Flight Day, May 6, 1994
by Juan Rivera, Telescope Operator
Off the ground after a 37 second roll. We took off at 11:45 PM and should arrive about 0400 Hawaii time after a 7.5 hour research flight that will take us south for about 1000 miles and then west towards Hawaii. The southerly legs are to enable us to clim b to our observing altitude and put us in position to head towards Hawaii with the telescope pointed towards the objects we want to observe. The telescope looks through a door in the left side of the aircraft and can only move forward and aft a few degree s, so we have to fly with the object we want to observe almost directly off the left side of the plane. Since the earth is rotating, the objects in the sky appear to travel across it. As a result, our observing legs are flown as arcs.
In the time it took me to write the last paragraph we have climbed past 20,000 feet. It's time to turn off the liquid nitrogen flow to the telescope cavity. We use liquid nitrogen to purge the cavity of damp air and also to precool the telescope optics. W e don't want to shock the optics with a blast of air that's -50 C when the plane has been siting on the ground and everything is nice and warm. We also don't want to freeze any water on the mirrors since that would mess up the optics.
We are now almost to 39,000 feet and are crossing over the major air traffic routes which are all east-west (We are cutting across at right angles). Soon I will turn on the air compressors which supply very pure filtered high pressure air to the telescope suspension system. The telescope is balanced at its center of mass on an air bearing. The bearing floats on a thin film of air and makes the telescope virtually friction-free.
We're about 30 minutes into the flight and I have the aperture door open and the telescope is floating on it's air bearing and air shock absorbers. We are still on a dead leg but tracking on an object of opportunity just to check out the systems. We have over an hour till we get south enough to turn onto our first observing leg.
Once things get squared away and settle down I'll dig out my lunch and my 1/2 gallon of orange juice. I'll drink the whole thing to keep from getting dehydrated in the high altitude/low humidity environment we fly in.
We are level at 37,000 feet and will drift up in altitude as we burn fuel and become lighter. We also have to have clearance from air traffic control of course. With a full "bag" of gas and all the equipment and supplies we have on board we are very heavy at the moment.
Here's some statistics for tonight's flight:
Maximum gross weight of our plane: 323,000 pounds Tonight's takeoff weight: 302,000 pounds Maximum fuel load: 153,000 pounds Tonight's fuel load: 115,000 pounds Fuel burn at cruise power: 11,000 pounds per hourI've now got our real-time track map running on my computer workstation so I can see our path over the ground as we fly along. It's a slick presentation with the background in black, white lines show the latitude and longitude and geographic outlines of t he landmasses - states, islands, etc. Our flight plan is in green and our actual track over the ground is in blue.
Waiting for outstanding responses...
> time="08:28:35" > time_left=16.7 mins > latitude=28.676 degs > longitude=-127.479 degs > altitude=36988.2 ft > heading=203.47 degs > cabin_altitude=8007.8 ft > pitch=1.86 degs > roll=-.12 degs > TP_hdg_bias=.000000 degs > TP_los_mode=1 > TP_dsrd_hdg=3.551165 rad > cabin_temp=23.0 C > AT_H2O_rad0_V=-.1048 V > zenith_h2o=6891.1 um Connection Terminated
It's 0148 California time and we just started observing our first object which is called "ALPHA HER (3.5, M5)". I've adjusted the focus and now I will touch up the fine balance for this particular telescope elevation. Well, everything has settled down to routine observing now. The telescope is running like a tall dog through short grass! Well as soon as I typed this of course something is going wrong. The experimenters say that they have lost half of their signals. Carl, the mission manager called up to t he flight deck to see if the pilots could see any clouds above us. Nothing above us that they could see...
Meanwhile I've got my lunch spread across my tiny desk. Orange juice, carrots, and a sandwich behind the keyboard, potato chips to the side... John, the computer operator - we call his position ADAM (Airborne Data Acquisition System) - anyway, he's eating his lunch and working on a program that graphs data for us in real-time.
The inside of the cabin looks like a cross between an office and a laboratory. We all sit in front of racks of equipment with television screen full of data and panels of flashing displays. Those of us who are part of the permanent crew all wear nomex fli ght suits with about 15 pockets all over them. I've got a flashlight and a bunch of pencils in my shoulder pocket, pair of nomex flight gloves in my right thigh pocket, and a survival knife in my knife pocket near my left calf. Here we are up here looking like a bunch of astronauts and no one can see us. But the reason for the nomex is not to look pretty. It's in case there is a fire on board and have to fight it. It's an unforgiving environment. We're in a confined space surrounded by an atmosphere that will not support life, about 1000 miles out over the ocean, in the middle of the night. We can't call 911 if we have a problem! Actually, that's one thing that makes the job interesting.
We're flying through some fairly heavy turbulence at the moment. The telescope is jumping all over the place, or at least it appears that way to us. But actually it's the aircraft jumping around. The telescope is just sailing along pointing at ALPHA HER.
It turned out that we were flying through some high clouds. It's hard to see them in the dark from the cockpit. We're up to 39,000 and soon we'll be light enough to climb up to 41,000 feet. There aren't too many clouds that high, but once in a while you s ee a few. In 11 minutes we'll hang a right and head more or less towards Hawaii. I'm starting to get tired. The first flight of my week is always a hard one for me since I'm used to days. On the little track map we've traveled about 2 inches and have abou t 5-1/2 to go. When everything is working perfectly I get bored. I have the most fun when everything starts to blow up. Then I can get busy and try to fix things. Every mission costs about $180,000 if you divide the cost of the project by the number of fl ights in a year. So there is a great feeling of satisfaction if you can patch up something in flight and save a mission.
Well, some time has passed since I wrote here. I had to dig an oscilloscope out from under a great pile of boxes and equipment so I could adjust a piece of equipment called TIPS (Telescope Inertial Pointing System). TIPS is a piece of equipment which is e ssential to keeping the telescope pointed properly. Every now and then it gets a little out of adjustment and needs some tender loving care. It's running smoothly now.
We have about one more inch to go on the little map now. I'll be very happy when I get my tired bones slid between the sheets. I've been told that our hotel is right on the water this time. Usually we are several blocks inland. When you spend three months out of five on the road living out of a suitcase little things like that make a big difference.
We have been at 41,000 for hours. I forgot to mention that earlier. The winds aloft have been blowing us north as we flew west. Now we're 34 miles north of our track. We can't correct for drift like a normal flight would since we have to keep the wing poi nted towards the object. Otherwise we could simply turn left a tad and crab into the wind. What we will have to do is break off our observations early on this leg and fly a dead leg to the south to get us back on track. Does that make sense? It's a lot ea sier to see when you have the map in front of you.
Once this next leg is completed we'll get very busy so I'll explain what is left to do while I still have the time... Actually there isn't much to explain. We close the aperture door and turn off the compressors, then stow all the loose gear and strap in for descent. Once we get on the ground we tuck the plane in for bed and hit the road!
That's all there is for now...
Juan Rivera, Telescope Operator