Talk:Hubble Space Telescope

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[edit] Comments on "new look" article

  • Looks great -- very impressed Rnt20 15:49, 5 Jun 2005 (UTC)

[edit] 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 πR2 = 4.3m2--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)
Absolutely not. The backup mirror is on permenant display at the Smithsonian. http://www.sciencedaily.com/releases/2001/10/011004070109.htm -- NeilFraser 06:52, 15 February 2006 (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)
It used a 1.2 gigabit tape drive originally. http://www.shuttlepresskit.com/sts-103/payload52.htm -- NeilFraser 06:52, 15 February 2006 (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)

[edit] 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)

[edit] 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, code0range). 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:

Thanks, NSK 00:02, 29 Jan 2005 (UTC)

.

[edit] 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)

[edit] 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 when a few references have been added to the article. - Taxman 19:13, Apr 22, 2005 (UTC)

[edit] 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)

[edit] infobox/table

beatiful. could do without the border though. otherwise quite nice.

[edit] 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:

  1. 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
  2. Construction and engineering
    How the telescope was built to withstand the rigours of the space environent
  3. Original instrumentation
    About the original instruments on the telescope when it was launched - probably summaries of relevant main articles
  4. Flawed mirror
    This could probably be an article in itself! How the fault arose, how it was identified and how it was resolved
  5. 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
  1. 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.
  2. Using the telescope
    Application process for telescope time, oversubscription ratio, director's discretionary time, early dedication of small amount of time to amateur observations
  3. Archival data
    Data is propreitory for one year and is then released publicly.
  4. Outreach activities
    Hubble Heritage Project, huge amount of publicity each time spectacular image produced, great boon for astronomy.
  5. 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)

[edit] 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:
  1. 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 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 (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).
  2. 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.
  3. 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)

I am the software project manager for the Hubble exposure time calculators for ACS, STIS and NICMOS (and coming soon COS and WFC3). I would happily entertain feedback from observational astronomers. I will also be happy to answer any questions that anyone has about the Hubble ETC or the instruments that it supports. Dfmclean 03:02, 21 March 2007 (UTC)

[edit] 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.
The use of these symbols for feet and inches are probably an inheritence as you suggest. Alternatively, it could be convergent evolution. In any domain, it must be tempting and convenient to represent common units by a simple mark. Bobblewik  (talk) 16:02, 20 Jun 2005 (UTC)


Oh, and foot, arcmin, arcsec and inch refer you to prime or double prime as appropriate. -- ALoan (Talk) 15:45, 20 Jun 2005 (UTC)
So they not only have a different name, but in some fonts they might look slightly different. Interesting. Bobblewik  (talk) 16:02, 20 Jun 2005 (UTC)
Just to confuse things even more, ° ' and " are also distances on the Earth, with ' corresponding to one nautical mile (one arcminute around the circumference of the Earth)! Rnt20 08:08, 31 January 2006 (UTC)

[edit] Low Earth Orbit

I checked the article--maybe I just didn't see it--but what's the deal with the Hubble's low earth oribt? It seems so dumb to keep it so low (orbit decay, occult). I'd like to see a clear explanation set aside as to why it's kept there. Keep on wikin'. --Atlastawake 18:56, 4 October 2005 (UTC)

Good question - I've added a brief answer under 'scheduling observations' - basically it's in that orbit so the Space Shuttle can reach it for servicing missions. The advantages of being able to repair it outweigh the disadvantages of decay (can boost its orbit at each servicing mission) and occultation (makes scheduling a bit awkward but in the end doesn't reduce the actual efficiency of the telescope at all). Worldtraveller 19:33, 4 October 2005 (UTC)

Sweetness. Thank you.--Atlastawake 00:50, 6 October 2005 (UTC)

NB I think occultation does decrease Hubble's efficiency quite a bit, as Hubble cannot rotate quickly enough to make use of the time when Earth is occulting its primary targets. I understand that this was a driving force for avoiding occultation with later orbiting observatories. Rnt20 08:05, 31 January 2006 (UTC)

[edit] Focal length?

