This website is kept for archival purposes only and is no longer updated.
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| ||||| Sunday, March 03, 2002 - 09:47 am why does the orbit have to be so far south of the states.i would like to look at it through my telescope,but i think it is to far south of alabama.or maybe iam not looking in the right direction. nice pictures from hubble. thanks | |
| ||||| Sunday, March 03, 2002 - 10:39 am The inclination of HST's orbit is equal to the latitude of Kennedy Space Center. That means at its northernmost, HST passes over that latitude. The reason for this is that, from Kennedy, that's the orbit that takes the least fuel to reach. Using less fuel means you can put more stuff in the payload bay. So if you're within 6-8 degrees or so of that latitude, you probably have a chance. Of course, the other problem with spotting satellites is that you have to catch them when a) they pass over you, which in this case means HST reaches the northernmost part of the orbit when you happen to be more or less underneath, and b) it's near sunrise or sunset, so the satellite is illuminated by the sun but the sky is still dark. | |
| ||||| Sunday, March 03, 2002 - 12:26 pm I guess I'm really lucky these days as I can see the HST and the shuttle each morning before I go to work--before 6AM local time here in Dubai, United Arab Emirates. Will be out again tomorrow morn. | |
| ||||| Sunday, March 03, 2002 - 12:39 pm I just noticed that if you click on "Mission Updates" and then "Where is Hubble?" (on the left sidebar), you get an applet that will tell you when HST will next be viewable from your location. Just put the mouse over your location on the map, and press and hold the button -- the time of next passage appears in the lower right corner. | |
| ||||| Monday, March 04, 2002 - 08:00 am I'd like to know how exactly the Columbia 'closes in' on the Hubble. I guess it cannot be direct firing of thrusters towards the HST. Are we increasing the angular velocity, so that the Shuttle's parking orbit increases its altitude from the earth, with the firing, and gets to orbit of the HST? One more thing, shouldn't the Shuttle's and the HST's ground tracks match? | |
| ||||| Monday, March 04, 2002 - 11:19 am Hello. My name is Kevin Dibble. I am 13. I am in my science class with Mr.Caya. We are studying your shuttle and the crew. You people. I would really like to hear back from you & if you could send some space things like things about being an astronaut. My older brother & I have always been interested in space!!! Please write back and send pictures & info. My email is rdibble05@juno.com. I would love to meet youbut that wont happen. Good-Bye and thank you for your time. | |
| ||||| Monday, March 04, 2002 - 11:37 am Hi, my name is Sarah. In science we are starting to study things about space. I was wondering if you could tell me what time you got to the Hubble? | |
| ||||| Monday, March 04, 2002 - 11:42 am Hi I am becca. I love space . We are studying space in school I go to school with spangage. She is really smart. We learned a lot so far. I love this site. | |
| ||||| Monday, March 04, 2002 - 12:08 pm Have you guys seen any allians? | |
| ||||| Monday, March 04, 2002 - 12:12 pm Sent the hubble to Wisconsin | |
| ||||| Monday, March 04, 2002 - 12:13 pm im gonaa shoot the hubble down!! | |
| ||||| Monday, March 04, 2002 - 12:14 pm curtis are u there yet? | |
| ||||| Monday, March 04, 2002 - 12:14 pm Yep | |
| ||||| Monday, March 04, 2002 - 12:14 pm what would you do if the Hubble hit the moon? | |
| ||||| Monday, March 04, 2002 - 12:16 pm hi justin | |
| ||||| Monday, March 04, 2002 - 12:16 pm Hey Guy's | |
| ||||| Monday, March 04, 2002 - 12:25 pm Let me try to answer a few of these. We got to the Hubble early Sunday morning, about 4:00 am. We have not seen any aliens. We might send it to Wisconsin when we bring it back from space, in about 8 years. Please don't shoot the Hubble down, it's real handy to have up there and it's impossible to get a new one. If the Hubble hit the moon we would be very bummed, but also surprised since Hubble never gets closer than about 250,000 miles to the moon. If you want to send a message to the astronauts, go to this page. | |
| ||||| Tuesday, March 05, 2002 - 10:08 am How does the HST maintain precise attitude in orbit in order to take it's high resolution images. A landbased telescope has to rotate in sync with the earths rotation. The HST has it's own orbit, so it is in motion relative to the astronomical object it's viewing. How does it compensate for that motion? TX, Mike | |
| ||||| Tuesday, March 05, 2002 - 10:53 am Why was powering down Hubble such an issue? Is there a chance that the restart will fail, why? | |
| ||||| Tuesday, March 05, 2002 - 10:55 am HST has an amazingly complicated attitude control system. To hold pointing during an observation, HST uses the Fine Guidance Sensors (FGS). There are three FGSs, and each one is given a relatively bright star (from the HST Guide Star Catalog) to look at, and its job is to report to the servo system if it moves, to an accuracy of about 0.001 arcsec. The servo system (which I guess is correctly called the Pointing Control System) then uses a combination of the reaction wheels (RWAs, one of which was replaced today) and magnetic torquers to respond, to keep those guide stars in place. The FGSs view these stars through the telescope, so if what they see is kept stationary, then what the science instruments see is also stationary. There's more to the pointing control system, parts that are used for guiding the telescope from one field to another, and parts that are used for coarse acquisition (to get the FGSs onto their targets), and parts that are used in emergency backup modes. But since you were asking about taking images, I'll spare you all that. | |
