Under pressure

At the Australian Astronomical Observatory, there had been a problem with irregular air pressure in the mechanics for the robot positioning the optical fibers for the AAOmega multi-object spectrograph, mounted on the 3.9m Anglo-Australian Telescope. This is of course not ideal, since it is crucial that the optical fibers are positioned accurately and correctly. If not, they will fail to catch the light from the stars they are meant to observe, and no light will reach the spectrograph. What was needed, was something that could even out those irregularities, and maintain the pressure at a steady level, so one did not suddenly have a fault at a critical time during observing.

Naturally, this calls for specialized equipment, which here means something like “reach for the nearest container that can withstand some pressure and attach to instrument.” Luckily, a very specific kind of container is usually found in ample supply around telescopes. These containers can withstand a pressure of around 100 PSI, or approximately 7 bar, before they burst, so unless you are dealing with really high pressure, they are fairly sturdy.

The high tech pressure vessel attached to the 2dF fiber positioner robot at the AAT. Photo credit: Anna Sippel

The high tech pressure vessel attached to the 2dF fiber positioning robot at the AAT. Photo credit: Anna Sippel

They look something like what you see in this photo, it should be familiar to most people. This “pressure vessel” did perform its job well, and managed to even out the irregularities in the pressure, so the instrument could continue to perform observations as planned. It was kept as a working solution for a couple of weeks, until a more suitable solution was found and installed.

The replacement happened to be installed just before the Minister of Science was due to visit the telescope. Not that these things were necessarily connected, but one could envision a few raised eyebrows, had the bottle still been on when the officials were given the grand tour of the telescope.

Good thing that astronomers need lots and lots of sugary, caffeinated drinks to keep them going through the long hours of observing. So keep drinking that coke. It may not be healthy, but you never know when you’ll be in urgent need of a pressure container to keep your instrument running!

The Allegheny lens napping

Astronomical observatories were not always as big as the huge constructs we see today, like the ESO VLT in Chile and the Keck Telescopes on Hawaii. Back in the day, they were much smaller.

Pittsburgh’s Allegheny Observatory has the 13″ (33cm) Fitz Refractor, which was the third largest in the world when it was built in 1861. A 13″ lens is not all that big, and, in fact, it is possible for a single person to carry it away. This was what happened in 1872,  when a thief stole the lens and held it for ransom.

The old story goes that Professor Samuel P. Langley received a letter from the thief that stated that he should meet with him in the woods behind the observatory at midnight or he would never see his lens again. Supposedly Langley did meet with the thief and told him that no ransom would be paid. Prof. Langley and the thief the parted ways, without having resolved the situation, and the lens was still missing.

It seems that a newspaper investigative reporter from the Pittsburgh Leader, who covered the case, was responsible for the eventual recovery of the lens. His investigation allegedly prompted the lens-napper to flee after a few months, for fear of discovery, leaving the lens behind in a hotel trash basket. The lens was badly scratched, so Prof. Langley sent it to the lens-maker Alvan Clark to re-polish, and it wound up better than before. Clark’s name was added to the now “Fitz-Clark Refractor” in gratitude.

To this day, the identity of the lens thief remains unknown. Since the entire affair is so shrouded in mystery, the belief is that Prof. Langley knew the person that stole the lens and that it’s “safe” return was conditioned so that the thief would remain anonymous.  It is of course debatable whether leaving the lens in a trash basket is considered safe, but at least it was recovered in the end.

With the size of modern day telescopes, such things are unlikely to happen again, although it would have a certain entertainment value to see someone trying to sneak away with one of the 1.8m wide mirror segments from the Keck telescopes, or one of the 8m primary mirrors from the VLT. But one would certainly have to go to somewhat more elaborate schemes than just walking in and removing it, if one wants to pull such things off today.

The world’s largest bug zapper

The 305m diameter radio dish of the Arecibo Observatory in Puerto Rico. Photo credit: NAIC

The 305m diameter radio dish of the Arecibo Observatory in Puerto Rico. Photo credit: NAIC

There are big telescopes, and then there are the truly humongous telescopes, like some of the radio telescopes. These bad boys are so big that the largest of them takes up an entire valley. This is the well-known Arecibo Observatory in Puerto Rico, that a lot of people likely know from Golden Eye, X-files or Contact, to name a few times it has been used in popular culture.

