Author Topic: Low Cost Batch Built Space Telescopes  (Read 84083 times)

Offline Jim

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Re: Low Cost Batch Built Space Telescopes
« Reply #220 on: 10/23/2021 12:48 pm »

I'm sure you can point out no end of difficulties in an inexpensive orbital scope but your argument would be on firmer ground if you didn't use straw dogs.


Then why do you use them?

Offline deadman1204

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Re: Low Cost Batch Built Space Telescopes
« Reply #221 on: 11/24/2021 04:30 pm »
All of this just assumes that space telescopes are bits of glass that look at visible light.
If your looking at ir, you need cooling. Xray? Nothing like a normal mirror setup works

Though the big one - instruments. This is an incredibly huge part of the cost. How are you detecting the light? Nothing commerical works, because commercial gear is orders of magnitude to weak/insensitive. Spectrographs? Coronographs? Different cameras for different wavelengths?

At the end of the day, this very topic only seems logical because most people don't understand how complex space telescopes actually are.

Offline Zed_Noir

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Re: Low Cost Batch Built Space Telescopes
« Reply #222 on: 11/24/2021 08:14 pm »
All of this just assumes that space telescopes are bits of glass that look at visible light.
If your looking at ir, you need cooling. Xray? Nothing like a normal mirror setup works

Though the big one - instruments. This is an incredibly huge part of the cost. How are you detecting the light? Nothing commerical works, because commercial gear is orders of magnitude to weak/insensitive. Spectrographs? Coronographs? Different cameras for different wavelengths?
....


If someone wants to build a large batch of non cutting edge Hubble size space telescopes in the UV/visible light spectrum. Then presumably they will have to produce the instruments also in series.


There seems to be enough user demand for at least several Hubble analogs.


Offline Asteroza

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Re: Low Cost Batch Built Space Telescopes
« Reply #223 on: 11/24/2021 10:35 pm »
All of this just assumes that space telescopes are bits of glass that look at visible light.
If your looking at ir, you need cooling. Xray? Nothing like a normal mirror setup works

Though the big one - instruments. This is an incredibly huge part of the cost. How are you detecting the light? Nothing commerical works, because commercial gear is orders of magnitude to weak/insensitive. Spectrographs? Coronographs? Different cameras for different wavelengths?
....


If someone wants to build a large batch of non cutting edge Hubble size space telescopes in the UV/visible light spectrum. Then presumably they will have to produce the instruments also in series.


There seems to be enough user demand for at least several Hubble analogs.

How would one go about gauging that latent demand though? Rejection rate for Hubble observation time? Is that open data?

Offline su27k

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Re: Low Cost Batch Built Space Telescopes
« Reply #224 on: 11/25/2021 03:26 am »
All of this just assumes that space telescopes are bits of glass that look at visible light.
If your looking at ir, you need cooling. Xray? Nothing like a normal mirror setup works

The optical/visible light observation is a big chunk of the astronomy, just reducing the cost for this chunk would be greatly beneficial, especially considering this segment will be increasingly difficult to do on Earth due to industrialization of near Earth space.


Quote
Though the big one - instruments. This is an incredibly huge part of the cost. How are you detecting the light? Nothing commerical works, because commercial gear is orders of magnitude to weak/insensitive. Spectrographs? Coronographs? Different cameras for different wavelengths?

Instrument is about 25% of the total mission cost, according to the paper Update to single-variable parametric cost models for space telescopes, so even if you assume instrument cost cannot be reduced (not a safe assumption), a radical reduction of the rest of the cost still brings significant cost savings.

Offline su27k

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Re: Low Cost Batch Built Space Telescopes
« Reply #225 on: 11/25/2021 03:44 am »
Some very interesting findings from the paper Update to single-variable parametric cost models for space telescopes:

Quote from: 3.3.1. Cost as a function of aperture diameter cost-estimating relationship
Regardless, the implication is that the basic engineering issues that drive cost as a function of aperture apply equally to all OTAs but that the lower the mass, i.e., the less stiff the OTA, the more difficult and more expensive it is to fabricate.

