Talk:Hubble Space Telescope
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Comments on "new look" article
- Looks great -- very impressed Rnt20 15:49, 5 Jun 2005 (UTC)
Older comments
compare: "Orbit period 100 min" (in the table on the right) and "...orbiting the Earth every 97 minutes." (in first sentence of Technical description).
97 or 100? Make up your midnd!
- It's 97, according to info found on http://hubble.nasa.gov
According to the article:Evidence of planets surrounding stars other than the Sun was obtained for the first time with Hubble. However, I think that this is wrong. I am pretty sure that the first exoplanets were discovered by ground-based telescopes rather than Hubble.
An event in this article is a April 24 selected anniversary (may be in HTML comment)
http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/07/ Should this be added to the article?
I believe the mirror diameter is 2.4m, which makes the collecting area 18m2.JamesHoadley 14:16, 2 Mar 2004 (UTC)
- Argh, yes you are right (well, I make it closer to 19 m2, but yes, whoever originally put that in got confused between the mirror and satellite diameters). I have now corrected this; thank you!! --Bth 14:27, 2 Mar 2004 (UTC)~
That was me, thanks. :) I must've misread the info in the article. However, I'd like to point out that if the diameter is 2.4, the radius is 1.2, and the area is <math>\pi R^2=4.3m^2<math>--zandperl 15:13, 2 Mar 2004 (UTC)
- Doh!Bth 16:14, 9 Mar 2004 (UTC)
LOL yes! JamesHoadley 15:38, 5 May 2004 (UTC)
If the HST loses height over time because of atmospheric drag, will it at the same time gain speed, since lower orbits require higher speeds? AxelBoldt
Yes Donald
The abberration in the mirror was not detected because the test equipment itself was not subject to rigorous calibration. 169.207.89.220 07:38, 2 Mar 2004 (UTC)
- I removed the sentence stating that it could have been detected "if sufficient funds were available" - this implies that more money would have solved the problem, which is incorrect. Tempshill 04:03, 3 Mar 2004 (UTC)
- I also added some language about the politics of HST
and how utterly incompetent the mirror mistake was. Roadrunner 08:58, 4 Mar 2004 (UTC)
In the words of Yoda: "There is...another." In this case, another space telescope mirror, constructed as a spare for the Hubble. I'm assuming that such a finely-tuned and expensive piece of optical equipment would not be destroyed, so can anyone tell me what if anything will be done with it? Lee M 01:28, 3 Mar 2004 (UTC)
- Both Hubble mirrors were made at the same time, but the "spare" was made correctly (without the aberration). Dozens of such mirrors are made for 2m-class telescopes every year, and even with the accurate polishing required for Hubble, a significant fraction of the manufacture cost is the low-expansion glass itself. Unless they can find someone who wants a mirror of exactly that size and focal length, I suspect they'll just melt it down and sell the glass. Rnt20 08:13, 23 May 2005 (UTC)
- Every day, the Hubble Space Telescope archives 3 to 5 gigabytes of data and delivers between 10 and 15 gigabytes to astronomers.
What does this mean? It sounds like it accumulates 3 to 5 gigs a day of pictures, slowly filling up some giant hard disk, just to look at once in a while when it gets lonely. Tempshill 04:03, 3 Mar 2004 (UTC)
- That is worth a whole article in itself. When the HST gets in range of a relay satellite, it starts transmitting the data to Earth via an elaborate system that existed before HST. 169.207.88.78 05:05, 3 Mar 2004 (UTC)
- I still don't understand. The current phrasing makes it sound like it archives data that it doesn't transmit, but presumably astronomers receive all data recorded by Hubble, right? Also, how can it archive gigabytes of data, when it was launched prior to thhe development of multi-gigabyte hard drives? --LostLeviathan 02:50, 18 Feb 2005 (UTC)
Corrected some information about the use of HST. Without adaptive optics you are never going to get more than 1-2 arcsec resolution regardless of where you put it. Also advances in telescope size are irrelevant for HST.
Also removed this sentence
- While NASA has long had a good relationship with the astronomy community, the agency's space-based astronomy programs have tended to operate on a parallel, independent track from ground-based astronomy efforts. Some observers believe that NASA and the National Science Foundation, which handles US government-funded ground-based astronomy, will soon be in discussions, and even that eventually both space and ground based astronomy will be directed under the same overall program.
