Boeing 747 Modified To Act As Infrared Telescope

xyz writes "A joint project of NASA and the German Aerospace Center has developed a highly modified Boeing-747SP aircraft to carry a 2.5-meter (98.4 inch) infrared telescope. The project SOFIA (Stratospheric Observatory For Infrared Astronomy) will observe radiation in the wavelengths from 0.3 microns to 1.0 millimeters, spanning the visible, infrared, and sub-millimeter portions of the electromagnetic spectrum. The observations will be taken at an altitude of 40,000 to 45,000 feet (12 to 14 km) which is above 99.8 percent of the water vapor in Earth's atmosphere, thus giving it a greater range of observations." Update: 10/31 13:27 GMT by T : Mea culpa -- headline changed to reflect that this telescope is intended for looking out at space rather than down at the Earth.

Comments

Mount tinfoil Hats!

[R2.0]

Sounds like it would make a great surveillance platform, too. It's in the name of science, after all.

Re:Mount tinfoil Hats!

[bornyesterday]

one of these days, people will realize that the aluminum and tinfoil companies have been coerced by the government into impregnating their materials with microscopic brain-scanning devices and that wearing tinfoil hats has actually been increasing the effectiveness of the governments ability to read the minds of its conspiracy theorist and overly private citizens.

Re:Mount tinfoil Hats!

[Anonymous Coward]

That's why you should roll your own foil.

Re:Mount tinfoil Hats!

[IndustrialComplex]

I've considered this, but the impurities are still smaller than the wavelength of the brain-control D-waves.

The real important thing to do is make sure that your tinfoil hat is properly grounded.

Re:Mount tinfoil Hats!

[Anonymous Coward]

Except that infrared radiation doesn't penetrate the atmosphere, and it would be completely blind to the happenings on earth...

2.5m is nothing for optical observations, there are satellites on orbit with apertures as large as **.* meters and they are getting ****** every day.

Re:Mount tinfoil Hats!

[MountainLogic]

(Kent's Room)
Kent: What?
Mitch: (os) What do you think...

(Chris & Mitch's Room)
Mitch: (into microphone) ...a secret phase conjugate...

(Kent's Room)
Mitch: (os) ...tracking system is for? A big mirror makes a big beam

Re:Mount tinfoil Hats!

[Anonymous Coward]

I cannot point the telescope toward the earth unless you fly the plane upside down. The opening in the airframe points in the upper hemisphere of its viewing space. It is going to be some time still before the aircraft is functional. SOFIA still needs to have much of the equipment that collects the data installed. The aircraft has not flown with the door open yet.

Re:Mount tinfoil Hats!

[Anonymous Coward]

right...except for the fact that it is above all the water vapor, which is what makes it hard to get good readings in this range anyways...

Earth-observing?

[Scutter]

Boeing 747 Modified To Act As Earth-Observing Telescope

FTFW:

SOFIA is an airborne observatory that will study the universe in the infrared spectrum.

So, by "Earth-observing", what you meant was "everything EXCEPT Earth", right?

Re:Earth-observing?

[morgan_greywolf]

Ummmm....TFS says they're using an infrared telescope. The water vapor shouldn't matter much, right? Especially since they're mostly trying to look at the atmosphere to study things such as global warming.

Re:Earth-observing?

[Scutter]

Ummmm....TFS says they're using an infrared telescope. The water vapor shouldn't matter much, right? Especially since they're mostly trying to look at the atmosphere to study things such as global warming.

They're not observing the Earth. It's a celestial telescope.

Re:Earth-observing?

[aliquis]

Does make sense to observe the earth THRU as much water as possible to if water amount matters.. Not.

Re:Earth-observing?

[aliquis]

But if the water vapor didn't mattered why mention it at all? :D

"Today I've answered to three Slashdot stories, but my breakfast was tea!"

Re:Earth-observing?

[morgan_greywolf]

Okay, yeah, I went back actually RTFA (don't fall over from a heart attack now!) so misleading headline, bad summary, typical Slashdot claptrap. They definitely want to be above the water vapor. They'll be collaborating to study the center of the Milky Way, checking out gases, etc. My question is -- how is this different from Kuiper telescope in the early 70s that did more or less the same thing?

Re:Earth-observing?

[aproposofwhat]

Sorry, Morgan, you're usually quite insightful, but water vapour is quite good at absorbing infra-red radiation - see here for some details.