I know the Hubble's length is 13,2 metres long and it's said its focal length is nearly 58 metres. How can this be if the focal length is nearly two times the distance between primary mirror and secondary mirror? Doesn't that give the maximum focal length of 26 metres (ignoring that the secondary mirror isn't at the very front of the telescope)? --83.171.160.254 23:25, 14 November 2005 (UTC)

The Cassegrain Reflector layout of its optical system gives it a long effective focal length. The secondary mirror defocuses the light from the primary, which probably has a focal length of around 5 metres. -- JamesHoadley 00:02, 15 November 2005 (UTC)

[edit] How many megapixels....

Can the Hubble Space Telescope capture?

It is not a survey telescope, so it does not have many Megapixels (it is primarly designed to look at small very faint objects in visible light). The black and white CCD cameras used in ACS are described at http://www.stsci.edu/hst/acs/documents/handbooks/cycle15/c03_intro_acs4.html#347765

[edit] Was the flawed mirror good for observing earth?

I wonder if the focal length of the mirror was made to be optically suitable for observing earth? If PE was also making mirrors for spy satellites, that could explain why they had optical devices that were wrong for the Hubble and why no one caught the error--they were used to expecting mirrors to be like that.

I realize that an investigation found that a particular mechanical problem with a particular optical instrument, combined with management malfeasance caused the flaw. However, suppose you imagine that the mirror was correctly made for observing the earth, perhaps at a single wavelength. Would that make sense?

(Optics is not my field, so this is a naieve question.)

This is an old conspiracy theory, and not really plausible. The mirror was incorrectly ground because of a mechanical fault in the machinery used. It would have been no better for observing the earth than it was for observing the sky. In any case, optically speaking a few hundred miles is more or less infinity anyway, so in any case I don't think you'd need a differently figured mirror to observe the earth as opposed to the stars. Worldtraveller 18:27, 30 December 2005 (UTC)
Indeed, for a 2.4m telescope a few hundred miles would be just about in the far field, with only a tiny change in the mirror shape for optimum focussing, much less than the big aberration that Hubble had. Rnt20 14:07, 31 December 2005 (UTC)

[edit] Why not bring the HST back to earth?

Apparently, since no one is talking about doing so, bringing the HST back to earth to be refurbished or to salvage the mirror is not the right thing to do. It seems like this would be a relatively simple robotic mission.

Could someone with knowledge of why this is not an option add that information to the article?

Thanks. I'll be watching for the answer. (apparently Jan 14 07:05 User:Rocky143)

Dude, first you've got to sign you comments with ~~~~!
I think the HST only has historical importance now. The mirror is precise, and probably still the most precise optical mirror in existence, but it doesn't have any particular use on Earth because it would sag under gravity. And to bring it back to earth would not be that simple, because it would have to survive reentry, so it would have to go inside a big reentry vehicle. In fact there was a plan IIRC to bring it back with the Space Shuttle, to be put in a museum, but there are any number of reasons why this won't happen now (it's basically a waste of money, and for shuttle safety reasons). So there are no real reasons to bring it back, except for sentimental ones. Personally I think it should be put into a ~5000km parking orbit, for future retrieval, rather than just trashing it. It would be more expensive and dangerous than de-orbit, but only slightly more so on both accounts. --JamesHoadley 05:32, 14 January 2006 (UTC)


Indeed -- there is nothing of value on Hubble except as museum pieces (actually there are plenty of mirrors which are more accuarate than Hubble's mirror). Rnt20 07:58, 31 January 2006 (UTC)

I prefer the parking orbit option myself. However, I have not gotten any information from the experts at http://uplink.space.com as to how big of a booster would have to be sent up. However, that booster could be added as part of the next servicing mission. We do not need a second mission for that. Any second mission might as well bring it back then. Actually, I was hoping the parking orbit would be higher. GEO satellites orbit at something like 24,000 miles up. Will 03:52, 16 September 2006 (UTC)

[edit] Irony

When it was conceived, the unique feature of Hubble was expected to be its resolution. With the development of new detector technologies and new imaging techniques, certain types of ground-based imaging already had higher resolution than Hubble before it was launched, and the sensitivity of conventional ground-based had reached the limits of atmospheric airglow, so the really unique feature of Hubble ended up being its visible-light sensitivity and not its resolution. Rnt20 08:01, 31 January 2006 (UTC)