I wouldn't call the relation between NASA and the astronomy community "good". They aren't horrible, but they can be strained at times. Also the "observers" who think that astronomy ought to be under one roof need to be identified. First of all, a lot of telescopes are privately funded. Second, most astronomers I know would *strongly* scream if this happened. The culture of NASA and NSF are way different. You are talking about different amounts of money. NSF grants practically require that you have outside sources of funding while NASA projects are generally expensive enough so that this is not an option. NASA is far more bureaucratic than NSF because it needs to be (i.e. bad things happen when rockets explode so NASA is much more risk averse than NSF). Also NASA projects require a large amount of internal involvement since NASA has its own staff for these things, whereas NSF doesn't. This means that NASA has a far more closed culture than NSF. Roadrunner 09:20, 4 Mar 2004 (UTC)
There is jargon in this page that should be expanded in plainer words to the general public (or linked to the proper articles when available). Example: "Gravity-gradient position". And about "307 nm orbit": not nanometers, I suppose? RodC 04:55, 5 Mar 2004 (UTC)
- Fixed those examples. Let me know if you want some other jargon expanded. Roadrunner 05:01, 5 Mar 2004 (UTC)
- Thanks. I think those were the conspicuous ones. It seems to me that NM, in capitals, would be the official abbreviation for nautical miles, right? (I much prefer not to abbreviate it, though) -- By the way, isn't it Wikipedia practice to use SI units in these cases? RodC
- You are correct, SI units are preferred. I have changed it in the text. Should the infobox number of 600 km be changed as well, or do we want to leave that number as is? I believe it is the originally specified height, not what the orbit has since degraded to. --zandperl 22:19, 5 Mar 2004 (UTC)
How to schedule an observation?
If somebody knows, could they add information about how scientists apply for a Hubble observation? Do they have to pay? Is it open to all nations? What do they have to submit and where, how long does the application process last, what are the criteria to decide who gets Hubble time? Thanks, AxelBoldt 11:00, 12 Aug 2004 (UTC)
- Ok, I found it. AxelBoldt 12:54, 12 Aug 2004 (UTC)
An external link
Hello, I propose to include this link in Hubble Space Telescope. It's my article from my site, which was republished on two other sites (Kuro5hin (http://www.kuro5hin.org/story/2005/1/22/13500/4359), code0range (http://www.code0range.net/node/1078)). My article is about the lack of budget for the fourth servicing mission and it includes an overview of the three past servicing missions, as well as an introduction to the telescope.
If you believe my article is informational, please feel free to use this link or change it as you like:
- The end of Hubble Space Telescope? (http://portal.wikinerds.org/node/183) - article by Wikinerds Portal on the lack of budget for the fourth servicing mission
Thanks, NSK 00:02, 29 Jan 2005 (UTC)
I added my link
I asked in the talk page and nobody objected me adding a link to my site. I asked in the mailing list and they told me to add my link if nobody objects in the talk page, and I waited more than a week. So I added my link now. NSK 06:00, 12 Feb 2005 (UTC)
As the HST and the NRO's KH-11/12 spy satillite use the same shipping container and Perkins-Elmer Corp. made at least 4 sets of mirrors plus the extreem cost of $2-3 billion. Does anyone else believe Perkins-Elmer ground the lens to the wrong tolerance? I think (due to compartmentation) that HST was built to the wrong focal length. Focused for looking 300 to 500 miles DOWN instead of out in space to infinity. Congressional Investigation anyone?
You seem to be misinformed, so I will add some facts: HST and KH-11 did not use the same shipping container. Perkin Elmer made one set of optics for HST, and contracted with Kodak for them to make one spare set. HST was built to the correct focal length, but with an error in the prescribed primary mirror conic constant. Taking images while looking downward is a physical impossibility for HST. Psi-phi-sage 01:43, 8 Jun 2005 (UTC)
- The story I heard (from someone at NASA) was that the dimensions, mass distribution, and other characteristics were sent to the company that makes the "crates" for holding satellites in place in the Space Shuttle, and the response on the telephone was "oh, so you're launching another KH-11 then?". The non-conspiracist explanation for why HST would be so similar, is that all the major mirror manufacturers, satellite bus / structure manufacturers etc had been competing previously for the KH-11 project, and so it was natural that all the preliminary designs they submitted for tenders of components for Hubble would just be "ripped-off" from very successful KH-11 designs.
- I have heard similar (non-attributiable) comments regarding the James Webb Space Telescope, which will have a primary mirror with a diameter of 6.5 metres that will unfold in space and so requires exceptional mechanical precision, micromotors, wavefront sensors, etc. Apparently, people who doubted the technical capability make it happen were told not to worry about it, the inference being that it had been done before by people looking the other way... -- ALoan (Talk) 15:30, 8 Jun 2005 (UTC)
Request for references
Hi, I am working to encourage implementation of the goals of the Wikipedia:Verifiability policy. Part of that is to make sure articles cite their sources. This is particularly important for featured articles, since they are a prominent part of Wikipedia. Further reading is not the same thing as proper references. Further reading could list works about the topic that were not ever consulted by the page authors. If some of the works listed in the further reading section were used to add or check material in the article, please list them in a references section instead. The Fact and Reference Check Project has more information. Thank you, and please leave me a message (http://en.wikipedia.org/w/wiki.phtml?title=User_talk:Taxman&action=edit§ion=new) when a few references have been added to the article. - Taxman 19:13, Apr 22, 2005 (UTC)
Servicing mission 4.