Re:Earth-observing?

[tomatensaft]

Author probably meant "Earth-based observing", although calling a Boeing 747 flying at 10-12 km above sea level "Earth-based" is kind of a stretch, even by Hubble telescope standards... :)

Re:Earth-observing?

[michaelwv]

It has a mirror that's more than two-and-a-half times larger, with correspondingly better resolution and sensitivity, and instrumentation that's several generations more advanced than Kuiper. Also, notably it will be flying and observing in the next decade and Kuiper hasn't flown since 1995. Science continues and new questions arise every day that need new observations to answer them.

Re:Earth-observing?

[I cant believe its n]

So, by "Earth-observing", what you meant was "everything EXCEPT Earth", right?

No, he is suggesting "Flip Flop Flyin' in an Aeroplane" to make earth observations possible.

Re:Earth-observing?

[kayditty]

I'd guess he meant everything INCLUDING Earth, since Earth is in the universe. it may have problems observing itself, though.

Re:Earth-observing?

[Anonymous Coward]

The headline was wrong of course... but about your comment:

What are all those satellites doing up there??

Re:Earth-observing?

[m50d]

IIRC, The ones which are there to observe the Earth do so from very eccentric orbits where they essentially dive briefly into the atmosphere to take photos, then pull out before they burn up (of course, they're in a stable orbital pattern rather than doing this under power). And they don't use infrared.

Re:Earth-observing?

[NotmyNick]

The water vapor shouldn't matter much, right? Especially since they're mostly trying to look at the atmosphere to study things such as global warming.

Sorry, Morgan, you're usually quite insightful, but water vapour is quite good at absorbing infra-red radiation - see here for some details.

No. He simply assumed the title Timothy pasted onto it was correct and didn't bother to read the summary or TFA. Just like Timothy.

Re:Earth-observing?

[Concerned Onlooker]

Good observation.

Might want to change the title

[Twitch42]

From the article:

"The flying observatory will begin its short science, or 'first light' observations, in early summer 2009, and will continue its program of ***celestial observations*** for the next 20 years."

Re:Might want to change the title

[iamlucky13]

Might also want to change the title to reflect the fact that the telescope itself isn't the news. The article is about the selection of the first three researchers to be in charge of the instruments.

The summary makes it sound like the SOFIA project itself is new. Rather, the project was first proposed in the 80's when NASA was still flying a relatively tiny 1 meter mirror on a C-141. It's been in development since 1996 and bounced up and down on NASA's priority list, contributing to the delays and cost growth it was suffering until two years ago when NASA suspended the program for review. At that point, they decided it was well worth the remaining cost and put the project onto a steady track. It's undergoing flight testing right now.

It's somewhat complementary to the Spitzer Space Telescope, having, I believe a greater resolution but lower sensitivity. Since it comes back after every observation, it also has the handy ability to be able to swap out instruments on the ground in order to have the best sensors for a given observation, or to upgrade in the future. It's also cheaper and will last longer than space-based telescopes. It won't replace Hubble, Spitzer, or JWST, but it will cover a lot of the observations those powerhouses aren't needed for.

Yup

[SmallFurryCreature]

All those of us in orbit and travelling the stars better look out. NASA got an eye on you.

Re:Yup

[Skater]

Would that be an Electric Eye or an Eye In The Sky?

Probably the latter though I prefer the former.

Earth-observing?

[m50d]

If they were observing the Earth, surely it would be better to do it from below all that water vapor.

Kuiper Airborne Observatory

[Anonymous Coward]

Been there, done that, in 1974 even

http://en.wikipedia.org/wiki/Kuiper_Airborne_Observatory

Re:Kuiper Airborne Observatory

[mbone]

SOFIA is much more sensitive.

Re:Kuiper Airborne Observatory

[Anonymous Coward]

SOFIA pwns Kuiper Airborn Observatory.

Re:Kuiper Airborne Observatory

[ibm1130]

Kuiper retired the best part of a decade ago IIRC. Even then SOFIA was in the works. Why is this suddenly news?

Re:Kuiper Airborne Observatory

[Anonymous Coward]

And SOFIA is meant to replace Kuiper. As it's 30+ years old.

