Monday, August 3, 2009

The Science Conducted by the Institute for Astronomy Eclipse Team

by Beverly Lynn-Wilson
Member of the Friends of the Institute for Astronomy

The Sun is so powerfully bright that the best time to study details of the Sun’s atmosphere—especially the part of the atmosphere closest to the Sun—is during a total eclipse, when the Moon blocks the intense sunlight. We know remarkably little about this nuclear reactor that makes life possible on Earth. Particles streaming out from the Sun can disrupt communications and GPS devices here on Earth, cause power surges, and put astronauts at risk. The more we learn, the more we can ameliorate these disruptions and risks.

Scientists generally begin planning for the next eclipse immediately after the previous one is over. Deciding what to study and determining the equipment needed to do the studies—and remember that all the equipment needs to be transportable to the viewing site—is time-consuming. All experiments must proceed flawlessly, since scientists have only minutes to acquire the data they need to do their research.

The eclipse on July 22 was the longest one this century. On Enewetak, an atoll in the Marshall Islands, we had five minutes and forty seconds of totality. However, only about 50% to 70% of the data are good because clouds moved across the Sun in the middle of totality. What data we did get will take weeks or months to analyze. Added to data collected during previous and future eclipses, scientists are slowly filling in missing pieces of the puzzle that is the Sun’s atmosphere.

Data collected during this eclipse primarily concerned looking at ionizations of iron and helium, taking spectra, and obtaining infrared data. Technology has only recently become advanced enough to study the corona in infrared, so we have very little data so far in that area. (Watch the IfA website for an announcement about team leader Dr. Shadia Habbal’s public talk, currently scheduled for early November, when some data analysis will have been done.)

The weeks before the eclipse trip involved non-stop equipment maintenance and calibration, the writing and refinement of observing programs, and the writing of scripts for equipment operators to follow. A few days before leaving we held a dress rehearsal. We set up the main observing tent in the IfA courtyard, moved in all the equipment, and then figured out how six people could run instruments and computers without tripping over one another or the tripods and cords—and without jiggling any of the instruments. Jiggle is the absolute enemy for obtaining good data.

The observing tents were off-the-shelf camping models modified by team engineer Judd Johnson for observing needs. In the larger tent he installed a clear plastic roof window using a zipper made for Jeep windows. He also made an opening to hold an air-conditioner, plus some other modifications that he managed to do on a standard sewing machine. Tripods with single mounts holding up to three instruments were lined up along the roof window.

IfA Eclipse Team

Team members, officially known as the Solar Wind Sherpas, posed by the main observing tent. Standing: Judd Johnson (left), Dr. Shadia Habbal, Dr. Adalbert Ding, Dr. Martina Arndt, Mindy Lekberg, Joni Lang (cook). Seated: Dr. Huw Morgan, Dr. Isabelle Scholl, Emily Mount, Bev Lynn-Wilson, Dr. Dave Harrington, Sarah Jaeggli.

The instrument filters required a constant temperature of 45C. They were inserted into protective housings, and the main use of the air-conditioner was to keep the filters at the temperature they needed. IfA grad student Sarah Jaeggli and post-doc Dave Harrington observed from the smaller tent, also with a viewing window installed. Sarah’s instruments didn’t require a constant temperature, so Sarah and Dave worked in the heat, about 100F in the outside shade for most of the daylight hours and hotter inside the tent.

Sarah's observing tent

Sarah prepares her equipment in the smaller observing tent.

Covering the tops of the tents with space blankets helped to reflect some of the heat and lower the temperatures in the tents. Shadia, Mindy Lekberg, a high school chemistry teacher associated with Haystack Observatory, and I spent a morning stapling and tying blankets together to make large enough blankets to cover the tops of the tents. In places where wind tended to lift the blankets off the tents, we used binder clips to anchor them to the tent walls.

Assembling space blankets

Shadia and Mindy create one large space blanket.

Once the tents and instruments were in place, observers spent more time practicing and refining movements. Observers needed to develop a light touch on the instruments as they adjusted positions of polarizers, filters, and occulters so that nothing jiggled. They also had to coordinate movements with the other person using an instrument on the same mount.

Mindy and equipment

Mindy rehearses her observing program.

In addition to working the instruments, observers also had to use laptop computers. Dr. Isabelle Scholl wrote a program that showed the observers what to do next and automatically ran the experiments. This was all timed down to the second. Observers wore the laptops encased in custom-designed cardboard holders that held the computers at waist height (or wherever the computer fit best between instruments and people) with cords looped around the neck.

Laptop holder

Shadia operates her laptop in the customized cardboard holder.

During totality no one spoke so as not to break another person’s concentration. Each observer had only one chance to get it right. I was so astounded by the beauty and wonder of the eclipse that I would have shouted with joy if the observers hadn’t needed quiet. I was outside answering questions and showing local residents and the cook we had brought from Majuro how to use the observing glasses. Most locals remained in their houses during the eclipse, even though we distributed observing glasses to all the families.

The European group set up a tent of the type used for lawn parties. They had one gigantic mount that held multiple cameras. In the days before the eclipse the extreme humidity caused the mount to malfunction. Peter Aniol jerry-rigged my hair dryer onto the mount to dry it out. (I never did use the dryer for my hair. The main reason I brought it was my previous experience of needing to dry out my camera in heavy humidity and rain.)

Drying the mount

Peter taped a hair dryer into the mount to dry it out.

Dr. Martina Arndt used her computer to monitor temperature, illumination, and UV exposure for the entire week. UV dropped a few minutes before totality and remained depressed until a few minutes after totality. Temperature and illumination dropped almost instantly at totality and went back up as soon as totality was over. The temperature dropped eight degrees to a relatively cool 88F. To keep the probe in the shade, Martina constructed a shelter out of cardboard boxes that had held some of our food and juice packs. Budget cuts force scientists to get creative.

Weather probe

A sheltered probe connected to a computer inside the door monitored temperature, illumination, and UV.

For more information about the Sun for teachers and children, please see the NASA site for children.

Stay tuned for more adventures in the Marshall Islands. Grants from NASA and the National Science Foundation funded this solar research.