The article currently states:
- Servicing Mission 4, planned for February 2005, was due to be the last servicing mission...
Unfortunately this doesn't make it clear wheather or not the servicing mission actually went ahead (or has been delayed, or cancelled). I feel that clarification on this matter (now dated in the past) would benefit the article.
--PJF (talk) 14:49, 24 Apr 2005 (UTC)
infobox/table
beatiful. could do without the border though. otherwise quite nice.
Proposed re-write
With apologies to those who have worked on this article, I recently nominated it on WP:FARC and it is now no longer a featured article. I think there's a lot of excellent content here, but my main worry was comprehensiveness. I'd love to see this back up to featured status, and I'm thinking about starting to re-write a lot of the article. I think we would need the following sections:
- Conception, design and aims
- A huge amount could be said about the lengthy planning stages, which lasted almost two decades, and the development of the specifications to which the telescope was built
- Construction and engineering
- How the telescope was built to withstand the rigours of the space environent
- Original instrumentation
- About the original instruments on the telescope when it was launched - probably summaries of relevant main articles
- Flawed mirror
- This could probably be an article in itself! How the fault arose, how it was identified and how it was resolved
- Servicing missions and new instruments
- In particular, the COSTAR optics to correct the mirror defect, and the replacement of old instruments for new at subsequent servicing missions.
- NB COSTAR was just an upgrade for the FOC and spectrographs -- the other instruments do not use COSTAR -- see e.g. http://www.spacetelescope.org/about/general/instruments/costar.html
- Scientific results
- Summary of some of the most significant discoveries: refining the Hubble constant, Hubble Deep Field, etc; overall impact of the telescope on research.
- Using the telescope
- Application process for telescope time, oversubscription ratio, director's discretionary time, early dedication of small amount of time to amateur observations
- Archival data
- Data is propreitory for one year and is then released publicly.
- Outreach activities
- Hubble Heritage Project, huge amount of publicity each time spectacular image produced, great boon for astronomy.
- The future
- Debate over whether to run one final servicing mission, proposals to retrieve the telescope for display in a museum, plans for the next generation space telescope.
What does anyone think about this? Many sections would be adequately filled by current content, but others would need some work. Would an article along these lines be comprehensive? Worldtraveller 14:36, 16 May 2005 (UTC)
- I think this is a good idea. Looking at recent Featured Articles shows how this one is not up to that standard. I'd like to help get it back to FA status. (P.S. Newbie here, so be nice. ;-)) Longshot 05:59, 23 May 2005 (UTC)
- I think you should include something about how the priorities of astronomers have changed. When Hubble was proposed in the 1950s and 60s it was assumed that what astronomers would want was an ultra-sensitive visible light telescope. Since the mid 1980s astronomers have been switching from visible light to the infrared (and sub-mm) in increasing numbers, as much more distant (and generally more interesting) sources can be observed in the infra-red, and these are generally not detectable in the visible. This is shown by the biggest current telescope developments -- JWST, Spitzer and ALMA (which cover infrared - submm, and all of which dwarf Hubble in capabilities and scope!). Rnt20 14:16, 30 May 2005 (UTC)
- Definitely good thing to include - possibly could fit into section on the future (which would need to mention the NGST of course)? Worldtraveller 00:05, 31 May 2005 (UTC)
- I think you should include something about how the priorities of astronomers have changed. When Hubble was proposed in the 1950s and 60s it was assumed that what astronomers would want was an ultra-sensitive visible light telescope. Since the mid 1980s astronomers have been switching from visible light to the infrared (and sub-mm) in increasing numbers, as much more distant (and generally more interesting) sources can be observed in the infra-red, and these are generally not detectable in the visible. This is shown by the biggest current telescope developments -- JWST, Spitzer and ALMA (which cover infrared - submm, and all of which dwarf Hubble in capabilities and scope!). Rnt20 14:16, 30 May 2005 (UTC)
Advantages of being outside the atmosphere
I have removed this sentence from the intro:
- A common misconception is that the principal benefit of observations from orbit is high-resolution -- in fact the sensitivity to faint objects is the biggest advantage, and ground-based interferometric observations of bright sources have much higher resolution than HST. Ground-based telescopes cannot observe faint targets at visible wavelengths because of the effects of atmospheric airglow.