Re:Kuiper Airborne Observatory

[N22YF]

True, the Kuiper Airborne Observatory (KAO) was retired in 1995 to free up funding for SOFIA. Work on SOFIA started in the 90s and it made its first flight with the telescope installed last year. SOFIA is a similar idea to KAO, but on a much larger scale (the telescope is 2.5 m in diameter, compared to 91.5 cm for the KAO) and representing a significantly larger engineering challenge.

But yeah, I don't know why this is news now. Science flights aren't supposed to start taking place until next year.

Interestingly, it won't really be ready for science flights next year, but every ten years the US National Research Council does its decadal surveys of all the science programs it's supporting and decides which ones to continue funding on. SOFIA's been so delayed that if it doesn't have any science results by mid-2009 (when the 2010 decadal survey will be taking its data), it runs a real risk of having its US government funding cut. If this happens, DLR (German Aerospace Center), another one of the big funders, will be likely to cut funding as well, resulting in a bleak future for the SOFIA program.

(I worked on SOFIA as an intern at NASA last year.)

Re:Kuiper Airborne Observatory

[treeves]

That's what SHE said.

For really rad IR videos, use the vomit comet

[syousef]

...switch the lights off just as you start the zero g, turn on the infra red on the video camera. Submit to funniest home videos. Win the home entertainment theatre prize. Think how much closer you'll be to funding your next orbital vehicle when you sell the prize!

Vibration?

[Schrodycat]

Can someone please explain how airborne telescoped deal with all the vibration? I mean, I spill my drink every time I fly.

Re:Vibration?

[ZeroExistenZ]

Can someone please explain how airborne telescoped deal with all the vibration? I mean, I spill my drink every time I fly.

Telescopes don't know fear...

Re:Vibration?

[andy19]

You're not drinking fast enough.

Re:Vibration?

[ari_j]

Your drink doesn't have $10 million worth of shock-mounting. But even so, I'm curious about the same thing, as there is simply no way that this can compete with an orbital telescope as far as a smooth ride goes.

Re:Vibration?

[tweak13]

It will probably be mounted on some kind of stabilized gimbal mount, much like the kind used to mount cameras to helicopters. A helicopter mount has to deal with probably 100x the vibration that a 747 in smooth air would have. Keep in mind they are going to not only be able to pick which days they fly, but pick the location as well. It won't be very hard for them to find good conditions. Example of helicopter mount here

Re:Vibration?

[Anonymous Coward]

It is gyroscopically stabilized much like a satellite. Telescopes don't care about translations, but they sure as heck care about rotations.

The fun part is keeping the aircraft body out of the way as it tracks stars. There is only +/- 2.8 deg of slop in azimuth before the telescope hits a stop.

Watch next week's ADASS conference for details...

Re:Vibration?

[Anonymous Coward]

There is a set of seven nitrogen-filled airbags with active controls to isolate as much as possible. The telescope itself is gyroscopically stabilized. And for the worrisome "dumbbell" flexure mode, there is an active image compensation calculation.

It's MUCH more sophisticated than KAO was. As well as substantially larger.

Re:Vibration?

[Guysmiley777]

It competes VERY favorably with an orbital telescope in one key aspect: price.

Re:Vibration?

[Quantos]

This is taken from the SOFIA site.

At visible wavelengths, it is neither atmospheric turbulence, the refractive action of mobile air cells which push light rays around, overhead (actually there is not much air left overhead) that causes the blurring problem, nor the aircraft and telescope shaking that causes the problem, but rather the "shear layer" stream of air shooting past the open airplane cavity where the telescope sits, at 500 mph. This air motion worsens the resolution (the opposite of blurring) to 3 arc secs at visible wavelengths.

But the problem at the long wavelengths is different - it's diffraction. Basically, the far-infrared light observed by SOFIA passes through the shear stream of air unperturbed. But this light has such a long wavelength, 100x to 1000 times the wavelength of visible light, that the SOFIA telescope is of insufficient size to focus it sharply, and blurriness results. At wavelengths in the far-infrared, like 60 micrometers, there is significant blurring due to this effect. The telescope is actually held extremely steady while observing occurs, even in turbulence. It's held about as stable as a mountaintop telescope sitting on a 10 meter cement foundation, but diffraction still blurs the image.

