"LIVE FROM THE STRATOSPHERE" P R O J E CT U P D A T E # 27 PART 1: Chilling with the needy dewar PART 2: Another mission log from Juan _______________________________________________________________________ [Editor's note: this April Whitt tale describes events right before the live television programs] CHILLING WITH THE NEEDY DEWAR April Whitt There doesn't seem to be time for lunch again. The Yerkes science team has demonstrated how to take care of the dewar. It's not quite like having an infant human in the house, but it still needs its cryogen feedings every twelve hours. And the "hours" can be 3:30 in the morning. If the cryogens boil off and the detector warms up, it will take 24 hours or longer to cool it back down, and there is not that much time between flights next week. Two cryogens are used: liquid nitrogen and liquid helium (the helium's more expensive). Huge "thermos flasks" of those gases (liquids) are wheeled over to the dewar. A fill tube at the top of the dewar is connected to one end of a hose-and-pipe arrangement, and the flask of cryogen's connected at the other end. Rhodri Evans and Dave Cole (both wearing thick gloves) set up the connection and open the valves on the liquid helium flask. White clouds smoke out, and you can tell when the dewar tank is full by the white geyser shooting out of the fill tube. The liquid nitrogen is added through a funnel stuck in the fill tube. The LN2 is drained from the big flask into an insulated beaker, then carried to the dewar and poured through the funnel. The funnel gets really cold of course, and some have cracked. Dave Cole tells the "ice plug story." The fill tubes are really cold, compared to the outside air, of course. Everyday ordinary convection currents can carry air from the room down the fill tubes, and if it's humid air, the water vapor can freeze inside the tube. The resulting ice plug keeps more air from entering, but also keeps the pressure of the boiling liquid helium from escaping. The LHe2 continues to build pressure inside, and an ice plug is stronger than the aluminum fill tube. Unless the pressure is released, something else will pop: a solder joint, the aluminum jacket, who knows what. The team has taken to poking a wooden stick down the fill tube to keep air of the cryogen tank (thereby serving as a weapon against vampires as well, although somewhat slender). On the occasion Dave described, the LHe2 went into the dewar and the stick was inserted. The stick, however, was moist from the outside air, and when it came it contact with the LHe2 in the fill tube, it expanded and froze, blocking the tube as an ice plug would have done. Realizing what had happened, the team tried to pull the stick back out. It broke off close to the end of the fill tube, and some frantic yanking with various gripping tools ensued. Must be fun working that close to a time bomb. They were able to get the stick-plug out and save the equipment and themselves. There is now a collection of sticks to use, all of them kept nice and dry. More meetings in the afternoon. Everyone who flies the KAO has to have an oxygen mask fitted and has to watch the safety video. Rather different than the announcements by the flight attendants on commercial airlines, too. During KAO flights, the mission director is the person to listen to - and watch for information. But if you haven't paid attention during the safety video, you're not ready to grab your oxy mask in the event of a sudden decompression (when you have four SECONDS of usable consciousness to get it on), or you won't know where the firefighting equipment is and how to use it. Juan Rivera said that he still checks the panels where the firefighting gear is stored every time he's on the plane (and he's been on the crew for years). Safety first. Brian and Mr. Haines-Stiles are off to the check in at the motel for some rest and supper, and federal-express some materials for the broadcast. Laura has not arrived yet - she'll be here for the practice flight tonight. Allan Meyer has kindly lent me the use of a computer in his office to keep up with email (although I seem to have cratered my Spacelink account yet again). We're supposed to get our snacks for the flight and reassemble for the pre-flight briefing an hour before take-off time. It suddenly occurs to me that the flight is less than two hours away, and I don't have my stuff together. It's back to the motel to find Brian and we stop by the convenience store across the street for sandwiches and bottles of water. The relative humidity up there in the stratosphere is less than at the south pole (of course it's dry up there - water vapor blocks the infra-red radiation we want to study and we're above most of the water vapor) and these human bodies need water. Lots and lots of water. Two liters during a long flight, at least. With our bags of food in hand, we attempt to return to base for the pre- flight briefing. We drive up to the gate in the little rental car and I show my visitor tag to the guard. He asks to see Brian's tag. But Brian doesn't have a visitor tag. When he came in this afternoon, Richard Morrison brought him on base with Richard's picture badge. I only have a lowly non-picture tag. There's a tag waiting for him in the badging office, but it's after 4:30, and he didn't pick it up by 4:30 (the badging office closes at 4:00 - go figure) so the attendant won't give it to him. I leave Brian and his sandwiches held hostage at the badging office and report to the producer, who finds Saint Walter Miller, who works everything out efficiently. Thank goodness for Walt! _______________________________________________________________________ THE SKILLS NEEDED TO TRACK STARS Benjamin Burress, Tracker Operator All in all, being a Tracker Operator on the KAO has been a very good experience. I used to lament on the fact that once upon a time I dreamed of being an astronomer, and that, as a Tracker Operator/Observing Assistant, I may be working very closely with astronomers, I am not one myself. However, my college astronomy professor pointed out to me that I am very lucky to have a job in this field, as they are scarce, even for PhD recipients. So, I feel very lucky. What part of my college education do I utilize at the KAO, one might ask? What skills does one need to be a successful Tracker Operator at such an observatory? Well, most of the math and physics and chemistry I learned in college don't get employed here, except in allowing me to converse with the scientists using their own jargon, and understanding what they are about. Some math skills are very important, such as trigonometry/spherical-trig, coordinate conversion, and some others. With my physics and chemistry, I am comfortable working with the scientists in our lab, knowing how to run oscilloscopes and other test equipment, as well as how to handle sometimes dangerous chemicals. As for astronomy--my minor in college--it does prove helpful when I am working with the astronomers and knowing what they are doing. Although someone with a different physical science background plus an interest in astronomy would do quite well in this position. Most often, however, I find myself leaning heavily on my computer skills, and this is a factor I would expect to find at just about any job these days. Basic computer operating skills are a must, as you would maybe expect. I frequently find myself writing programs for one thing or another, developing a batch of personal software tools, in IDL, HyperCard as well as UNIX scripting. I have also learned a great deal on the job over the last seven years. The broad blending of different technology and technique here have put me in close proximity to many things, such as cryogenics, electronics, imaging systems, computer systems, radiometer systems, infrared detection apparati, optics systems, tracking systems, aircraft systems, etc., etc., etc. It's not like working at a computer chip manufacturing plant, where one might be exposed to PC board manufacture, and little else, or a ground-based observatory, where the telescope and computer systems are the majority of the equipment. Having the knowledge and skill to do a certain job is important, of course, but interest in a job or career is really what fuels the fire. Conversely, you can have all the skill and knowledge in the world, but if you aren't interested in what you are doing, you might as well not be doing it. It is my interest in astronomy, and my fascination for this particular, unique observatory, that has kept me happy and satisfied here at the KAO. I hope I am as fortunate in all of my ventures and adventures.