The misconception is really the other way around. Hubble's mirror is small by telescope standards at 2.4m in diameter. The Keck telescopes have mirrors 10m in diameter, giving them both over 16 times the light-gathering power that Hubble has - airglow doesn't outweigh that advantage. At the time Hubble was launched adaptive optics was still years away from being useful, and the huge advantage of a space observatory was that it could achieve a resolution ten times better than ground-based observatories were able to. Nowadays, that's less true, and ground-based resolution can approach that of a space observatory. Interferometry can't give you actual images with <0.1 arcsecond resolution, whereas Hubble can, and that's still its main advantage. Worldtraveller 00:05, 31 May 2005 (UTC)
- Some of these comments contradict parts of the article. Just a few of my own comments about this:
- Airglow limits Keck visible imaging to observations of targets typically brighter than about V~28 (see e.g. text and examples at Airglow#How_to_calculate_the_effects_of_airglow, and table at Apparent magnitude). This is similar to the 8m VLT telescopes, where according to e.g the FORS exposure time calculator (http://www.eso.org/observing/etc/bin/gen/form?INS.NAME=FORS1++INS.MODE=imaging) you need 40 hours of observing time to reach V=28 under the darkest conditions, while Hubble only takes 4 hours for a point source according to the ACS exposure time calculator (http://apt.stsci.edu/webetc/acs/acs_img_etc.jsp) (under the darkest realistic conditions). The ground-based observations are completely dominated by sky background (airglow) which does not effect Hubble (although I guess there is still Zodaical light -- the airglow is 200 times brighter per arcsecond than V=28, and remember that there is no adaptive optics in the visible at large telescopes, so you get almost a square arcsecond worth of airglow per PSF). Hubble can (and does) go much fainter than this, although I guess that is with longer observations -- that's why as it says in the Hubble article "The Hubble Ultra Deep Field (http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/07/), the 'deepest portrait of the visible universe ever achieved by humankind'". Of course airglow has much less effect on spectroscopy (you look between the airglow lines), so this is usually done from the ground (as are infrared observations, as these are better done from the ground -- that's one reason why 8m telescopes do most of the spectroscopy and imaging in the infrared and Hubble works mostly on visible imaging).
- As discussed in the Hubble article "optical imaging observations of bright sources using speckle interferometry or optical interferometry in the 1980s had far higher resolution than Hubble ever achieved" (and certainly better resolution than 0.1" -- many of the sources imaged were less than 0.05" in diameter!). Example images can be seen at http://www.mrao.cam.ac.uk/telescopes/coast/betel.html -- these have far higher resolution than Hubble. This method was developed long before Hubble was launched, but is limited to bright sources.
- Note that one of the most successful adaptive optics system is at the CFHT, and this started operating in the mid-1990s.
- Hope this information is useful for the new Hubble article :-) . Rnt20 06:27, 31 May 2005 (UTC)
Hm, well I've never liked exposure time calculators, many seem to be designed for instrumentation specialists rather than observational astronomers, and they seem to be biased in favour of stellar rather than nebular observations as well. But I found this page: http://www.eso.org/paranal/sv/svhdfs.html, which says that the VLT can reach Vmag=28 in a three hour exposure. Anyway, this kind of discussion should certainly be mentioned in the article, I know a lot of questions have been asked about whether it's wise to spend 10 times as much on a space telescope as you need to spend for state of the art AO on the ground. I've started a re-draft of the article at Hubble Space Telescope/temp, based on the section headings I suggested above. Worldtraveller 11:50, 2 Jun 2005 (UTC)
Units
The article mentions: a circle 0.1" in diameter
I changed this to: a circle 0.1 in (2.5 mm) in diameter
It was reverted. Is there a particular reason for removing metric units? Bobblewik (talk) 11:29, 20 Jun 2005 (UTC)
- The " is not in this case a symbol representing inches but one representing arcseconds, an angular measure. For the avoidance of this ambiguity, we could replace the " with arcsec, but providing a centimetre conversion is definitely wrong! Worldtraveller 13:05, 20 Jun 2005 (UTC)
- Aha. That explains it. I had completely misunderstood what the text was trying to communicate. Thanks. I support your suggestion to say 'arcsec' in parallel with the suggestion that we should try to use 'in' for inches. I wonder if we should mention this issue at Arcsecond and Inch? Bobblewik (talk) 14:50, 20 Jun 2005 (UTC)
- The use of " comes from the angles - ° ' " - although I wonder if feet and inches simply copied the last two - yards are something different (a superscript cross, IIRC). There is a (probably archaic now) form of of symbol for arcmin (usually ') and arcsec (usually ") with a bracket "(" rotated 90 degrees over the top of the ' or " to denote the "arc" - minutes of arc / seconds of arc, you see. -- ALoan (Talk) 15:39, 20 Jun 2005 (UTC)
- It is amazing what you learn. I did know about the symbols ° ' " and what they represent in terms of angle. I had heard the term 'arcsecond' but was never sure of what it was. It certainly seems better to call it an 'arcsecond' than a merely a 'second'. The rotated "(" to represent the arc is complete news to me and is delightful to learn about.