How about the "ground breaking" observations from Hubble. Ironic given how far Hubble is from the ground. Stephen B Streater 20:33, 24 April 2006 (UTC)

[edit] servicing mission

It seems that NASA under Michael Griffen are planning a Hubble servicing mission with one of the few flights left pre retirement in 2010. Info about the rest of the 2006 FY budget here: http://www.spacedaily.com/reports/NASA_Postpones_Or_Kills_Several_Major_Projects.html

The relevant paragraph being:

"NASA affirmed its budget includes full funding for a space shuttle servicing mission to the Hubble Space Telescope, probably in late 2008 or early 2009 - although that still depends on whether the agency can solve the existing problems with the orbiter and certify it ready for safe return to flight. I suspect that the main article should be modified to acknowedge this"

I've updated the article. JamesHoadley 14:19, 8 February 2006 (UTC)

[edit] Comparison with KH-11 Kennan or KH-12 Crystal satellites

The text:

Hubble's spacecraft overall size, shape and design is believed to be very similar to (if not directly borrowed from) the large American spy satellites, specifically the KH-11 Kennan or KH-12 Crystal series [1] [2] [3]. was removed by Worldtraveller at 23:59, 15 February 2006. Now I don't know any relevant written sources offhand, but this is a very commonly discussed point in the astronomy and aerospace communities. The non-conspiracy theory explanation for this is that when the Hubble team put out bids for all the components (mirrors, spacecraft bus etc) the cheapest options were always those which were already being mass-produced for the KeyHole (KH) satellites, so that Hubble ended up being almost identical to a KeyHole satellite, but not by design. Rnt20 07:15, 16 February 2006 (UTC)

I removed the text because the links really didn't support the claim. They just pointed out that the two satellites look similar, and you'd have to say there are loads of satellites that look similar without being built by the same people or based on each other. If there is a reputable source that suggests this, that would be great, but I don't think it's very good to just repeat speculation. Worldtraveller 09:49, 16 February 2006 (UTC)
Would it not be worth adding a comment that they all have (or are thought to have) a primary mirror of a similar size, and it is rumoured that their overall size, shape and design is believed to be quite similar (they are, after all, all 2.3/2.4 metre space telescopes, so they all ought to be pretty similar). KH-11 currently says "NASA's Hubble Space Telescope is rumored to be a derivative of the KH-11, though with different instrumentation, sensitivity levels, and a vastly different focal range. The two were supposedly transported in the same shipping container, lending credence to the speculation." and KH-12 says "Like the KH-11 (Crystal), the KH-12 is believed to use a large mirror to capture light, and probably resembles the Hubble Space Telescope (HST) in size and shape." (although it also says that the primary could be up to 4m, which seems rather unlikely to me). At the very least, we ought to mention rumours that they are all similar. -- ALoan (Talk) 11:13, 16 February 2006 (UTC)
So the question is, is this because of convergent evolution, or was there some kind of technological hand-off, possibly with the caveat that "serial numbers be filed off"? Urhixidur 03:31, 22 February 2006 (UTC)

It is my understanding that the KH-12 is a radar sat called LaCrosse.--Will 05:10, 10 August 2006 (UTC)

The Hubble Wars destroys this spy satellite comparison. It was written by a scientist on the team who writes all about the conflicts between the science and engineering groups. He specifically bemoans the CIA/NSA not sharing their knowledge with the engineers, one of the worst flaws being Hubble's thick solar wing structures, which expand a lot more when moving into daylight than the spy satellites' solar wings, which are much thinner. The thicker wings cause a lot of vibration which destroys Hubble's ability to take photos for a while each time it passes into light. Tempshill 06:23, 1 September 2006 (UTC)

The Hubble Wars though did provide its own links to the spy satellites. However, a lot of the differences appear to have been "Not Invented Here". One thing that was kept was the encrypted TRDS satellite system. This drove up the cost compared to communicating with standard communication satellites. I doubt that encryption was a high priority for astronomers. Will 03:57, 16 September 2006 (UTC)

[edit] Vandal

Someone is Vanilizing alot and I suspect the IP adress is chaning becose Edits on one IP start where other stops

[4]    
[5]
[6]
[7]

E-Bod 01:31, 23 March 2006 (UTC)

[edit] Why so sucky?

