Sofia, the Historic Airplane-Borne Telescope, Lands for the Last Time | Hacker News Reader

Sofia, the Historic Airplane-Borne Telescope, Lands for the Last Time

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77 pointsItchyner28 comments

Two points:

Firstly SOFIA is a modified Boeing 747SP. The SP first flew in 1975 and the final SP was delivered in 1987: Boeing never made many of this type (a short-arse extra-long-range 747 that was designed for certain long-haul routes, back before high bypass turbofans had the fuel economy -- hence range -- we expect of today's airliners) and this was one of the last ones still flying.

Secondly, it's an infrared telescope. JWST does the same job much, much better. If JWST had failed, then we'd presumably see a hasty program to build a next-generation SOFIA airborn telescope around now. But given JWST's success to date, it's simply no longer needed.

I don't think the latter is completely true. JWST can capture a smaller range of infrared for starters, and is obviously impossible to change, whereas an airborne platform can carry additional instruments if needed. And for observations in the solar system, the ability to move can be helpful too. E.g. if an occlusion is visible anywhere on earth SOFIA can move there, JWST is either in the right spot by accident or is no.

Not just that, but Jwst 's time is at an absurd premium, while sofia' s less so, allowing less filtering of what it's time can be used for, indeed having more than one infrared telescope is better than just having one

The proportions on that plane are all sorts of funny: https://aeroin.net/wp-content/uploads/2021/02/sofia_take_off...

SOFIA also had pretty good PR value - they had a program to put teachers on each science flight. I know a few of my local teachers got to go and it seemed like a nice program. I suppose it might now make a nice museum piece along with the shuttle carrier planes.

The environmentally and fiscally conscious astronomy community abhors it. It’s scientific value compared to those operational and environmental costs is terrible

> The environmentally and fiscally conscious

Sending telescopes to space being famously cheap and environmentally friendly.

They might not want to look into how many other jets are in the air at any given time then. And I doubt many of them are providing any scientific value.

> JWST does the same job much, much better.

Close: JWST is near-infrared. SOFIA was the last and remaining far-infrared telescope. There's debate though if far-infrared was worth it though.

Not sure what you call near IR but JWST has a range from 600nm to 28micrometers. Typicaly people start talking about mid-air from 2 micrometers. So I would say JWST definitely covers beyond near IR

> Not sure what you call near IR but JWST has a range from 600nm to 28micrometers. Typicaly people start talking about mid-air from 2 micrometers. So I would say JWST definitely covers beyond near IR.

JWST covers the mid-infrared too, as you implied. But @exabrial's point still stands, that SOFIA's coverage included much longer wavelengths than JWST does. SOFIA had instruments that could observe wavelengths as long as 1600 microns[0].

[0] https://www.sofia.usra.edu/about-sofia/sofia-overview

Interesting 1600microns is mm waves, so that must be a different instrument? I don't think you could use the same "telescope* for imaging optical and what is essentially rf waves. Unfortunately the website doesn't give enough details without diving into the abbreviated instruments.

> There's debate though if far-infrared was worth it though.

I don't think there's debate about whether the far-infrared is valuable. The far-infrared has unique diagnostic power for some astrophysical phenomena, and the 2020 Decadal Survey for Astronomy specifically called for the far-infrared to be considered for a $1B "probe-class" mission. What was debated was the specific role and cost of SOFIA.

There’s an epic omega tau podcast episode about this if you want to find out more about SOFIA.

http://omegataupodcast.net/touren-tours/sofia/

> $85M/year

At what point with SpaceX launch cost reductions would a space version become cheaper? Maybe already?

Ignoring development costs, that is approximately the cost to launch one SOFIA telescope to LEO (19T x 1000 kg/T x $2500/kg = $48M) with change. So I think space based telescopes definitely win out.

The costs to operate a space telescope don’t end at launch.

Exactly what I thought when I saw the dimensions and tonnage. Honestly they could probably just refurbish this equipment, add some telemetry and station keeping jets and load it onto a Falcon 9. That’d be a great first if it was a refurbished telescope deployed by a refurbished rocket.

It costs a lot more to run a telescope in space! For the JWST, the annual cost is, $175.2M/yr. Calculated from the $861M that NASA budgeted for its first 5 years of operations.

As always, the most expensive costs aren't the hardware; it's the people!

The second highest operational cost is probably Deep Space Network time. Each contact can be calculated using this formula, (1057 * 1 * (0.9+(7/10)) * (1 + 4) [note: this is in 2017 dollars, I've inflation adjusted the amount], each contact is for 4 hours/day and must be done every day, that's $9,286.5/day for DSN time, inflation adjusted. Or, $3,389,572.5/yr for network time alone. I am sure that there are additional costs that make it even higher.

