Live from the Hubble Space Telescope
UPDATE # 11
Last week we asked:
ANSWER: Earth is blue because it is mostly covered in water, and water is blue.
Neptune is blue for two reasons, and neither has anything to do with water. The atmospheric gas that has the most effect on Neptune's color is methane, and methane molecules absorb red light. Take away the red light, and what do you have left? Blue. Also, the particles in Neptune's clouds are actually slightly bluish in color. Both things make the planet blue.
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Challenge Question for this week:
But there were some lights that DID move! These wandered across a particular path in the sky they called the Zodiac. The Greeks called them "Planets" or "Wanderers". (We HST folks call them "Moving Targets").
To solve this Challenge Question, you will need a good star chart that shows right ascension and declination and the boundaries of the constellations (see page 23 of Teacher's Guide). You may have to dig a little to solve the following two-part riddle:
Use your tables and a star chart from the Library or a source like Sky and Telescope or Astronomy magazine to...
March 1, 1996
Well, they are almost all done now, so I have a chance to describe what a week like this can be like.....
One of the observing programs is for a very fortunate amateur astronomer. Most of the astronomers who use HST are professional astronomers who work as college professors or researchers at science labs or institutes (they have earned the formal title "Dr."). However, once in awhile our director gives some of his personal HST time to an amateur astronomer who has submitted an interesting observing proposal that would make good use of HST's abilities. I have worked with several of these HST amateur astronomers over the years: they have observed other planets and their moons, exploding stars, gravitationally lensed objects, galaxies, and quasars.
The amateur astronomer I am currently working with will take pictures of a strange galaxy called NGC 1808 that has mysterious pillars of material spouting out from it's center. Nobody is quite sure if these "fountains" of galactic material are caused by a black hole in the center of the galaxy, or possibly by a burst of star formation near the center. Only HST can see into the center of the galaxy to see what is going on there.....I can't wait to learn the answer!
Four of the other observing programs were difficult to implement because we are planning to use special orbits where the target (a planet, stars, or a galaxy, etc...) is visible for a larger-than-usual amount of time.
HST orbits the Earth every 96 minutes. If HST is pointing at a target and orbiting the Earth, it's not hard to imagine how for about half of the orbit, the target is not visible because the Earth itself is in the way (until HST swings back around the Earth, and then the target is visible again).
Remember that even though HST is in "outer space", it is really never more than about 300 miles away from Earth (that's it's orbital altitude) -- so it's never really very far away. In fact, it's so close to the Earth that the Earth is blocking much of the view at any given moment. So we have to observe each target only when we know it will be most visible. Most HST observing programs involve many consecutive orbits. But we may only be able to see the target for about 55 or 60 minutes of the 96 minute orbit because the Earth is in the way during the other 40 or so minutes.
However, if you imagine pointing at a target that is more towards the north or south, you can see that even though HST is spinning around the Earth, that target can be visible during the whole orbit (the Earth never gets in the way). We call these areas the "Continuous Viewing Zone", or "CVZ" for short.
You can see what I mean if you hold a globe right in front of your nose. Then look at some small object anywhere in the room (like a light switch or something on a table). Then start slowly moving around the globe (but stay close to it, and keep staring at the small object!). You'll notice that at some point you can't see the object because the globe is in the way. If you continue "orbiting" the globe, it will become visible again. Now try the same experiment again, but look at a spot on the ceiling. You'll notice that as you orbit the Earth, the spot on the ceiling is always visible -- the Earth never gets in the way! Most of the spots on the ceiling (or the floor) are in your CVZ.
We try to observe targets in the CVZ as much as possible because then we have almost twice as much time in each orbit to take pictures, etc.
There are many objects in HST's continuous viewing zones, including some very important objects that are studied very often by many astronomers, because they hold special clues about how our galaxy formed (and perhaps how other galaxies form).
One such CVZ object is a globular cluster called 47 Tuc. (pronounced "47 Tuck", which is just a name given to it in a catalog: object number 47 in the constellation Tucana, which means "Toucan" in Latin (a bird with an interesting beak.... you know about this is you eat Fruit Loops cereal for breakfast!). 47 Tuc is a collection of millions of stars that all formed together billions of years ago (probably around the same time that our Milky Way galaxy was forming), and remain clustered together today because they all exert a gravitational pull on each other, which holds in each star in the cluster. This cluster is in orbit around the center of our galaxy (as are all the stars in the Galaxy, including our Sun), so we can study individual stars in it try to learn exactly how old and far away the cluster is.