Why do Hubble's gyros suck so much? This seems to be the major reason for the constant repair missions. Other spacecraft built during the same time have had thier gyros working for decades. If Hubble's are so crappy why don't they just replace them with something like the ring laser gyros on Cassini that don't have any moving parts?--Deglr6328 19:18, 3 July 2006 (UTC)

It's simple. Hubble's are more actively used than any other mission in existance. Gyros are used to re-position, to which Hubble does constantly. Other missions simple point themselves at earth, and only move a very little bit to keep pointing that way. Tuvas 22:13, 3 July 2006 (UTC)
Are you sure? I believe you are referring to the reaction wheels while I am talking merely about the attitude rate change sensors (gyros). All the gyros have to do is sit and spin at a constant rate and use thier internal sensors to "feel" a squish in a particular direction as a result of gyroscopic forces when hubble turns. My question is why do the keep replacing them with the same crap mechanical gyros when others like Cassini use extremely robust hemispherical resonator laser-gyros [8]?--Deglr6328 23:13, 3 July 2006 (UTC)
I always mix up reaction wheels and gyros... Grrr. Anyways, the enviroment of Hubble is really alot harsher than Cassini, there's the rotational factor arount the Earth, as well as the night/day factors, which dramatically change the heat of the spacecraft. LEO is a scary place really. I'm sure they have the best gyros that they can have, but for Hubble, they have to be extremely precise. Do you think NASA would spend billions on such a mission, and become a cheap skate at some small factor as the gyros? Also, it's remotely possible that Hubble pre-dates laser gyros, it was build in the late 80's and early 90's. Whatever the reason, it just doesn't. If you really want to know, you might study about the lifetime of these laser gyros, and wha their affects are. Tuvas 16:28, 4 July 2006 (UTC)
  • One of the issues with Hubble is that the pointing accuracy has to be exceptionally good (a few milliarcseconds stability during a long exposure of several minutes). As Earth observation satellites orbit the Earth every 90 mins, they also have to rotate every few minutes to point at targets on the surface, and to track these targets as they fly past. Their pointing accuracy is usually less important, as the target can be a few pixels out of position in a short exposure image without causing too much trouble. Rnt20 05:37, 4 July 2006 (UTC)

[edit] Current Spaceflight

I removed the Template:Current spaceflight as there is nothing particularly unusual happening with Hubble at the moment, according to news searches. Rnt20 08:36, 15 September 2006 (UTC)

[edit] Hubble picture of the moon??

The article says:

"and there are also sizable exclusion zones around the Sun (precluding observations of Mercury), Moon and Earth, which cannot be observed." what does this mean?? This can be read as though it cannot take photos of the moon, which it has done:

Photo of the moon, taken by Hubble, 1999
Photo of the moon, taken by Hubble, 1999

So what does the above sentence mean? Scaremonger 06:02, 23 September 2006 (UTC)

As I understand the text, light from Sun, Moon, and Earth can 1. destroy sensitive instruments (the FGSs) and 2. shine into the telescope at an angle, get scattered inside, and thus spoil observations. Pictures of Sun, etc, can be taken by other instruments when the FGSs are switched off.
I would prefer a kind of sequence where a paragraph starts with a general description, then -- after a cue like "to be more exact" -- the details. That would make the article accessible to both casual readers and specialists.Geke 11:42, 15 January 2007 (UTC)

[edit] WFPC Details

The article states that the original WFPC "contained four CCD chips, three of which were 'wide field' chips while the fourth was the 'planetary camera' (PC)." I remember the original WFPC to be 4 WF and 4 PC CCD chips. I can not find a reference for this at the moment. The WFPC2 made the change to the strange shape you see today due to the 3 WF chips and a single PC chip. I remember a bunch of scientists being very upset with the change. If I find a reference to this, I will come back and change the article. I could not find one online, I will take a quick look at some of the books I have on Hubble at home and use that as a reference. The reason I know this is that I used to work at the Space Telescope Science Institute and have looked at an incredible number of Hubble images!

