divided in 3 different segments called Cable A, Cable B and Cable C. Multi-fibers connectors assure precise connection among all optical fibers of the segments, providing flexibility for instrument changes. Cable B is permanently installed at Subaru Telescope structure starting in a Connector Bench device and finishing at another different Connector Bench device. By this way, Cable B represent a link between the light entrance, from Cable C, and the light delivery, to Cable A. This cable will be routed to minimize the compression, torsion and bending caused by the cable weight and telescope motion. In this work, we present the current stage of development of Cable B as well as the detailing of its structures. In addition, we present the optical fiber cabling methodology and the test procedures involved in its characterization. A prototype of Cable B was constructed to help us to better understanding the real situation and was tested at Subaru Telescope.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~1.6 - 2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.
The Fiber Optical Cable and Connector System, ”FOCCoS”, subsystem of the Prime Focus Spectrograph,
“PFS”, for Subaru telescope, is responsible to feed four spectrographs with a set of optical fibers cables. The light
injection for each spectrograph is assured by a convex curved slit with a linear array of 616 optical fibers. In this paper
we present a design of a slit that ensures the right direction of the fibers by using masks of micro holes. This kind of
mask is made by a technique called electroforming, which is able to produce a nickel plate with holes in a linear
sequence. The precision error is around 1-μm in the diameter and 1-μm in the positions of the holes. This nickel plate
may be produced with a thickness between 50 and 200 microns, so it may be very flexible. This flexibility allows the
mask to be bent into the shape necessary for a curved slit. The concept requires two masks, which we call Front Mask,
and Rear Mask, separated by a gap that defines the thickness of the slit. The pitch and the diameter of the holes define
the linear geometry of the slit; the curvature of each mask defines the angular geometry of the slit. Obviously, this
assembly must be mounted inside a structure rigid and strong enough to be supported inside the spectrograph. This
structure must have a CTE optimized to avoid displacement of the fibers or increased FRD of the fibers when the device
is submitted to temperatures around 3 degrees Celsius, the temperature of operation of the spectrograph. We have
produced two models. Both are mounted inside a very compact Invar case, and both have their front surfaces covered by
a dark composite, to reduce stray light. Furthermore, we have conducted experiments with two different internal
structures to minimize effects caused by temperature gradients.
This concept has several advantages relative to a design based on Vgrooves, which is the classical option. It is
much easier and quicker to assemble, much cheaper, more accurate, easier to adjust; and it also offers the possibility of
making a device much more strong, robust and completely miniaturized.
In this paper we describe the recent advances in the development of new technologies applied in the
construction of Integral Field Units (IFUs) at Laboratório Nacional de Astrofísica (LNA). Our prototype is the
Eucalyptus lenslet IFU constructed for the 1.6m telescope at Pico dos Dias Observatory (OPD), Brazil. This first
concept was the basis to build two other IFUs with significantly improved concepts: the SOAR Integral Field Unit
Spectrograph (SIFS) and FRODOSPEC. All the new technologies used in the construction of these IFUs are described
in detail in this paper and can be replicated in similar instruments with optical fibers, with considerable advantages over
the traditional technologies.
Extremely low temperatures may damage the optical components assembled inside of an astronomical instrument due to the crack in the resin or glue used to attach lenses and mirrors. The environment, very cold and dry, in most of the astronomical observatories contributes to this problem.
This paper describes the solution implemented at SOAR for remotely monitoring and controlling temperatures inside of a spectrograph, in order to prevent a possible damage of the optical parts. The system automatically switches on and off some heat dissipation elements, located near the optics, as the measured temperature reaches a trigger value. This value is set to a temperature at which the instrument is not operational to prevent malfunction and only to protect the optics. The software was developed with LabVIEWTM and based on an object-oriented design that offers flexibility and ease of maintenance.
As result, the system is able to keep the internal temperature of the instrument above a chosen limit, except perhaps during the response time, due to inertia of the temperature. This inertia can be controlled and even avoided by choosing the correct amount of heat dissipation and location of the thermal elements. A log file records the measured temperature values by the system for operation analysis.
FOCCoS, "Fiber Optical Cable and Connector System" has the main function of capturing the direct light from the focal plane of Subaru Telescope using optical fibers, each one with a microlens in its tip, and conducting this light through a route containing connectors to a set of four spectrographs. The optical fiber cable is divided in 3 different segments called Cable A, Cable B and Cable C. Multi-fibers connectors assure precise connection among all optical fibers of the segments, providing flexibility for instrument changes. To assure strong and accurate connection, these sets are arranged inside two types of assemblies: the Tower Connector, for connection between Cable C and Cable B; and the Gang Connector, for connection between Cable B and Cable A. Throughput tests were made to evaluate the efficiency of the connections. A lifetime test connection is in progress. Cable C is installed inside the PFI, Prime Focus Instrument, where each fiber tip with a microlens is bonded to the end of the shaft of a 2-stage piezo-electric rotatory motor positioner; this assembly allows each fiber to be placed anywhere within its patrol region, which is 9.5mm diameter.. Each positioner uses a fiber arm to support the ferrule, the microlens, and the optical fiber. 2400 of these assemblies are arranged on a motor bench plate in a hexagonal-closed-packed disposition. All optical fibers from Cable C, protected by tubes, pass through the motors’ bench plate, three modular plates and a strain relief box, terminating at the Tower Connector. Cable B is permanently installed at Subaru Telescope structure, as a link between Cable C and Cable A. This cable B starts at the Tower Connector device, placed on a lateral structure of the telescope, and terminates at the Gang Connector device. Cable B will be routed to minimize the compression, torsion and bending caused by the cable weight and telescope motion. In the spectrograph room, Cable A starts at the Gang Connector, crosses a distribution box and terminates in a slit device. Each slit device receives approximately 600 optical fibers, linearly arrayed in a curve for better orientation of the light to the spectrograph collimator mirror. Four sets of Gang Connectors, distribution boxes and Slit devices complete one Cable A. This paper will review the general design of the FOCCoS subsystem, methods used to manufacture the involved devices, and the needed tests results to evaluate the total efficiency of the set.