desj@brahms (David desJardins) (10/15/86)
In article <180@ka9q.bellcore.com> karn@ka9q.bellcore.com (Phil Karn) writes: > >It has been remarked (I don't remember where) that the Space Telescope is >basically an unclassified, civilian version of the KH-11 spysat. Of course, >the instrumentation is probably quite different, and I suspect that it would >fry instantly if pointed at the earth. I can well imagine why the source of such an absurd statement would try to remain anonymous. About the only technology that I can imagine that would be applicable to both is the pointing instrumentation. In every other respect the objectives and technologies are completely different. -- David desJardins
klinner@sun.UUCP (10/16/86)
> In article <180@ka9q.bellcore.com> karn@ka9q.bellcore.com (Phil Karn) writes: > > > >It has been remarked (I don't remember where) that the Space Telescope is > >basically an unclassified, civilian version of the KH-11 spysat. Of course, > >the instrumentation is probably quite different, and I suspect that it would > >fry instantly if pointed at the earth. > When I was working on the Science Operations Ground Station proposal at TRW we too asked what would happen if the telescope was pointed at the ground. You're right, most of the instruments would be damaged. And since most of the instrumentation was designed by researchers from various universities, the space telescope is definitely NOT a version of any kind of spysat. Kent Klinner Sun Microsystems
art@ACC.ARPA (10/16/86)
> Is there anyone out there that knows details on the Space Telescope > (ST)? My questions are : > > (1) Will the transmissions from the ST be PUBLIC DOMAIN? (free to > be recieved by anyone with the satellite equipment to pick them up) > > (2) Will the transmissions be scrambled or encrypted in any way to > prevent interception? (other than encoding necessary to send the > video data to earth) > > (3) What Image Processing equipment would be required to obtain a > suitable input to a PC or VCR. > > (4) If the answers to the above are favorable, does anyone have > projects in the works to do this? > > I would be extremely grateful for any help. The ST is about the only > thing going up that would make it worth getting a satellite reciever, > Who needs HBO when you can watch the STARS!!! I don't have any answers, but I have the following recollections (a bit rusty) from working on a comm project for the Space Telescope Science Institute. Data from Hubble Telescope (LEO) sent to TDRS (GEO). TDRS relays data to White Sands (New Mexico). White Sands sends data via commercial satellite to NASA Goddard (Maryland). Goddard sends data via terrestrial T1 circuit to Science Institute (Johns Hopkins). I don't believe that the TDRS traffic would be accessable, but possibly the relay to Goddard would. The data will be digital at very high bit rates. The data volume will be huge (I seem to remember something like up to 10**10 bits/day). Remember that the data will be things like multi- spectral, high resolution images. As a hypothethical example, a single 3 color 1024X1024 image with 8 bit pixel resolution would be over 3 megabytes of data. It will take some sophisticated image processing equiptment to turn the data into photographs or video images. I would suspect that the data will be handled somewhat like the LANDSAT info, tapes of specific data could be bought and somebody (NASA maybe) will probably sell finished photographs. Also, remember that a small amount of observing time is being given to qualified amateurs. I would be very interested if someone has any current information about all of this and if the Telescope has been assigned a new shuttle launch date. <Art@ACC.ARPA> ------
jwp@uwmacc.UUCP (Jeffrey W Percival) (10/17/86)
In article <4270002@hpfcla.HP.COM> ajs@hpfcla.HP.COM (Alan Silverstein) writes: >> Will the ST ever be pointed at the Earth? > >Certainly possible, but it would constitute a gross defeat of free >scientific endeavor. It would mean stealing precious time from the >astronomers lined up to use the scope. ST will look at the earth for calibration purposes. Some of the instruments need a diffuse, uniform source of illumination so they can map out their aperture locations, and the earth or moon would suffice for this. There is an earth/moon flag available to the flight software on board, that indicates when the ST is within some small angle of these objects; the instruments can take action or not, depending on the situation. You can bet there's a sun flag, too. -- Jeff Percival ...!uwvax!uwmacc!sal70!jwp or ...!uwmacc!jwp
karn@petrus.UUCP (Phil R. Karn) (10/17/86)
