In addition to the support assignments already mentioned, some of the scientist-astronauts were involved with specific experiments flown on the workshop, as either principal or co-investigators. Each of these support roles had their own story to tell.
Programme scientist: Parker's role as programme scientist was to ensure that the science requirements for the manned missions were compatible with programme requirements and safety issues. During Skylab flight operations, Parker would liaise between the programme director and managers to ensure the in-flight science requirements were being met by the flight crews, utilising his background as both a scientist and an astronaut, and drawing upon his recent experience as mission scientist for Apollo 17.
Though pleased with the initial data, Parker found that the investigators felt starved of sufficient time in the flight plan to accomplish their particular experiment. Parker had difficulty securing their trust and reflected that, although he was the programme scientist and was an astronomer himself, in their eyes he was now an astronaut and no longer "one of them''. Parker recalled that most of the investigators thought that their experiment was the one that had been short-changed in the planning, and it was a constant battle to convince them otherwise. The general feeling on the first mission seemed to be "that they had put an awful lot of their time and NASA money into getting very little data, and they had jolly well better get more next time.'' For the second and third missions, Parker worked hard to placate his scientific colleagues, introducing a programme of periodic planning sessions that helped each
PI gain an understanding of the others' problems. Even more helpful was the ever-increasing flow of data from Skylab as the flights progressed.
Back-up crewman: Story Musgrave gave an insight into his preparation as a back-up to the Skylab 2 mission in a lecture he gave in October 1973.14 He recalled that shortly after returning to Houston from flight school, they began more detailed briefings and schematic reviews on the Skylab space station, with a part-task approach to sub-systems and mechanisms. According to Musgrave, after several years of briefings, getting simulator time on various spacecraft systems, working on the hardware design and mission development (potentially for some considerable time) and supporting other flights in specific areas or as Capcom, gave a crew member ''a good start prior to commencing with formal mission training.'' The general approach to learning spacecraft systems and operations, according to Musgrave's experience as an assigned back-up science pilot was:
• Instruction on the mission requirements and objectives.
• Briefings on the rationale, science and technology behind the spacecraft design.
• Briefings on spacecraft systems and schematic reviews.
• Part-task systems training in simulators.
• Nominal systems operations in simulators.
• Systems malfunction procedures in simulators.
• Normal operations of the entire spacecraft.
• Normal operations and malfunctions of the total spacecraft through specific mission events, such as launch, rendezvous, on-orbit operations and re-entry.
• Integrated simulations where the spacecraft simulator is patched into the mission control centre and both the real-time mission computers and the spacecraft simulator operations are supported by those flight controllers who are assigned to the mission.
Musgrave stated that training on mission experiments followed a similar timetable, except that far more effort was put into acquiring both the fundamental scientific principles and the special objectives peculiar to each experiment. On Skylab, there were approximately 100 experiments in medicine, physiology, biology, solar physics, remote sensing and Earth resources, astronomy, manufacturing in space, habitation, navigation, particles and radiation, crew manoeuvring units, technology, and student experiments. The key to the development of adequate learning processes, according to Musgrave, was early training on each experiment, conducted by the principal investigator.
Capcom: Musgrave also gave an insight into the role of Capcom during the three missions. The Capsule Communicator, or Capcom (derived from the early days of the space programme, where a spacecraft was referred to as a ''Capsule'' and those who talked to the crew from the ground were ''Communicators'' - traditionally an astronaut support role), at least in the case of Skylab, was trained for specific tasks that were being performed in flight. The Capcom knew the science hardware and procedures involved and was a test bed for any voice call or teleprinter message. If he could not understand the call or carry off the procedure, it was unlikely that the flight crew could either. The Capcom usually worked and trained with the flight crew for years, coming to know both the crew themselves and the way they would approach the mission or a specific task. This approach was modified during Shuttle missions, because the Capcom would work on several missions and with different crews during a ''tour'' in the role, but it was still, in a sense, an additional member of the flight crew who remained on the ground.