Quote from: 3.3.2. Cost as a function of mass
Several obvious conclusions can be drawn. All free-flying space telescopes have approximately the same cost per kilogram, independent of aperture diameter. All ground telescopes also have approximately the same cost per kilogram, independent of aperture diameter. Space telescopes cost about 1000/kg more than ground telescopes. Additionally, UIT, WUPPE, and HUT, which flew attached to the space shuttle, are 5 to 10 less expensive per kilogram. SOFIA, which flies attached to a 747, is 20 to 30 less expensive. One explanation is that each of these mission types are built to different design rules. While all three types need similar wavefront shape and pointing stabilities as a function of aperture diameter, they have different static gravity and dynamic jitter environments. They also have different mass budgets with which to achieve the required wavefront shape and pointing stability. Free-flying telescopes have mass budgets that are severely constrained by the launch vehicle. Therefore, significant engineering cost is required to achieve the required performance for the allowed mass. While the attached missions did fly on the space shuttle and SOFIA flies on a 747, the carrying capacities of these vehicles allows for different mass margin design rules.

Quote from: 4. Discussion on Mass
And, as indicated by Fig. 6, changing the design rule to allow for a larger mass budget might reduce total cost.Additionally, there are multiple cautionary indicators against a pure mass model. For example, consider JWST and HST. Hubble is more massive than JWST at both the OTA (150%) and mission (200%) level (Figs. 5 and 7). But JWST is 2 more expensive than HST at both the OTA and mission level. A pure mass model would predict that JWST would be half as expensive as HSTand it would be wrong. The reason is that HST is more massive, stiffer, and less complex than JWST. Next, consider the three shuttle-attached missions. For the same aperture diameter, attached missions are ∼3 more massive and ∼10 less expensive. This is an interesting comparison because the attached missions were space-rated. Of course, there are multiple mitigating factors, such as their limited design life, but given that most OTAs have very few limited lifetime components, these authors believes it to be a valid comparison. Finally, ground-based OTAs are 10 to 100 more massive than free-flying space OTAs and 1000/kg less expensive.

Quote from: 5. Conclusions
Second, we continue to find that telescopes designed to a larger mass budget (for a given aperture), i.e., designed to be stiffer, have a lower cost. This finding is supported by comparisons of free-flying space telescopes, Hubble to JWST, and Hubble to SOFIA. It is also supported by analysis of areal cost (cost per kilogram), which indicates that different classes of telescopes are designed to different design rules. The reason for different classes is the launch vehicle. The total mission mass for a space telescope is constrained by the vehicle used to launch the mission. Additionally, there is a direct connection between the available mass budget and the engineering costs that must be expended to design a lightweight telescope of the desired aperture with the required wavefront shape and pointing stability for its operational environment. It is factual to assert that space telescopes are designed to mass.

So what do you know, here we have a paper showing exactly what we have been talking about: Bigger mass budget results in lower cost for space telescope, and the cost reduction appears to be significant (10x reduction is observed, without the other cost reduction factors we were talking about, such as mass production/bigger LV/commercial methodology).
« Last Edit: 11/25/2021 03:46 am by su27k »

Offline Dizzy_RHESSI

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Re: Low Cost Batch Built Space Telescopes
« Reply #226 on: 11/26/2021 11:36 am »
Some very interesting findings from the paper Update to single-variable parametric cost models for space telescopes

So what do you know, here we have a paper showing exactly what we have been talking about: Bigger mass budget results in lower cost for space telescope, and the cost reduction appears to be significant (10x reduction is observed, without the other cost reduction factors we were talking about, such as mass production/bigger LV/commercial methodology).