Another important CVZ target is the Large Magellanic Cloud, or "LMC" for short. This is a small galaxy that is in orbit around our much larger home galaxy (the Milky Way). People who live in the southern hemisphere can see it at night -- it looks like a fuzzy white patch in the night sky (that's obviously how it got it's name, but it is certainly NOT a cloud!). Astronomers are very interested in the LMC for many reasons: it is a nearby (and easy to observe) example of the type of small irregularly shaped galaxies that are seen all over the universe. It may also hold clues about how our Milky Way galaxy formed and got so big: did a bunch of smaller galaxies like the LMC collide to form the bigger galaxies? Will the LMC crash into our galaxy someday?
I have worked on several programs to observe these targets, and since they all use the CVZ, this means they must all occur at the same time. So that's why I had to work on so many programs all at once this week. It usually involves extra work to design them to use CVZ, but as you can see, it is well worth the effort.
Now I'm looking forward to going home and playing with my 5-month-old daughter all weekend.........she's a blast! I also have to finish fixing my roof because it has been leaking since the "blizzard of the century" that hit the east coast in January. I grew up in Wisconsin so I am used to big blizzards.... this last one was so big that it made me homesick!
Katherine Williams Southall
March 7, 1996:
Next time you go to the swimming pool (deep end), jump into the middle of the pool. Does your body sink or float to the top or stay somewhere in the middle? If you sink, you are negatively buoyant. If you float, you are positively buoyant. And if you are somewhere in the middle, you are neutrally buoyant.
So what does this have to do with the Hubble Space Telescope?
Here's my story.
I was underwater the first time that I came into contact with the Hubble Space Telescope in the early 90's. As a NASA employee in Huntsville, Alabama, I was currently working as a Space Station Freedom Project Office employee for Marshall Space Flight Center (MSFC). However, all certified divers at MSFC NASA could register at the Neutral Buoyancy Tank to do volunteer work in the Tank. All of these volunteers underwent a rigorous underwater test in order to enter the MSFC Tank that involved donning and doffing scuba diving equipment at the bottom of a pool that contained 1.32 million gallons of clear water as well as maintaining an up-to-date certification in first-aid and cardiopulmonary resuscitation and passing a rigorous physical examination.
On that particular day, I was assigned to take pictures of the HST Goddard Space Flight Center simulation using an underwater movie camera (position usually denoted as "the swim camera"). After the test, the video could be used to review the happenings of the day. Procedures, that would later be followed by the astronauts in space, could be corrected and equipment redesigned in order to enhance extravehicular activity (EVA). During the test, engineers, technicians, and other personnel monitored subjects from a control room which contained several consoles with small monitors and headsets connected to the communications network. These facilities allowed the test director, test conductor, safety, and other personnel to view the test and give instructions to the suited subjects and divers, observer, safety, utility, and photography.
Thus water in the tank was used as the medium for neutral buoyancy to simulate weight-lessness encountered in space. Underwater, the HST equipment that was tested was actually a structural mockup, built for tank environment and specifications. The suited subjects (participants wearing special underwater pressurized space suits that were neutrally buoyant) were able to perform critical EVA functions in preparation for the First Servicing Mission by using this mockup.
Remember the saying, "practice makes perfect". NASA Goddard Space Flight Center (in Greenbelt, Maryland where I now currently work in Operations preparing for the Second Servicing Mission), was using the neutral buoyancy tests as a tool to prepare for the upcoming First Servicing mission by having subjects practice in the simulated weightless environment. Two weeks of on-orbit servicing proved to be a brief interruption to scientific operations compared with having to return the HST to Earth which would have posed significantly greater risk of contamination or damage to the Telescope's delicate components. As a result, unmatched space data and pictures have resulted in increasing our knowledge of the Universe.
So, next time you go swimming (and you are neutrally buoyant as defined in the first paragraph), remember reading this journal and pretend that you are an Astronaut in Space getting ready to perform an EVA. Pick a task, preferably a short one since you'll be holding your breath, that would show you how different it is working in a weightless environment. Remember, you will be allowed to flip upside down while performing this task. Maybe attach small floats to a very heavy object that you would not be able to easily lift on the ground, like a watermelon, and practice moving it from one place to the next.
Who knows, maybe you'll be performing an EVA in space one day!