Support crewman: The support crew roles during the Apollo era were filled by a third tier of astronauts, normally unflown, who would use their technical assignment skills in either the Apollo CSM or LM to help alleviate the workload on the prime and back-up crews. This assignment was seen as a stepping stone towards a potential future flight and included the role of shift Capcom. This role developed in 1966 and lasted until the end of Apollo-type missions in 1975. It evolved partly in response to CB concerns that, with Apollo contractors spread across the United States and the added complexity of each lunar mission, crew representation was being lost on important decisions and developments. This role was even more relevant to Skylab, where the mission duration would increase dramatically over the short Apollo flights. Additionally, there was a larger scientific programme to contend with on Skylab than there had been on Apollo. The support crew would also relieve the prime and back-up crews of some of the more mundane activities. The scientist-astronauts assigned to the Skylab support crew (alongside Bob Crippen and Hank Hartsfield) were Henize and Thornton. Crippen and Thornton had worked together on the SMEAT test chamber exercise in 1972.
Principal investigator: In September 1967, Karl Henize left Northwestern University to enter astronaut training, but continued as a professor (on leave) until 1972. He then transferred his affiliation, as well as his Skylab experiment (S019 - ultraviolet stellar astronomy) to the University of Texas at Austin, where he became an adjunct professor. During the Gemini programme in the mid 1960s, Henize provided a small hand-held camera that could be used during stand-up EVAs to capture UV spectrometer images of hot stars. Flown on the last three Gemini missions in 1966, the camera obtained some good results, and Henize continued this research with a follow-up camera for Skylab. He developed a six-inch aperture telescope with an objective prism that could penetrate deeper into the far UV region. In assigning his experiment to a manned spacecraft, the idea was to obtain ''quick-look'' data that was not readily available from larger unmanned astronomical observatories. These were not trivial experiments, but a development towards a better understanding of astronomy observations from space using limited resources and hardware.
Henize looked at the feasibility of deploying and operating the experiment during an early Apollo Earth-orbital mission (Block I Earth-orbital or early AAP mission). However, after the Apollo 1 pad fire, the redesign of the side hatch and the renewed commitment to getting Apollo to the Moon by 1969, few ''science experiments'' were carried on the early Apollo missions (7-11). Henize was told that the experiment would be reassigned to Skylab, with a three year delay to 1972 or 1973. During those three years, some of the more interesting and easier observations were accomplished via sounding rockets. However, they could only record data of a few dozen stars.
Henize's experiment covered a much broader scale and thus gave him data with which he could classify stars based on their UV spectrum.15
The S019 UV Stellar Astronomy experiment was designed to take UV photographs of large areas of the Milky Way in which young, hot stars are abundant. Located in the Skylab Air Lock (SAL) on the side of the Orbital Workshop, the manually-operated equipment featured a six-inch reflecting telescope and moveable mirror. The objective was to image fifty areas of five degrees by four degrees two or three times each, with exposures of thirty, ninety and 270 seconds. Each film cassette held 164 frames of special UV-sensitive film. A fourth exposure capability was available if the stability of the workshop permitted. The experiment was operated by all three crews, resulting in 1,600 photos of 188 star fields. Though some images were smeared due to the movement of the station, these were subsequently processed through computers to recover as much data as possible.
Henize was appreciative of the frustrations of the other principal investigators, but was equally well aware of the difficulties facing both the flight crew and Mission Control. He felt that the PIs' frustration was bordering on paranoia: "You never quite knew what the other man's problems were, and you would put in your requirements and get them back all mangled. Everybody was mad at each other.''12
Henize clearly demonstrated (as did Thornton and Lind) that on Skylab, a balance of astronaut duties and research science was achievable given suitable attention to detail and priorities at the right time. No one said it would be easy, but no one said it could not be done either. The choice was down to the individual.
Simulation crewmember: Bill Thornton was selected for a ground-based fifty-six-day Skylab simulation in June 1971 and began training the following month. The "mission" was known as the Skylab Medical Experiment Attitude Test (SMEAT) and was conducted in the 6 m altitude chamber located in Building 7 at the Manned Spacecraft Center in Houston. Thornton would serve as the science pilot on the "crew", alongside Robert Crippen (commander) and Karol Bobko (pilot). The simulation lasted from 26 July to 20 September 1972 and not only established a baseline medical data bank for the experiments, but also provided a wealth of information on crew habitability, hardware design and procedural issues. The test helped to iron out several problems that would otherwise have needed to be dealt with on orbit during the actual missions.4
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