I think it's very important to highlight the limitations of this work. Firstly these are single parameter models. By definition they do not attempt to account for other differences. For example their only large "attached" telescope is SOFIA, which by all their analysis is extremely low cost. It's an extreme outlier. The big reason for this is not included in this paper at all, and that's the precision of the mirror surface. SOFIA is compared to HST in their models, but SOFIA was built for long wavelength infrared and it's only diffraction limited above 20 microns in wavelength (compared to 1 micron for HST).  Because these models are based on single parameters they don't account for this, and it falsely creates the impression that it's cheaper.  If one looks at figure 4 (top) we can see that in fact SOFIA's OTA cost is almost exactly in line with Hershel. Herschel is a much better comparison. This problem is noted in the text and it is the reason why they exclude Herschel from many of the fits and plots, but they don't apply this logic to SOFIA. Stahl has done multi-parameter models, which would suffer less from this problem. SOFIA's OTA is an order of magnitude more massive than Herschel's, and yet the cost is more or less the same. Where is this big cost saving?

Secondly for attached missions they are only modeling the OTA cost, which is the minority of the cost. By their metrics SOFIA is very cheap, and yet we know this was not the case. It was more-or-less as expensive as Herschel after more than a decade of delays and huge cost over-runs. Being attached and having a higher mass budget didn't really make much difference in total cost. These metrics also don't quantify scientific value. By this analysis SOFIA looks very appealing, when in reality it was a development disaster and a scientific flop. Not just scientific output but duty cycle is also important, how much observing time is available. SOFIA is much more expensive per hour than Herschel (more than three times more expensive). Another thing missing from their analysis is operations costs. SOFIA is as expensive to operate as Hubble, despite its low scientific output. In the end this cost will be a significant fraction of it's development costs. This is something that cannot be ignored in future attached missions.
« Last Edit: 11/26/2021 11:42 am by Dizzy_RHESSI »

Offline su27k

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Re: Low Cost Batch Built Space Telescopes
« Reply #227 on: 11/27/2021 02:55 am »
Some very interesting findings from the paper Update to single-variable parametric cost models for space telescopes

So what do you know, here we have a paper showing exactly what we have been talking about: Bigger mass budget results in lower cost for space telescope, and the cost reduction appears to be significant (10x reduction is observed, without the other cost reduction factors we were talking about, such as mass production/bigger LV/commercial methodology).

I think it's very important to highlight the limitations of this work. Firstly these are single parameter models. By definition they do not attempt to account for other differences. For example their only large "attached" telescope is SOFIA, which by all their analysis is extremely low cost. It's an extreme outlier. The big reason for this is not included in this paper at all, and that's the precision of the mirror surface. SOFIA is compared to HST in their models, but SOFIA was built for long wavelength infrared and it's only diffraction limited above 20 microns in wavelength (compared to 1 micron for HST).  Because these models are based on single parameters they don't account for this, and it falsely creates the impression that it's cheaper.  If one looks at figure 4 (top) we can see that in fact SOFIA's OTA cost is almost exactly in line with Hershel. Herschel is a much better comparison. This problem is noted in the text and it is the reason why they exclude Herschel from many of the fits and plots, but they don't apply this logic to SOFIA. Stahl has done multi-parameter models, which would suffer less from this problem. SOFIA's OTA is an order of magnitude more massive than Herschel's, and yet the cost is more or less the same. Where is this big cost saving?

Secondly for attached missions they are only modeling the OTA cost, which is the minority of the cost. By their metrics SOFIA is very cheap, and yet we know this was not the case. It was more-or-less as expensive as Herschel after more than a decade of delays and huge cost over-runs. Being attached and having a higher mass budget didn't really make much difference in total cost. These metrics also don't quantify scientific value. By this analysis SOFIA looks very appealing, when in reality it was a development disaster and a scientific flop. Not just scientific output but duty cycle is also important, how much observing time is available. SOFIA is much more expensive per hour than Herschel (more than three times more expensive). Another thing missing from their analysis is operations costs. SOFIA is as expensive to operate as Hubble, despite its low scientific output. In the end this cost will be a significant fraction of it's development costs. This is something that cannot be ignored in future attached missions.


