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]

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

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

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!


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

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.

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