cbm

[edit] Launch date

The article says: Launch date April 24, 1990. However, Nasa says: April 25, 1990, at 12:33:51 UTC [9]. The article should specify timezone, and UTC is the best one in this case, is it not? - Kricke 13:06, 8 October 2006 (UTC)

I just realised that they say April 24 for STS-31 [10] which carried Hubble into space... Hm... anyway, it should specify timezone. - Kricke 13:24, 8 October 2006 (UTC)

[edit] New Hubble servicing mission to be decided

Link --Jack Zhang 02:03, 31 October 2006 (UTC)

Hooray! This is excellent news for the astronomical and scientific communities! -- DiegoTehMexican 16:42, 31 October 2006 (UTC)

About this article [11] from the Washington Post - it's highly unlikely that there will be a second shuttle on the pad, as Launch Complex 39B is scheduled to be deactivated in 2007, after STS-116, so it can be converted to the Ares I pad.

[edit] Angular Momentum?

The sidebar says that the "angular momentum" of the HST is 5.28×10^10 m²/s. Those aren't even units of angular momentum, which would have SI units of kg * m^2/s. I've removed this obviously incorrect value from the main article. Maybe someone could clarify what they really meant. --Eliasen 22:51, 5 November 2006 (UTC)

[edit] Impossible to return HST for mirror replacement

I added a "citation needed" tag to the following claim:

While Kodak had ground a back-up mirror for Hubble,
it would have been impossible to ... bring the telescope
temporarily back to Earth for a refit.

This tag was removed by 128.40.1.175 whose log read:

vast expense of two shuttle missions, technical difficulty
of replacing mirror, all covered in existing refs so no
need for a cite tag

I put the tag back, but I hit "enter" by accident and my log message was truncated. What I meant to say was that "difficult" and "expensive" do not equal "impossible." The HST was designed to be returned to earth by shuttle; see STS-144. I would agree that it is now impossible to return HST to earth by shuttle, because only Columbia was able to do so. But someone should either explain why it was impossible back then, or re-word the sentence to say "too expensive" or whatever. -- Coneslayer 18:52, 17 November 2006 (UTC)

[edit] Changes

Someone made some very drastic changes to some sections of the article. For example, 'The flaw meant that Hubble could obtain data about as good as that achievable with a large ground-based telescope' was changed to 'In its aberrated condition the telescope still had angular resolution nearly an order of magnitude finer than was available from any conventional ground-based telescope'. No sources were cited for these changes. I restored the previous version but the unsourced statements have been restored, with the claim that 'deleted info was good'. On what basis was that statement made? Also, the part about 'At this location, the image was conjugate to the pupil of the telescope itself' adds little value, I think. It makes no sense to me, and probably you need to be an optical scientist to know what's meant by 'conjugate to the pupil'. What was wrong with the previous? Compare:

The design of the Wide Field and Planetary Camera (WFPC) included four relay mirrors to direct light onto the eight separate CCD chips making up the camera, and so the relay mirrors on the replacement Wide Field and Planetary Camera 2 could be figured to correct the aberration

and

The design of the Wide Field and Planetary Camera (WFPC) included relay mirrors to direct light onto the eight separate CCD chips making up its two cameras. Fortunately, these relay mirrors were located at a place[1], that allowed an inverse error to be applied to their surfaces that would completely cancel the aberration of the primary in the replacement Wide Field and Planetary Camera 2.
  1. ^ At this location, the image was conjugate to the pupil of the telescope itself.