The conclusion doesn't rely entirely on SOFIA, I believe 10x number comes from Shuttle attached, space-rated telescopes, not SOFIA. And yes, the author has later papers that use multi-parameter models, but even those models cannot explain the difference between HST and JWST, from Multivariable Parametric Cost Model for Ground and Space Telescope:

Quote from: Mass Cost Models
While many cost models use mass as a CER, our research finds that mass is not a good CER. The problem with mass is that it is not an independent variable. It is correlated with aperture. The best example of the inappropriateness of mass is the fact that at 3180 kg HSTs OTA is 1.5X more massive than JWSTs 2170 kg OTA. Thus, a mass-based cost model would estimate JWST to be 66% the cost of HST when in reality JWST was approximately 2.6X more expensive than HST.

While the following is supposition on the part of the author and cannot be tested, one reason for the difference between HST and JWST cost relative to their mass may be launch vehicle mass capacity and design margin. Because the space shuttle had a launch mass of 16,000 kg to LEO while the Ariane-5 can only launch 6600 kg to SE-L2, JWST had to be designed to a lower mass than HST. The advantage of having extra mass available is that it enables stiffer, more robust and stable optical components and structure which are easier to manufacture with less risk and lower total cost.


Also the paper made it clear that it only covers OTA, which only constitutes a small fraction of the total mission cost, although I do believe that using the term "telescope" to describe OTA is appropriate. However this limitation doesn't reduce the importance of the conclusion of the paper to this thread, because as some of us already pointed out in the Astro2020 thread, we have existence proof that mass production and big mass margin can reduce spacecraft and mission cost significantly, the proof is Starlink and HLS Starship. However in that thread we were told that space telescope is somehow unique, not a normal spacecraft, and its state of art construction precludes the rules of normal spacecraft from being applied to it. Well OTA is a big part of what's making space telescope unique and state of art, and here we have evidence that its cost do benefit from large mass margins, just like a normal spacecraft.

So yeah, you can still get an expensive mission with a cheap OTA if you mess up the spacecraft part or the management part, but we already know how to reduce the cost for those latter parts, this paper fills in the missing link for low cost space telescopes.

Offline Dizzy_RHESSI

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Re: Low Cost Batch Built Space Telescopes
« Reply #228 on: 11/27/2021 09:00 am »
The conclusion doesn't rely entirely on SOFIA, I believe 10x number comes from Shuttle attached, space-rated telescopes, not SOFIA. And yes, the author has later papers that use multi-parameter models, but even those models cannot explain the difference between HST and JWST, from Multivariable Parametric Cost Model for Ground and Space Telescope:

SOFIA was an example of the issue, the real problem is the method. There are lots of differences which drive costs which are not included in the paper at all. In the case of HST vs JWST, the operating temperature has been ignored. When you go to single parameter models all these additional factors are ignored. If you look for a mass dependence you will find a mass dependence. Here is your quote but highlighting some different statements:

While many cost models use mass as a CER, our research finds that mass is not a good CER. The problem with mass is that it is not an independent variable. It is correlated with aperture. The best example of the inappropriateness of mass is the fact that at 3180 kg HSTs OTA is 1.5X more massive than JWSTs 2170 kg OTA. Thus, a mass-based cost model would estimate JWST to be 66% the cost of HST when in reality JWST was approximately 2.6X more expensive than HST.

While the following is supposition on the part of the author and cannot be tested, one reason for the difference between HST and JWST cost relative to their mass may be launch vehicle mass capacity and design margin. Because the space shuttle had a launch mass of 16,000 kg to LEO while the Ariane-5 can only launch 6600 kg to SE-L2, JWST had to be designed to a lower mass than HST. The advantage of having extra mass available is that it enables stiffer, more robust and stable optical components and structure which are easier to manufacture with less risk and lower total cost.

Two take away points. In this multi-parameter model they don't use mass at all. They do use operating temperature and shortest diffraction limited wavelength. Interesting that these are more informative than the mass. Secondly the statement about mass margin and stiffness has been downgraded to an untested supposition. In the early single parameter paper this was claimed as a robust conclusion, but not so here. Adding additional parameters has eliminated the evidence for this effect.

