HARMONI is a visible and near-infrared (0.5 to 2.45 μm) integral field spectrograph, providing the E-ELT's core spectroscopic capability, over a range of resolving powers from R (λ/Δλ) ~ 3500 to ~18000. The instrument provides simultaneous spectra of ∼32000 spaxels arranged in a sqrt(2):1 aspect ratio contiguous field. The pre-optics take light entering the science cryostat (from the telescope or calibration system), reformatting and conditioning to be suitable for input for the rest of the instrument. This involves many functions, mainly relaying the light from the telescope focal plane to the integral field unit (IFU) focal plane via a set of interchangeable scale changing optics. The pre-optics also provides components including a focal plane mask wheel, cold pupil masks, spectral order sorting filters, a fast shutter, and a pupil imaging capability to check telescope/instrument pupil alignment. In this paper, we present the optical design of the HARMONI pre-optics at Preliminary Design Review and, in particular, we detail the differences with the previous design and the difficulties salved to the Preliminary Design Review.
HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrograph, providing the ELT's core spectroscopic capability at first light. A pre-optics subsystem provides four selectable spatial pixel scales, in addition to other beam conditioning functions such as shutter and pupil masks. For the validation of the mechanisms in charge of these functions (fast shutter and the plane mask wheel) we have planned some prototypes to test the design solutions.
The focal plane mask wheel sits in the input focus of the cryostat. It provides 16 user-selectable positions for masks (28x40 mm) used in observation. The key driver for this mechanism is the high repeatability (±2.5 μm) required, equivalent to ~1mas in the input focal plane. The IAC has previously designed, manufactured, tested and put in operation cryogenic wheels with high repeatability; however, the challenge of obtaining a wheel with such repeatability requires testing new concepts of detent positioning systems.
The shutter allows for exposures shorter than the minimum read time of the near-IR detectors and is needed for any CCD observations with the visible cameras. A dual shutter design is needed to achieve the necessary open/close times (<20 ms), but this also provides some redundancy and a graceful failure mode for this critical device. To mitigate risks on the proper behaviour of a fast cryogenics shutter a prototype based on a simple concept has been manufactured. We present the design and results for the performed cryogenic tests of a mask wheel and a shutter prototypes that we have developed.
HARMONI is the E-ELT’s first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 × 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the E-ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers (R ~3500, 7500 and 20000) and instantaneous wavelength coverage spanning the 0.5 – 2.4 μm wavelength range of the instrument. In autumn 2015, the HARMONI project started the Preliminary Design Phase, following signature of the contract to design, build, test and commission the instrument, signed between the European Southern Observatory and the UK Science and Technology Facilities Council. Crucially, the contract also includes the preliminary design of the HARMONI Laser Tomographic Adaptive Optics system. The instrument’s technical specifications were finalized in the period leading up to contract signature. In this paper, we report on the first activity carried out during preliminary design, defining the baseline architecture for the system, and the trade-off studies leading up to the choice of baseline.
Proc. SPIE. 9908, Ground-based and Airborne Instrumentation for Astronomy VI
KEYWORDS: Sensors, Control systems, Computer programming, Photonic integrated circuits, Computer aided design, Commercial off the shelf technology, Cryogenics, Camera shutters, Prototyping, Temperature metrology
HARMONI is an integral field spectrograph working at visible and near-infrared wavelengths. The instrument will be part of the first-light complement at the E-ELT. The IAC is in charge of several work packages and the design of two important components is ongoing: A 'Cryogenic Pupil Mask Rotator' based on a direct drive brushless motor, and a 'Cryogenic Fast Shutter' based on voice coil. One of the main goals of these developments is the use of COTS (Commercial-Off-The-Shelf) parts since their use will reduce costs and short the schedule. Nevertheless, the application of COTS parts in cryo-vacuum is often very difficult and represents a technological challenge.
HARMONI is an integral field spectrograph working at visible and near-infrared wavelengths over a
range of spatial scales from ground layer corrected to fully diffraction-limited. The instrument has been
chosen to be part of the first-light complement at the European Extremely Large Telescope (E-ELT). This
paper describes the instrument control electronics to be developed at IAC. The large size of the
HARMONI instrument, its cryogenic operation, and the fact that it must operate with enhanced reliability
is a challenge from the point of view of the control electronics design. The present paper describes a
design proposal based on the current instrument requirements and intended to be fully compliant with the
ESO E-ELT standards, as well as with the European EMC and safety standards. The modularity of the
design and the use of COTS standard hardware will benefit the project in several aspects, as reduced
costs, shorter schedule by the use of commercially available components, and improved quality by the use
of well proven solutions.
HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrometer, providing the E-ELT's core
spectroscopic capability, over a range of resolving powers from R (≡λ/Δλ)~500 to R~20000. The instrument provides simultaneous spectra of ~32000 spaxels at visible and near-IR wavelengths, arranged in a √2:1 aspect ratio contiguous field. HARMONI is conceived as a workhorse instrument, addressing many of the E-ELT’s key science cases, and will
exploit the E-ELT's scientific potential in its early years, starting at first light. HARMONI provides a range of spatial
pixel (spaxel) scales and spectral resolving powers, which permit the user to optimally configure the instrument for a
wide range of science programs; from ultra-sensitive to diffraction limited, spatially resolved, physical (via morphology),
chemical (via abundances and line ratios) and kinematic (via line-of-sight velocities) studies of astrophysical sources.
Recently, the HARMONI design has undergone substantial changes due to significant modifications to the interface with
the telescope and the architecture of the E-ELT Nasmyth platform. We present an overview of the capabilities of
HARMONI, and of its design from a functional and performance viewpoint.
In order to improve the signal-to-noise ratio of HARMONI (E-ELT first light visible and near-infrared integral field VIR
spectrometer), a pupil mask has been identified to be included at the fore-optics to limit the background radiation coming
into the spectrographs. This mask should rotate synchronously with the telescope pupil during observations, taking into
account the combined effects of the telescope tracking and the de-rotation of the FOV. The implementation of the pupil
mask functionality will require complex movements with high precision at cryogenic temperatures which implies an
important technological challenge.
This paper details a set of experiments completed to gain knowledge and experience in order to accomplish the design
and control of cryogenic mechanisms reaching this type of pupil motion. The conceptual design of the whole mechanism
started from the feedback acquired from those experiments is also described in the following sections.
OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) was the optical Day One instrument
for the 10.4m Spanish telescope GTC. It is installed at the Observatorio del Roque de Los Muchachos (La Palma, Spain).
This instrument has been operational since March-2009 and covers from 360 to 1000 nm. OSIRIS observing modes
include direct imaging with tunable and conventional filters, long slit and low resolution spectroscopy. OSIRIS wide
field of view and high efficiency provide a powerful tool for the scientific exploitation of GTC. OSIRIS was developed
by a Consortium formed by the Instituto de Astrofísica de Canarias (IAC) and the Instituto de Astronomía de la
Universidad Nacional Autónoma de México (IA-UNAM). The latter was in charge of the optical design, the manufacture
of the camera and collaboration in the assembly, integration and verification process. The IAC was responsible for the
remaining design of the instrument and it was the project leader. The present paper considers the development of the
instrument from its design to its present situation in which is in used by the scientific community.
OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) is the optical Day One instrument for the 10.4m Spanish telescope GTC (Gran Telescopio Canarias). The instrument spectral range covers from 365 up to 1000 nm. One of the most important elements of OSIRIS is its two commercial ICOS ET100 wide field Fabry-Perot tunable filters, that will provide a powerful tool to analyse faint emission line objects. Currently, the unique controller available for such device is the so called CS100. Due to the necessity of improvement and addition of some specifications of such controller, a first prototype electronic module has been made and tested successfully. Now, it has developed the final product: a compact mini-module integrated in the CS100 controller, offering a 16-bit resolution over the full range cavity spacing; be able to synchronize cavity changes with an external trigger; full remote control over the front panel of the device and capability to monitor all their signals. It also offers the possibility to load a preprogrammed table sequence of cavity spacing changes, programmable security limits of dynamic range and slew rate applied; and it has high stability over time too. The electronic control is based on an embedded microcontroller into a FPGA.
Real-time control has been clearly identified as a separate challenging field within Adaptive Optics, where a lot of computations have to be performed at kilohertz rate to properly actuate the mirror(s) before the input wavefront information has become obsolete. When considering giant telescopes, the number of guide stars, wavefront samples and actuators rises to a level where the amount of processing is far from being manageable by today's conventional processors and even from the expectations given by Moore's law for the next years. FPGA (Field Programmable Gate Arrays) technology has been proposed to overcome this problem by using its massively parallel nature and its superb speed. A complete laboratory test bench using only one FPGA was developed by our group , and now this paper summarizes the early results of a real telescope adaptive optics system based in the FPGA-only approach. The system has been installed in the OGS telescope at "Observatorio del Teide", Tenerife, Spain, showing that a complete system with 64 Shack-Hartmann microlenses and 37 actuators (plus tip-tilt mirror) can be implemented with a real time control completely contained within a Xilinx Virtex-4 LX25 FPGA. The wavefront sensor has been implemented using a PULNIX gigabit ethernet camera (714 frames per second), and an ANDOR IXON camera has been used for the
evaluation of the overall correcting behavior.
