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Edited by: Dennis Crabtree
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The NRC Herzberg News E-Cass Report
These reports will 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
about 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
Dr Tim Robishaw has accepted a continuing
position in the Radio Astronomy Program as a member of the DRAO science group.
Tim is an expert on radio polarization science, ranging from observations of
Zeeman splitting in OH Megamasers to wide-field studies of galactic polarized
emission. He is also very experienced at working directly with telescope
systems, as exemplified by his role in understanding the polarization
properties of the GBT during his PhD. Following his PhD at UC Berkeley working
with Carl Heiles, he was an Australia Research Council Super Fellow at the
University of Sydney before coming to NRC Herzberg as the Covington Fellow.
Over the past two years he has been working extensively on the 26-m telescope
at DRAO to measure the Zeeman signature from galactic HI. Recently, he has been
supporting the CHIME consortium efforts to use the 26-m for calibration of the
CHIME Pathfinder.
In December Jim Hesser completes 11 years of
service that began on the ALMA Coordinating Committee and then on the ALMA Board,
the sole Board member to have served continuously since ALMA construction
commenced. Sean Dougherty replaces him in January, as ALMA moves steadily
towards full science operations.
Optical Astronomy
ngCFHT
In the May 2013 the ngCFHT project team submitted a request
to SAC to support an ngCFHT project office. In the May meeting SAC chose not to
recommend support for a project office as they felt the level of detail in the
proposal left several important questions unanswered.
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In response the ngCFHT project team submitted a more
detailed proposal to SAC for consideration at their September meeting. The SAC
has “noted on previous occasions that the scientific aims of the ngCFHT project
are of the highest standard and represent a bold yet technically achievable
evolution of the CFHT facility”.
Following
their May meeting the CFHT SAC issued a recommendation on ngCFHT: “The SAC
recommends that the Board support the proposal to create a ngCFHT project
office”. The CFHT Board meets in early December (after this article was
submitted for translation). |
Figure 1 CV1RR test data superposition of the two NIRISS GR150 low resolution grisms. The zeroth and first orders of each grism appear as yellow points and lines. The direct image has been subtracted leaving a negative residual of the undispersed source. |
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Space Astronomy
The
first Cryo-Vacuum test campaign (CV1RR) of the science instrument module of the
James Webb Space Telescope (JWST) took place from August to November. This was
a particularly exciting time for the Canadian contingent as we got to see the
end-to-end performance of our instrument FGS/NIRISS for the first time. The
testing was a tremendous success with all modes of the instrument performing as
expected. There was excellent on-site testing support provided by CSA, prime
contractor COM DEV, instrument science team members from the Universite de
Montreal and CSA-supported contractors based at STScI. This was also a
successful major test of the ground testing equipment at NASA's Goddard Space
Flight Center. The next instrument cryo-test is scheduled to commence in June
2014 and will include all four JWST science instruments.
The whole JWST project continues to make excellent progress
towards the October 2018 launch date. All four science instruments have been
delivered to NASA. All mirror segments are complete and will be delivered to
NASA by December 2013. The center section of the primary mirror backplane
support structure is complete and underwent cryogenic
testing in October. Development continues on the enormous 5 layer sunshield
that will keep the telescope cool.
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There
will be a JWST lunch session at the CASCA 2014 meeting in Quebec City where we
invite the community to come and hear the latest news on the project and start
to think about how they will use JWST for their science. |
Figure 2 Comparison of CV1RR test data with a previous simulation from UdeM of the NIRISS GR700 exoplanet transit grism. The upper trace is the first order and the lower trace the second order. This grism has an intentionally broad PSF along the spatial direction |
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Astronomy Technology
Progress on the Advanced Focal Array Demonstrator (AFAD)
Traditionally radio astronomy has been
dominated by telescopes with single beams. Over the last decade, advancements
in electromagnetics and digital signal processing have made array receivers
possible. This new technology could greatly increase the survey speed of
telescopes by making multiple beams available, increasing the instantaneous
field-of-view. This would be done by placing a small phased array at the focal
plane of a reflector antenna.
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NRC Herzberg has been investigating this
technology as a contribution for the Square Kilometre Array survey telescope in
Western Australia. Our efforts have focused on minimizing sources of noise in
the antenna structure since noise is also a key determining factor in the
survey speed. The noise is reduced by placing the receivers as close as
possible to the feed point of the antenna elements and to make those elements
thick so that surface currents are spread over a larger area, reducing
resistive loss. |
Figure 3 |
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AFAD array with an analogue beamformer has recently been completed . This
phased-array feed demonstrator consists of 41 Vivaldi elements. Figure 1 to the
right shows a single element. These elements are 5 mm thick and this allows the
low-noise amplifier (LNA) to be placed very close to the feed point of the
antenna element, thereby reducing input transmission line loss and noise. The
green and gold LNA board is visible in the figure. |
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Figure 4 |
Figure 5 |
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The complete array is shown in Figure 2. The analogue
beamformer is in the framework below the thick Vivaldi array. Nine elements are
combined in a network composed of combiners, amplifiers, and step attenuators
to produce a single boresight beam for noise measurements. The topology of the
beamformer has been carefully chosen to ensure phase and gain tracking between
elements and across the
operating band (0.7 -- 1.5 GHz).
We have just begun testing AFAD in NRC's Hot/Cold Test
Facility (see Figure 3]. This facility has a ground screen so that the sky can
be used as a cold load with little contamination from ground radiation. The
other part of the facility is a movable roof with microwave absorber on the
underside and is used as a hot load.
Contributions from Jim Hesser, Bruce Veidt, Chris Willott