February 23, 1996
Well, my strategy worked pretty well except for one minor problem, I hadn't really finished the maps. Oh, it was pretty close to being done, and up until about 2 hours before my talk I thought it WAS done. But, as I mentioned in my previous journal entry, as a scientist I must always think about and question my results. Alan Stern and I were talking on the phone just before I was to give my talk. We were arguing about problems we'd seen in the maps because STScI was chasing after us to get final figures submitted for the upcoming press release (that's today as I write this). Alan had seen some things in the pictures I had last sent to STScI and he was already insisting that the pictures be redone. As we were arguing (in a nice way, really) about what to do, I had one of those sinking realizations of a mistake I had made in creating the maps. Simply put, if you rotate the Pluto image before extracting the map, you must also rotate the PSF by the same amount. If you don't, the answer is wrong. I knew in that instant that this was an error that couldn't be ignored and that all the work had to be redone. That's right, another 2 days of computer time but I still had a talk to give in just 2 hours.
The astute readers among you may have already recognized the name of the university where I was giving my talk. This is the present day home of Clyde Tombaugh, the discoverer of Pluto. Clyde normally attends the colloquia at the university but he was certainly making a special effort to come hear a talk about Pluto. Wouldn't you?
I was a little disappointed in having discovered another problem with the new map but that's just part of the scientific process of discovery. I have found it very rare to face a new result or discovery as if crossing through a door of understanding. It never happens that you suddenly know the answer.
Let me try to explain what really happens with a different analogy. Imagine, if you will, a field somewhere in the forest. I'd use the more traditional word, meadow, except it sounds too small. So, a field in forest. The forest stands for the entire field of study within Planetary Science. I spent all that time in school learning how to find and understand the trails within the forest. Now I'm out on my own trying to blaze new trails. These trails are paths of what we know and understand and lead to a variety of different meadows and fields in this great forest. Every once in a long while, you might discover something while wandering the trails but usually you don't get anywhere new until you break from the trail and head off into a new direction. That's what it's like to tackle a new project. You simply step off into the unknown and start thrashing around. Pretty soon, if you're lucky, you will come upon a field, a break in the trees. As you make you're way into the field you realize that something new and wonderful lies before you.
Do you think you're done now? No, not at all. At this point, you know you're onto something wonderful. You can tell from the color that there are some truly amazing flowers to be found here in the field and you now have the job of finding the best one! Finding that best flower is equivalent to having found the absolute best answer that explains your new discovery. Now imagine what's it's like to search for that best flower. First, you just wander around until you find your first flower, sometimes this first one is right there in front of you, sometimes not. Is this the best one? Well, it's always possible that the first flower (idea?) is the right one but usually not. But you'll take a careful look just the same and begin learning about these flowers. Of course, you need to look at more than just one to know what makes a good flower and a bad flower. That takes more examinations, flower by flower. Along the way you will learn something about how big a difference there is between good flowers and bad flowers. The longer you work on this problem, the more and more subtle the differences you begin to look for in search of the one perfect flower. The only truly fail-safe way to know you've found the perfect flower is to look at every flower in the field. If you indulge this concept this field might take the rest of your life (or more). Many times, it's the best we can do to just indicate areas within the field that one finds the better flowers. Even that much work is often enough to warrant telling everyone else of what you've found. In the meantime, you might continue looking for a better flower (answer?) while others are looking too.
That's a long-winded explanation of what it means to do research. Every day you try to learn more or come up with a better answer and many times you do. Each time you do, you get a little thrill out of seeing an answer that makes just a little bit more sense. After a while you stop getting better answers but you never quite know that there isn't one just a little better waiting to be found. Each new answer gets you closer to true understanding but you rarely recognize it when the instant of true understanding arrives. Instead, it's after much time has past and no one (including yourself) has found a better answer that you begin to realize that perhaps you had found the best answer.
Anyway, here it was just before my talk, in front of Pluto's discoverer, and I'd just learned that I didn't know as much as I thought I knew. I didn't let it bother me though. This happens all the time in research and as long as you let everyone know where the limits of your understanding are, you've still done a good job.
I always enjoy talking about Pluto, particularly when I get a chance to let people in on what I've learned. This particular talk was a once-in-a-lifetime treat that few ever get to experience. Here I was, talking about my favorite planet, in front of the man who found Pluto in the first place. Not only that, but I had an opportunity to thank him in person. I feel very fortunate to have had the chance to thank the person responsible for what has become my life's work. Not many people are this fortunate.
Oh, the talk went well and no one fussed that I didn't quite have the final answer. I was a little disappointed when there weren't many questions afterward. I always feel like I've failed when there are no questions. There is no such thing as complete knowledge and I love to excite the curiosity of an audience.
