This week there have been a few press releases from the HET partners about our progress on the HETDEX survey so far. The graphical presentation of the data is amazing and the whole survey will represent a major accomplishment for observational cosmology once completed. Read more at the following links below.
Meanwhile, our hearts are with the radio astronomy community as they mourn the not-unanticipated structural failure of the Arecibo radio telescope this week. Send warm thoughts to all the large aperture telescopes being maintained out there – they are are precious tools to view the cosmos and is is quite sad to lose such a giant.
https://mcdonaldobservatory.org/news/releases/20201201
https://news.psu.edu/story/640405/2020/12/01/research/hobby-eberly-telescope-dark-energy-experiment-survey-begins-full
https://phys.org/news/2020-12-hetdex-track-probe-dark-energy.html
This week the VIRUS spectrograph reached another milestone with 70 active units on sky. Below is a reconstructed/magnified image of one observation (the units actually have gaps between them but are shown magnified here). White squares show the locations for 8 remaining units.
Each dithered VIRUS observation now contains 31,000 spectra covering 46 square arcminutes. Next stop: the full 78 units!
VIRUS units continue to multiply! Shown below is a representation of 52 units on the sky:
The grey squares with stars on them are looking at the sky (with more than 23,000 fiberoptic cables taking simultaneous spectra!), and the white squares are empty slots for future units.
The VIRUS units (grey squares) do not actually touch each other, but are shown doubled in size to fill in the gaps between them, graphically.
Much like it is for the blogger, it is a real milestone for VIRUS to hit 50. In the case of VIRUS it is 50 units. This was achieved over this past weekend after spending several months with just 47 units.
Reconstruction from 50 IFU/VIRUS units on the sky. Each small square is 50 arcseconds on a side. There is actually a gap of 50 arcseconds between each IFU/VIRUS unit but it has been compacted in this view to avoid to much white space.
This means with every 6 minute exposure we take on the sky we get over 22,000 spectra!
On Monday we installed 2 more units bringing us to 52!!! Well on our way toward HETDEX science!
This week at the HET we have taken the top end of the telescope so that we can rework the layout of the IFU fibers and add 11 new fibers. That will leave just 17 IFU fibers to be installed. Just to be clear this is not spectrographs being installed but just the IFU fibers that feed future spectrographs. At the moment we have 41 spectrographs units installed and stable. This means we are not more than half way towards our total goal of ~78 units.
It has been a while since I posted and I think one of our biggest pieces of new is that we are now regularly observing with HPF. Not only is this instrument being used to observe host stars for planets but there are astronomers who are using it to observe planetary nebulae looking for new elements being born in the deaths of stars just slightly heavier than our sun. This new instrument is easy to use, reliable and a great addition to the HET.
The other big news is that we now have 40 double barreled spectrographs installed within VIRUS. That means that we are now more than half way to have VIRUS fully populated.
This week we had a number of break through moments. Perhaps the most prominent is that after weeks of rewiring and adding new shielding we may finally be at a point where the VIRUS array is fairly stable. We have 36 VIRUS units installed (each unit is 2 spectrographs) so a total of 72 spectrographs up for the last 5 days.
Another big breakthrough is in observing automation. We have a piece of software called OCD (Observatory Conditions Decision tool) which monitors the metrology (seeing, transmission and sky brightness) from the telescope and decides if HETDEX observations can be made. If allowed it will also take over the control of the TCS and VIRUS instrument and start observing HETDEX targets with only brief pauses to get confirmation from the telescope operator that we are on the right setup star. Using this new tool we were able to observe a full night of HETDEX targets with a minimum of overhead (even a few targets with just 3 minute setup times). This is faster than the fastest resident astronomer and telescope operator pair working together. Congratulations to the HETDEX software team who traveled out from Germany to help us get it all working efficiently.
In the last week we have had a few updates for two of our instruments. For VIRUS we are up to 29 working spectrographs. We actually have several more units but some of the oldest and slightly mis-behaving units have been sent back to Austin for realignment and recommissioning. For HPF we are thrilled to announce that a NIST laser comb has been installed in the calibration room in the HET basement. This allows us to send a picket fence of spectral features through a separate fiber next to the science fibers. During the data reduction and analysis of the HPF spectra they can look at the position of these pickets and determine how the instrument might be subtly moving and correct for it. So far it seems like it is working great.