> ... And since most of the instrumentation was designed by > researchers from various universities, the space telescope is definitely > NOT a version of any kind of spysat. I'm sorry, people seemed to take my quote too literally. By "unclassified version of a spysat", I understood the original author to mean that the two spacecraft were of roughly the same physical size, mass, pointing capability and resolution, not that a surplus KH-11 was actually converted into the ST. (I'm still trying to dig up the source of this quote; I'm quite sure that I didn't invent it.) The ST and the KH-11 are OBVIOUSLY designed for entirely different missions. The KH-11 operates in an elliptical orbit and probably has orbit-changing rockets designed to optimize low-altitude coverage of interesting ground sites; the ST will operate in a circular orbit and doesn't need an orbit-changing capability. The ST is designed to optimize both image resolution and light-gathering power; obviously the KH-11 doesn't need much of the latter. Still, if the instrumentation could withstand it (e.g., through use of a neutral density filter) the ST would probably make very nice high-resolution pictures of the earth. Since it's resolution and not light-gathering power that the spooks are after, I wonder if they've tried optical aperture synthesis yet. If they could figure out a way to coherently combine the photons from two or more widely separated sets of optics (separated by, say, more than the diameter of a Titan III payload fairing or the Shuttle cargo bay which would be the ultimate limit on the diameter of a single-piece objective) then this might result in much better ground resolution than we've given them credit for. Phil
henry@utzoo.UUCP (Henry Spencer) (10/17/86)
> There is an earth/moon flag available to the flight software on board, > that indicates when the ST is within some small angle of these > objects; the instruments can take action or not, depending on > the situation. > > You can bet there's a sun flag, too. Possibly not. My recollection is that the attitude-control system is forbidden to point the ST at the Sun, and won't even point it near the Sun unless specially ordered to. There is also a completely independent system, which cannot be turned off, which closes the telescope's lid if the line of sight starts to intersect the Sun. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,decvax,pyramid}!utzoo!henry
al@aurora.UUCP (Al Globus) (10/25/86)
> >> Will the ST ever be pointed at the Earth? > I'm not absolutely sure, but while I was reviewing some of the ST software I remember that the cover closed automatically when viewing a bright object (such as the Sun or even the Earth) to protect telescope electronics. If my memory is correct, then the ST cannot be pointed at Earth without ruining it. Al Globus Sterling Software
DIETZ@slb-test.CSNET ("Paul F. Dietz") (10/26/86)
Not only will pointing the ST at earth damage some of its sensors, but there's a possibility that looking at bright debris in earth orbit could damage one of the more sensitive detectors. The article I read that in points out that in the 17 year lifespan of the telescope there's a good chance it will be hit by a millimeter sized chunk of orbital debris or meteor (and about a 1% chance of a collision with a large chunk that would nearly certainly destroy the satellite). Much larger scopes will have to be built in high orbit.
jwp@uwmacc.UUCP (Jeffrey W Percival) (10/30/86)
In article <7240@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >> There is an earth/moon flag available to the flight software on board, >> that indicates when the ST is within some small angle of these >> objects; the instruments can take action or not, depending on >> the situation. >> >> You can bet there's a sun flag, too. > >Possibly not. My recollection is that the attitude-control system is >forbidden to point the ST at the Sun, and won't even point it near the >Sun unless specially ordered to. There is also a completely independent >system, which cannot be turned off, which closes the telescope's lid if >the line of sight starts to intersect the Sun. >-- > Henry Spencer @ U of Toronto Zoology > {allegra,ihnp4,decvax,pyramid}!utzoo!henry I'm not sure what the "possibly not" refers to... There *is* a sun flag, but it is generated differently than the earth/moon flag. The sun flag is wired to sensors on ST, and is set by this hardware system. The door gets closed, and the sun flag alerts the flight software. The earth/moon flag, however, is uplinked to the HST, and is not connected to any sensor. The ground software is supposed to compute the earth/moon flag based on the timeline, and has the responsibility to uplink it at the appropriate times (and clear it too, of course). What trivia, huh? -- Jeff Percival ...!uwvax!uwmacc!sal70!jwp or ...!uwmacc!jwp