This season is witnessing yet another celebration of Christmas on board the International Space Station (ISS) which has been continuously occupied since November 2000 (see “Christmas 2000 on the ISS“). If we go back before the ISS to the nearly continuous occupation of the Soviet Mir space station extending back to 1987, Christmas celebrations in space have been the norm for an entire generation of space enthusiasts. But for old timers like myself, we remember when a crew spending the holidays in space was an exceptional, newsworthy event.

In order to find the first time a crew spent Christmas on board a space station in orbit around the Earth, we have to go back over four decades to 1973 and the last mission to America’s first space station, Skylab. The 77-metric ton Skylab space station was the sole part of a once wide ranging Apollo Applications Program to actually fly. Originally intended to be an interlude between increasingly advanced Apollo lunar missions, Skylab instead was the beginning of the end of the manned spaceflights using Apollo-era hardware as the nation’s manned space program transitioned to the reusable Space Shuttle whose development had been officially approved at the beginning of 1972.

Diagram showing the major components of the Skylab space station. Click on image to enlarge. (NASA/MSFC)

Skylab consisted of the S-IVB third stage of a Saturn V launch vehicle that had been converted into a large orbital workshop to support three astronauts on missions lasting for weeks at a time. Other major components of Skylab included a large airlock with a hatch for extravehicular activities (EVAs), a multiple docking adapter with a pair of docking ports for Apollo-based ferries and the Apollo Telescope Mount (ATM) which housed a suite of instruments designed to observe the Sun at visible, ultraviolet (UV) and X-ray wavelengths. Launched on May 14, 1973 on the last Saturn V to fly, Skylab sustained severe damage during ascent with the loss of its combined micrometeoroid shield/sunshade and one of a pair of deployable main solar panels. The station was repaired by its first crew launched on the SL-2 mission on May 25 which stayed on board the space station for a record-breaking 28 days. The second mission, SL-3 launched on July 28, performed further repairs as part of an experiment-filled extended stay of 56 days on the space station.

Portrait of the SL-4 crew: (left to right) Gerald P. Carr, Edward G. Gibson and William R. Pogue. (NASA)

The final mission to Skylab was SL-4 launched on November 16, 1973. The first all-rookie space crew to be launched by the US in eight years consisted of Gerald P. Carr as commander, William R. Pogue as the pilot and Edward G. Gibson as science pilot. The baseline mission of SL-4 was a repeat of the 56-day mission of SL-3 with an open ended option to extend it to as long as 84 days if all went well. In addition to a mix of experiments similar to those performed during the first two Skylab missions, this crew was also tasked with making observations of Comet Kohoutek. Discovered on March 7, 1973 by Czech astronomer Lubos Kohoutek almost ten months before reaching perihelion, astronomers had more time than usual to prepare for the arrival of this comet. Comet Kohoutek received much attention from the press and was expected to make a prominent display around the time of its closest pass of the Sun on December 28. Skylab, with its suite of instruments, was uniquely situated to observe the comet around this time.

Artist depiction showing the position of Comet Kohoutek relative to the Earth on Christmas Eve 1973. (NASA)

Unlike most people back home, the three Skylab astronauts would not have an opportunity to take time off on Christmas Day 1973. Just as had happened on Thanksgiving Day, two of the Skylab crew members were scheduled to perform an EVA on December 25 with yet another EVA to follow just four days later. For Christmas Day, Carr and Pogue were originally assigned to reload photographic film for the ATM and make observations of Comet Kohoutek which had been dubbed the “Christmas Comet” by some in the press. The original EVA was extended so that the astronauts could also fix a pair of ATM instruments that had developed problems. Gibson would monitor the instruments and the station’s control systems from inside the multiple docking adapter.

After a brief exchange of holiday greetings on Christmas morning, the three astronauts began their preparations for the EVA. At 10:00 AM CST, Carr and Pogue stepped out of the Skylab airlock to begin their work on an EVA that was scheduled to last 3 hours and 50 minutes. For this EVA, Pogue’s workstation was at the ATM mount with Carr working at the end of the ATM pointing towards the Sun. The first scheduled activity was observations of the comet. At this time Comet Kohoutek was too close to the Sun to be easily observed from Earth but at the same time too distant to be observed using the solar instruments of the ATM. Unable to see the comet themselves, the first round of observations by the astronauts were made using the T025 Multi-Filter Coronagraph camera which was already on board to support other experiments. This camera had an occulting disk to block out the Sun so that visible and UV images could be acquired.