This is a huge long article and conciseness is an enormous virtue. What does the second version tell us that the first doesn't in half the space? 81.178.208.69 01:27, 12 January 2007 (UTC)

Hi! I think the idea that the aberrated mirror's effects depended on the observation that was attempted is an important distinction. This concept comes up all the time when different telescopes are compared. The previous statement 'The flaw meant that Hubble could obtain data about as good as that achievable with a large ground-based telescope' is misleading at best - some data was much better (UV spectroscopy for example), some much worse, and some about as good.
I added the source showing the aberrated PSF, the corrected PSF, and ground based PSF, which is the basis for the different effects on different observations. However, there were two parts describing these effects in the article. I combined these, which puts a reference right where the statement is made (and makes the article shorter).
For the second part about the congujate, it was just luck that the relay mirror was in the right spot. I moved the technical jargon to the footnote, where the casual reader will never see it, but an interested reader can. (I also did this with a bunch of info about how the actual mistake was made as well.) I've further re-worded it so it's about as short as the original (in the main text) but no longer leaves the reader the impression that any instrument that contains a mirror could be corrected. LouScheffer 03:57, 12 January 2007 (UTC)
The graphs show that the aberrated PSF was considerably worse than a ground-based observation in 1" seeing conditions. I believe the article already said that spectroscopy was not badly affected, and I think the previous text is more accurate except we should specify, when saying data was about as good as ground-based, that that refers to imaging data.
As for the footnote, I think the middle of a sentence is just about the worst place possible to put a footnote for any reason, and leading the reader away from the sentence to a footnote that is essentially meaningless to most people seems very unnecessary. Again, I cannot see what the current version gives that the previous did not. The current text is much more confusing, and footnotes are supposed really to be used for referencing. If a footnote is needed to explain some text, that text is probably too complicated anyway. We're not writing for optical scientists, we're writing for the general public, and seeing as 99% of people who want to read about the HST will not have a clue what 'conjugate' means in this context, I see no value at all in including it.
By the way, I wish you'd been a bit more careful with reinstating the changes, LouScheffer, because you also reinstated all the 'ball aerospace' spamming, and a link to a youtube video that's spectacularly pointless and irrelevant. 81.178.208.69 13:09, 20 January 2007 (UTC)
I apologize for accidentally re-instating some garbage, and agree that a footnote in the middle of a sentence is bad practice (I tightened it up again, moved more to the footnote, and put it at the end of the sentence.)
On the other hand, I think footnotes are a great place to stick technical jargon. I fully agree that 99% of readers won't care, but that's exactly the 99% that won't follow a footnote reference either. That's certainly what I do - when I read an article where I'm not familiar with the subject, I hardly ever follow the footnote.
On the third hand, the width of the PSFs, aberrated vs ground, is not the full story. It was much easier to process (via deconvolution and other techniques) aberrated Hubble images as compared to ground images. This is because the error is exactly known and constant, as opposed to seeing which is unknown and variable. But this strays off into scientific image processing and was only of temporary interest until they fixed the telescope.
Finally, it still might be worth noting that the public images from the Hubble (such as the famous 'pillars of creation') are composed of images shot through various filters. I suspect that a lot of casual readers think it works like a souped up consumer type digital camera, and delivers color images in one click. LouScheffer 06:10, 21 January 2007 (UTC)

As I recall, prior to COSTAR, Hubble mainly had problems with glare. Dim objects near bright objects were erased by the glare. For images of Jupiter or deep field images, Hubble had no real problems. Will (Talk - contribs) 04:26, 12 January 2007 (UTC)

I have deleted the section on the Hubble Origins Probe as a Hubble follow-on. The HOP is only one of several mission concepts that would serve to replace Hubble's capabilties. It presently is not funded, nor is there any existing program that focusses specifically on making a true Hubble replacement. Other candidates for this role are HORUS, SNAP, TPF-C, and so on. Trlauer 19:25, 25 January 2007 (UTC)

[edit] Technical formatting problem

We seem to have a problem with the <ref> tags starting on , 11 January 2007, with the middle of GMHenninger's three changes. He started to use the cite_web template, (maybe the first for this article?) and not all of the referenes list anymore. I am still investigating. -- 199.33.32.40 00:54, 30 January 2007 (UTC)

Oh, he used >> rather than two close-curly-brackets. The "cite" template does not get closed properly but the <ref> tag somehow preserves the text, but the refs do not list in the <references /> section. Fixed, but we should all learn to recognize that symptom. -- 199.33.32.40 01:16, 30 January 2007 (UTC)