So how do you do this? First, you isolate the telescope from the airplane by mounting it on a spherical pressurized oil bearing. The plane shakes and quakes, but the telescope doesn't feel it. Second, you direct the wind away from the telescope by shaping the side of the airplane so as to deflect it, and install a little deflector fence on the edge of the telescope cavity as well. Third, you stabilize the telescope against sudden motion (wind does get through) by spinning three orthogonal gyroscopes which are rigidly attached to the structure, and fourth, you steer the telescope so as to keep it steady, by tracking a distant star and giving the telescope magnetical nudges to point it toward a fixed direction.

Re:Vibration?

[michaelwv]

Vibration transferred from the plane is relatively straightforward to solve (although it can expensive to do it to tolerance). The biggest challenge that caused the most delay (years) for SOFIA was the layer of air that was happy to be going around the side of the plane and then suddenly sees a 3m gap in the side of the plane. This led to a significant amount of turbulence and both shaking of the telescope and degradation of the "seeing" (the sharpness of images through the atmosphere and optics; in this case the very local atmosphere). Significant redesign and careful consideration of the exact shape, baffling, etc. of the hold and telescope mount was necessary to overcome this problem.

Re:Vibration?

[vrmlguy]

Mod parent up!

I spent several minutes perusing the SOPHIA site without finding this information. Looking at the pictures, I'd just about convinced myself that there was a large pane of glass covering the opening, even though I knew that it would cause some distortion. No doubt about it, SOPHIA needs a FAQ.

So, I'm guessing that there's no one standing in the rear when they open the shutter?

Re:Vibration?

[Anonymous Coward]

The biggest challenge that caused the most delay (years) for SOFIA was the layer of air that was happy to be going around the side of the plane and then suddenly sees a 3m gap in the side of the plane.

I like to call SOFIA a "giant aluminum whistle." A lot of effort has gone into preventing acoustic vibrations (which are A LOT worse than just screwing with the seeing -- a resonant acoustic vibration can break the airframe!), including large CFD projects, a series of wind tunnel tests (the model is in the NASA Ames visitor center), and -- soon -- airborne tests with pressure transducers in the cavity.

But it's undeniable that the design looks a whole heck of a lot like a flute. Maybe we can pop a few windows out and make finger holes? :D

Now there is a little worry about limitations at low elevations due to thermal plumes from the engine. But that's not a deal killer, as it should be negligible at 60 deg. Which we're driven to anyway as that minimizes (most efficiently) the residual precipitable water vapor at a given latitude and altitude. It's only a few microns to a few tens of microns, rather than the centimeter or two at the ground, but it's not zero.

Re:Vibration?

[ari_j]

What are the actual numbers? An orbital telescope doesn't burn fuel while it's up there the way a 747 does, and it can take pictures continuously while it's up. But a 747 doesn't need a manned orbital flight to make repairs the way an orbital telescope does and doesn't even need repairs when unused the way an orbital telescope does. I'm sure that this weighs in favor of the 747 method, but by how much?

Re:Vibration?

[Quantos]

They have one, that's where I pulled that from. I just forgot to add the link.
Here it is.

Re:Vibration?

[tweak13]

I didn't read the article when I posted that (are you surprised?) and thus didn't learn until later that they were basically chopping a hole in the aircraft for this assembly. That of course leads to many other considerations like controlling the turbulence as the boundary layer breaks up and not letting a resonance tear the entire aircraft apart. I guess I just assumed the telescope would fit in the aircraft and look through some sections of fuselage made transparent in IR.

Re:Vibration?

[michaelwv]

Transparent in IR is relatively easy (although not necessarily all the way out to 500 microns). Not emitting in the IR is hard. You have to be very cold (3 degrees Kelvin would be good). Much colder then you'd like the skin of the plane to be. Obviously the air is not that cold, but it's much thinner and so doesn't emit nearly as much as a solid sheet of whatever transparent material you could think of.

Re:Vibration?

[Quantos]

Now there is a little worry about limitations at low elevations due to thermal plumes from the engine.

The opening for the telescope is well above the plane of the engine plumes, especially at it's cruising speed. Also, since the telescope can't be pointed down that wouldn't be a factor.

Re:Vibration?

[tweak13]

Interesting. My only experience with IR is IR photography, and pretty limited experience at that. So an IR filter for a camera is of course made to pass IR while blocking most visible light. I'm assuming this works because the IR range film captures is much shorter wavelength than what would be emitted by a filter at room temperature. I guess I never would have thought of radiation being an issue. Now I kinda wish I would have paid more attention in astrophysics class :-)

Re:Vibration?