The saving grace for the afternoon was the presentation for Clyde Tombaugh after my talk. Reta Beebe brought in a bunch of elementary school kids to act as representatives for many of you participating in the LHST program. There were boxes and boxes of cards, a couple of hand painted T-shirts and a video with some kids singing happy birthday to Clyde (he turned 90 just a couple of weeks earlier). What I didn't know was that Reta would troop the kids in and sit them down to see my new Pluto maps. Reta asked me to show my video tape of the maps and I was only too happy to oblige. <10> I showed my new maps, explaining what we were seeing (you'll see them soon too). Then, to my surprise, I was flooded with questions! Why can't we see craters? What's the surface made of? I can't remember all of the questions, there were so many. I concluded with telling them about the mission to Pluto that NASA has been studying that could begin to answer all these questions in full detail. I think we all got caught up in the excitement and promise such a mission provides for the future. Let's hope that somehow we can all find a way to get there together.
Lynn Foster Bassford
[Editors note: I don't expect that many people will be able to fully follow the happenings below. But it may be interesting to see the special language that HST controllers communicate with]
March 5, 1996:
Our main responsibility is to watch & analyze Real Time telemetry from HST. Here are a few examples of some of the activities that a Shift Supervisor might do in parallel. (Note that the SI Flight Controller is watching the science and the DMS Flight controller is watch his data at the same time (it's like putting together a puzzle) as the Shift Supervisor is doing the following:)
19:20 (2:20pm) Staffing - Bassford On/Cooper Off Verified Ground System Computer Configuration 19:31 NSSC1 Load - Uplinked N28B9850L to Payload computer on HST (NASA Standard Spacecraft Computer=3DNSSC1). 19:44 NSSC1 Load - Completed. Science Instruments Flight Controller verified Command counter and successful transmit for a good load. 19:00 Forward Service to HST ended for this Event 19:50 Talked with Data Management Subsystem Engineer about a report for our next weeks schedule (called NEWRUL) that may have a few invalid data points. Need to use alternate report until NEWRUL has been fixed (for about 40min). 20:01 LOS - return service for this event completed ( we get our telemetry/data from a return service) 20:10 Gave briefing to STGT Controller for upcoming service 20:15 AOS - both the return and forward services for this event begin 20:18 Sent commands to HST & GCMR to STGT to begin tracking HST (Went Mode 1). 20:29 Sent commands to HST to complete tracking ('went Mode 2') 21:06 LOS for this event 21:07 Gave briefing to STGT Controller for upcoming service 21:07 AOS for this event 21:10 Answered questions from several SE's about current commanding configuration and our data base. 21:39 LOS 21:50 Gave briefing to STGT Controller for upcoming service 21:58 AOS 22:10 Received/logged/& photo-copied TDRS schedule changes from NCC for several times over next few days. 22:35 Sent commands to HST & GCMR to STGT to begin tracking HST (Went Mode 1). 22:47 Sent commands to HST to complete tracking (went Mode 2) 22:49 LOS for this event 23:05 Straightened out console documentation 23:10 Gave briefing to STGT Controller for upcoming service 23:13 AOS 23:29 LOS 23:35 Talked with Data Operations Control Center for initial requirements for setting up out Back up control center 23:47 Gave briefing to STGT Controller for upcoming service 23:52 AOS 00:00 Day change to GMT day 066. 00:20 Worked on construction a new rotating shift schedule 00:27 LOS 00:29 Gave briefing to STGT Controller for upcoming service 00:34 AOS 00:50 Continued work on new schedule 01:12 LOS 01:17 Gave briefing to STGT Controller for upcoming service 01:20 Answered questions from FC's about tomorrow Servicing Mission 2 Simulation. 01:23 AOS (for both our Return & Forward Services) 01:30 Talked with Mike Kohout about configuring our VDS (phone systems) to each Flight controller's needs for the Simulation. 01:40 Logged on to MVIP (terminal) to check out system for Simulation 02:10 Gave briefing to STGT Controller for upcoming service 02:16 LOS 02:17 AOS (both Return and Forward services begin) 02:20 Wrote up briefing for next shift's Shift Supervisor (my relief) 02:40 Verified validity of MVIP (terminal) brought into back up string for our back up command center. Set up back up system to match current Real Time string system. 02:49 Forward Service ends 02:55 LOS (return Service ends) 03:00 Tested back up system by sending a command through our line. 03:10 Started transferring Flight Controllers over to back up system at our back up commanding facility. We'll use our back up facility for the next day to run Real Time operations. Our normal facility (MOR) will be used to run tomorrow Servicing Mission 2 Simulation. 03:25 Shift Briefing given for next 20 min to my relief. At same time: 03:26 NSSC1 Load sent to HST's payload computer. 03:50 (10:50pm) 8 hour day completed. Time for me to go home while another Shift Supervisor's day begins.