Before getting caught up with teaching I promised to write a brief summary of the aircraft eclipse experiment from Panama:
The the 9.5hr C130 flight to Panama from Boulder 10 days before the eclipse was noisy and tiring, but uneventful. Haosheng and I had cooled dewars and prepared the IR spectrograph and imaging system for operation before the flight -- the dewars even went to Panama cooled. By the next day, tuesday, we were testing and aligning optics. >From Howard airforce base (where we were based) we used a simple mirror on top of the plane and "sea level flights (pushing the airplane around the tarmac)" to set up for a series of 3 test flights over the Pacific later that week and the day immediately before the eclipse. The airbase provided superb logistical support including LN2, airconditioning, and weather data for us while we worked in the plane in the tropical sun on the airport tarmac. Most of our prep time before the eclipse was devoted to devising photometric and spectroscopic calibration schemes, although we had some interesting experiences learning how to, for example, store and transfer LN2 in the tropical heat and humidity. Our experiment crew of 9 (2 from Max Planck/Lindau, 3 from Rhodes, 3 from NSO and MSU, and one from HAO) was notably busy handling tasks ranging from turning mirrors on the roof of the C130 to dealing with the press crews that toured the experiment. There were also 8 people in the aircraft crew and all of us were lodged across the only bridge in the Republic of Panama that crosses The Canal. During the height of Carnaval crossing this bridge was a daily adventure. Luckily, our rather pessimistic fears for how many of us or our cars would be lost or damaged by the traffic were never realised.
Several scientific goals were to be met with these instruments. The spectrograph was designed to confirm and search for new IR emission lines between 1-2.5 microns, and to spectroscopically measure the dynamics of F-coronal dust around the sun. We were also interested in looking for a peculiar HeI (cool) outer coronal component which we observed in the '94 experiment. The new 1-5 micron, high dynamic range IR imager (newly designed and built at MSU in collaboration with the NSO) would be used with a tunable IR Lyot filter and fixed narrow and broad-band IR filters and polarizers for several experiments aimed at diagnosing the spatial temperature and density structure of the corona, and the thermal properties of the circumsolar dust. A high priority of the new photometer was to look for evidence of a predicted, and highly magnetically sensitive emission line at a wavelength of 3.9 micron.
Since the small opening in the roof of the airplane restricted the range of unvignetted viewing angles of the instrument pointing spar it was always necesary to use the airplane as part of the "telescope." This complicates the airplane flight path since the instantaneous airplane heading had to match the proper azimuth range for the current solar position. Since the lunar shadow was only 150 km in diameter and moving at 1800 km/hr while the airplane was moving at 450km/hr, our flight path required careful planning. Our three test flights were used to good advantage calibrating and learning the operational principles needed to steer airplane and telescope.
On thursday, the day of the eclipse, we arrived at Howard airforce base before 7:00am (Carnaval had just ended) in time to study the satellite imagery the Howard AFB weather group was gathering for us. Growing cirrus clouds to the west of Panama left few options but to choose our primary intercept point with the moons shadow at a far rendezvous point, 800km into the Pacific. We decided to approach this intercept by flying southwest along the computed eclipse path trajectory. We arrived at our second contact point early enough to complete additional calibration, and we "waited" for the lunar shadow by executing a standard aircraft holding pattern at about 18,000 ft. The shadow arrived on time, and with the C130 properly aligned on the eclipse centerline and heading parallel to the shadow. We were rewarded with the longest period of totality (almost 5 minutes) that could be observed. All instruments and experimenters performed as designed and rehearsed, and we acquired data with few technical disappointments. The instruments accumulated nearly 100Mbytes of data which we have now only begun to analyse. Although we have no quantitatively results we did have computers fired up on the 10 hour flight back. A quick look shows that the spectroscopic data cleanly measures IR emission lines near 1 and 1.43 microns. If there is coronal HeI it is very weak, as are other emission lines out to 2.2 microns. The spectroscopic F-coronal signal will take more time to analyse. The photometric data shows high S/N J and K band F-coronal signal over the full 6 degrees of the field-of-view. There is also an interesting signal at 3.9 microns which we are anxious to track down when computers and data are once again available. In short the data appears to be exceptional and unique -- we are optimistic about realizing the scientific goals of the mission.
Jeff Kuhn (for the C130 eclipse experiment group: Bob MacQueen, Ingrid Mann, Haosheng Lin, Jack Streete, Dan Edmunds, Phil Judge, Peter Hillebran, and Gerry Tansey)