'Snowtrack'

When it began to rain during lunch down in the valley, I suspected we might be in for a somewhat colder version of precipitation at the CARMA Cedar Flat site, elevation ~8000 feet. We were briefed on the snow policy for the telescope, and headed back up the mountain to watch over the antennas during the snow storm and for the duration of the weekend.

The first task in a snow storm is to divide the antennas into sub-arrays, one which included the larger antennas (10-meter, which collect the most snow), one for the central (6-m) antennas which have a possibility of colliding, and a third sub-array comprised of the smallest (3.5-m) antennas.  For the 10-m antennas, we issue the command 'snowtrack', which measures the wind direction and points the antennas with their back to the wind, minimizing the accumulation of snow on the collecting area of the antennas.  We then 'stow' the 6-m antennas, pointing towards the zenith (straight up).  For the 3.5-m antennas, we keep them tracking a source in the sky that never sets.

That's the easy, and warm (done from the control room), part of our responsibilities during the recent ~24 hour snowstorm.  During that time, we monitor the snow-fall rate, and any time more than 2 inches of snow accumulates on the 10-m antennas, we trek out to the array and begin clearing snow.  Now, I'll reiterate that the antennas are 10-m in diameter, so we can really only reach the bottom half, even with long extend-able squeegees.  The other part we didn't consider is that when you start clearing snow from over your head, the only place the snow will go is... down... on top of us!  The second time we went to clear snow, we suited up in fully waterproof overalls and parkas, what we deemed our "spacesuits".  The third time, we suited up with even more layers, and much to our relief, the snowfall had lightened and the snow was no longer sticking to the antennas.  The command 'snowtrack' had done its job so that we didn't have to do ours! 

Hiking out to the array with the squeegees, around 6 pm, the first of our trips to clear snow.

We continued to monitor the snowfall rate, and in the morning pointed the telescopes toward the sun to dry them out.  In all, we had about 6 inches of snow, coming down at 0.25-1 inch per hour over about 24 hours.  At some point, feeling cooped up, with icy roads and no where to go, we decided to try out the bikes on the snowy paths nearby, and my co-observer spotted the perfect sledding hill.  In our spacesuits, we cleared a luge and enjoyed a few sledding runs down the hill, soaking in some of the Saturday afternoon sun.  Then, when the telescopes appeared clear, it was back to science and business as usual.

A day (or night) in the life

Observing at CARMA is a unique experience, certainly compared to my daily life as a grad student, and even compared to observing at other telescope facilities.  For one, we can observe all night and all day here, because the visible light from the sun during the day doesn't affect the detection of radio-wavelength light.  And second, in queue mode, we're taking data for other scientists and operating the telescope for projects that we may know little about.  Granted, we have learned how to operate the array, and we have some idea of what kind of science is possible with these observations (I use CARMA data for my own research), but we can be somewhat anonymous during the whole process.

Because this is such a break from the norm for me (and maybe it would be for you too), I've been trying to think of a way to describe what we do here.  Because I like to cook when I'm not studying, an analogy came to mind.

In a way, this week is like cooking a meal for people you don't know.  Imagine that you really like to cook (and maybe you do), and you are going to treat a group to a dinner party.  The deal is that they will provide you with the raw ingredients, tell you what kind of food they want you to make, and you will actually go to cook those ingredients in someone else's kitchen.  Sure, you've used a stove before, but never a stove exactly like the one provided. And, you think you know how to use the microwave, but there's a unique combination of buttons you must push to make it work properly (the instruction manual is provided, but it's long and seems like some important parts are hidden just to test whether you can find them).  In fact, some of the raw ingredients you have never actually seen before, so you'll just guess what they might be used for.

You begin cooking, and the first part is very time consuming -- lots of preparing the ingredients just so, and making sure that you're not falling behind schedule.  Then you figure out how to use the appliances, and you begin to bake the food in the oven.  Finally, you can take it easy for a while, as the food cooks (and maybe you can make a bite to eat for yourself!).  Then, an ALARM.  You need to quickly diagnose the problem.  Is the whole house going to catch on fire, at which point you better call the fire department (remember, it's not even your house)?  Or, is it just the food burning in the oven?  This isn't the best outcome, and dinner will be late (again, the food isn't even for you), but you can try again.  Or, there is some possibility that the fire alarm is faulty, and there's really no problem with the house or the food after all, but you should just change the battery on the alarm. Regardless, your guests are expecting a nice meal, and soon.  You'll be busy again when it's time to serve the meal, and you really hope they like the food and the service, understanding how difficult it was for you to prepare this meal. 

