We packed a lot into Thursday 16th February: Cosmology lecture, Lunar and Planetary imaging, a visit to Lunt, the Mirror Lab, amazing images of Mars, a meal with the UofA astro club and finally some observation….
There was an early start today to walk to campus for a 9:30 Cosmology lecture. That had the potential to be quite heavy-going, but it was anything but… Mike decided to come too, even though he thought he might get lost within the first few minutes. As it turned out it was pitched perfectly for him, as it was aimed at non-physics/astronomy students. It was akin to a Royal Society Christmas Lecture – complete with demonstrations and audience interaction (that’s where the Oreos came in!). The highlight for me was seeing Mike’s (smug) face when he got the first question right!
As well as the content it was fascinating watching Don’s approach and seeing what worked best. It was lecturing at a whole new level to what is standard in the UK (and it might be in the US too), but was very effective.
From there we went to meet up again with Jim Scotti, this time in the Lunar and Planetary Imaging Centre.
This was unstructured, but having free access to the picture archives of NASA missions was great fun and allowed each of us to pursue our own interests. While many looked at the Apollo photographs I was particularly interested in the Voyager files, as it was Voyager that fired up my astronomy interest 30 years ago.
From there Mike and I traveled to Lunt to pick up my solar filters. We were also given a tour of their small, but precision, manufacturing and testing facility for solar scopes and filters. (Given it is a commercial facility we took no pictures.) It was really interesting to see how the filters I’ve used for years are produced, and given the fine tolerances it became clear why they are expensive.
We dashed back to campus for the Mirror Lab Tour. This was optical manufacturing on an astronomical scale!! The facility is based underneath the football stadium – it needs to be because of its scale. The facility uses an innovative spin-cast process which gives an excellent figure for the mirror while reducing weight and the amount of glass used. (The 6.5m telescope we had seen the previous day at Whipple had been produced by the mirror lab in 1992.) Larry, our guide, showed us a time lapse of all the stages which go into the setting up, production and finishing of the mirrors. A honeycomb structure of hexagonal ceramic fibre cores is used as the base for the mirror and is critical to not only to reducing weight (80% of the core is empty) and allowing more rapid thermal equilibrium, but makes it possible for adaptive optics mechanisms to be used. Pieces of Ohara borosilicate (pictured below) are strategically placed on top of the honeycomb structure by hand. The furnace cover is then placed over the mould ready for firing.
The oven takes 5 days to reach the peak temperature of 2130F. Spinning the oven at 7rpm causes the required mirror figure to be formed by the centrifugal and gravitational forces on the glass. The cooling is carefully managed, and the mirror monitored – it takes around 110 days to cool. The mirror blank is then ready for the next stages: removing the moulding material, grinding and polishing the back then attaching load spreaders to the back. It is then turned over and the fine work starts on figuring the front of the mirror. This is done using stressed-lap polishing. It is regularly tested and then more work undertaken until the figure is exactly as it should be.
The precision on these mirrors is almost beyond belief – if the mirror was the size of North America, then the highest mountain would be just half an inch!
We then got to see the actual production area and the mirrors in progress – including an enormous 8m one. We were shown how the mirror supports and the mechanisms for the adaptive optics were attached for both primary and secondary mirrors – ensuring the best possible figure despite gravitational and atmospheric changes.
The next session had been added just the day before. It was related to the HiRise programme which is producing high resolution images of Mars from the Mars Reconnaissance Orbiter. The camera has such good resolution that it can pick out features around a metre across from an orbit of almost 200 miles. The detail in the surface pictures is just amazing. See here for a great factsheet.
Ari, the public outreach lead, gave us an introduction. He was enthusiastic and engaging. He’d even tried to translate a few picture captions into Welsh for us! We then got to see some images hot off the CCD on the orbiter and heard how students are employed to help analyse and process the images – what a fantastic student job! We saw the results, which included 3-D imagery and animations. I’ll be keeping an eye on their site to see the latest wonderful data – have a look here to see what I mean.
We then used the tram for the first time (once we’d all queued to get tickets) and headed into town for a meal with the astroclub.
Later we headed back to Campus for an hours’ viewing with the 21 inch scope in the campus observatory – what a wonderful facility for students and outreach. Finally a clear night with the campus scope!
We bagged a few lovely views, and chatted again, before heading back to the hotel. It had been a long but stimulating day…by