Offline su27k

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Re: Low Cost Batch Built Space Telescopes
« Reply #229 on: 11/28/2021 02:45 am »
The conclusion doesn't rely entirely on SOFIA, I believe 10x number comes from Shuttle attached, space-rated telescopes, not SOFIA. And yes, the author has later papers that use multi-parameter models, but even those models cannot explain the difference between HST and JWST, from Multivariable Parametric Cost Model for Ground and Space Telescope:

SOFIA was an example of the issue, the real problem is the method. There are lots of differences which drive costs which are not included in the paper at all. In the case of HST vs JWST, the operating temperature has been ignored. When you go to single parameter models all these additional factors are ignored. If you look for a mass dependence you will find a mass dependence. Here is your quote but highlighting some different statements:

While many cost models use mass as a CER, our research finds that mass is not a good CER. The problem with mass is that it is not an independent variable. It is correlated with aperture. The best example of the inappropriateness of mass is the fact that at 3180 kg HSTs OTA is 1.5X more massive than JWSTs 2170 kg OTA. Thus, a mass-based cost model would estimate JWST to be 66% the cost of HST when in reality JWST was approximately 2.6X more expensive than HST.

While the following is supposition on the part of the author and cannot be tested, one reason for the difference between HST and JWST cost relative to their mass may be launch vehicle mass capacity and design margin. Because the space shuttle had a launch mass of 16,000 kg to LEO while the Ariane-5 can only launch 6600 kg to SE-L2, JWST had to be designed to a lower mass than HST. The advantage of having extra mass available is that it enables stiffer, more robust and stable optical components and structure which are easier to manufacture with less risk and lower total cost.

Two take away points. In this multi-parameter model they don't use mass at all. They do use operating temperature and shortest diffraction limited wavelength. Interesting that these are more informative than the mass. Secondly the statement about mass margin and stiffness has been downgraded to an untested supposition. In the early single parameter paper this was claimed as a robust conclusion, but not so here. Adding additional parameters has eliminated the evidence for this effect.

The reason they didn't use mass in the multi-parameter model is explained in the sentence right after your highlight, it's because it's correlated with the aperture. And no, the operating temperature is not going to explain away the cost discrepancy between HST and JWST OTA, if you actually tried to use the model on HST and JWST you'll see this: The model predicted HST OTA cost pretty well (predicted $564M vs actual $530M), but if you use it on JWST the predicted cost deviate wildly away from actual cost (predicted $787M using segmented model, $1,019M using non-segmented model, actual cost is $1,380M)

So there is definitely some discrepancy when comparing HST and JWST, and this is not explained by operating temperature or any other parameters used in the multi-parameter model. The author proposed mass margin as a reasonable explanation. The fact that he calls this "untested supposition" is not a downgrade, this is no different from what he did in previous paper: He saw a discrepancy and proposed a good explanation. To make this not a supposition will require testing, and testing requires using two identical teams building two identical telescopes, using different mass margins. Safe to say this is not going to happen any time soon. But just because it's "untested supposition" doesn't mean it's not actionable, there're some good examples in aerospace right now if you look around...

Offline Dizzy_RHESSI

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Re: Low Cost Batch Built Space Telescopes
« Reply #230 on: 11/28/2021 10:42 am »
Quote
And no, the operating temperature is not going to explain away the cost discrepancy between HST and JWST OTA

That wasn't what I said. My point was that in the single parameter models all these other differences are simply ignored. And note that it doesn't explain the discrepancies in their model. The statement is model dependent, these models are not unique.

Quote
The reason they didn't use mass in the multi-parameter model is explained in the sentence right after your highlight, it's because it's correlated with the aperture.

