Any day that starts with two flat tires is bound to be an interesting day.
Yes, not one, but two flat tires in a matter on moments. I felt the first tire blow out and as we inspected the damage a hissing could be heard from the opposite side. The summit road is known to be a problem, and flat tires are not an uncommon event. We do get practice changing tires on this road. Fortunately other Keck vehicles were coming up behind us, and we could ask for another spare to be brought down from the summit. In the meantime we spent a pleasant half hour waiting for the second spare. The weather was beautiful, and so was the view from high on the side of Mauna Kea.
I had planned on working on one of the cameras in Interferometry. The camera has been having trouble automatically filling with liquid nitrogen. In addition I had a list of smaller issues that needed to be dealt with. Unfortunately one of those minor issues turned out to be not so minor.
Thus I spent much of the day troubleshooting Fast Delay Line #5. Used to compensate the optical path between the two telescopes, the delay line is a cart that runs on rails, carrying a set of mirrors. The cart should track very smoothly, changing the path length on the order of micrometers (a few ten thousandths of an inch), instead it visibly jittered and jumped along the rail, something wrong in the motor control software or circuitry. It took much of the day, but in the end it was tracking smoothly.
The entire day was busy from beginning to end. I attempted to finish the last few tasks on my list as the last few minutes of the day sped away. The rest of the guys were ready to leave about a quarter to five, while I was still connecting a few last metrology cables. “Yes, I am coming!” I answered on the radio for the second time. I grabbed my tool bag and headed to the door as the clock hit 17:00.
One of those days I return home exhausted. I will have to head up again, quite soon, to deal with other problems still unfinished. Hopefully a somewhat less complicated day.