[michaelwv]

Yes exactly. For room-temperature (300 degrees K, 27 degrees C), the blackbody radiation peaks around 9-10 microns. IR in the context of CCD cameras is around 1 micron, so it's not that important to be colder than room temperature (although it's still helpful). If you want to observe at 10 microns then you would like to be down at perhaps 100 K (conveniently liquid nitrogen is at 77 K) and down to 3 K (liquid helium refrigeration) if you want to get out to 500 microns. See http://spectralcalc.com/blackbody_calculator/blackbody.php for an easy way to visualize the spectrum of a blackbody at different temperatures (they occasionally pop up ads for something or other but it is a good visualization aid for this sort of stuff). Set the wavelength range from a lower limit of 1 micron (um) to 1000 um to display the range we're talking about here.

SOFIA looks up

[mbone]

Not down. It's not Earth observing, it's observing from Earth.

Details, details.

Impressive engineering

[hcdejong]

The telescope will be exposed to the elements during flight: this photo of the telescope installation shows that the aircraft will be flying around with a 3x3 m hole in its fuselage.

The buffetting and general vibration levels must be huge.
here is how they plan to compensate.

Re:Impressive engineering

[camg188]

I'd like to see this compared to Hubble (but not enough to actually look it up). Seems like Hubble would have a less obstructed, steadier view, but SOFIA has got to be cheaper to operate and easier to maintain and upgrade.

Re:Impressive engineering

[bohemian72]

I don't think there are all THAT many elements up where this thing will be observing. Some to be sure, but above 99.8% of the water.

Re:Impressive engineering

[hcdejong]

From the link in my post:

Q: Can SOFIA see the Lunar Module crash sites on the surface of the Moon and get a record of them for history?

A: You asked if SOFIA can see very detailed features on the surface of the Moon. The short answer is "No - such features are too small."

Here is the long answer: The best resolution (ability to see fine detail) of any of the world's telescopes is about a tenth of an arc second (explained below). This is achieved by the Hubble Space Telescope. (This statement applies only to telescopes that use visible light and make images or photographs.) The next best telescopes are the Keck Telescopes in Hawaii and some telescopes in Chile. These can see details about three tenths of an arc second. SOFIA does not do as well as these telescopes, seeing details of one or two arc seconds at the very best.

Re:Impressive engineering

[MRe_nl]

Also, re: comparisson with Hubble (or other spacecraft), from an earlier article;
"We can do follow-up spectroscopic work with more complex instrumentation that is simply too heavy and too expensive to put aboard a spacecraft," says Eric Becklin, SOFIA chief scientist and director-designate for the University Space Research Association (USRA). USRA will manage SOFIA's science operations for NASA."

Allthough I have to wonder, what would be too expensive to put aboard a spacecraft?

Re:Impressive engineering

[Anonymous Coward]

Sure, it's above 99%+ of the water, but the wind is equivalent to about 350 knots on the ground. That's an "element." It's 475 knots at stratospheric altitude (somewhat higher than 500 MPH).

And SOME weather does go above the operational limit of 45,000 feet (though, odds are, no observing will be attempted in an anvil cloud, and the cavity door will just be closed)

Re:Impressive engineering

[mbone]

They operate in different wavelength bands - Hubble is not an long-wave IR telescope. The space analogy for SOFIA is the 85 centimeter Spitzer telescope.

These telescopes operate in the IR so their wavelengths are longer and thus their resolutions are poorer for a given size telescope.

Here are the numbers :

So the score card is: Hubble 0.1 Arc Sec (best); Keck 0.3 Arc Sec many other telescopes are doing as well as the Keck; SOFIA greater than 2.0 arc sec

Note that radio Very Long Baseline Interferometry (VLBI) can routinely do factions of a milliarcsecond resolution, or a factor of 100 times better than Hubble. This requires synthesizing a telescope the size of the Earth, which you can do in the radio.

Re:Impressive engineering

[michaelwv]

I think by "too expensive" he means that there are instruments that work 80% of the time but need to be (kicked | disassembled | mucked around with) occasionally. Making these instruments 10x lighter, 98% reliable, and with no need for outside intervention might be one to two orders of magnitude more expensive to develop for a spacecraft that you never get to touch again (or that you have to pay ~$500 million for each repair). So an instrument that was $10 million is now several hundred million dollars. Even for a spacecraft that's real money. When people put stuff up in space you want to be conservative. So spacecraft are not good platforms for the latest and greatest instruments and new ideas. Part of the idea of an observatory that returns to the ground a lot is that you can try out new instruments much more easily and much more cheaply. In the case of the infrared it's important enough to get above the water vapor that it's worth making a flying observatory.

