NRC Herzberg News




Edited by: Dennis Crabtree


June 2014


The NRC Herzberg News E-Cass Report

These reports appear in each issue of E-Cass with the goal of informing the Canadian astronomical community on the activities at NRC Herzberg.

Feedback is welcome from community members on how NRC-Herzberg is doing in fulfilling our mandate to “operate and administer any astronomical observatories established or maintained by the Government of Canada” (NRC Act).

General News

May 13, 2014 was the 100th anniversary of the public announcement that a 72-inch telescope, now named the Plaskett telescope, would be built in Victoria. As the front-page article of the Daily Colonist proclaimed “Huge Telescope for Victoria”. Indeed, the Plaskett would be the world’s largest operating telescope for a few months before the 100-inch on Mt. Wilson was successfully put into operation.

The May 13, 1914 edition of the Daily Colonist is online for anyone interested in reading the coverage of this monumental event in the history of Canadian astronomy.

Space Astronomy

The James Webb Space Telescope (JWST), a joint project of NASA, ESA and CSA, continues to make excellent progress. Most of the flight hardware has been manufactured and the focus is now firmly on integration and testing with a scheduled launch in 2018. All four science instruments have been delivered and integrated into the Integrated Science Instrument Module (ISIM). The second cryo-vacuum test of the ISIM begins in June 2014. Over a three month period all the instruments will get extensively tested to verify their performance. The enormous Chamber A at Johnson Space Center in Houston, once used to test the Apollo spacecraft, has been extensively renovated in preparation for testing of the telescope in 2017.


Figure 1 The integrated ISIM with all four science instruments labelled, shortly before the second cryo-vacuum test at Goddard Space Flight Center. Photo credit: NASA.

On the Canadian side, there is considerable activity supporting the second cryo-vacuum test this summer and completing the fabrication and testing of new detectors, dual wheel motors, a grism and an electronics board which will be swapped into the FGS/NIRISS instrument later this year. The science team is active simulating the main NIRISS observing modes and making plans for commissioning, calibration and operations.

Optical Astronomy

Plaskett Telescope
For more than a decade it has been known that the quality and durability of the aluminum mirror coating on the Dominion Astrophysical Observatory’s (DAO) 1.8-m Plaskett telescope’s primary mirror has been less than optimal because of an aging vacuum coating facility that produced coatings with poor adhesion properties and, as a result, relatively poor reflectivities.  Unfortunately, because of commitments of NRC Herzberg staff to other higher priority international instrumentation and telescope projects, scheduling time for the DAO Plaskett and 1.2-m telescopes is not always easy!  However, this spring a lengthy project to upgrade the telescope’s coating chamber was finally completed and in mid-May, just after its 96th anniversary of first light, the Plaskett telescope was finally treated to a new high-quality aluminum coating for its primary mirror.  Shortly thereafter the Cassegrain secondary was also swapped for a spare with a fresh enhanced aluminum coating with a reflectivity of approximately 95%.  The accompanying photograph shows the primary mirror shortly after it was recoated and before it was returned to service.


Observations obtained shortly after the mirror installations suggest that the throughput of the telescope has improved by a factor of 3 to 3.5 with the new mirror coatings.  No, that is not a typo - the mirrors were not in good shape at all!   A likely incomplete list of NRC Herzberg staff involved in the coating project includes Jim Jennings, Gordon Hnylycia, Colin Ganton, Felipe Miranda, Les Saddlemyer and Dmitry Monin.   I was lucky enough to be the first user of the ‘new’ telescope on the May long weekend and can confirm that the telescope is acting like a 2-m class facility again.  NRC Herzberg’s long-term ‘business plan’ now also includes an annual commitment of staff for work on the two DAO telescope primary mirrors and so we expect each telescope to receive fresh aluminum in alternating years in the future.

The focus of our work on the Plaskett telescope will now be concentrated on completing efforts to enable robotic operation of the facility using lessons learned from automation of the 1.2-m telescope and high-resolution McKellar spectrograph.CADC

After 23 years of operation, the HST archive is still alive and well at CADC. During those 23 years, technological and operation improvements have made the HST archive more scientifically relevant than ever.

Astronomy Technology

GRACES: A successful first light for the longest astronomical fibre system 

The GRACES (Gemini Remote Access to CFHT ESPaDOnS ) experiment completed its very successful first light run  ( May 6th to May 19th) with the performance of the system exceeding the predictions. GRACES is an innovative partnership between Gemini Observatory, the Canada-France-Hawaii Telescope (CFHT) and National Research Council (NRC) Herzberg in Victoria B.C. with the development being done across the three organizations.