| ||||| Tuesday, March 05, 2002 - 11:11 am About powering down, I know that people don't usually sweat it about turning off a piece of equipment to work on it. There's two things that make this more of an issue for a satellite. The first is that turning power on and off is generally stressful for any piece of equipment. Not very stressful, but things are slightly more likely to break then than at other times. With a piece of equipment in your office, this is no big deal because you get it fixed or buy or borrow a replacement. But if something breaks on Hubble, there won't likely be a replacement right there on the shuttle. The second issue is that satellites have a bigger problem with thermal control than things on Earth. This is because of the absence of air, which on Earth acts as a moderating influence on the temperature of most things. In space you're stuck between the sun at a few thousand degrees, the Earth at, well, check the weather report, and deep space which is pretty close to absolute zero. The solution to this thermal problem revolves around shiny stuff to keep the sun off, thermal radiators to keep you cool, and heaters to keep you warm. While the power is off, we won't have those heaters, and we won't have any telemetry to tell us what the temperatures are. A lot of careful planning has gone into this part, to make sure we don't exceed our thermal limits. | |
| ||||| Tuesday, March 05, 2002 - 11:16 am I would like to comment on a point raised by Pradeep Johnson on March 04. He asked if the orbiter closes in on HST by increasing its angular velocity to raise its altitude to that of the HST. Orbital kinematics are a bit strange, unless you look a little into what makes things happen to orbiting bodies. Objects in orbit at higher altitudes not only have lower angular velocities, they also have lower tangential velocities. Because of the laws of motion, if the orbiter does a burn as if to push it faster in the direction it's traveling, it will rise to a higher orbital altitude and thus end up at a lower speed than it had before the burn! Weird, huh? Think of that "burn in the forward direction" giving the orbiter more total energy. In orbital mechanics that raises altitude while lowering speed. It's as if you stepped on the gas in your car and slowed down but found yourself traveling at a higher altitude above ground. For you high school and college physics students out there, you can see what's happening if you set two equations equal to each other. One is the equation for the law of universal gravitation, F=GMm/r2 and the other is the equation for centripetal motion, F=mv2/r where M is the mass of the Earth and m is the mass of the orbiter. Then, m drops out. You can use some simple algebra from here to solve for v and you will see that as r gets larger, v gets smaller. This also shows you why a 50 kg astronaut orbits the Earth at the same speed as the 25 000 kg orbiter he or she is "riding" in. So, to drive the orbiter, step on the "go forward faster" pedal to go higher and slower! J.R. Frysinger, CAMS Dept. of Physics and Astronomy College of Charleston Charleston, SC 29424 http://www.cofc.edu/~frysingj | |
| ||||| Tuesday, March 05, 2002 - 11:28 am My orbit is around this site Hi spangage | |
| ||||| Tuesday, March 05, 2002 - 11:29 am Hi. My name is Sarah. I used to be really interested in astronomy. I was wondering, where would you go if you wanted to be an astronomer or an astronaut, like who would you talk to? | |
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| ||||| Tuesday, March 05, 2002 - 11:35 am This message is for Digger. Meeting you in California during the Electric APU program for the Space Shuttle Upgrades effort was an incredible experience for this Iowa farmboy! At that time you had yet to be assigned a mission. And what a mission you are now undertaking! This must be an incredible experience for an F-16 pilot to now be in command of Columbia! We at Hamilton Sundstrand are very proud of the various equipment we provide for the space program. We all hope for complete mission success and a safe flight back home! GOD BLESS AMERICA AND THE CREW OF COLUMBIA! | |
| ||||| Tuesday, March 05, 2002 - 11:53 am Hi again, Digger! My last e-mail to you had an error in the address. Please send any mail to the correct address attached to this message! Thanks and "GO HUBBLE"!!! | |
| ||||| Tuesday, March 05, 2002 - 01:03 pm Greatings from West-Germany... Hope all is good in the Air. Best wishes to you. | |
| ||||| Tuesday, March 05, 2002 - 01:20 pm This is for Sarah -- to become an astronomer, the first thing you want to do is study hard in your science and math classes. Especially physics. And see if there's an astronomy club in your area that you could join. After that, most astronomers studied physics or astronomy in college, and then go to graduate school. These things would also be a good start to become an astronaut. To find out more about this, take a look at the Human Space Flight web site. | |
| ||||| Tuesday, March 05, 2002 - 01:32 pm 3/5/02 We hear obout the ISS beiing boosted to correct for orbit decay usually during an ISS servicing mission. Does this HST service mission provide any orbital boosting or readjustment to the Hubble or does it's orbit keep it far enouogh out of any atmospheric drag? Thanks in advance for answering and I hope the rest of the mission is as successful as it's been so far!! | |
| ||||| Tuesday, March 05, 2002 - 02:02 pm Yes, often HST servicing missions include an orbit boost. The exact amount of the reboost is based on a number of factors not the least of which is how much fuel the orbiter has left. A curious balance also arises in that you do not want to boost it so high that you can't reach it on the next servicing mission. | |
| ||||| Tuesday, March 05, 2002 - 02:14 pm Yes HST's orbit needs to be reboosted regularly like any spacecraft in Low Earth Orbit. From my recollections, the reboost needed was minimal on the previous mission in '99 as orbital decay was less than expected. | |
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