The quote considers only a pure mass model, when really their model has extra parameters and additional complexity. The scaling with mass does not have to be linear. Just because two parameters are correlated doesn't mean there isn't information there. If one really believed that the the mass margin was important then areal density could be added with a negative exponent.  The authors could have tested their assertion in this way. It wouldn't prove their assertion was correct but it would be a test. It absolutely does not require building new telescopes in controlled conditions, it's no different to the rest of the fitting in the paper. It is a downgrade, in the previous paper they reference examples to give backing to the claim but here it is just "untested".  As I have described there is a counter-example to their original list, but Herschel was inconsistently removed from the paper. Again, if the difference between HST and JWST was really due to mass margin then why wasn't their a huge difference for SOFIA and Herschel?



« Last Edit: 11/28/2021 10:42 am by Dizzy_RHESSI »

Offline su27k

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Re: Low Cost Batch Built Space Telescopes
« Reply #231 on: 11/29/2021 03:09 am »
Again, if the difference between HST and JWST was really due to mass margin then why wasn't their a huge difference for SOFIA and Herschel?

Ok, let's look at SOFIA and Herschel then:

1. From the first paper [1]'s Fig. 4 (a), we can try to read out the OTA Cost of SOFIA and Herschel, roughly SOFIA OTA cost = $30M, Herschel OTA cost = $45M. Right here we can already see your claim that "SOFIA's OTA .... cost is more or less the same [as Herschel's]" is incorrect, in fact SOFIA's OTA cost is quite a bit cheaper, it's just the log scale of the plot makes them similar.

2. First paper is using FY11 $ as cost, to compare the cost to the numbers calculated in the 2nd paper [2], we need to convert it to FY17 $. This conversion factor can be calculated using HST OTA cost: 530/470 = 1.13, so in FY17 $ SOFIA OTA cost = $34M, Herschel OTA cost = $51M.

3. The 2nd paper provided Herschel's parameters in Table 5, so we can plug in this to the multi-parameter model and get predicted Herschel OTA cost as $60M, which is fairly close. BTW, it should be pointed out the Herschel's data is included in creating the multi-parameter model, it's not excluded.

4. Unfortunately the 2nd paper didn't provide SOFIA's parameters, so we'll have to look it up:
Diameter = 2.5m [3]
WDLP = 15 micron [3]
Temperature = 240K [3]
YOD = 1997 [4]
Plug in these to the multi-parameter model, we get predicted SOFIA OTA cost = $66M, a lot higher than actual cost, and higher than predicted Herschel OTA cost. This right here is your huge difference, the model predicted SOFIA should be 1.1x more expensive than Herschel, while in reality SOFIA is 33% cheaper than Herschel.

5. Also it's not clear to me SOFIA's WDLP is actually 15 micron, as [4] pointed out, SOFIA's angular resolution is limited by seeing at lower wavelengths: "For wavelengths shorter than 3 μm, the local seeing at 13 km altitude will be about 2˝ to 4˝. Beyond 15 μm, SOFIA will be diffraction limited (Table 3).", so WDLP = 15 micron may very well be the number that has taken seeing into account. Should be obvious from the ground based telescope WDLP in [2] that WDLP used in the model doesn't take atmosphere seeing into account. From what I read, SOFIA's primary mirror is not solely optimized for far-infrared like Herschel, it's just a normal mirror like other ground based telescopes, so it's possible it has a lot better WDLP, could be in the range of 2 to 6 micron like other ground based infrared telescopes (UKIRT, WHT), in which case the discrepancy in cost would be even larger.


References:

[1] Update to single-variable parametric cost models for space telescopes
[2] Multivariable Parametric Cost Model for Ground and Space Telescope
[3] Eric E. Becklin, Sean C. Casey, and Xander Tielens, "SOFIA An Observatory for THz Science and Technology"
[4] Alfred Krabbe, "The SOFIA Telescope"
« Last Edit: 11/29/2021 03:14 am by su27k »

Offline Dizzy_RHESSI

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Re: Low Cost Batch Built Space Telescopes
« Reply #232 on: 11/29/2021 04:52 pm »
Quote
This right here is your huge difference, the model predicted SOFIA should be 1.1x more expensive than Herschel, while in reality SOFIA is 33% cheaper than Herschel.