 GRACES is a groundbreaking experiment in fibre fed spectroscopy and intra-observatory facility cooperation.  The experiment links the Gemini North telescope to the ESPaDOnS ( Echelle SpectroPolarimetric Device for the Observation of Stars) spectrograph at CFHT with a 270m fibre link. Light is injected into the fibre at the Gemini telescope via an injection module installed in the GMOS spectrograph ( replacing the GMOS intergral field unit). Two 270m fibers  carry the light ( star & sky ) from the Gemini telescope to the CFH dome then  to the ESPaDOnS spectrograph in the CFH Coude room. A receiver unit feeds the light into the spectrograph providing two operation modes: a star/sky mode with a resolution of 37k and a star only mode with a resolution of 55k. The receiver unit is designed to allow a remote operation change between ESPaDOnS being feed by the CFHT telescope and ESPaDOnS being feed from Gemini telescope. 

 NRC Herzberg was responsible for the design and construction of the opto-mechanical system, with the fibre cable being developed in partnership with FiberTech Optica in Kitchener Ontario.  NRC Herzberg delivered the system to the telescopes at the end of april with the fibre being installed between the two telescopes on April 24th, and the integration of the opto-mechnical systems at the telescope starting on April 27th. First light was achieved on May 6th, on schedule! ( a testament of the superb teamwork between Gemini, CFHT and NRC Herzberg staff). On sky performance test have confirmed the spectrograph resolutions of 37k/55k and transmission has exceed expectations with a SNR=1 sensitivity as high as 22 mag per 1 hour exposure. The combination of the silver coatings on Gemini,  the superb red efficiencies on ESPaDOnS ( with the prism cross dispersers and the silver coated relay mirrors) make GRACES  a competitive 8m class spectrograph over the designed wavelength range ( 450nm to 1000nm).

Gemini High-Resolution Optical Spectrograph (Ghost)

Sometimes GHOSTs can be real!

Merriam Webster dictionary defines a ghost as: a disembodied soul; especially :  the soul of a dead person believed to be an inhabitant of the unseen world or to appear to the living in bodily likeness.

It would be fair to say that the notion of ghosts has endured from generation to generation and has managed to capture the imagination of people from many cultures across the planet. Perhaps more famously ghosts are associated with movies; where they appear as typically malicious spirits bent on haunting an innocent and unsuspecting family which moves into an otherwise perfectly seeming house in some innocuous suburban neighbourhood.

It’s this notion of “haunting” that brings us to the point. For the past few years the Canadian and broader astronomical community have been haunted by the promise of adding a workhorse spectrograph to the Gemini suite of tools. A few years back just such an instrument seemed poised for design, fabrication and deployment but like all good stories there was a twist. The Gemini High-resolution Optical Spectrograph (GHOS) seemed set to launch. Led by a coalition of Australian partners (Australian Astronomical Observatory (AAO), Australian National University (ANU) and KiwiStar Optics Ltd.) the project seemed set to roll forward.

Unforeseen in this mix was that KiwiStar would be bought out by a parent company which would lose appetite to continue with the GHOS project. For two years GHOS appeared dead in its track but like all good spirits, its memory haunted the community until a new partner emerged to replace KiwiStar and provide the spectrograph portion of the instrument. This partner is Canada’s very own NRC Herzberg. In an effort led by the AAO, NRC Herzberg has entered the mix as a sub-contractor tasked with designing and building the spectrograph portion of the instrument. ANU will continue-on in their role of leading the software design and AAO will provide the Cassegrain interface and the fiber feed connection to the spectrograph routed through their slit assembly.

GHOS was originally envisioned as a 4-arm white pupil Echelle spectrograph - GHOST, as it has been officially renamed, launched mid-April 2014. This workhorse is being designed to provide high-resolution spectra with large simultaneous wavelength coverage and has the ambitious aim of being on-sky mid-2017.

The NRC team has recently returned from upbeat kickoff meetings with our counterparts in Sydney as well as the Gemini project leadership and is excited to be moving forward with this long awaited project! The NRC team will feature John Pazder as Optical design lead and Project Engineer; Project Scientist: Alan McConnachie; Mechanical Engineering: led by Andre Anthony with support from Ivan Wevers; Detectors: led by Greg Burley; Software: led by Jennifer Dunn with support from Bob Wooff. The project will be managed by Eric Chisholm. As the GHOST project comes back to life we’ll update you frequently on both NRC’s and the overall progress of the project.


Facility Adaptive Optics System – NFIRAOS

In 2013, two major trade studies took place to re-examine the NFIRAOS baseline configuration since its Preliminary Design Update (PDU) in 2011.


During 2013, we undertook an extensive trade study on changing the size of one or both deformable mirrors (DMs), with the aim to reduce risk and cost by have two common size DMs that are interchangeable with one conjugates at ground level, i.e. DM0, and one conjugates at 11.2 km, i.e. DM11.2. By having common DMs, the DM0 position will always be filled should one of the two DMs were to break.

On the face of it, if DM0 were to break and with no replacement, then NFIRAOS would be inoperable and resulting severe setback during integration and commissioning. Full commissioning and even first light on TMT (defined as capturing of the first diffraction-limited images) would be delayed for several years until a replacement DM can be obtained. Budgets and manufacturing capacity make it unlikely that we actually would have a spare DM on-hand during this critical phase. In principle, if DM11 broke, a flat mirror could replace it and NFIRAOS will operate in LTAO mode.  Although LTAO mode falls far short of the scientific aspirations of MCAO mode, meaningful astronomical observations are still possible.