You can see the formula here, https://space.stackexchange.com/questions/21005/what-makes-t...

That 175 mil / year allowed for 24x7x365 days of observations. The 85 mil for this aircraft allows for what 12 x 3 hours of observations?

Launches are not the most expensive part of a space telescope. Even for something like Hubble, which cost almost 10x more to launch than a Falcon 9 payload today, the launch cost was a single digit percentage of the overall budget.

solving the micro-vibrations for that telescope must have been a tough nut to crack

Before SOFIA there was AOA, "airborne optical adjunct", a military project probably funded by the fake Star Wars anti-missile program that spooked USSR into crashing their economy. Same configuration, a 747 with a hole in the top, IR telescope inside. It is just possible it was the same actual airframe.

My brother worked on that stabilization. It had 3 levels of it.

Star Wars worked beautifully for its actual intended purpose, which you mentioned.

It was kind of hard on Russian people, though, considering they had so little say in how things were done at the time. Not as hard as Stalin, or even Lenin. But it seems like if more had been done, we would not be in the present fix.

Disclaimer: I am biased. I've talked to some of the people on the team. And am friends with one of the many people who've worked on the project.

So a few points here;

First, a lot of people are pointing to the JWST as the heir apparent, but that's not quite correct nor true. SOFIA is the only observatory that looks at the Far Infrared wavelength, the only one on Earth. The rest are in LEO. There are some who will say that it's not valuable, but the truth is that we don't know if it's valuable or not. We've only been doing these observations since 1983 with a handful of telescopes (the first one was the Infrared Astronomical Satellite or IRAS, IIRC).

However, we've already made significant finds, including water vapor on Ceres and observations of the galactic center + stellar nurseries.

Second, you can't change a space telescope without a Shuttle-style mission, but you can endlessly tool and re-tool SOFIA. What this means is that SOFIA can adapt to different observation targets and we can try new technologies on board.

Third, SOFIA can image wider sections of the sky, whereas JWST is great at looking at particular targets/regions. More technically, they have completely different fields of view from the specs;

    SI Fields of View 
    
    SOFIA:  HAWC+ > ~10 arcm2
    JWST:   < 10 arcm2 per SI

We don't know what's out there. Or, to put it in a more Rumsfeldian fashion, we don't know what we don't know, and it is important to do wider surveys. SOFIA is the only Far Infrared telescope in the world with such a wide field of view.

Fourth, it is absurd to me that we're arguing if we need a telescope. It's like arguing that a single camera is enough for a family. Why shouldn't we capture more of our universe in a world filled with sensors? And peer ever deeper into creation?

The more of these instruments we have, the greater the number of people who have the opportunity to point it at something and discover something new.

More directly; I don't think scientists should spend most of their time writing and judging applications for a limited number of spots on observatories. I think they should spend most of their time doing actual science. The greater the number of capable observatories that are out there in the world, the observation time there is to go around, allowing for newer/riskier ideas to be tried.

Fifth, I struggle to articulate this point, but we keep removing assets instead of adding capabilities when it comes to NASA. A great example of this is the loss of Arecibo. Or the loss of the ability to bring large payloads back down from orbit. This obsession with getting the most science per dollar is understandable and desirable, but pursuing it by removing capabilities from our toolbox is suboptimal.

Could you imagine if any country ran a military in the same way? Getting rid of amphibian assault capabilities because you have parachute regiments doesn't make sense.

Each new capability adds to the whole, making something greater than the sum of its parts. Here's an example that I have lifted from a slide that's a part of a presentation that was given by a SOFIA project scientist and the PI for the JWST's MIRI + NIRCam, Tom Greene, in 2017,

Let's say we wish to understand and image gas and shocks in protostellar jets. We need to image at multiple wavelengths to capture all of the processes at play.

There are so many processes going on here that really can't answer "simple" questions like, "how is energy transferred from accretion disks to the jets of young stars?" or "How does this relate/feedback into the molecular disks where stars are formed?"

We can imagine a scenario where SOFIA spots a protostellar jet, we re-tool it to get a better look at particular wavelengths, hand it over to JWST + Hubble to image the protostellar jet, and add in observatories across the world. And then, we can use all of this data to construct a richer picture of these processes.

Please call your congressperson and ask them to fund more science. After all, of what use is a baby?

How about a revamped scope on a different, modern aircraft that has vastly less costs to operate? That might be more financially possible.

She’s taking a well-deserved break so she can map out a strategy for all those frequent flyer miles

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