I made that comparison in response to the first paper, the single parameter model paper. According to that model Herschel should be 60% more expensive, and it is.  For the purposes of the accuracy of the model I would say 30 vs 45 is more-or-less the same, but whatever. I originally said SOFIA and Herschel were in line in cost, which they are in terms of the model.

"Huge difference". SOFIA's OTA is an order of magnitude heavier but only 33% cheaper. But let's follow this logic through. If this is due to the mass ratio then you can work out what the effect should be on the JWST cost under-prediction. If a factor of 10 in OTA mass gets you a saving of 33% then we can work out what the cost difference for JWST/HST using the same power law method they use. The OTA mass ratio seems to be about 2/3, which would imply JWST should be 7% more expensive, negligible. This was my point, if the difference between JWST and HST was driven by the small difference in mass (as originally claimed) then you would expect a very large difference going from SOFIA to Herschel. This is not observed.

FYI: Your source on the optical performance is a design document, it lists the goals. In practice SOFIA's image quality didn't reach the targets. It's only diffraction limited above about 30 microns. And SOFIA isn't limited by seeing, it's mostly jitter. Seeing from the ground is typically 1-2 arcsec in the visible, it gets better with altitude and at longer wavelengths. SOFIA's mirror has larger wavefront errors than even a typical ground based telescope.

https://www-sofia.atlassian.net/wiki/spaces/OHFC1/pages/1147343/4.+FORCAST#4.1.2-Performance
« Last Edit: 11/29/2021 05:42 pm by Dizzy_RHESSI »

Offline Ben Baley

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Re: Low Cost Batch Built Space Telescopes
« Reply #233 on: 07/17/2023 02:42 am »
https://theconversation.com/a-new-thin-lensed-telescope-design-could-far-surpass-james-webb-goodbye-mirrors-hello-diffractive-lenses-206055

When I read this article my first thought was that it is really applicable to this topic.

I'm no expert on telescopes,  but It seems like a lense based design has a lot of benefits for a low cost fleet of space based telescopes.

I know I'm resurrecting a defunct thread but it fits well with the topic and it seems like a good time to revisit the discussion.

Offline Eka

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Re: Low Cost Batch Built Space Telescopes
« Reply #234 on: 07/18/2023 03:19 am »
https://theconversation.com/a-new-thin-lensed-telescope-design-could-far-surpass-james-webb-goodbye-mirrors-hello-diffractive-lenses-206055

When I read this article my first thought was that it is really applicable to this topic.

I'm no expert on telescopes,  but It seems like a lense based design has a lot of benefits for a low cost fleet of space based telescopes.

I know I'm resurrecting a defunct thread but it fits well with the topic and it seems like a good time to revisit the discussion.
Those lenses should also work for long range laser links. Long range being planet to planet.
We talk about creating a Star Trek future, but will end up with The Expanse if radical change doesn't happen.

Online laszlo

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Re: Low Cost Batch Built Space Telescopes
« Reply #235 on: 07/18/2023 11:55 am »
https://theconversation.com/a-new-thin-lensed-telescope-design-could-far-surpass-james-webb-goodbye-mirrors-hello-diffractive-lenses-206055

When I read this article my first thought was that it is really applicable to this topic.

I'm no expert on telescopes,  but It seems like a lense based design has a lot of benefits for a low cost fleet of space based telescopes.

I know I'm resurrecting a defunct thread but it fits well with the topic and it seems like a good time to revisit the discussion.

Interesting concept. My biggest question is if a 29.5 foot (8.5 meter) diameter, 0.2 inch (0.5 cm) thick lens will be stiff enough to use or will it flex too much from thermal and other effects to keep the kind of focus needed to take advantage of that kind of aperture. I know structure and thermal isolation can be added to fix these issues, but will it end up as big and heavy as the traditional mirror telescopes in that case?

Another question is micrometeoroid protection. Is a 0.2 inch thick lens rugged enough to take a few impacts and survive, let alone keep functioning, especially with the lens not buried deep in a cylinder the way the Hubble is?