The observatories are, of course, mainly used to do astronomical observations, and not as fancy movie sets. The planetary radar transmitter here, and at the Goldstone Deep Space Network site in California are used extensively to observe asteroids, the terrestrial planets, and the larger satellites of Jupiter and Saturn.  To do this, they run hundreds of kilowatts of UHF signal out through each telescope.  By the time the beam is distributed across the many thousands of square meters of the primary telescope reflector, it’s diluted to the point that it doesn’t pose a hazard to anything.  However, along the beam path from the transmitter feed to the tertiary and then to the secondary reflectors, it is significantly more concentrated. This means that every now and then, the telescopes turn into something very different from instruments for peacefully observing the Universe.

The Gregorian dome of the Arecibo Observatory. Photo credit: NAIC

The Gregorian dome of the Arecibo Observatory. Finding your way out is not as easy as it seems. Photo credit: NAIC

At Arecibo, the transmitters, receivers, tertiary, and secondary are all contained inside a Gregorian dome. Birds tend to fly in and get confused about how to exit again. As interesting as it may be to inspect the inside of the world’s largest radio telescope, this is not without risk! If the birds happen to be between the transmitter and the tertiary reflector when the transmitter goes on, they are very rapidly microwaved. The birds’ remains may then land on the tertiary, where they get cooked into char. They can be removed from the tertiary’s surface from the access platform by using sophisticated tools, like a large wad of sticky tape on the end of a stick.

At Goldstone, birds can fly out of the beam line more easily, since the transmitter is not contained within a dome. But on one occasion, a swarm of bees were in the beam when the radar started transmitting. The telescope briefly acted as the world’s most expensive bug zapper. The resulting cloud of steam and fried bees caused a dramatic back-reflection of the beam until it dispersed.

There are no reports (yet) of larger things being fried by any of these instruments, and, admittedly, it would take quite some work to get anything without wings to be in the right place. But you could host a rather impressive and efficient BBQ party there. Just be mindful of  where you are, once the beam goes off. We don’t want any accidents!

Thanks to Michael Busch for providing this anecdote.

One of the Goldstone Deep Space Network Antennas. Photo courtesy NASA/JPL-Caltech

One of the Goldstone Deep Space Network Antennas. Photo courtesy NASA/JPL-Caltech

The McDonald gun shooting incident

On the 5th of February, 1970, a rather bizarre incident happened at the McDonald Observatory, at the 2.7m reflector telescope. A newly hired employee was apparently very dissatisfied with his new job, or, something else was very wrong. Whatever the reason was for said person to be angry with the world, he had decided to take it out on the telescope itself.

Bringing with him a 9mm gun, he first fired a shot at his supervisor, and then fired seven shots, point blank, into the primary mirror of the telescope, no doubt hoping to shatter it. Alas, big chunks of glass like telescope mirrors, do luckily not break so easily, so the bullets merely created small holes in the mirror. Not being happy with this outcome, he also attacked the mirror with a hammer, but to no avail. The mirror did still not shatter. Shortly after, the person was subdued by the rest of the astronomer staff, rushing to the site.

The primary mirror of the 2.7m telescope at McDonald Observatory. The bullet holes can clearly be seen. Photo credit: McDonald Observatory.

The primary mirror of the 2.7m telescope at McDonald Observatory. The bullet holes can clearly be seen. Photo credit: McDonald Observatory.

When the sheriff arrived, the employee was arrested and later committed to a mental health institution. In the report following the incident, the sheriff, clearly being unfamiliar with telescope designs, stated that the mirror had indeed been destroyed as it had a big, circular hole, right in the middle! Thus, it was allegedly reported widely that the telescope had essentially been destroyed. However, most astronomical telescopes do in fact have holes in the middle of the primary mirror, as it allows you to attach instruments to the bottom of the telescope (the Cassegrain focus). Because of such erroneous stories, the director of the observatory, Dr. Harlan J. Smith, released a report setting the facts straight:

“… The harm suffered by the mirror from his bullets and his several preliminary blows with a hammer was extraordinarily small. The damage is limited to small craters about 3 to 5cm in radius, which reduce the light collecting efficiency by about 1 percent and introduce a very small amount of diffraction …… Astronomical observations of all types are essentially unimpaired by this tragic episode; the telescope resumed its observing program the following night, producing some of the best photographs (of quasar fields) so far obtained with this instrument in its first year of use.”

The full report can be read here.

This is likely the only telescope in the world who has been a victim of a handgun assault, and it will hopefully stay this way. The bullet holes can still clearly be seen in the primary mirror. Fortunately, no people were hurt during this rather tragic incident.

Blame the animals, it wasn’t our fault!