An SL-4 astronaut at the base of the ATM mount during an EVA. (NASA)

Next, Carr reloaded the ATM cameras with a fresh batch of photographic film for the upcoming round of comet observations with this large instrument suite. Carr also pinned open a malfunctioning aperture door on the ATM’s S082A Extreme UV Spectroheliograph staying an extra couple of minutes afterwards at Gibson’s insistence to enjoy the spectacular view from this unique vantage point. Carr and Pogue then clamped the S201B Far UV Camera in place to begin taking a prescribed sequence of images of Comet Kohoutek with the ATM’s solar array serving to block out the Sun. This film-based electrographic Schmidt camera was a modified version of the backup unit originally built for the Apollo 16 lunar mission to make far UV astronomical observations from the surface of the Moon (see “The Original Lunar Observatories”) and had been flown up with the SL-4 crew specifically for these observations of the comet. It was ideally suited for imaging the comet’s extended hydrogen halo.

An enhanced false color UV image of Comet Kohoutek taken by the Skylab astronauts during their EVA on December 25, 1973 using the S201B Far UV Camera operating at a wavelength of 125 to 160 nm. (NASA)

During this time, however, venting from the astronauts’ EVA suits (which generated a tiny 0.01 newtons of force) combined with working for many tens of minutes at a time in one position up to 7.6 meters from the station’s center of gravity produced torques on the station which eventually resulted in excessive momentum buildup in the gyroscopes used to control the station’s attitude. Inside the space station, Gibson had to switch to the nitrogen gas attitude control thrusters to keep the station and its instruments properly pointed with a total of about 17 kilonewton-seconds of impulse required to restore proper station attitude – almost 40% more than had been originally budgeted for the EVA. Dealing with these unplanned issues and keeping the instruments pointed properly took more time than originally planned.

A Skylab astronaut shown working on the ATM in a display at the National Air & Space Museum. (A.J. LePage)

Six hours into the EVA, Carr then moved to repair the stuck filter wheel of the ATM’s S056 X-ray Telescope. With difficulty, he verified that the filter wheel was indeed stuck between two positions as had been suspected and used a screwdriver to push the wheel to the open “no filter” position so that unfiltered observations could at least be made. While attempting to perform this procedure for which he had not trained and out of contact with ground control, Carr slipped resulting in the shutter closing and the screwdriver bending one of its thin metal blades. After contact with controllers had been regained as scheduled, it was decided to simply bend the metal blades out of the way leaving the aperture fully open. After completing this task, the astronauts waited through another half-hour communication gap until contact with ground controllers was reestablished and they verified the fix.

With their scheduled work concluded, Carr and Pogue made their way back into the airlock with the EVA ending at 5:01 PM CST spending a total of seven hours and one minute in a vacuum. The issues with the attitude control and the extra time to troubleshoot the X-ray telescope had added over three hours to the EVA’s scheduled length. This unintentionally long EVA ended up being a record-breaking spacewalk whose length would not be surpassed until the STS 51-I mission in 1985. After stowing their gear, the astronauts enjoyed a well deserved Christmas dinner and some rest.

A television view of the Christmas tree the Skylab crew had fashioned out of empty food containers in 1973. (NASA)

While Americans were following reports about the SL-4 crew at work on Skylab and enjoying their television broadcasts showing their improvised Christmas tree, there was another crew in orbit around the Earth at this time working through Christmas 1973 whose activities received virtually no attention in the West. Soviet cosmonauts Pyotr Klimuk and Valentin Lebedev were launched into orbit aboard Soyuz 13 on December 18, 1973 for the second manned Soyuz flight since the tragic loss of the Soyuz 11 crew who perished in 1971 while returning from their stay on the world’s first space station, Salyut 1. This was the first Soviet space mission to use the then-new Kaliningrad Mission Control Center which is still used today to support ISS operations.