Finally, what kind of focal length are we looking at, I wonder.

This sounds like a very promising technology. It'll be fun to see where it goes.



Offline Eka

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Re: Low Cost Batch Built Space Telescopes
« Reply #236 on: 07/18/2023 11:29 pm »
https://theconversation.com/a-new-thin-lensed-telescope-design-could-far-surpass-james-webb-goodbye-mirrors-hello-diffractive-lenses-206055

When I read this article my first thought was that it is really applicable to this topic.

I'm no expert on telescopes,  but It seems like a lense based design has a lot of benefits for a low cost fleet of space based telescopes.

I know I'm resurrecting a defunct thread but it fits well with the topic and it seems like a good time to revisit the discussion.

Interesting concept. My biggest question is if a 29.5 foot (8.5 meter) diameter, 0.2 inch (0.5 cm) thick lens will be stiff enough to use or will it flex too much from thermal and other effects to keep the kind of focus needed to take advantage of that kind of aperture. I know structure and thermal isolation can be added to fix these issues, but will it end up as big and heavy as the traditional mirror telescopes in that case?

Another question is micrometeoroid protection. Is a 0.2 inch thick lens rugged enough to take a few impacts and survive, let alone keep functioning, especially with the lens not buried deep in a cylinder the way the Hubble is?

Finally, what kind of focal length are we looking at, I wonder.

This sounds like a very promising technology. It'll be fun to see where it goes.

The thermal issues I can see easy methods around them.

As for micro meteoroids, that's harder, but a shade, which also helps with thermal issues, can also help reduce the number of micrometeoroids by catching some of them it's self. The glass they use can also be a big help. If it is one that doesn't propagate cracks, it should be able to survive a few hits.
We talk about creating a Star Trek future, but will end up with The Expanse if radical change doesn't happen.

Offline Ben Baley

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Re: Low Cost Batch Built Space Telescopes
« Reply #237 on: 07/19/2023 08:28 am »
https://theconversation.com/a-new-thin-lensed-telescope-design-could-far-surpass-james-webb-goodbye-mirrors-hello-diffractive-lenses-206055

When I read this article my first thought was that it is really applicable to this topic.

I'm no expert on telescopes,  but It seems like a lense based design has a lot of benefits for a low cost fleet of space based telescopes.

I know I'm resurrecting a defunct thread but it fits well with the topic and it seems like a good time to revisit the discussion.

Interesting concept. My biggest question is if a 29.5 foot (8.5 meter) diameter, 0.2 inch (0.5 cm) thick lens will be stiff enough to use or will it flex too much from thermal and other effects to keep the kind of focus needed to take advantage of that kind of aperture. I know structure and thermal isolation can be added to fix these issues, but will it end up as big and heavy as the traditional mirror telescopes in that case?

Another question is micrometeoroid protection. Is a 0.2 inch thick lens rugged enough to take a few impacts and survive, let alone keep functioning, especially with the lens not buried deep in a cylinder the way the Hubble is?

Finally, what kind of focal length are we looking at, I wonder.

This sounds like a very promising technology. It'll be fun to see where it goes.

From the article
Quote
Second, lens-based telescopes work well even when not aligned perfectly, making these telescopes easier to assemble and fly in space than mirror-based telescopes, which require extremely precise alignment.

This seems to imply that thermal effects on focus shouldn't be as much of a problem.


Offline rsdavis9

Re: Low Cost Batch Built Space Telescopes
« Reply #238 on: 07/19/2023 02:47 pm »
So to my mind this seems like a giant diffraction grating focusing light? Is that right?
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
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Online DanClemmensen

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Re: Low Cost Batch Built Space Telescopes
« Reply #239 on: 07/19/2023 02:53 pm »
So to my mind this seems like a giant diffraction grating focusing light? Is that right?
Look up Fresnel lens. It's not a diffraction grating.
    https://en.wikipedia.org/wiki/Fresnel_lens
They are used extensively in theatre lighting instruments and in many other applications.

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