FPGA (Field Programmable Gate Array) technology has become a very powerful tool available to the electronic designer, specially after the spreading of high quality synthesis and simulation software packages at very affordable prices. They also offer high physical integration levels and high speed, and eases the implementation of parallelism to obtain superb features. Adaptive optics for the next generation telescopes (50-100 m diameter) -or improved versions for existing ones- requires a huge amount of processing power that goes beyond the practical limits of today's processor capability, and perhaps tomorrow's, so FPGAs may become a viable approach. In order to evaluate the feasibility of such a system, a laboratory adaptive optical test bench has been developed, using only FPGAs in its closed loop processing chain. A Shack-Hartmann wavefront sensor has been implemented using a 955-image per second DALSA CA-D6 camera, and a 37-channel OKO mirror has been used for wavefront correcting. Results are presented and extrapolation of the behavior for large and extremely large telescopes is discussed.
One of the problems found in the design of the electronics for astronomical instruments is the difficulty to find precise digitizers (16 bits) at high speed. In fact, most of the chips which claim to have 16-bit actually have a lower ENOB (Effective Number Of Bits), normally around 14, when considering their noise effects. In this paper, a technique based in auto-adjustable gain amplifiers is proposed as a way to relax the A/D requirements for astronomical CCDs and infrared detectors. The amplifiers will automatically toggle between 2 different gains depending on the pixel value. The technique is based on the fact that, due to the shot (photon) noise of the detectors, the maximum signal to noise ratio achievable in most of these devices is relatively low, allowing the use of A/D converters with an ENOB of only 14 (or even 12) bits when combined with auto-adjustable gain amplifiers. It will be shown that the lower resolution of the A/D converters will not affect the accuracy of the science data, even when many images are averaged out to compensate the effects of the shot noise. Furthermore, given that many real A/D converters do not reach an ENOB of 16, for low level signals the accuracy can be even slightly improved with the technique described in this paper. On the other hand, this relaxing of the A/D requirements can allow the use of off-the-shelf boards for the acquisition systems.
OSIRIS (Optical System for Imaging and low/intermediate-Resolution Integrated Spectroscopy) and EMIR (InfraRed MultiObject Spectrograph) are instruments designed to obtain images and low resolution spectra of astronomical objects in the optical and infrared domains. They will be installed on Day One and Day Two, respectively, in the Nasmyth focus of the 10-meter Spanish GTC Telescope. This paper describes the architecture of the Data Acquisition System (DAS), emphasizing the functional and quality attributes. The DAS is a component oriented, concurrent, distributed and real time system which coordinates several activities: acquisition of images coming from the detectors controller, tagging, and data communication with the required telescope system resources. This architecture will minimize efforts in the development of future DAS. Common aspects, such as the data process flow, concurrency, asynchronous/synchronous communication, memory management, and exception handling, among others, are managed by the proposed architecture. This system also allows a straightforward inclusion of variable parts, such as dedicated hardware and different acquisition modes. The DAS has been developed using an object oriented approach and uses the Adaptive Communication Environment (ACE) to be operating system independent.
OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) is the optical Day One instrument for the 10.4m Spanish telescope GTC to be installed in the Observatorio del Roque de Los Muchachos (La Palma, Spain). This instrument, operational in mid-2004, covers from 360 up to 1000 nm. OSIRIS observing modes include direct imaging with tunable and conventional filters, long slit and multiple object spectroscopy and fast spectrophotometry. The OSIRIS wide field of view, high efficiency and the new observing modes (tunable imaging and fast spectrophotometry) for 8-10m class telescopes will provide GTC with a powerful tool for their scientific exploitation. The present paper provides an updated overview of the instrument development, of some of the scientific projects that will be tackled with OSIRIS and of the general requirements driving the optical and mechanical design.
OSIRIS (Optical System for Imaging and low/intermediate-Resolution Integrated Spectroscopy) is an instrument designed to obtain images and low resolution spectra of astronomical objects in the optical domain (from 365 through 1000nm). It will be installed on Day One (middle of 2004) in the Nasmyth focus of the 10-meter Spanish GTC Telescope. This paper shows an overview of the OSIRIS instrument software. Its architecture is distributed with real time features, having in mind to build a reusable, maintainable and inexpensive system. In this paper, we outline the main performances of the current design and some examples already implemented are given.