Flexible Observatory Operation

At the beginning of every orbit, the crews had a planned set of observa­tions but also the freedom to deviate if they saw a more information-bear­ing feature or event on the sun’s surface; that is, they approached the obser­vatory operations with an open mind but not an empty one. The planned observations, which were usually sent up from the ground on a teleprinter pad, were organized into Joint Observing Programs that defined how each instrument was to be operated as a particular feature was observed, such as a solar filament, bright point, or active region. They also had a jop to cover the occurrence of a flare, a very time critical and film-consuming set of joint observations. Very useful background data on the solar state was also provided from noaa (National Oceanic and Atmospheric Administra­tion) and the Pis. Periodically they also had voice conferences with the Pis, which turned out to be useful but rather stiff because of the many restric­tions on communication with the crew. Fortunately these restrictions have softened since then, and Shuttle crews are now able to discuss joint exper­iment concerns and procedures with ground-bound observers in a less for­mal and restraining way.

The rapid rearrangement of magnetic field structures on the sun often leads to large explosive flares that are accompanied by large coronal mass ejections. Large masses of gas are hurled high into the solar atmosphere some­times with enough energy to escape the sun entirely. Occasionally some of that mass in the form of high-energy particles enters the solar wind and sub­sequently rains down on Earth, causing the northern and southern lights (the aurorae) and major disturbances in electrical distribution grids. The ejection of these masses upward through the corona was dynamic, majestic, and very rewarding if captured in the data from beginning to end. On the third Skylab manned mission, a major cme was recorded from its inception because of a real-time tip from an observatory in Hawaii that saw a large prominence start to lift off. Later in the mission, the largest such event was observed by Skylab. “This liftoff of a major arch of gas, which covered one – eighth of the solar circumference, has become an icon of the Skylab solar observations,” Gibson explained. “Much to our embarrassment, it was all recorded by the ground’s remote operation of our instruments as we float­ed in our sleep.”

The grand prize for any Skylab observer was to record the birth and life of a flare. All the clues on how and why a flare occurs are revealed by the details of its inception. “Our flare warning systems told us when a flare was occurring, but not when and where one was about to occur,” Gibson said. “Also, since the jop for a flare demanded a high burn rate of the limited film housed in most instruments, a shotgun approach was unacceptable; we had to find a way to pick off one with a rifle. The answer lay in patience and close inspection of the most energetic active region as seen in x-rays and the xuv. As the magnetic field structure of an active region became more unstable, one or more bright points would surge and pulsate in intensity. It gave one the impression of a pot of water just starting to boil. The trick was to pick the right bright point, then the right time to call a surge in brightness the early eruption of a flare. This technique practiced on the third mission rewarded us with the capture of a flare rise just as were about to conclude our obser­vations and come back home. It was rewarding yet frustrating—why didn’t we fully develop this technique earlier?”

Though certainly not designed for it, the atm took advantage of a real target of opportunity: Comet Kohoutek. The comet was much fainter than anticipated and certainly very much fainter than the bright solar features that the atm was designed to observe. “Nonetheless, we did get some inter­esting yet faint pictures, some with the coronagraph as we pointed at the center of the sun and some as we pointed the whole Skylab cluster at the comet before and after it swept around the sun,” Gibson said. “These later maneuvers were cumbersome (twenty keystrokes were required for a single maneuver) yet a testimony to the ingenuity of the ground control team that we could make any off-sun observations with the atm at all!

“In addition to what we could capture on film, we recorded on paper what our most sensitive and versatile optical instruments onboard could detect—the human eye,” Gibson continued. “The comet came out from behind the sun on the day we had scheduled a spacewalk to replace the atm film. Even with the strong filtering of our space helmet visors, the spike of brightness that pointed at the sun and away from the tail was evident. Over the next week we monitored Kohoutek, especially its sunward spike, and made sketches of what we saw, which are now on display in the Smithso­nian in Washington DC.”

Ed Gibson said, “The operation of the atm observatory was complex, exhilarating, frustrating, rewarding, tiring, and totally absorbing. All refer­ence to where the space station was over the ground would be lost; only the time remaining in daylight was of importance. The c&D panel was com­plex, demanded one’s full attention, and invited errors—even after all the effort that went into its design. I sometimes forgot some of its nomenclature, even though I was central in the design process. Some of the readouts were in decimal (base ten) and some were in octal (base eight), which could also cause confusion. The combined procedures were sometimes very complex or required alerts and timers to remind the observer of actions to take or inter­locks to make sure the some actions were not taken. During design we all tried our best to put these alerts, timers, and interlocks in place, but we fell short of optimum. Also the more an observer knew about solar physics, the larger the dilemma he faced: ‘Do I use some of our valuable time in daylight to search the sun for potentially more rewarding targets than sent up from the ground, or do I just punch the buttons on cue as requested?’ The com­promises made were often followed by many could-of’s and should-of’s.

“And yet, as the weeks went by a simplicity of operations emerged for me: If one fully understood the capabilities of each instrument, the physics of the sun’s surface, and the needs of each pi, the jops could be pushed into the background. The task really became one of matching the state of the sun’s surface with the capabilities and needs of each instrument; that is, the sheet music (jops) were put away and the atm played by ear (full utilization of one’s knowledge and intellect). Of course, I never took this extreme lat­itude on those days that the atm was scheduled to be operated. However, on Sundays, our day off, I chose to give the Pis some bonus data and operate the observatory in this way. I felt somewhat like a piano player in the silent movie theater; the instrument was played to match the visible action. After six to seven continuous orbits of observation, I felt exhilarated yet drained, rewarded yet frustrated by what was left undone.

“Of course, each of us could have performed better with more in-flight time, more training, additional displays and interlocks, and more direct com­munication with the ground scientists. Even so, the atm observatory oper­ations were a milestone that far surpassed the contributions that a scientif­ic operator in orbit had so far demonstrated and set the bar high for future human utilization on space missions.”