For the above reason, we studied the possibility of redesigning NFIRAOS with two DMs of the same size. In that way, DM11.2 could serve as a spare for DM0. We considered having both DMs equal in size to DM0, or both equal to the DM11.2 size, or to some intermediate size. We examined a series of variants that changed the size of the pupil and metapupil (Table 1). The main challenge was to find an optical prescription that meets all the existing requirements such as distortion, exit pupil location, and instrument back focal distance etc. while maintaining the current instrument space envelope of NFIRAOS.

Table 1 Options of the common size DM trade study – actuator counts indicate the physical DM diameters and the beam size required to maintain “clear aperture” with Option A representing the baseline PDU design. (Note: DM0 is mounting on the Tip Tilt Stage which provides tip/tilt offload from DM0.)

Initially we believed if the ground-conjugated DM diameter were larger than the baseline DM0 of 63x63 actuators, then we would need to replace the existing Tip Tilt Stage with a larger unit, because DM0 nests inside. Since we already have acquired the Tip Tilt Stage and plan to upgrade its electronics before installing it in NFIRAOS, buying a new stage would be expensive and impractical. However, during the trade study under Option C, we realized that DM11 could be mounted on the Tip Tilt Stage with an adaptor. The adaptor would move the optical surface forward, but to compensate, the stage itself could be moved back onto a second mounting location in NFIRAOS. The stage would need additional counterweights to balance the larger DM11 whose centre of gravity would then lie ahead of the stage tilt axis.  We also verified that the additional moment of inertia would be within the capability of the existing voice-coil actuators to provide sufficient correction bandwidth and yield acceptable heat dissipation.

As we tried to package the optical variants, we recognized that increasing either DM diameter was expensive, and that the opto-mechanical effort to shrink DM11 and/or expand DM0 was running into space constraints (Figure 1). The follow-on effort and risk to rework the structure, subassemblies and thermal optics enclosure for NFIRAOS posed a large risk to our schedule and resources. Taken together with the realization that DM11 can act as a temporary spare for DM0, we decided to retain the PDU baseline design with DM0 having 63x63 actuators and DM11 having 76x76 actuators as outlined in Option C.

Figure 2 Comparison of footprint of the opto-mechanical structure: Option E exceeds the NFIRAOS space envelope as defined by Option A


As well, during 2013, we revisited computing architecture for the NFIRAOS Real Time Controller which processes the WFS data and creates command vectors to control the DM shape for AO corrections. At the last 2011 review, the baseline RTC used custom boards with Field Programmable Gate Arrays (FPGA) running an iterative algorithm. Because the NFRIAOS RTC arithmetic operations required are nearly one hundred times larger than any existing AO systems, the iterative algorithm technique drastically reduced the number of computations compared with the standard Matrix-Vector Multiplication (MVM) method. However, the custom nature of these FPGA boards and the labour-intensive specialist programming required meant that this approach was costly and specialized acknowledge are difficult to develop and maintain.

Meanwhile advances in commercial computation hardware offered hope that a RTC architecture using conventional CPU boards and techniques is within reach. We benchmarked with MVM on clusters of CPU servers, with and without accelerators such as Graphical Processing Units (GPUs), and Intel Xeon Phi. Half a dozen dual-GPU boards can do the required computation in ~ 900 µs with jitter of a few 10s of µs. This architecture provides sufficient performance margin when compared with the required frame period of 1.25 ms. While we found a server cluster with 12 Xeon Phis computes most frames quickly enough but occasionally their internal operating system suspends the RTC work and resulting in unacceptable jitter of up to 10 ms in the worst case. Since real-time control is not the marketing niche for the Xeon Phi processor and its operating system is proprietary with no real-time upgrade expected, we have ruled it out for our RTC.

Using CPUs alone with a real-time patch applied to the Linux operating system, our benchmark work showed that six servers, each with two dual-CPU motherboards can process the WFS data and create DM command vectors in typically 700 µs, with low jitter resulting in a worst case of slightly more than 800 µs as shown in Figure 2. Although GPU accelerators can reduce the number of server chassis and total power consumption, we concluded that for ease of development and minimizing the variety of hardware and software components in the RTC made an all-CPU solution attractive, especially when considering maintenance over the lifetime of NFIRAOS. Our baseline is now an all CPU architecture.

Figure 3 2 Benchmark timing of CPU-based RTC - For this benchmark, simulated pixels representing half of the LGS WFS are streamed in a 500 µs burst over 10 Gb/s Ethernet to one server which processed pixels (computing slopes and statistics) and then applied MVM


Contributions from David Bohlender, Eric Chisholm, John Pazder, Kei Szeto and Chris Willott