When doing radio interferometry observations, one needs to combine observations from a number of different telescopes, at different locations, to get good quality data. This of course means that there is a potential for a lot of different things going wrong, as one needs to deal with multiple sites. Some of the problems that may come up, are completely out of your hands. However, even if one is having problems with the observations for these reasons, as the good scientists we are, we investigate the problems in detail. This is to make sure that it was indeed out of our hands, and not just us overlooking some obvious step we could have taken to avoid the issue in the first place. A situation that occurs more frequently than one would imagine.  Such inspection can also allow us to at least put the blame for loss of observations in the right place. Whether this means it will not happen again, is a completely different story. A beautiful example of this is the following excerpt from a paper by N. Bartel and colleagues on radio observations of the galaxy M82:

“No data were taken at station D during the period 0830 to 1630 GST due to the presence of a red racer snake (Coluber constrictor) draped across the high-tension wires (33,000 V) serving the station. However, even though this snake, or rather a three-foot section of its remains, was caught in the act of causing an arc between the transmission lines, we do not consider it responsible for the loss of data. Rather we blame the incompetence of a red tailed hawk (Buteo borealis) who had apparently built a defective nest that fell off the top of the nearby transmission tower, casting her nestlings to the ground, along with their entire food reserve consisting of a pack rat, a kangaroo rat, and several snakes, with the exception of the above-mentioned snake who had a somewhat higher density. No comparable loss of data occurred at the other antenna sites.”

At the very least, that snake will not be interrupting the observations again in the future. If you are interested in the actual outcome of the observations, the paper can be read in full here.

The telescope that ran over a car

It is well known that cars are often involved in accidents, either by crashing into something, running over things, slipping off the roads and similar nasty business. This is also true in astronomy, where accidents do happen from time to time. What is different though, is that while cars can run into things almost everywhere, having something running over your car is a much rarer experience.

The Nordic Optical Telescope. Photo credit: NOT, Thomas Mellergaard Amby.

The Nordic Optical Telescope. Photo credit: NOT, Thomas Mellergaard Amby.

Meet the Nordic Optical Telescope (NOT): A nice, 2.5m telescope of a somewhat peculiar design. Whereas all telescopes have some sort of turning dome, that allows the telescope to point to many different parts of the sky, the NOT is constructed in such a way that not only the dome, but the entire telescope building turns, when you want to aim your telescope at a different patch of sky. This of course involved some engineering challenges, like, plumbing (there’s no bathroom in the telescope), as well as an entry staircase that is attached to the telescope. Which, amongst other things, means that you never really know what direction you are facing when you leave the telescope.

One day, the day-time crew were in need of hoisting equipment into the telescope dome, from the observatory pickup. For the crane to be able to reach the equipment, it needs to be positioned right at the wall of the telescope building. Thus, the pick-up was backed up, really close to the telescope, to make it easier to get the equipment in. This being an everyday operation, the crew unloaded the pickup, closed the dome, and proceeded with whatever they were doing.

The one warning sign you do want to pay attention to.

The one warning sign you do want to pay attention to.

Shortly after, someone decided that the telescope should be put in the parking position, so it was ready for the night to come. A sensible thing to do, except that no one had checked if the pickup had been moved away from the building. Thus, as the building turned, the entry staircase rammed into the side of the pickup, with the telescope effectively running over the car. Fortunately, the impact cut the wires to the safety system, which happened to run along the staircase, forcing the telescope to an emergency stop. Had this not happened, the telescope building could have been severely damaged, and the pickup as well.

The damages were luckily so small that the pickup could drive out of there, and at the time of writing, is still being used at the telescope. This is also one of the times where it really pays off to pay attention to the warning sign outside the telescope building.

Getting your priorities right

Astronomers tend to be very dedicated to their work, and giving it very high priority in their lives. This is likely true for any branch of science, but sometimes you wonder if we are getting those priorities quite right. Here’s a story from back in the days;

Friedrich Argelander was observing at the observatory of Turku, Finland, on the 4th of September 1827, when a fire broke out and destroyed practically all of the city, including the university. Argelander’s observation log contains the following line:

“Hic observationes terribili illo interceptae sunt incendio, quod totam fere urbeam ad ineres reduxit, observatorium vero, gratiae habeantur Deo O.M., salvum intactumque reliquit.”

Argelanders' observing log on display at Helsinki University. Photo credit: Olli Wilkman.

Argelanders’ observing log on display at Helsinki University. Photo credit: Olli Wilkman.

which roughly translates to:

“Here the observations were interrupted by a terrible fire, which reduced the entire city to ashes. The observatory was, thank God, spared.” A couple of days later the astronomical observations continued as normal. One could argue that most other people would likely have a rather different opinion on what should be considered important during such a disaster.

After the fire the university was moved to Helsinki, where it remains, now called the University of Helsinki.