Soviet cosmonauts Pyotr Klimuk and Valentin  Lebedev shown in orbit aboard Soyuz 13 which spent its last full day in space on Christmas Day 1973. (Planeta Publishers)

Soyuz 13 was a modified version of the new 7K-T spacecraft designated 7K-T/AF (the “AF” standing for “astrophysics”). Since this was a “solo” flight not intended to dock with a space station,  the docking gear on Soyuz 7K-T No. 33 had been replaced with an astronomical instrument package called Orion 2.  Building on the experience of its predecessor that had flown on Salyut 1, Orion 2 included a trio of UV spectrographs designed to take spectra of stars at wavelengths from 91 nm to 4000 nm and an X-ray telescope meant to image the Sun in the 0.1 to 6 nm wavelength range (equivalent to energy in the 0.1 to 2 keV range). The Soyuz 13 crew had completed their science mission on December 24 making observations of the star ε Orionis and the planets Saturn and Mars. Apparently, no observations of Comet Kohoutek were made during this mission. Klimuk and Lebedev spent an uneventful Christmas Day stowing the film they had exposed and other equipment for their return to Earth.  There was no means for the crews of Soyuz 13 and Skylab, who were in very different orbits, to communicate with each other during their mission and exchange holiday greetings. Soyuz 13 landed on December 26 with the crew successfully recovered in the middle of a snowstorm at their landing site.

Diagram showing the layout of the Orion 2 astronomical observatory on Soyuz 13. The components are 1) the Soyuz Orbital Module, 2) the observatory cupola, 3) the instrument package, 4) sluice chambers for the film, 5) the sighting device and 6) the control panel. (NASA)

Learning from the experiences of the Skylab crew’s Christmas EVA, extra precautions were taken to minimize the attitude control issues for their next EVA on December 29 meant to make more observations Comet Kohoutek. While the “Christmas Comet” was a bust for those of us back on Earth hoping for a spectacular show, Skylab’s observations added much to the scientific study of this object. And despite issues with balky gyroscopes on the space station as well as other minor problems, the SL-4 mission was eventually extended to a full 84-day stay with the crew returning safely to Earth on February 8, 1974.

The space endurance record of the SL-4 mission would remain unbroken for another four years when a pair of cosmonauts launched into orbit on Soyuz 26, Yuri Romanenko and Georgi Grechko, spent 96 days on the ancestor of the Russian modules of today’s ISS, the Soviet Salyut 6 space station. Coincidentally, Romanenko and Grechko spent Christmas 1977 on board Salyut 6 – the first people to spend Christmas in space since the SL-4 and Soyuz 13 crews of 1973. It would be another 19 years before both Russians and Americans would spend Christmas in orbit as part of the joint Mir-Space Shuttle missions which preceded those of the ISS.


Related Video

Here is an excellent NASA documentary on the Skylab program from the mid-1970s titled “Skylab: Space Station I”.



Related Reading

“The Original Lunar Observatories”, Drew Ex Machina, August 21, 2014 [Post]

“Christmas 2000 on the ISS”, Drew Ex Machina, December 24, 2015 [Post]

“Vintage Micro: The Talking Atlas”, Drew Ex Machina, December 18, 2014 [Post]


General References

Erwin J. Bulban, “Skylab Harvests Vast Data on Kohoutek”, Aviation Week & Space Technology, pp. 16-17, January 7, 1974

Phillip Clark, The Soviet Manned Space Program, Orion Books, 1988

W. David Compton and Charles D. Benson, Living and Working in Space: A History of Skylab, SP-4208, NASA, 1983

G.A. Gurzadyan et al., “Space Astrophysical Observatory ‘Orion-2′”, Astrophysics and Space Science, Vol 40, pp. 393-446, April 1976

Charles A. Lundquist (editor), Skylab’s Astronomy and Space Sciences, SP-404, NASA, 1979

“Skylab Puts out the Welcome Mat for Comet”, NASA Press Release No. 73-229, November 5, 1973