Re:Impressive engineering

[icebrain]

Perhaps he meant that modifying the equipment to go on a spacecraft would be too expensive. Lots of things are quite cheap here on earth, but getting them space-rated and qualified, and light enough to be launchable, costs a lot of money.

Re:Impressive engineering

[Anonymous Coward]

Given the way this is mounted, it's clearly sited in an unpressurized compartment. Is there no access possible in flight? Bit of a bummer to get up to 12km high and find somebody forgot to take the lens cap off.

Re:Impressive engineering

[PPH]

Its been done before here.

Stupid tagging

[Anonymous Coward]

Who tagged this as bigbrother? Are they actually implying the boeing will fly upside down so the telescope can point downwards. The telescope enclosing and the door position makes it impossible for the telescope to point downwards. Besides it is a far infrared telescope.

Sounds like a new Cobra Ball

[wiredog]

Cobra Ball

is an Air Force airborne intelligence platform (RC-135) which carries infrared telescopes for tracking ballistic-missile tests at long range. COBRA BALL operates out of Offutt AFB NE and deploys to various locations around the world.

Re:Sounds like a new Cobra Ball

[Anonymous Coward]

No. It is A LOT bigger than that. It's mounted differently. And SOFIA has a pressurized cabin.

I suspect the bands are very different as well (far-IR and submillimeter are substantially more interesting for cool objects, rather than hot thermal plumes).

And SOFIA has an 8 arcminute field of view. Not so great for tracking stuff you don't already know the location of. Fine for stars, planets, comets, etc., as they don't move on the sky very quickly and their locations can be predicted ahead of time.

Aside from the words "IR" and "aircraft", these are totally different telescopes.

Re:

[Anonymous Coward]

thats why people make their own tinfoil by coldrolling some aluminum :o

Cost comparison

[WhiplashII]

Ignoring maintenance (so far, I don't think many satellites have been repaired except for Hubble), an Atlas V rocket launch costs about $140M. A 747 costs about $150M to buy, more to customize for this application. The satellite is free to fly after launch, of course. A 747 costs about $27,000 per hour to fly - $230M/yr if flown continuously (which most airlines try to do - they are too expensive to have sitting on the ground).

So, a satellite is way cheaper - even if you were to completely replace it every fews years. The only reason I can think of for wanting this system is ease of maintenance and operations - basically, the telescope must be a LOT cheaper than an equivalent satellite telescope.

Re:Cost comparison

[Guysmiley777]

Shuttle flights run in the neighborhood of $400-500 million a pop. So far there have been 5 flights, the initial launch and 4 servicing flights. So that's $2-2.5 billion for the Hubble so far.

That doesn't include the operating expenses. So far the U.S. has put in between $5-6 billion dollars, the ESA another $600 million euros. Satellites ain't cheap.

Re:Cost comparison

[WhiplashII]

Well, yeah, but Rosat, Gamma, SARA, EUVE, Eureca, ASCA, Alexis, GGS-Wind, IRTS/SFU, Surfsat, ISO, Rossi, MSX, and 23 other satellite telescopes have been launched since Hubble - and yet only Hubble has been serviced in space. So I think the norm can be called as "no in space maintenance."

Re:Cost comparison

[petermgreen]

basically, the telescope must be a LOT cheaper than an equivalent satellite telescope.
And it wouldn't surprise me if it was for one simple reason: reliability.

If you are going to put something in space it has to be extremely reliable since the only way to service it is with a very expensive shuttle mission (if indeed you can service it at all). That means you spend a huge ammount of time and money checking, double checking, triple checking and so on. Of course backup systems are an option but over time if the main fails the backup may well do so as well and backup systems add weight which is always at a premium on spacecraft.

On the other hand if it's mounted on a plane and something fails it's no big deal, switch to the backup and replace the primary when you are next in for servicing.

Re:Cost comparison

[RockDoctor]

The satellite is free to fly after launch, of course.