[edit] From the article Future section

I'm not much more than a layperson on science stuff so I'm just reading the article as the intended audience would. The 'Future' section of the article states that the power system of the Space Telescope Imaging Spectrograph (STIS) failed, rendering the instrument inoperable. The electronics had originally been fully redundant, but the first set of electronics failed in May 2001. It seems unlikely that any science functionality can be salvaged without a servicing mission. and then it never says if it was fixed or not. Certainly Hubble isn't up there with no juice, so could someone who knows a WHOLE lot more than me put something in there that doesn't imply that it's dead? JohnCub 00:11, 11 February 2007 (UTC)

While I don't have a source, what I've heard is that the Spectrograph is still down. Each instrument (again, as far as I've heard) has it's own power system, so one instrument can fail, without taking out the whole telescope. --Falcorian (talk) 00:44, 11 February 2007 (UTC)

[edit] Worth the costs ?

Someone has written a chapter on the Swedish Wikipedia article about Hubble that the telescope has not been worth the costs compared to other methods of observation. Even if a lot of important scientific discoveries has been made with Hubble, so much costs has been associated with it, that the same money used on ground based telescopes would have given more results. Today is possible to create many of the images made by Hubble using ground based telescopes with techniques like adaptive optics and "speckle" techniques. Would you agree with these statements ? -- 217.208.215.203 18:28, 1 March 2007 (UTC)

Did you notice that the cost-effectiveness is discussed in the article? Hubble_Space_Telescope#Impact_on_astronomy. Worldtraveller 18:48, 1 March 2007 (UTC)
Although I am not prepared to do a full cost-benefit analysis of HST, especially when the benefits (and possibly the cost, too) are such a subjective matter. However, I will say that I disagree with those statements. Even if ground-based telescopes using adaptive optics can now "re-create" the images taken from Hubble, which is arguable, it isn't fair to compare the telescopes of today with a telescope that has been in service for nearly 20 years. Furthermore, no amount of money put into ground-based telescopes would have been able to produce the ultraviolet astronomy results that HST has achieved. Much of the "bread and butter" work of large ground-based telescopes, i.e. the high-redshift universe, needs to have accompanying rest-frame ultraviolet studies of the local universe in order to be placed in the proper context. AmberRobot 15:22, 2 March 2007 (UTC)

It's essentially impossible to credit alternative histories that presume that a large investment of money, but still less than what was spent on HST, would have resulted in superior capabilities. HST retains unique capabilties 17 years after its launch that cannot be duplicated from the ground, and that have little prospect for duplication looking ahead another decade or so. It is frankly a fallacy that the advent of adaptive optics on large ground telescopes supplants much of the capabilities of HST. HST obtains deep diffraction-limited images in the optical wavelengths over angularly large areas with a highly stable PSF. AO currently works on angularly small areas in the near-IR and must contend with a high backgound with an often poorly known PSF. When used with telescopes of 8-m aperture or so, AO can top HST for individual relatively bright objects, where the field of view is not important for the science - as such this is a wonderful compliment to the bulk of work done with HST, not a competition to it. There are notions for how wide-field optical AO might be done, but the problems are profoundly difficult. If we wind the clock back 35 years to when the real development of HST started, there could have been no credible argument (nor was one ever made) that the same pot of money would have allowed this path to have worked. The path to HST was hard enough, but it was based on technology that was vastly better understood.Trlauer 03:59, 3 March 2007 (UTC)

The trouble with scientific research is that one cannot describe the benefit in financial terms. The HST has done more to increase our understanding of the universe than any other single scientific instrument in history. Being in space will always give you access to fainter objects (viewed in visible or IR) than anything ground-based due to atmospheric absorption. HST can obsereve in the UV, which cannot be done on the ground (one of my pet annoyances about the James Webb Telescope is that it own't observe in the UV, so that capacility will be lost to science). Finally, the HST produces more good PR for NASA than anything else - the public love the pictures showing the wonders of the universe. Tompw (talk) 09:39, 3 March 2007 (UTC)
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