Well, there is no real moral to the story.  In fact, we get all of these types of alarms.  Luckily, nothing has caught on fire here at the telescope.  The septic has stopped working, but that's minor I guess.  And, we have "burned" some of the data we should have been taking because we didn't use the right settings, but we give those observations a second chance.  More often, there are alarms that we can't diagnose or fix, and we ask the experts who built this place and work here full time to solve the problem for us -- a humbling experience, but at least the science is taken care of.   It's truly about the learning experience, which is why grad students are taught to run the observations here. 

There might be one other reason why they have grad students working here: no one else wants to stay up all night just to clear snow off the antennas every two hours.  I'll get to that story in my next post.  Before that, I'll show you the array in good 'A+' weather:

Early morning post

As you may know, my research uses radio and sub-mm wavelength observations.  Is my job like Jodie Foster in the movie Contact?  I saw that movie for the first time recently, just so that I could answer that question.  And the answer is: yes and no.  I do travel to observatories, like Arecibo and the VLA which were featured in the movie, and the locations of the observatories are often (always?) remarkable.  Although I haven't been to those two particular observatories (and I would like to!), I have used both types of telescopes: "single dish" (like Arecibo in Puerto Rico) and "interferometer" (like VLA, and CARMA).  But, I have never "listened" to my data, nor have I been in a spacecraft like in Jodie Foster's adventure.

There are also several "modes" of observing, two of which are queue observing and non-queue (well, I don't actually know the proper name for that).  Here at CARMA we are doing queue observing, in which many scientists from all over the world have applied for telescope time, and told us what they would like observed, so that we can schedule most efficiently.  That means that I am not currently observing for myself, nor is my own data flowing in.  Rather, the data get piped out to the respective scientists, and they don't have to lose sleep over the data acquiring.  They also miss out on all the fun ;).

That "fun" comment seems fitting, as it's 5:21 am, and I'm awake waiting for the current observation to finish, an alarm will go off, and I can proceed with the observations.  In fact, we're running two observations at once, because we have split the array of 23 antennas into one array of 15 and the other of 8 antennas.  I woke up at 4:30 to run the second array, and in a short while, the first array will finish what it's currently observing and we can move onto the next target. The brilliant thing is that I can run a "queue" script and (if I do it properly), it should proceed with the observations automatically, so I can "sleep on the job" until it's time to start the day for real.  But, when something goes wrong, that alarm will sound with circus music, and I will (bleary-eyed) attempt to diagnose the problem.   So, as I said, I have never listened to my data like Jodie Foster, but I do in fact keep a keen ear listening "for" the data, and no noise is what I like to hear.

I leave you with a photo:

This is my co-observer.  I'm looking in from outside to take the photo, through the blinds of the window with the greatest view of the antennas.  The blue and white screen towards the right is the control computer.  Right now, I'm sitting at one of these desks as I write, and I'm looking out at the sun reflecting off the antennas, waiting for the snow to come.

Guest Observer

Greetings from CARMA, the Combined Array for Research in Millimeter-wave Astronomy.  I have had this idea to blog about my observing runs for several months now, and in fact I have been on several observing runs during that time.  The problem is that observing can be very intense and tiring, and when I finally make it to the mountain, I become so focused on the task at hand, I hardly find time to properly document the experience.  But, lest I forget the true joy and novelty of what I do, I am committed to share these wonderful trips with you.  I regret that I didn't write about my previous observing runs (Chile, Hawaii, then Chile again), but I start now, with my current observing responsibilities at CARMA in California.

I should briefly explain the title of this blog.  It was inspired by a required component of observing, which is keeping a detailed log of all sources that were observed during the run.  The first place I kept an observing log was at Cerro Tololo Inter-American Observatory (CTIO) in Chile, and in fact, at CARMA, we instead complete a "Nightly Report", but the idea is the same.  It is very important to document the observations.  Later, when we come down the mountain with our data, or when we send the data to the scientists who proposed the observations, it is imperative that we/they know exactly what was observed, when the observations occurred, and some specific information about the set-up of the observations (as well as any errors encountered). 

I will be observing for four more nights (and days -- we observe round-the-clock here!), and I will try to document some of the day-to-day business.  If you have specific questions at any point, please comment.  I hope you will enjoy the adventure while I am here at CARMA, and as I travel to other telescopes in the future.  Thanks for following!

The setting of the observatory "low site", Owens Valley (CA)