Certainly it's free, as long as you don't do anything with the data that it sends down. That's both the imaging data and the engineering data. If you don't do that, and don't listen to it, then you don't need to build and maintain Earth-based reception stations to pick up the signals, nor pay for the ground-based (or satellite-based) network links to get the data to the researchers who aren't going to be looking at the data. you also won't need to pay for any engineering teams to listen to any of the equipment status, nor to maintain any archives of the "as designed" and "as built" records of the equipment. Those programmers who understand the software that runs the satellite - you can get rid of them too, because you're never going to find any of the bugs that may or may not be there, and even if you did, you're not going to be uploading any new software.
Come to think of it, since you're not going to be listening to any of the data that comes down, you might as well not bother with that infrastructure for allocating time on the telescope, optimising time usage, etc. Fire the lot of them, I say!
What else can you trim from the budget, now that you're not going to be spending anything after the satellite is launched? Oh, you can get rid of the guy who's liaison with the "space junk" department. Who cares if your satellite gets hit by a dropped glove and smashed into a thousand pieces - you're not going to know, because you've not got any ground infrastructure to hear the signal go "Is there anyone there? ... Please, Is there anyone there? ... Is there an$5&$^£! [No Carrier]".

Oh, so you've got an international legal agreement to monitor the flight path of your satellites, to avoid generating more "space junk". Gosh darn it. Perhaps, to avoid that on-going cost, we'd better deliberately bring the satellite down now. Make that guys last job, as he packs up his desk and picks up his P45, to calculate where in the orbit to fire the retro rockets. Damn, we need that ground-based infrastructure. And where's that Flight Engineer? Left? Well, hire him back ... from China?! ... and he's demanding how much!!? OK, we'll train someone from the Friendly Manuals. What do mean - the Friendly Manuals weren't written, to save costs?? /SARCASM

The costs of ground-based infrastructure may be lower than the cost of the satellites, but it's non-zero, and often significant.

Re:Cost comparison

[WhiplashII]

About half of what you said would be needed for the 747 based satellite as well - analyzing the data, positioning, troubleshooting of software bugs, etc. Of the rest, most of it is performed by a third party (doesn't come out of your budget). (NASA/DOD watches all LEO objects over a certain size for free - they do not care about country of origin.)

Some of what you said were real costs - like ground radio - are true additional costs. However, depending on the satellite design, these costs can be extremely small. (Burst transmission to an existing research facility.) It's not like these things are going into deep space!

If you look closely, I think you'll find that the satellite itself (ammortized over the years, if you like) dominates the program cost - that's why this 747 idea makes sense. Non-satellite telescopes are just orders of magnitude cheaper.

Re:Cost comparison

[RockDoctor]

If you look closely, I think you'll find that the satellite itself (ammortized over the years, if you like) dominates the program cost - that's why this 747 idea makes sense. Non-satellite telescopes are just orders of magnitude cheaper.

That's not in dispute. (Except by whoever wrote "So, a satellite is way cheaper - even if you were to completely replace it every fews years." ; the spelling mistake should make it easy to locate the author.) But the original statement that "The satellite is free to fly after launch, of course." remains flat-out wrong.

Actually, I wonder how much the costs would balance out for long-lived satellites. Hubble has the complicating factor of servicing missions, but for something like a relatively run-of-the-mill EOS satellite that's up for a decade and a half or even two, that's a long time to run ground systems.
Plus, of course, "whose" budget it comes out of is always a bit unclear. Does it really matter (except in a fairly bean-counter-ish way) whether the costs are borne by tax payers via NASA and central government, or by tax payers via an Astronomy department, a university board, and the equivalent of PPARC, from central government.

Re:Cost comparison

[WhiplashII]

Does it really matter ... whether the costs are borne by .. an Astronomy department

Well, it matters to the astronomy department ;-}

The tracking budgets are pretty small, and the incremental cost of adding one satellite to the tens of thousands being tracked is insignificant.

I guess I should have said a satellite launch is insignificant. What I really meant was that if you were using the same equipment either way, a satellite would be cheaper - the real difference is in the equipment.

I wonder how much the costs would balance out for long-lived satellites.

Oddly enough, the sweet spot is in the opposite direction... if you only plan on the telescope being operational for a year, the satellite version approaches the cost of the aerial version. At that point, it is cheaper to launch it into orbit. It is expensive to make things last a long time with no maintenance in the harsh environment of space.

Re:creators' planet/population rescue modified...

[Anonymous Coward]

What is this spam I always see in Slashdot comments? State-of-the-art AI article generation or something? It sure isn't very good at it...