# Did Skylab astronauts really "go outside" to look at comet Kohoutek? If so, why?

Today in The BBC's Skylab: The myth of the mutiny in space it says:

The Skylab space station was a research platform in orbit where astronauts helped scientists to study the human body's response to space flight, carried out experiments and made observations of the Sun and Earth. Skylab 4 was the final mission and as a result it had a long list of tasks to fulfil.

The 84-day mission - the longest ever at that point - was on a tight schedule. Nasa was very concerned about someone getting sick, which would have meant losing precious time.

Nasa accepts that mission planners had not given the crew the typical period of adjustment to acclimatise to working weightlessly in orbit and had packed their schedules with large amounts of work. The number of spacewalks was also doubled, to four, to observe a newly discovered comet, Kohoutek.

Answers to Is the Skylab 4 mutiny just a myth? cover a lot of background on the "mutiny" question, as does the BBC article. But my question is about the last sentence which states that two extra spacewalks were scheduled in order to observe comet Kohoutek.

It surprises me because spacewalks are time and resource consuming and dangerous and I can't imagine one would be scheduled just so someone could say "yep, there it is!" and because a few billion people could do that on Earth as well!

Question: Did Skylab astronauts really "go outside" on a spacewalk to look at comet Kohoutek? If so, why?

The Skylab 4 crew on the radio to Czech astronomer Lubos Kohoutek, who gave his name to the comet

• Well, they did observe it and snatched an ultraviolet photo during the spacewalk on december 25th, 1973. But I can not find any indication that this spacewalk was specifically sheduled for that to happen.The did a lot of observing with on-board tools, cf. history.nasa.gov/SP-404/ch4.htm Mar 20 at 12:58
• @Polygnome With this? I never really thought about it but I'd never thought that it was a handheld camera! I'd assumed that it was point-able from the inside but I never thought about how. Maybe they had to go outside to change the film cassette? Or maybe it was associated with the Skylab Apollo Telescope Mount (ATM)
– uhoh
Mar 20 at 13:01
• en.wikipedia.org/wiki/Far_Ultraviolet_Camera/… says the camera was mounted on the ATM. I'm at this point uncertain if these spacewalks had anything to do with the observations beyond mere coincidence of timing. Mar 20 at 13:08
• @Polygnome your sources "Kohoutek Visually Observed" section says "These sketches are based on the crew's collective impressions of the comet's appearance on December 29, 1973, as observed through 10-power binoculars." which has me now wondering How far will I have to hold my “space binoculars” from my eyes during a space walk?
– uhoh
Mar 20 at 13:25
• Did they do that on a spacewalk or while on station, through a window? Did Skylab have a window? Mar 20 at 13:44

### Yes, but the EVAs were to mount and unmount cameras, not to look at it with their own eyes

There were 13 experiments during Skylab 4 to observe various characteristics of the comet Kohoutek. There are described in the NASA technical report MSFC Skylab Kohoutek Experiments Mission Evaluation. The mission summary clearly states that EVAs were involved:

The Comet Kohoutek's, (1973f) appearance and orbital trajectory provided NASA with a unique opportunity to perform an observing program on the Skylab SL-4 mission. The comet was observed on over one hundred occasions by thirteen Skylab experiments in spectral bands from X-rays, through ultraviolet and visible bands. Observations were performed: by corollary experiments through the scientific airlock (SAL); by hand held photography (HH); during extravehicular activity (EVA) and by the Apollo Telescope Mount (ATM) experiments.

Experiment S201 was the Far-UV Electronographic Camera. Although most images were obtained from the Scientific Airlock, EVAs were also performed to mount and unmount the camera on the truss of the Apollo Telescope Mount:

In the EVA mode, the crewman would attach the S201 to the ATM truss using a modified SO20 mounting bracket and point the camera at the comet using an integral sight. A vehicle roll about the longitudinal axis up to 16 degrees during pre-perihelion and up to 45 degrees post-perihelion was utilized to put the camera in the ATM solar panel shadow. This was required during EVA operations while the spacecraft was in sunlight and the comet was near perihelion.

Experiment T025 was Coronagraph Contamination Measurements, another camera that was used both in the Scientific Airlock as well as mounted to the body of the station during EVAs:

The hardware was modified for EVA sequences. These modifications included changing the TO25 occulting disc and the addition of an EVA mount (see figure 8).

[...]

TO25 was performed for ~ 50 minutes on December 25 and December 29 during the daylight portion of the EVAs taking 40 exposures each time.

There are no reports of astronauts looking with their own eyes. Considering that the comet was near perihelion, that would involve staring almost directly at the sun.

• After some reading in meta I'd found that the "pound signs" are the preferred method for big words (the --- can have problems, not sure what they are) and the number of #'s allows one to adjust the bigness.
– uhoh
Mar 23 at 6:02
• +1 gonna ask next "What's a scientific airlock?"
– uhoh
Mar 23 at 6:04
• @uhoh sometimes it's for umbrellas space.stackexchange.com/q/48377/6944 Mar 23 at 11:40