The instruments aboard the atm accord a nasa document about how they achieved even greater precision quote this was accomplished with a solar pointing control system. Pcs the pcs sensed the suns center to a few tenths of a second of arc and sent error signals into the torque motors that controlled the rotational positions of the atm canister kimble's offset pointing in utah or in pitch by steps of one point. Two five seconds of arc up to twenty four minutes of arc could be introduced by counter rotating a pair of quartz wedges placed in these solar beam incident on the yaw solar sensor or a similar pair for pitch these solar sensors were one of the few items inherited from the eight. Oh oh oh okay In quote right there. So jonathan here. Here's a side note. The ao s o stands for advanced orbiting solar observatory. Which was a project that nasa had planned in the nineteen sixties but ultimately had scrap when it was clear that the tech wasn't really ready yet and the expense of the project would be way beyond nasa's budget. All right. let me get back to the quote control of offset pointing by rotating. The prisons was accomplished by the crewmen with his panel joystick digital indicators readout yaw and pitch to one second of arc and roll to one minute of arc end quote all right. That's really complicated. It gets really technical. But essentially what it's saying is that the system could correct for those motions and keep the canister relatively stable with regard to whatever it was aimed at so kind of like if you think of like stabilization technologies and digital cameras. Its in concept similar to that so much of the observational work done aboard skylab had to do with the sun with instruments taking multiple images of the sun at a specific wavelength of light these instruments are called spectra healy graphs and they produce a monochromatic image. So black and white image. So why would you focus. On a specific wavelength of light. Well it's one way to study. The various elemental components of a star as different materials will give off different wavelengths of light so by looking at which wave links are the most intense you can kind again idea of which elements are the most plentiful in something like a star like the sun on board. Skylab astronauts performed all sorts of scientific experiments including medical experiments and some designed by students back on earth the crew conducted some observations of earth which was quite an achievement because the planned experiments and instruments for that purpose had been part of the previously cancelled. Nasa project called the apollo applications mission. The history of nasa is one. That's filled with lots of projects that were meant to be but never came to fruition or were only partially developed before they were abandoned. And it's not always possible to salvage stuff from that. But in this case skylab was able to incorporate some of the plans for the apollo applications mission and incorporate some earth observation experiments with skylab in all the astronauts oversaw more than one hundred experiments ranging from using x ray and ultraviolet cameras and spectral graphs to stay the sun to measuring stuff like mineral loss in a human body due to an extended stay in microgravity some of the student projects included things like observing earth's atmosphere's ability to absorb radiant heat x ray emissions from jupiter and capillary action studies in a state of freefall while the collective time spin aboard skylab amounted to one hundred one days For all of the crewed missions..